Showing papers in "Planta in 2021"

Zinc toxicity in plants: a review.

Abstract: This review highlights the most recent updated information available about Zn phytotoxicity at physiological, biochemical and molecular levels, uptake mechanisms as well as excess Zn homeostasis in plants. Zinc (Zn) is a natural component of soil in terrestrial environments and is a vital element for plant growth, as it performs imperative functions in numerous metabolic pathways. However, potentially noxious levels of Zn in soils can result in various alterations in plants like reduced growth, photosynthetic and respiratory rate, imbalanced mineral nutrition and enhanced generation of reactive oxygen species. Zn enters into soils through various sources, such as weathering of rocks, forest fires, volcanoes, mining and smelting activities, manure, sewage sludge and phosphatic fertilizers. The rising alarm in environmental facet, as well as, the narrow gap between Zn essentiality and toxicity in plants has drawn the attention of the scientific community to its effects on plants and crucial role in agricultural sustainability. Hence, this review focuses on the most recent updates about various physiological and biochemical functions perturbed by high levels of Zn, its mechanisms of uptake and transport as well as molecular aspects of surplus Zn homeostasis in plants. Moreover, this review attempts to understand the mechanisms of Zn toxicity in plants and to present novel perspectives intended to drive future investigations on the topic. The findings will further throw light on various mechanisms adopted by plants to cope with Zn stress which will be of great significance to breeders for enhancing tolerance to Zn contamination.

Contribution of strigolactone in plant physiology, hormonal interaction and abiotic stresses.

Abstract: Strigolactones (SLs) are carotenoid-derived molecules, which regulate various developmental and adaptation processes in plants. These are engaged in different aspects of growth such as development of root, leaf senescence, shoot branching, etc. Plants grown under nutrient-deficient conditions enhance SL production that facilitates root architecture and symbiosis of arbuscular mycorrhizal fungi, as a result increases nutrient uptake. The crosstalk of SLs with other phytohormones such as auxin, abscisic acid, cytokinin and gibberellins, in response to abiotic stresses indicates that SLs actively contribute to the regulatory systems of plant stress adaptation. In response to different environmental circumstances such as salinity, drought, heat, cold, heavy metals and nutrient deprivation, these SLs get accumulated in plant tissues. Strigolactones regulate multiple hormonal responsive pathways, which aids plants to surmount stressful environmental constraints as well as reduce negative impact on overall productivity of crops. The external application of SL analog GR24 for its higher bioaccumulation can be one of the possible approaches for establishing various abiotic stress tolerances in plants.

Assembly of the complete mitochondrial genome of an endemic plant, Scutellaria tsinyunensis, revealed the existence of two conformations generated by a repeat-mediated recombination

Abstract: We assembled the complete mitochondrial genome of Scutellaria tsinyunensis in this study. Repeat-mediated recombination resulted in the formation of two conformations of the mitochondrial genome in S. tsinyunensis. Scutellaria tsinyunensis belongs to the family Lamiaceae, distributed only in the Jinyun Mountain, Chongqing, China. As a valuable endemic and small population species, it is regarded as a natural resource potentially with significant economic and ecological importance. In this study, we assembled a complete and gap-free mitochondrial genome of S. tsinyunensis. This genome had a length of 354,073 bp and the base composition of the genome was A (27.44%), T (27.30%), C (22.58%), and G (22.68%). This genome encodes 59 genes, including 32 protein-coding genes, 24 tRNA genes, and 3 rRNA genes. The Sanger sequencing and Oxford Nanopore sequencing confirmed a pair of direct repeats had mediated genome recombination, resulting in the formation of two conformations. The gene conversation between plastome and mitochondrial genome was also observed in S. tsinyunensis by detecting gene migration, including six tRNA genes (namely, trnW-CCA, trnI-CAU, trnH-UUU, trnD-GUC, trnN-GUU, and trnM-CAU), five protein-coding gene fragments, and the fragments from 2 rRNA genes. Moreover, the dN/dS analysis revealed the atp9 gene had undergone strong negative selection, and four genes (atp4, mttB, ccmFc, and ccmB) probably had undergone positive selection during evolution in Lamiales. This work reported the first mitochondrial genome of S. tsinyunensis, which could be used as a reference genome for the important medicinal plants of the genus Scutellaria, and also provide much-desired information for molecular breeding.

Concentrations-dependent effect of exogenous abscisic acid on photosynthesis, growth and phenolic content of Dracocephalum moldavica L. under drought stress.

Abstract: The drought conditions and the application of ABA reduce the photosynthetic activity, and the processes related to the transpiration of Dracocephalum moldavica L. At the same time, the plant increases the production of phenolic compounds and essential oil as a response to stress conditions. In the semi-arid regions, drought stress is the most important environmental limitations for crop production. Abscisic acid (ABA) plays a crucial role in the reactions of plants towards environmental stress such as drought. Field experiments for two consecutive years in 2016 and 2017 were conducted to evaluate the effect of three watering regimes (well-watered, moderate and severe drought) and five exogenous ABA concentrations (0, 5, 10, 20 and 40 μM) on growth, photosynthesis, total phenolic and essential oil content of Dracocephalum moldavica L. Without ABA application, the highest photosynthetic rate (6.1 μmol CO2 m−2 s−1) was obtained under well-watered condition and, moderate and severe drought stress decreased photosynthesis rate by 26.39% and 34.43%, respectively. Some growth parameters such as stem height, leaf area, leaf dry weight and biological yield were also reduced by drought stress. ABA application showed a decreasing trend in photosynthesis rate and mentioned plant growth parameters under all moisture regimes. The highest seed yield (1243.56 kg ha−1) was obtained under well-watered condition without ABA application. Increasing ABA concentration decreased seed yield in all moisture regimes. The highest total phenolic content (8.9 mg g−1 FW) and essential oil yield (20.58 kg ha−1) were obtained from 20 and 5 μM ABA concentration, respectively, under moderate drought stress.

Plant mineral transport systems and the potential for crop improvement

Abstract: Nutrient transporter genes could be a potential candidate for improving crop plants, with enhanced nutrient uptake leading to increased crop yield by providing tolerance against different biotic and abiotic stresses. The world’s food supply is nearing a crisis in meeting the demands of an ever-growing global population, and an increase in both yield and nutrient value of major crops is vitally necessary to meet the increased population demand. Nutrients play an important role in plant metabolism as well as growth and development, and nutrient deficiency results in retarded plant growth and leads to reduced crop yield. A variety of cellular processes govern crop plant nutrient absorption from the soil. Among these, nutrient membrane transporters play an important role in the acquisition of nutrients from soil and transport of these nutrients to their target sites. In addition, as excess nutrient delivery has toxic effects on plant growth, these membrane transporters also play a significant role in the removal of excess nutrients in the crop plant. The key function provided by membrane transporters is the ability to supply the crop plant with an adequate level of tolerance against environmental stresses, such as soil acidity, alkalinity, salinity, drought, and pathogen attack. Membrane transporter genes have been utilized for the improvement of crop plants, with enhanced nutrient uptake leading to increased crop yield by providing tolerance against different biotic and abiotic stresses. Further understanding of the basic mechanisms of nutrient transport in crop plants could facilitate the advanced design of engineered plant crops to achieve increased yield and improve nutrient quality through the use of genetic technologies as well as molecular breeding. This review is focused on nutrient toxicity and tolerance mechanisms in crop plants to aid in understanding and addressing the anticipated global food demand.

Effects of heat stress on photosystem II activity and antioxidant enzymes in two maize cultivars.

Abstract: The main reason for the maize genotype “DKC7221” to be heat tolerant is to have higher photosynthetic activity under heat stress conditions The genotype “P3167” is sensitive to high temperature because of the heat-induced inhibition in photosynthetic electron transport reactions In the present study, the effect of heat stress (45 oC for 20 min) on some physiological changes was investigated through a chlorophyll afluorescence technique, and some endogenous resistance mechanisms (activities of some antioxidant enzymes, free proline, and reduced ascorbate contents) in two maize cultivars (Zea mays L cvs P3167 and DKC7221) Chlorophyll fluorescence measurements demonstrated that heat stress led to the reduction in the efficiency of the Hill reaction, accumulation of inactive reaction centers, inhibition of electron flow from reaction centers to the plastoquinone pool, and induction of non-photochemical dissipation of absorbed light energy Changes in Φo/(1 – Φo), SFIABS and PIABS indicated that electron transport reactions in P3167 were almost completely inhibited by heat stress In DKC7221, however, photosynthetic electron transport reactions were maintained under heat stress conditions As a result of impairment in the photosynthetic efficiency in P3167 under heat stress, oxidative stress appeared as shown by lower antioxidant activity, accumulation of H2O2, malondialdehyde, and formazon and photooxidative injuries in chlorophyll pigments in the leaf tissue DKC7221, on the other hand, had a higher antioxidant efficiency and lower oxidative damage under heat stress FeSOD activity was found to be responsible for the dismutation of superoxide radicals in both maize genotypes under heat stress As a result, it may be concluded that the genotype DKC7221 is more tolerant to heat stress than P3167

Identification and phylogenetic analysis of five Crataegus species (Rosaceae) based on complete chloroplast genomes

Abstract: The chloroplast genomes of the five Crataegus species were shown to have a conserved genome structure. Complete chloroplast genome sequences were more suitable than highly variable regions for the identification and phylogenetic analysis of Crataegus species. Hawthorn, which is commonly used as a traditional Chinese medicine, is one of the most popular sour fruits and has high economic value. Crataegus pinnatifida var. pinnatifida and C. pinnatifida var. major are frequently adulterated with other Crataegus species on the herbal medicine market. However, most Crataegus plants are difficult to identify using traditional morphological methods. Here, we compared five Crataegus chloroplast (CP) genomes comprising two newly sequenced (i.e., C. pinnatifida var. pinnatifida and C. pinnatifida var. major) and three previously published CP genomes. The CP genomes of the five Crataegus species had a conserved genome structure, gene content and codon usage. The total length of the CP genomes was 159,654–159,865 bp. A total of 129–130 genes, including 84–85 protein-coding genes, 37 tRNA genes and 8 rRNA genes, were annotated. Bioinformatics analysis revealed 96–103 simple sequence repeats (SSRs) and 48–70 long repeats in the five CP genomes. Combining the results of mVISTA and nucleotide diversity, five highly variable regions were screened for species identification and relationship studies. Maximum likelihood trees were constructed on the basis of complete CP genome sequences and highly variable regions. The results showed that the former had higher discriminatory power for Crataegus species, indicating that the complete CP genome could be used as a super-barcode to accurately authenticate the five Crataegus species.

Kiwifruit bacterial canker: an integrative view focused on biocontrol strategies.

Abstract: Phage-based biocontrol strategies can be an effective alternative to control Psa-induced bacterial canker of kiwifruit. The global production of kiwifruit has been seriously affected by Pseudomonas syringae pv. actinidiae (Psa) over the last decade. Psa damages both Actinidia chinensis var. deliciosa (green kiwifruit) but specially the susceptible Actinidia chinensis var. chinensis (gold kiwifruit), resulting in severe economic losses. Treatments for Psa infections currently available are scarce, involving frequent spraying of the kiwifruit plant orchards with copper products. However, copper products should be avoided since they are highly toxic and lead to the development of bacterial resistance to this metal. Antibiotics are also used in some countries, but bacterial resistance to antibiotics is a serious worldwide problem. Therefore, it is essential to develop new approaches for sustainable agriculture production, avoiding the emergence of resistant Psa bacterial strains. Attempts to develop and establish highly accurate approaches to combat and prevent the occurrence of bacterial canker in kiwifruit plants are currently under study, using specific viruses of bacteria (bacteriophages, or phages) to eliminate the Psa. This review discusses the characteristics of Psa-induced kiwifruit canker, Psa transmission pathways, prevention and control, phage-based biocontrol strategies as a new approach to control Psa in kiwifruit orchards and its advantages over other therapies, together with potential ways to bypass phage inactivation by abiotic factors.

Enhancing artemisinin content in and delivery from Artemisia annua: a review of alternative, classical, and transgenic approaches

Abstract: This review analyses the most recent scientific research conducted for the purpose of enhancing artemisinin production. It may help to devise better artemisinin enhancement strategies, so that its production becomes cost effective and becomes available to masses. Malaria is a major threat to world population, particularly in South-East Asia and Africa, due to dearth of effective anti-malarial compounds, emergence of quinine resistant malarial strains, and lack of advanced healthcare facilities. Artemisinin, a sesquiterpene lactone obtained from Artemisia annua L., is the most potent drug against malaria and used in the formulation of artemisinin combination therapies (ACTs). Artemisinin is also effective against various types of cancers, many other microbes including viruses, parasites and bacteria. However, this specialty metabolite and its derivatives generally occur in low amounts in the source plant leading to its production scarcity. Considering the importance of this drug, researchers have been working worldwide to develop novel strategies to augment its production both in vivo and in vitro. Due to complex chemical structure, its chemical synthesis is quite expensive, so researchers need to devise synthetic protocols that are economically viable and also work on increasing the in-planta production of artemisinin by using various strategies like use of phytohormones, stress signals, bioinoculants, breeding and transgenic approaches. The focus of this review is to discuss these artemisinin enhancement strategies, understand mechanisms modulating its biosynthesis, and evaluate if roots play any role in artemisinin production. Furthermore, we also have a critical analysis of various assays used for artemisinin measurement. This may help to develop better artemisinin enhancement strategies which lead to decreased price of ACTs and increased profit to farmers.

ROS-induced oxidative stress in plant cryopreservation: occurrence and alleviation

Abstract: Reactive oxygen species (ROS)-induced oxidative stress results in low success or even total failure of cryopreservation. Better understanding of how the plant establishes resistance/tolerance to ROS-induced oxidative stress facilitates developments of robust cryopreservation procedures. Cryopreservation provides a safe and efficient strategy for long-term preservation of plant genetic resources. ROS-induced oxidative stress caused damage to cells and reduced the ability of the plant to survive following cryopreservation, eventually resulting in low success or even total failure. This paper provides updated and comprehensive information obtained in the past decade, including the following: (1) ROS generations and adaptive responses of antioxidant systems during cryopreservation; (2) expressions of oxidative stress-associated genes and proteins during cryopreservation; (3) ROS-triggered programmed cell death (PCD) during cryopreservation; and (4) exogenous applications of enzymatic and non-enzymatic antioxidants in improving success of cryopreservation. Prospects for further studies are proposed. The goal of the present study was to facilitate better understanding of the mechanisms by which the plant establishes resistance/tolerance to oxidative stress during cryopreservation and promote further studies toward the developments of robust cryopreservation procedures and wider application of plant cryobiotechnology.

Sorghum mitigates climate variability and change on crop yield and quality.

Abstract: Global food insecurity concerns due to climate change, emphasizes the need to focus on the sensitivity of sorghum to climate change and potential crop improvement strategies available, which is discussed in the current review to promote climate-smart agriculture. Climate change effects immensely disturb the global agricultural systems by reducing crop production. Changes in extreme weather and climate events such as high-temperature episodes and extreme rainfalls events, droughts, flooding adversely affect the production of staple food crops, posing threat to ecosystem resilience. The resulting crop losses lead to food insecurity and poverty and question the sustainable livelihoods of small farmer communities, particularly in developing countries. In view of this, it is essential to focus and adapt climate-resilient food crops which need lower inputs and produce sustainable yields through various biotic and abiotic stress-tolerant traits. Sorghum, “the camel of cereals”, is one such climate-resilient food crop that is less sensitive to climate change vulnerabilities and also an important staple food in many parts of Asia and Africa. It is a rainfed crop and provides many essential nutrients. Understanding sorghum’s sensitivity to climate change provides scope for improvement of the crop both in terms of quantity and quality and alleviates food and feed security in future climate change scenarios. Thus, the current review focused on understanding the sensitivity of sorghum crop to various stress events due to climate change and throws light on different crop improvement strategies available to pave the way for climate-smart agriculture.

Rice histone deacetylase HDA704 positively regulates drought and salt tolerance by controlling stomatal aperture and density.

Abstract: HDA704 enhances drought and salt tolerance via stomata-regulated mechanism. HDA704 negatively regulates stomatal aperture and density, repressing the transcription of DST and ABIL2 by histone deacetylation modification. Drought and salinity can damage crop growth and reduce yield. Stomata play an important role in abiotic stress tolerance. In this study on rice, we identified the RPD3/HDA1-type histone deacetylase HDA704 as a positive regulatory factor in drought and salt tolerance. HDA704 was induced by drought and salt stresses. Overexpression of HDA704 in transgenic rice promoted stomatal closure, decreased the number of stomata and slowed down the rate of water loss, consequently resulting in increased drought and salt tolerance. By contrast, knockdown of HDA704 in transgenic rice decreased stomatal closure and accelerated the rate of water loss, leading to decrease drought and salt tolerance. We detected the transcript expression of DST (Drought and Salt Tolerance) and ABIL2 (Abscisic Acid-insensitive Like2), which positively regulate stomatal aperture and density in rice. Our results showed that HDA704 directly binds to DST and ABIL2, repressing their expression via histone deacetylation modification. Collectively, these findings reveal that HDA704 positively regulates drought and salt tolerance by repressing the expression of DST and ABIL2. Our findings provide a new insight into the molecular mechanisms of stomata-regulated abiotic stress tolerance of plants.

Comparative RNA-Seq analysis reveals genes associated with masculinization in female Cannabis sativa

Abstract: Using RNA profiling, we identified several silver thiosulfate-induced genes that potentially control the masculinization of female Cannabis sativa plants. Genetically female Cannabis sativa plants normally bear female flowers, but can develop male flowers in response to environmental and developmental cues. In an attempt to elucidate the molecular elements responsible for sex expression in C. sativa plants, we developed genetically female lines producing both female and chemically-induced male flowers. Furthermore, we carried out RNA-Seq assays aimed at identifying differentially expressed genes responsible for male flower development in female plants. The results revealed over 10,500 differentially expressed genes, of which around 200 potentially control masculinization of female cannabis plants. These genes include transcription factors and other genes involved in male organ (i.e., anther and pollen) development, as well as genes involved in phytohormone signalling and male-biased phenotypes. The expressions of 15 of these genes were further validated by qPCR assay confirming similar expression patterns to that of RNA-Seq data. These genes would be useful for understanding predisposed plants producing flowers of both sex types in the same plant, and help breeders to regulate the masculinization of female plants through targeted breeding and plant biotechnology.

Large vs small genomes in Passiflora : the influence of the mobilome and the satellitome

Abstract: While two lineages of retrotransposons were more abundant in larger Passiflora genomes, the satellitome was more diverse and abundant in the smallest genome analysed. Repetitive sequences are ubiquitous and fast-evolving elements responsible for size variation and large-scale organization of plant genomes. Within Passiflora genus, a tenfold variation in genome size, not attributed to polyploidy, is known. Here, we applied a combined in silico and cytological approach to study the organization and diversification of repetitive elements in three species of this genus representing its known range in genome size variation. Sequences were classified in terms of type and repetitiveness and the most abundant were mapped to chromosomes. We identified long terminal repeat (LTR) retrotransposons as the most abundant elements in the three genomes, showing a considerable variation among species. Satellite DNAs (satDNAs) were less representative, but highly diverse between subgenera. Our results clearly confirm that the largest genome species (Passiflora quadrangularis) presents a higher accumulation of repetitive DNA sequences, specially Angela and Tekay elements, making up most of its genome. Passiflora cincinnata, with intermediate genome and from the same subgenus, showed similarity with P. quadrangularis regarding the families of repetitive DNA sequences, but in different proportions. On the other hand, Passiflora organensis, the smallest genome, from a different subgenus, presented greater diversity and the highest proportion of satDNA. Altogether, our data indicates that while large genomes evolved by an accumulation of retrotransposons, the smallest genome known for the genus has evolved by diversification of different repeat types, particularly satDNAs.

CRISPR/Cas9 technology for improving agronomic traits and future prospective in agriculture.

Abstract: In this review, we have focused on the CRISPR/Cas9 technology for improving the agronomic traits in plants through point mutations, knockout, and single base editing, and we highlighted the recent progress in plant metabolic engineering. CRISPR/Cas9 technology has immense power to reproduce plants with desired characters and revolutionizing the field of genome engineering by erasing the barriers in targeted genome editing. Agriculture fields are using this advance genome editing tool to get the desired traits in the crops plants such as increase yield, improve product quality attributes, and enhance resistance against biotic and abiotic stresses by identifying and editing genes of interest. This review focuses on CRISPR/Cas-based gene knockout for trait improvement and single base editing to boost yield, quality, stress tolerance, and disease resistance traits in crops. Use of CRISPR/Cas9 system to facilitate crop domestication and hybrid breeding are also touched. We summarize recent developments and up-gradation of delivery mechanism (nanotechnology and virus particle-based delivery system) and progress in multiplex gene editing. We also shed lights in advances and challenges of engineering the important metabolic pathways that contain a variety of dietary metabolites and phytochemicals. In addition, we endorsed substantial technical hurdles and possible ways to overcome the unpredictability of CRISPR/Cas technology for broader application across various crop species. We speculated that by making a strong interconnection among all genomic fields will give a gigantic bunt of knowledge to develop crop expressing desired traits.

Genome-wide characterization and analysis of the CCT motif family genes in soybean ( Glycine max )

Abstract: Soybean possesses 19 CMF genes which mainly arose from duplication events. Their features and motifs are highly conserved but transcriptional data indicated functional diversity in metabolism and stress responses. CCT [for CONSTANS, CONSTANS-like (CO-like), and timing of CAB expression1 (TOC1)] domain-containing genes play important roles in regulating flowering, plant growth, and grain yield and are also involved in stress responses. The CMF (CCT motif family) genes, included in the CCT family, contain a single CCT domain as the only identifiable domain in their predicted protein sequence and are interesting targets for breeding programs. In this study, we identified 19 putative GmCMF genes, based on the latest soybean (Glycine max) genome annotation. The predicted GmCMF proteins were characterized based on conserved structural features, and a phylogenetic tree was constructed including all CMF proteins from rice and Arabidopsis as representative examples of the monocotyledonous (monocot) and dicotyledonous (dicot) plants, respectively. High similarities in the conserved motifs of the protein sequences and the gene structures were found. In addition, by analyzing the CMF gene family in soybean, we identified seven pairs of genes that originated from segmental chromosomal duplication events attributable to the most recent whole-genome duplication (WGD) event in the Glycine lineage. Expression analysis of GmCMF genes in various tissues and after specific treatments demonstrated tissue and stress-response specific differential expression. Gene expression analysis was complemented by the identification of putative cis-elements present in the promoter regions of the genes through a bioinformatics approach, using the existing soybean reference genome sequence and gene models. Co-functional networks inferred from distinct types of genomics data—including microarrays and RNA-seq samples from soybean—revealed that GmCMF genes might play crucial roles in metabolism and transport processes. The results of this study, the first systematic analysis of the soybean CCT gene family, can serve as a strong foundation for further elucidation of their physiological functions and biological roles.

Nanotechnology advances for sustainable agriculture: current knowledge and prospects in plant growth modulation and nutrition

Abstract: Advances in nanotechnology make it an important tool for improving agricultural production. Strong evidence supports the role of nanomaterials as nutrients or nanocarriers for the controlled release of fertilizers to improve plant growth. Scientific research shows that nanotechnology applied in plant sciences is smart technology. Excessive application of mineral fertilizers has produced a harmful impact on the ecosystem. Furthermore, the projected increase in the human population by 2050 has led to the search for alternatives to ensure food security. Nanotechnology is a promising strategy to enhance crop productivity while minimizing fertilizer inputs. Nanofertilizers can contribute to the slow and sustainable release of nutrients to improve the efficiency of nutrient use in plants. Nanomaterial properties (i.e., size, morphology and charge) and plant physiology are crucial factors that influence the impact on plant growth. An important body of scientific research highlights the role of carbon nanomaterials, metal nanoparticles and metal oxide nanoparticles to improve plant development through the modulation of physiological and metabolic processes. Modulating nutrient concentrations, photosynthesis processes and antioxidant enzyme activities have led to increases in shoot length, root development, photosynthetic pigments and fruit yield. In parallel, nanocarriers (nanoclays, nanoparticles of hydroxyapatite, mesoporous silica and chitosan) have been shown to be an important tool for the controlled and sustainable release of conventional fertilizers to improve plant nutrition; however, the technical advances in nanofertilizers need to be accompanied by modernization of the regulations and legal frameworks to allow wider commercialization of these elements. Nanofertilizers are a promising strategy to improve plant development and nutrition, but their application in sustainable agriculture remains a great challenge. The present review summarizes the current advance of research into nanofertilizers, and their future prospects.

Comparative transcriptomic and metabolomic analyses of carotenoid biosynthesis reveal the basis of white petal color in Brassica napus.

Abstract: The molecular mechanism underlying white petal color in Brassica napus was revealed by transcriptomic and metabolomic analyses. Rapeseed (Brassica napus L.) is one of the most important oilseed crops worldwide, but the mechanisms underlying flower color in this crop are known less. Here, we performed metabolomic and transcriptomic analyses of the yellow-flowered rapeseed cultivar ‘Zhongshuang 11’ (ZS11) and the white-flowered inbred line ‘White Petal’ (WP). The total carotenoid contents were 1.778-fold and 1.969-fold higher in ZS11 vs. WP petals at stages S2 and S4, respectively. Our findings suggest that white petal color in WP flowers is primarily due to decreased lutein and zeaxanthin contents. Transcriptome analysis revealed 10,116 differentially expressed genes with a fourfold or greater change in expression (P-value less than 0.001) in WP vs. ZS11 petals, including 1,209 genes that were differentially expressed at four different stages and 20 genes in the carotenoid metabolism pathway. BnNCED4b, encoding a protein involved in carotenoid degradation, was expressed at abnormally high levels in WP petals, suggesting it might play a key role in white petal formation. The results of qRT-PCR were consistent with the transcriptome data. The results of this study provide important insights into the molecular mechanisms of the carotenoid metabolic pathway in rapeseed petals, and the candidate genes identified in this study provide a resource for the creation of new B. napus germplasms with different petal colors.

Identification and verification of genes related to pollen development and male sterility induced by high temperature in the thermo-sensitive genic male sterile wheat line

Abstract: Bioinformatic analysis identified the function of genes regulating wheat fertility. Barley stripe mosaic virus-induced gene silencing verified that the genes TaMut11 and TaSF3 are involved in pollen development and related to fertility conversion. Environment-sensitive genic male sterility is of vital importance to hybrid vigor in crop production and breeding. Therefore, it is meaningful to study the function of the genes related to pollen development and male sterility, which is still not fully understand currently. In this study, YanZhan 4110S, a new thermo-sensitive genic male sterility wheat line, and its near-isogenic line YanZhan 4110 were analyzed. Through comparative transcriptome basic bioinformatics and weighted gene co-expression network to further identify some hub genes, the genes TaMut11 and TaSF3 associated with pollen development and male sterility induced by high-temperature were identified in YanZhan 4110S. Further verification through barley stripe mosaic virus-induced gene silencing elucidated that the silencing of TaMut11 and TaSF3 caused pollen abortion, finally resulting in the declination of fertility. These findings provided data on the abortive mechanism in environment-sensitive genic male sterility wheat.

Transcriptomic analysis of grapevine Dof transcription factor gene family in response to cold stress and functional analyses of the VaDof17d gene

Abstract: Dof genes enhance cold tolerance in grapevine and VaDof17d is tightly associated with the cold-responsive pathway and with the raffinose family oligosaccharides. DNA-binding with one finger (Dof) proteins comprise a large family that plays important roles in the regulation of abiotic stresses. No in-depth analysis of Dof genes has been performed in the grapevine. In this study, we analyzed a total of 25 putative Dof genes in grapevine at genomic and transcriptomic levels, compiled expression profiles of 11 selected VaDof genes under cold stress and studied the potential function of the VaDof17d gene in grapevine calli. The 25 Dof proteins can be classified into four phylogenetic groups. RNA-seq and qRT-PCR results demonstrated that a total of 11 VaDof genes responded to cold stress. Comparative mRNA sequencing of 35S::VaDof17d grape calli showed that VaDof17d was tightly associated with the cold-responsive pathway and with the raffinose family oligosaccharides (RFOs), as observed by the up-regulation of galactinol synthase (GolS) and raffinose synthase genes. We found that the Dof17d-ED (CRISPR/Cas9-mediated mutagenesis of Dof17d-ED) mutant had low cold tolerance with a decreased RFOs level during cold stress. These results formed the fundamental knowledge for further analysis of the biological roles of Dof genes in the grapevine’s adaption to cold stresses.

Pleiotropic function of the SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE gene TaSPL14 in wheat plant architecture.

Abstract: The function of SQUAMOSA PROMOTER-BINDING PROTEIN-BOX gene TaSPL14 in wheat is similar to that of OsSPL14 in rice in regulating plant height, panicle length, spikelet number, and thousand-grain weight of wheat, but differs during tiller development. TaSPL14 may regulate spike development via ethylene-response gene EIN3-LIKE 1 (TaEIL1), ETHYLENE-RESPONSIVE TRANSCRIPTION FACTOR 2.11 (TaRAP2.11), and ETHYLENE-RESPONSIVE TRANSCRIPTION FACTOR 1 (TaERF1), but not DENSE AND ERECT PANICLE 1 (TaDEP1) in wheat. The SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE gene OsSPL14 from rice is considered to be a major determinant of ideal plant architecture consisting of few unproductive tillers, more grains per spike, and high resistance of stems to lodging. However, the function of its orthologous gene, TaSPL14, in wheat is unknown. Here, we reported the functional similarities and differences between TaSPL14 and OsSPL14. Similar to OsSPL14 knock-outs in rice, wheat TaSPL14 knock-out plants exhibited decreased plant height, panicle length, spikelet number, and thousand-grain weight. In contrast to OsSPL14, however, TaSPL14 did not affect tiller number. Transcriptome analysis revealed that the expression of genes related to ethylene response was significantly decreased in young spikes of TaSPL14 knock-out lines as compared with wild type. TaSPL14 directly binds to the promoters of the ethylene-response genes TaEIL1, TaRAP2.11, and TaERF1, and promotes their expression, suggesting that TaSPL14 might regulate wheat spike development via the ethylene-response pathway. The elucidation of TaSPL14 will contribute to understanding of the molecular mechanisms that underlie wheat plant architecture.

Late blight in tomato: insights into the pathogenesis of the aggressive pathogen Phytophthora infestans and future research priorities.

Abstract: This review provides insights into the molecular interactions between Phytophthora infestans and tomato and highlights research gaps that need further attention. Late blight in tomato is caused by the oomycota hemibiotroph Phytophthora infestans, and this disease represents a global threat to tomato farming. The pathogen is cumbersome to control because of its fast-evolving nature, ability to overcome host resistance and inefficient natural resistance obtained from the available tomato germplasm. To achieve successful control over this pathogen, the molecular pathogenicity of P. infestans and key points of vulnerability in the host plant immune system must be understood. This review primarily focuses on efforts to better understand the molecular interaction between host pathogens from both perspectives, as well as the resistance genes, metabolomic changes, quantitative trait loci with potential for improvement in disease resistance and host genome manipulation via transgenic approaches, and it further identifies research gaps and provides suggestions for future research priorities.

Sorghum under saline conditions: responses, tolerance mechanisms, and management strategies

Abstract: An overview is presented of recent advances in our knowledge of responses and mechanisms rendering adaptation to saline conditions in sorghum. Different strategies deployed to enhance salinity stress tolerance in sorghum are also pointed out. Salinity stress is a growing problem worldwide. Sorghum is the fifth key crop among cereals. Understanding responses and tolerance strategies in sorghum would be therefore helpful effort for providing biomarkers for designing greatest salinity-tolerant sorghum genotypes. When sorghum exposed to salinity, salinity-tolerant genotypes most probably reprogram their gene expression to activate adaptive biochemical and physiological responses for survival. The review thus discusses the possible physiological and biochemical responses that confer salinity tolerance to sorghum under saline conditions. Although it is not characterized in sorghum, salinity perceiving and transmitting signals to downstream responses via signaling transduction pathways most likely are essential strategy for sorghum adaptation to salinity stress. Sorghum has also shown to withstand moderate saline environments and retain the germination, growth, and photosynthetic activities. Salinity-tolerant sorghum genotypes show the ability to exclude excessive Na+ from reaching shoots and induce ion homeostasis. Osmotic homeostasis and ROS detoxification are also evident as salinity tolerance strategies in sorghum. These above mechanisms lead to re-establishment of cellular ionic, osmotic, and redox homeostasis as well as photosynthesis efficiency. It is noteworthy that these mechanisms act individually or co-operatively to minimize the salinity hazards and enhance acclimation in sorghum. We conclude, however, that although these responses contribute to sorghum tolerance to salinity stress, they seem to be not adequate at higher concentrations of salinity, which agrees with sorghum ranking as moderately salinity-tolerant crop. Also, some of these tolerance strategies reported in other crops are not well studied and documented in sorghum, but most probably have roles in sorghum. Further improvement in sorghum salinity tolerance using different approaches is definitely necessary to meet the requirements of its harsh production environments, and therefore, these approaches are addressed.

Molecular hydrogen in agriculture

Abstract: H2 gas, usually in the form of H2-saturated water, could play a useful role in improving many aspects of plant growth and productivity, including resistance to stress tolerance and improved post-harvest durability. Therefore, molecular hydrogen delivery systems should be considered as a valuable addition within agricultural practice. Agriculture and food security are both impacted by plant stresses, whether that is directly from human impact or through climate change. A continuously increasing human population and rising food consumption means that there is need to search for agriculturally useful and environment friendly strategies to ensure future food security. Molecular hydrogen (H2) research has gained momentum in plant and agricultural science owing to its multifaceted and diverse roles in plants. H2 application can mitigate against a range of stresses, including salinity, heavy metals and drought. Therefore, knowing how endogenous, or exogenously applied, H2 enhances the growth and tolerance against numerous plant stresses will enhance our understanding of how H2 may be useful for future to agriculture and horticulture. In this review, recent progress and future implication of H2 in agriculture is highlighted, focusing on how H2 impacts on plant cell function and how it can be applied for better plant performance. Although the exact molecular action of H2 in plants remains elusive, this safe and easy to apply treatment should have a future in agricultural practice.

An integrated transcriptome and metabolome approach reveals the accumulation of taste-related metabolites and gene regulatory networks during watermelon fruit development.

Abstract: Accumulation patterns and gene regulatory networks of sugars and cucurbitacins and related primary and secondary metabolites during cultivated watermelon ‘Cheng Lan’ and wild watermelon ‘PI 632,751’ fruit development were identified. Metabolites are the end products of cellular regulatory processes and play important roles in fruit taste formation. However, comprehensive studies on the accumulation patterns of watermelon fruit metabolites and transcriptional regulatory networks are still scarce. In this study, 451 annotated metabolites were identified at four key fruit developmental stages in wild watermelon ‘PI 632,751’ and modern cultivated watermelon ‘Cheng Lan’. Interestingly, 11 sugars and 25 major primary metabolites were mainly accumulated in ‘Cheng Lan’ during fruit development, which are considered to be the potential metabolites beneficial to the formation of watermelon taste. Cucurbitacins and the main flavonoids were mainly specifically accumulated in ‘PI 632,751’, not being considered to be responsible for the taste. Moreover, forty-seven genes involved in carbohydrate metabolism, glycolysis, and TCA cycle were highly expressed in ‘Cheng Lan’, which was positively correlated with the accumulation of major primary metabolites. Alternatively, seven UDP-glycosyltransferase genes are closely related to the glycosylation of cucurbitacins through co-expression analysis. Our findings established a global map of metabolite accumulation and gene regulation during fruit development in wild and cultivated watermelons and provided valuable information on taste formation in watermelon fruit.

Transcriptome analysis identifies putative genes involved in triterpenoid biosynthesis in Platycodon grandiflorus

Abstract: Comprehensive transcriptome analysis of different Platycodon grandiflorus tissues discovered genes related to triterpenoid saponin biosynthesis. Platycodon grandiflorus (Jacq.) A. DC. (P. grandiflorus), a traditional Chinese medicine, contains considerable triterpenoid saponins with broad pharmacological activities. Triterpenoid saponins are the major components of P. grandiflorus. Here, single-molecule real-time and next-generation sequencing technologies were combined to comprehensively analyse the transcriptome and identify genes involved in triterpenoid saponin biosynthesis in P. grandiflorus. We quantified four saponins in P. grandiflorus and found that their total content was highest in the roots and lowest in the stems and leaves. A total of 173,354 non-redundant transcripts were generated from the PacBio platform, and three full-length transcripts of β-amyrin synthase, the key synthase of β-amyrin, were identified. A total of 132,610 clean reads obtained from the DNBSEQ platform were utilised to explore key genes related to the triterpenoid saponin biosynthetic pathway in P. grandiflorus, and 96 differentially expressed genes were selected as candidates. The expression levels of these genes were verified by quantitative real-time PCR. Our reliable transcriptome data provide valuable information on the related biosynthesis pathway and may provide insights into the molecular mechanisms of triterpenoid saponin biosynthesis in P. grandiflorus.

Metabolic engineering of osmoprotectants to elucidate the mechanism(s) of salt stress tolerance in crop plants.

Abstract: Previous studies on engineering osmoprotectant metabolic pathway genes focused on the performance of transgenic plants under salt stress conditions rather than elucidating the underlying mechanism(s), and hence, the mechanism(s) remain(s) unclear. Salt stress negatively impacts agricultural crop yields. Hence, to meet future food demands, it is essential to generate salt stress-resistant varieties. Although traditional breeding has improved salt tolerance in several crops, this approach remains inadequate due to the low genetic diversity of certain important crop cultivars. Genetic engineering is used to introduce preferred gene(s) from any genetic reserve or to modify the expression of the existing gene(s) responsible for salt stress response or tolerance, thereby leading to improved salt tolerance in plants. Although plants naturally produce osmoprotectants as an adaptive mechanism for salt stress tolerance, they offer only partial protection. Recently, progress has been made in the identification and characterization of genes involved in the biosynthetic pathways of osmoprotectants. Exogenous application of these osmoprotectants, and genetic engineering of enzymes in their biosynthetic pathways, have been reported to enhance salt tolerance in different plants. However, no clear mechanistic model exists to explain how osmoprotectant accumulation in transgenic plants confers salt tolerance. This review critically examines the results obtained thus far for elucidating the underlying mechanisms of osmoprotectants for improved salt tolerance, and thus, crop yield stability under salt stress conditions, through the genetic engineering of trehalose, glycinebetaine, and proline metabolic pathway genes.

Light- and hormone-mediated development in non-flowering plants: An overview

Abstract: Light, hormones and their interaction regulate different aspects of development in non-flowering plants. They might have played a role in the evolution of different plant groups by conferring specific adaptive evolutionary changes. Plants are sessile organisms. Unlike animals, they lack the opportunity to abandon their habitat in unfavorable conditions. They respond to different environmental cues and adapt accordingly to control their growth and developmental pattern. While phytohormones are known to be internal regulators of plant development, light is a major environmental signal that shapes plant processes. It is plausible that light-hormone crosstalk might have played an important role in plant evolution. But how the crosstalk between light and phytohormone signaling pathways might have shaped the plant evolution is unclear. One of the possible reasons is that flowering plants have been studied extensively in context of plant development, which cannot serve the purpose of evolutionary comparisons. In order to elucidate the role of light, hormone and their crosstalk in the evolutionary adaptation in plant kingdom, one needs to understand various light- and hormone-mediated processes in diverse non-flowering plants. This review is an attempt to outline major light- and phytohormone-mediated responses in non-flowering plant groups such as algae, bryophytes, pteridophytes and gymnosperms.

A single transcript CRISPR/Cas9 mediated mutagenesis of CaERF28 confers anthracnose resistance in chilli pepper (Capsicum annuum L.)

Abstract: T-DNA-free homozygous mutant lines developed through a single transcript CRISPR/Cas9 system harboring the desired modification in the CaERF28 locus exhibited significantly enhanced resistance to the anthracnose pathogen Colletotrichum truncatum coupled with the improved expression of defense responsive genes. Anthracnose, caused by Colletotrichum species, is a major disease of chilli (Capsicum annuum) accounting for significant pre- and post-harvest yield losses across the tropical and subtropical regions of the world. Management of chilli anthracnose using traditional methods have not met with noticeable success. In the present study, we have demonstrated an enhanced anthracnose resistance through a single transcript unit CRISPR/Cas9 mediated alteration of the susceptibility gene CaERF28 in C. annuum. A construct with a single Pol II promoter-driven expression of Cas9, sgRNA and a hammerhead ribozyme (RZ) was designed to modify the CaERF28 gene in the susceptible chilli genotype Arka Lohit. Fourty-five C-ERF28-induced mutant lines (72.5%) were identified from 62 T0 transgenic plants. Further, simultaneously targeted multiple sites within CaERF28 showed increased mutation (85.7%) efficiency. DNA sequence analysis showed that these plants harboured multiple InDels at the target site. The allelic mutants of C-ERF28 were transferred to the following generations by simple Mendelian inheritance. Segregation in the T1 and T2 generations resulted in the identification of T-DNA free and marker-free C-ERF28 mutant lines. Five homozygous mutants demonstrated enhanced resistance to anthracnose compared to wild type as demonstrated by reduced spore count and fungal growth as well as induced expression of defense-related genes. Our results demonstrated that the STU-CRISPR/Cas9 mediated editing of the CaERF28 gene is a rapid, safe and versatile approach for enhancing anthracnose resistance in chilli pepper and pave way for its utilization in the improvement of other solanaceous crops.

Hydrogen-rich water promotes the formation of bulblets in Lilium davidii var. unicolor through regulating sucrose and starch metabolism

Abstract: HRW increased the content of starch and sucrose via regulating a series of sucrose and starch synthesis genes, which induced the formation of bulblets and adventitious roots of Lilium davidii var. unicolor. Hydrogen gas (H2), as a signaling molecule, has been reported to be involved in plant growth and development. Here, the effect of hydrogen-rich water (HRW) on the formation of bulblets and adventitious roots in the scale cuttings of Lilium davidii var. unicolor and its mechanisms at the molecular levels were investigated. The results revealed that compared with distilled water treatment (Con), the number of bulblets and adventitious roots were significantly promoted by different concentrations of HRW treatment. Treatment with 100% HRW obtained the most positive effects. RNA sequencing (RNA-seq) analysis found that compared with Con, a total of 1702 differentially expressed genes (DEGs, upregulated 552 DEGs, downregulated 1150 DEGs) were obtained under HRW treatment. The sucrose and starch metabolism, cysteine and methionine metabolism and phenylalanine metabolism were significantly enriched in the analysis of the Kyoto encyclopedia of genes and genomes (KEGG). In addition, the genes involved in carbohydrate metabolism were significantly upregulated or downregulated (upregulated 22 DEGs, downregulated 15 DEGs), indicating that starch and sucrose metabolism held a central position. The expressions of 12 DEGs were identified as coding for key enzymes in metabolism of carbohydrates was validated by qPCR during bulblet formation progress. RNA-seq analysis and expression profiles indicated that the unigene levels such as glgc, Susy, otsA and glgP, BMY and TPS were well correlated with sucrose and starch metabolism during HRW-induced bulblet formation. The change of key enzyme content in starch and sucrose metabolism pathway was explored during bulblet formation in Lilium under HRW treatment. Meanwhile, compared with Con, 100% HRW treatment increased the levels of sucrose and starch, and decreased the trehalose content, which were agreed with the expression pattern of DEGs related to the biosynthesis pathway of sucrose, starch and trehalose. Therefore, this study suggested that HRW could promote the accumulation of sucrose and starch contents in mother scales, and decreased the trehalose content, this might provide more energy for bulblet formation.