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Showing papers on "Biotic stress published in 2011"


Journal ArticleDOI
TL;DR: In this article, the authors exploit the properties of microorganisms such as their unique properties of tolerance to extremities, their ubiquity, genetic diversity, their interaction with crop plants and develop methods for their successful deployment in agriculture production.
Abstract: Increased incidences of abiotic and biotic stresses impacting productivity in principal crops are being witnessed all over the world. Extreme events like prolonged droughts, intense rains and flooding, heat waves and frost damages are likely to further increase in future due to climate change. A wide range of adaptations and mitigation strategies are required to cope with such impacts. Efficient resource management and crop/livestock improvement for evolving better breeds can help to overcome abiotic stresses to some extent. However, such strategies being long drawn and cost intensive, there is a need to develop simple and low cost biological methods for the management of abiotic stress, which can be used on short term basis. Microorganisms could play a significant role in this respect, if we can exploit their unique properties of tolerance to extremities, their ubiquity, genetic diversity, their interaction with crop plants and develop methods for their successful deployment in agriculture production. Besides influencing the physico-chemical properties of rhizospheric soil through production of exopolysaccharides and formation of biofilm, microorganisms can also influence higher plants response to abiotic stresses like drought, chilling injury, salinity, metal toxicity and high temperature, through different mechanisms like induction of osmo-protectants and heat shock proteins etc. in plant cells. Use of these microorganisms per se can alleviate stresses in crop plants thus opening a new and emerging application in agriculture. These microbes also provide excellent models for understanding the stress tolerance, adaptation and response mechanisms that can be subsequently engineered into crop plants to cope with climate change induced stresses.

555 citations


Journal ArticleDOI
TL;DR: It is argued that PAs should not be taken only as a protective molecule but rather like a double-faced molecule that likely serves as a major area for further research efforts.

459 citations


Journal Article
TL;DR: This review presents an overview about some of the mechanisms by which plants protect themselves against herbivory, pathogenic microbes and various abiotic stresses as well as specific plant responses to pathogen attack, the genetic control of host-pathogen interactions.
Abstract: In all natural habitats, plants are surrounded by an enormous number of potential enemies (biotic) and various kinds of abiotic environmental stress. Nearly all ecosystems contain a wide variety of bacteria, viruses, fungi, nematodes, mites, insects, mammals and other herbivorous animals, greatly responsible for heavy reduction in crop productivity. By their nature, plants protect themselves by producing some compounds called as secondary metabolites. Secondary metabolites, including terpenes, phenolics and nitrogen (N) and sulphur (S) containing compounds, defend plants against a variety of herbivores and pathogenic microorganisms as well as various kinds of abiotic stresses. This review presents an overview about some of the mechanisms by which plants protect themselves against herbivory, pathogenic microbes and various abiotic stresses as well as specific plant responses to pathogen attack, the genetic control of host-pathogen interactions.

457 citations


Journal ArticleDOI
TL;DR: The fungal symbioses, fungal Symbionts and their role in abiotic stress tolerance are described and a putative mechanism of stress tolerance by symbionts has been covered.
Abstract: Fungal symbionts have been found associated with every plant studied in natural ecosystem, where they colonize and reside entirely in the internal tissues of their host plant or partially. Fungal endophytes can express/form a range of different lifestyle/relationships with different host including symbiotic, mutualistic, commensalistic and parasitic in response to host genotype and environmental factors. In mutualistic association fungal endophyte can enhance growth, increase reproductive success and confer biotic and abiotic stress tolerance to its host plant. Since abiotic stress such as, drought, high soil salinity, heat, cold, oxidative stress, heavy metal toxicity is the common adverse environmental conditions that affect and limit crop productivity worldwide. It may be a promising alternative strategy to exploit fungal endophytes to overcome the limitations to crop production brought by abiotic stress. There is increasing interest in developing the potential biotechnological applications of fungal endophytes for improving plant stress tolerance and sustainable production of food crops. Here we have described the fungal symbioses, fungal symbionts and their role in abiotic stress tolerance. A putative mechanism of stress tolerance by symbionts has also been covered.

359 citations


Journal ArticleDOI
TL;DR: The mechanisms of ROS (reaction oxygen species) generation and removal in plants under biotic and abiotic stress conditions have been reviewed and may be genetically stable and useful in crop improvement.

322 citations


Journal ArticleDOI
TL;DR: Some common patterns of stress response are identified, such as a tendency towards increasing concentrations in protein and antioxidants in stressed crops, and a loss in quality in terms of feed value, starch and lipid concentration, or physical/sensory traits.

314 citations


Journal ArticleDOI
TL;DR: This review presents examples demonstrating the importance of crosstalk between ABA and the key biotic stress phytohormone salicylic acid in determining the outcome of plant–pathogen interactions and discusses future directions for studies of ABA in plant immunity.
Abstract: Defence against abiotic and biotic stresses is crucial for the fitness and survival of plants under adverse or suboptimal growth conditions. The phytohormone abscisic acid (ABA) is not only important for mediating abiotic stress responses, but also plays a multifaceted and pivotal role in plant immunity. This review presents examples demonstrating the importance of crosstalk between ABA and the key biotic stress phytohormone salicylic acid in determining the outcome of plant–pathogen interactions. We then provide an overview of how ABA influences plant defence responses against various phytopathogens with particular emphasis on the Arabidopsis–Pseudomonas syringae model pathosystem. Lastly, we discuss future directions for studies of ABA in plant immunity with emphasis on, its role in the crosstalk between biotic and abiotic stress responses, the importance of distinguishing direct and indirect effects of ABA, as well as the prospect of utilizing the recently elucidated core ABA signaling network to gain further insights into the roles of ABA in plant immunity.

304 citations


Journal ArticleDOI
TL;DR: The 44K and 22K microarray results suggest that 53 and 52 non-redundant genes in this family were up-regulated in response to biotic and abiotic stresses, respectively.
Abstract: We identified 163 AP2/EREBP (APETALA2/ethylene-responsive element-binding protein) genes in rice. We analyzed gene structures, phylogenies, domain duplication, genome localizations and expression profiles. Conserved amino acid residues and phylogeny construction using the AP2/ERF conserved domain sequence suggest that in rice the OsAP2/EREBP gene family can be classified broadly into four subfamilies [AP2, RAV (related to ABI3/VP1), DREB (dehydration-responsive element-binding protein) and ERF (ethylene-responsive factor)]. The chromosomal localizations of the OsAP2/EREBP genes indicated 20 segmental duplication events involving 40 genes; 58 redundant OsAP2/EREBP genes were involved in tandem duplication events. There were fewer introns after segmental duplication. We investigated expression profiles of this gene family under biotic stresses [infection with rice viruses such as rice stripe virus (RSV), rice tungro spherical virus (RTSV) and rice dwarf virus (RDV, three virus strains S, O and D84)], and various abiotic stresses. Symptoms of virus infection were more severe in RSV infection than in RTSV and RDV infection. Responses to biotic stresses are novel findings and these stresses enhance the ability to identify the best candidate genes for further functional analysis. The genes of subgroup B-5 were not induced under abiotic treatments whereas they were activated by the three RDV strains. None of the genes of subgroups A-3 were differentially expressed by any of the biotic stresses. Our 44K and 22K microarray results suggest that 53 and 52 non-redundant genes in this family were up-regulated in response to biotic and abiotic stresses, respectively. We further examined the stress responsiveness of most genes by reverse transcription-PCR. The study results should be useful in selecting candidate genes from specific subgroups for functional analysis.

285 citations


Journal ArticleDOI
TL;DR: Exogenous application of PAs putrescine, spermidine and spermine to Arabidopsis seedlings induced NO production as observed by fluorimetry and fluorescence microscopy and pave a new insight into PA-mediated signalling and NO as a potential mediator of PA actions.

282 citations



Journal ArticleDOI
TL;DR: This work states that once stress-tolerant cultivars are developed, regional probability distributions describing yield response across years will be necessary and this information can then aid in identifying environmental conditions for positive and negative responses to genetic modification to guide farmer selection of stress- tolerance cultivars.

Journal ArticleDOI
TL;DR: This mutation, in a conserved region of SDH1-1, is a unique plant mitochondrial mutant that exhibits phenotypes associated with lowered mROS production and provides critical insights into Complex II function with implications for understanding Complex II's role in mitochondrial diseases across eukaryotes.
Abstract: Mitochondria are both a source of ATP and a site of reactive oxygen species (ROS) production. However, there is little information on the sites of mitochondrial ROS (mROS) production or the biological role of such mROS in plants. We provide genetic proof that mitochondrial complex II (Complex II) of the electron transport chain contributes to localized mROS that regulates plant stress and defense responses. We identify an Arabidopsis mutant in the Complex II subunit, SDH1-1, through a screen for mutants lacking GSTF8 gene expression in response to salicylic acid (SA). GSTF8 is an early stress-responsive gene whose transcription is induced by biotic and abiotic stresses, and its expression is commonly used as a marker of early stress and defense responses. Transcriptional analysis of this mutant, disrupted in stress responses 1 (dsr1), showed that it had altered SA-mediated gene expression for specific downstream stress and defense genes, and it exhibited increased susceptibility to specific fungal and bacterial pathogens. The dsr1 mutant also showed significantly reduced succinate dehydrogenase activity. Using in vivo fluorescence assays, we demonstrated that root cell ROS production occurred primarily from mitochondria and was lower in the mutant in response to SA. In addition, leaf ROS production was lower in the mutant after avirulent bacterial infection. This mutation, in a conserved region of SDH1-1, is a unique plant mitochondrial mutant that exhibits phenotypes associated with lowered mROS production. It provides critical insights into Complex II function with implications for understanding Complex II's role in mitochondrial diseases across eukaryotes.

Journal ArticleDOI
TL;DR: The functions of PEPC, NADP-ME and PPDK appear to be more important for plants under stress than under optimal growth conditions.

Journal ArticleDOI
TL;DR: In this paper, the authors tracked the expression of twelve defense marker genes over time using qRT-PCR and concluded that silicon primed plants, thereby alleviating biotic stress imposed by the pathogen, could not only be explained with its mechanical properties.

Journal ArticleDOI
TL;DR: In this article, the phytotoxic atmospheric pollutant ozone was used as a model reactive oxygen species (ROS) inducer in Arabidopsis (Arabidopsis thaliana) and gene expression was analyzed with microarrays.
Abstract: Reactive oxygen species (ROS) are ubiquitous signaling molecules in plant stress and development. To gain further insight into the plant transcriptional response to apoplastic ROS, the phytotoxic atmospheric pollutant ozone was used as a model ROS inducer in Arabidopsis (Arabidopsis thaliana) and gene expression was analyzed with microarrays. In contrast to the increase in signaling via the stress hormones salicylic acid, abscisic acid, jasmonic acid (JA), and ethylene, ROS treatment caused auxin signaling to be transiently suppressed, which was confirmed with a DR5-uidA auxin reporter construct. Transcriptomic data revealed that various aspects of auxin homeostasis and signaling were modified by apoplastic ROS. Furthermore, a detailed analysis of auxin signaling showed that transcripts of several auxin receptors and Auxin/Indole-3-Acetic Acid (Aux/IAA) transcriptional repressors were reduced in response to apoplastic ROS. The ROS-derived changes in the expression of auxin signaling genes partially overlapped with abiotic stress, pathogen responses, and salicylic acid signaling. Several mechanisms known to suppress auxin signaling during biotic stress were excluded, indicating that ROS regulated auxin responses via a novel mechanism. Using mutants defective in various auxin (axr1, nit1, aux1, tir1 afb2, iaa28-1, iaa28-2) and JA (axr1, coi1-16) responses, ROS-induced cell death was found to be regulated by JA but not by auxin. Chronic ROS treatment resulted in altered leaf morphology, a stress response known as “stress-induced morphogenic response.” Altered leaf shape of tir1 afb2 suggests that auxin was a negative regulator of stress-induced morphogenic response in the rosette.

Journal ArticleDOI
TL;DR: The key role that SnRKs play at the interface between metabolic and stress signalling make them potential candidates for manipulation to improve crop performance in extreme environments.
Abstract: Sucrose non-fermenting-1 (SNF1)-related protein kinases (SnRKs) take their name from their fungal homologue, SNF1, a global regulator of carbon metabolism. The plant family has burgeoned to comprise 38 members which can be subdivided into three sub-families: SnRK1, SnRK2, and SnRK3. There is now good evidence that this has occurred to allow plants to link metabolic and stress signalling in a way that does not occur in other organisms. The role of SnRKs, focusing in particular on abscisic acid-induced signalling pathways, salinity tolerance, responses to nutritional stress and disease, and the regulation of carbon metabolism and, therefore, yield, is reviewed here. The key role that SnRKs play at the interface between metabolic and stress signalling make them potential candidates for manipulation to improve crop performance in extreme environments.

Journal ArticleDOI
TL;DR: The construction of RiceNet, an experimentally tested genome-scale gene network for a monocotyledonous species, is reported on, which enables the identification of genes regulating important crop traits, facilitating engineering of pathways critical to crop productivity.
Abstract: Rice is a staple food for one-half the world's population and a model for other monocotyledonous species. Thus, efficient approaches for identifying key genes controlling simple or complex traits in rice have important biological, agricultural, and economic consequences. Here, we report on the construction of RiceNet, an experimentally tested genome-scale gene network for a monocotyledonous species. Many different datasets, derived from five different organisms including plants, animals, yeast, and humans, were evaluated, and 24 of the most useful were integrated into a statistical framework that allowed for the prediction of functional linkages between pairs of genes. Genes could be linked to traits by using guilt-by-association, predicting gene attributes on the basis of network neighbors. We applied RiceNet to an important agronomic trait, the biotic stress response. Using network guilt-by-association followed by focused protein–protein interaction assays, we identified and validated, in planta, two positive regulators, LOC_Os01g70580 (now Regulator of XA21; ROX1) and LOC_Os02g21510 (ROX2), and one negative regulator, LOC_Os06g12530 (ROX3). These proteins control resistance mediated by rice XA21, a pattern recognition receptor. We also showed that RiceNet can accurately predict gene function in another major monocotyledonous crop species, maize. RiceNet thus enables the identification of genes regulating important crop traits, facilitating engineering of pathways critical to crop productivity.

Journal ArticleDOI
TL;DR: Data suggest that PGN functions in regulation of reactive oxygen species homeostasis in mitochondria during abiotic and biotic stress responses, likely through involvement in retrograde signaling.
Abstract: Pentatricopeptide repeat (PPR) proteins (PPRPs) are encoded by a large gene family in Arabidopsis ( Arabidopsis thaliana ), and their functions are largely unknown. The few studied PPRPs are implicated in different developmental processes through their function in RNA metabolism and posttranscriptional regulation in plant organelles. Here, we studied the functions of Arabidopsis PENTATRICOPEPTIDE REPEAT PROTEIN FOR GERMINATION ON NaCl ( PGN ) in plant defense and abiotic stress responses. Inactivation of PGN results in susceptibility to necrotrophic fungal pathogens as well as hypersensitivity to abscisic acid (ABA), glucose, and salinity. Interestingly, ectopic expression of PGN results in the same phenotypes as the pgn null allele, indicating that a tight regulation of the PGN transcript is required for normal function. Loss of PGN function dramatically enhanced reactive oxygen species accumulation in seedlings in response to salt stress. Inhibition of ABA synthesis and signaling partially alleviates the glucose sensitivity of pgn , suggesting that the mutant accumulates high endogenous ABA. Accordingly, induction of NCED3 , encoding the rate-limiting enzyme in stress-induced ABA biosynthesis, is significantly higher in pgn , and the mutant has higher basal ABA levels, which may underlie its phenotypes. The pgn mutant has altered expression of other ABA-related genes as well as mitochondria-associated transcripts, most notably elevated levels of ABI4 and ALTERNATIVE OXIDASE1a , which are known for their roles in retrograde signaling induced by changes in or inhibition of mitochondrial function. These data, coupled with its mitochondrial localization, suggest that PGN functions in regulation of reactive oxygen species homeostasis in mitochondria during abiotic and biotic stress responses, likely through involvement in retrograde signaling.

Journal ArticleDOI
TL;DR: These findings provide evidence that activation of EDS1/PAD4-dependent plant immune responses rapidly disrupts ABA signal transduction and that this occurs at the level of Ca(2+) signaling, illuminating how the initial biotic stress pathway interferes with ABA signaling.

01 Jan 2011
TL;DR: In this article, the authors studied the role of PPRPs in regulation of reactive oxygen species homeostasis in mitochondria during abiotic and biotic stress responses, likely through involvement in retrograde signaling.
Abstract: Pentatricopeptide repeat (PPR) proteins (PPRPs) are encoded by a large gene family in Arabidopsis (Arabidopsis thaliana), and their functions are largely unknown. The few studied PPRPs are implicated in different developmental processes through their function in RNA metabolism and posttranscriptional regulation in plant organelles. Here, we studied the functions of Arabidopsis PENTATRICOPEPTIDE REPEAT PROTEIN FOR GERMINATION ON NaCl (PGN) in plant defense and abiotic stress responses. Inactivation of PGN results in susceptibility to necrotrophic fungal pathogens as well as hypersensitivity to abscisic acid (ABA), glucose, and salinity. Interestingly, ectopic expression of PGN results in the same phenotypes as the pgn null allele, indicating that a tight regulation of the PGN transcript is required for normal function. Loss of PGN function dramatically enhanced reactive oxygen species accumulation in seedlings in response to salt stress. Inhibition of ABA synthesis and signaling partially alleviates the glucose sensitivity of pgn, suggesting that the mutant accumulates high endogenous ABA. Accordingly, induction of NCED3, encoding the rate-limiting enzyme in stress-induced ABA biosynthesis, is significantly higher in pgn, and the mutant has higher basal ABA levels, which may underlie its phenotypes. The pgn mutant has altered expression of other ABA-related genes as well as mitochondria-associated transcripts, most notably elevated levels of ABI4 and ALTERNATIVE OXIDASE1a, which are known for their roles in retrograde signaling induced by changes in or inhibition of mitochondrial function. These data, coupled with its mitochondrial localization, suggest that PGN functions in regulation of reactive oxygen species homeostasis in mitochondria during abiotic and biotic stress responses, likely through involvement in retrograde signaling.

Journal ArticleDOI
TL;DR: The goal of this mini-review is to provide latest findings showing how both ROS and RNS comprise a coordinated oxidative and nitrosative signaling network that modulates cellular responses in response to environmental stimuli.
Abstract: Reactive oxygen species (ROS) and reactive nitrogen species (RNS) constitute key features underpinning the dynamic nature of cell signaling systems in plants Despite their importance in many aspects of cell biology, our understanding of oxidative and especially of nitrosative signaling and their regulation remains poorly understood Early reports have established that ROS and RNS coordinately regulate plant defense responses to biotic stress In addition, evidence has accumulated demonstrating that there is a strong cross-talk between oxidative and nitrosative signaling upon abiotic stress conditions The goal of this mini-review is to provide latest findings showing how both ROS and RNS comprise a coordinated oxidative and nitrosative signaling network that modulates cellular responses in response to environmental stimuli

Journal ArticleDOI
TL;DR: The data infer that SA is initially located in the chloroplasts, and plants expressing NahG in thechloroplasts are unable to accumulate SA induced after pathogen or UV exposure.

Journal ArticleDOI
TL;DR: Recent findings on CDPK and MAPK signalling with respect to potential cross-talk and the subcellular localization of the involved components are discussed.
Abstract: Plants use different signalling pathways to acclimate to changing environmental conditions. Fast changes in the concentration of free Ca(2+) ions - so called Ca(2+) signals - are among the first responses to many stress situations. These signals are decoded by different types of calcium-dependent protein kinases, which - together with mitogen-activated protein kinases (MAPK) - present two major pathways that are widely used to adapt the cellular metabolism to a changing environment. Ca(2+)-dependent protein kinase (CDPK) and MAPK pathways are known to be involved in signalling of abiotic and biotic stress in animal, yeast and plant cells. In many cases both pathways are activated in response to the same stimuli leading to the question of a potential cross-talk between those pathways. Cross-talk between Ca(2+)-dependent and MAPK signalling pathways has been elaborately studied in animal cells, but it has hardly been investigated in plants. Early studies of CDPKs involved in the biotic stress response in tobacco indicated a cross-talk of CDPK and MAPK activities, whereas a recent study in Arabidopsis revealed that CDPKs and MAPKs act differentially in innate immune signalling and showed no direct cross-talk between CDPK and MAPK activities. Similar results were also reported for CDPK and MAPK activities in the salt stress response in Arabidopsis. Different modes of action are furthermore supported by the different subcellular localization of the involved kinases. In this review, we discuss recent findings on CDPK and MAPK signalling with respect to potential cross-talk and the subcellular localization of the involved components.

Journal ArticleDOI
TL;DR: It appears that the plant focuses the metabolism on production of scopoletin and lignin at the expense of flavonol production, and this crosstalk involves antagonistic regulation of two opposing MYB transcription factors.
Abstract: Plants respond to both abiotic and biotic stresses with alterations in the expression of genes required to produce protective metabolites. Sometimes plants can be challenged with different stresses simultaneously and as they cannot evade from this situation, priorities have to be set to deal with the most urgent threat. The abiotic stress ultraviolet-B (UV-B) light induces the production of UV-protective flavonols in Arabidopsis Col-0 cell suspension cultures and this accumulation is attenuated by concurrent application of the bacterial elicitor flg22 (simulating biotic stress). This inhibition correlates with strong suppression of the flavonol biosynthesis genes. In parallel, flg22 induces the production of defence-related compounds, such as the phytoalexins, camalexin and scopoletin, as well as lignin, a structural barrier thought to restrict pathogen spread. This correlated positively with flg22-mediated expression of enzymes for lignin, scopoletin and camalexin production. As flavonols, lignin and scopoletin are all derived from phenylalanine, it appears that the plant focuses the metabolism on production of scopoletin and lignin at the expense of flavonol production. Furthermore, it appears that this crosstalk involves antagonistic regulation of two opposing MYB transcription factors, the positive regulator of the flavonol pathway MYB12 (UV-B-induced and flg22-suppressed) and the negative regulator MYB4 (UV-B- and flg22-induced).

Journal ArticleDOI
TL;DR: Comparison of common and specific gene networks affected by elevation of endogenous PAs support the view that these compounds actively participate in stress signaling through intricate crosstalks with abscisic acid (ABA), Ca(2+) signaling and other hormonal pathways in plant defense and development.
Abstract: Plant development and productivity are negatively regulated by adverse environmental conditions. The identification of stress-regulatory genes, networks, and signaling molecules should allow the development of novel strategies to obtain tolerant plants. Polyamines (PAs) are polycationic compounds with a recognized role in plant growth and development, as well as in abiotic and biotic stress responses. During the last years, knowledge on PA functions has been achieved using genetically modified plants with altered PA levels. In this review, we combine the information obtained from global transcriptome analyses in transgenic Arabidopsis plants with altered putrescine or spermine levels. Comparison of common and specific gene networks affected by elevation of endogenous PAs, support the view that these compounds actively participate in stress signaling through intricate crosstalks with abscisic acid (ABA), Ca(2+) signaling and other hormonal pathways in plant defense and development.

DOI
28 Feb 2011
TL;DR: The genes conferring drought resistance provide foundation for scientific improvement of the crop’s productivity under arid conditions and contribute to improvement and stabilization of cotton yield and farmers' income.
Abstract: Abiotic stress negatively influences survival, biomass production and crop yield. Being multigenic as well as a quantitative trait, it is a challenge to understand the molecular basis of abiotic stress tolerance and to manipulate it as compared to biotic stresses. Abiotic stresses including drought are serious threats to the sustainability of crop yields accounting for more crop productivity losses than any other factor in rainfed agriculture. Success in breeding for better adapted varieties to abiotic stresses depend upon the concerted efforts by various research domains including plant and cell physiology, molecular biology, genetics, and breeding. Use of modern molecular biology tools for elucidating the control mechanisms of abiotic stress tolerance, and for engineering stress tolerant crops is based on the expression of specific stress-related genes. Plant responses to water deficit can be analysed by systematically identifying genes that relate to drought tolerance followed by analysis to the cellular, biochemical and molecular basis of the gene (traits). Mechanism of drought tolerance and expression of these drought resistance genes in high yielding varieties will help to improve the drought condition. The genes conferring drought resistance provide foundation for scientific improvement of the crop’s productivity under arid conditions and contribute to improvement and stabilization of cotton yield and farmers' income. Stress-induced gene expressions are of genes encoding proteins with known enzymatic or structural functions, proteins with as yet unknown functions, and regulatory proteins. Key words: Abiotic stress, stress induced genes, regulatory proteins, transgenics.

Journal ArticleDOI
TL;DR: This work shows that specific short DNA sequences in some plant genes recognize such changes in calcium levels and allow these genes to be activated; this information aids the understanding of how plants respond to specific environmental stresses.
Abstract: Increases in intracellular calcium concentration ([Ca2+]c) mediate plant responses to stress by regulating the expression of genes encoding proteins that confer tolerance. Several plant stress genes have previously been shown to be calcium-regulated, and in one case, a specific promoter motif Abscisic Acid Responsive–Element (ABRE) has been found to be regulated by calcium. A comprehensive survey of the Arabidopsis thaliana transcriptome for calcium-regulated promoter motifs was performed by measuring the expression of genes in Arabidopsis seedlings responding to three calcium elevations of different characteristics, using full genome microarray analysis. This work revealed a total of 269 genes upregulated by [Ca2+]c in Arabidopsis. Bioinformatic analysis strongly indicated that at least four promoter motifs were [Ca2+]c-regulated in planta. We confirmed this finding by expressing in plants chimeric gene constructs controlled exclusively by these cis-elements and by testing the necessity and sufficiency of calcium for their expression. Our data reveal that the C-Repeat/Drought-Responsive Element, Site II, and CAM box (along with the previously identified ABRE) promoter motifs are calcium-regulated. The identification of these promoter elements targeted by the second messenger intracellular calcium has implications for plant signaling in response to a variety of stimuli, including cold, drought, and biotic stress.

Journal ArticleDOI
TL;DR: This study represents the first large-scale transcriptomic analysis of A. hypochondriacus, considered to be a highly nutritious and stress-tolerant crop, and could further the understanding of the mechanisms that contribute to multiple stress-resistance in plants, a trait that has potential biotechnological applications in agriculture.
Abstract: Amaranthus hypochondriacus, a grain amaranth, is a C4 plant noted by its ability to tolerate stressful conditions and produce highly nutritious seeds. These possess an optimal amino acid balance and constitute a rich source of health-promoting peptides. Although several recent studies, mostly involving subtractive hybridization strategies, have contributed to increase the relatively low number of grain amaranth expressed sequence tags (ESTs), transcriptomic information of this species remains limited, particularly regarding tissue-specific and biotic stress-related genes. Thus, a large scale transcriptome analysis was performed to generate stem- and (a)biotic stress-responsive gene expression profiles in grain amaranth. A total of 2,700,168 raw reads were obtained from six 454 pyrosequencing runs, which were assembled into 21,207 high quality sequences (20,408 isotigs + 799 contigs). The average sequence length was 1,064 bp and 930 bp for isotigs and contigs, respectively. Only 5,113 singletons were recovered after quality control. Contigs/isotigs were further incorporated into 15,667 isogroups. All unique sequences were queried against the nr, TAIR, UniRef100, UniRef50 and Amaranthaceae EST databases for annotation. Functional GO annotation was performed with all contigs/isotigs that produced significant hits with the TAIR database. Only 8,260 sequences were found to be homologous when the transcriptomes of A. tuberculatus and A. hypochondriacus were compared, most of which were associated with basic house-keeping processes. Digital expression analysis identified 1,971 differentially expressed genes in response to at least one of four stress treatments tested. These included several multiple-stress-inducible genes that could represent potential candidates for use in the engineering of stress-resistant plants. The transcriptomic data generated from pigmented stems shared similarity with findings reported in developing stems of Arabidopsis and black cottonwood (Populus trichocarpa). This study represents the first large-scale transcriptomic analysis of A. hypochondriacus, considered to be a highly nutritious and stress-tolerant crop. Numerous genes were found to be induced in response to (a)biotic stress, many of which could further the understanding of the mechanisms that contribute to multiple stress-resistance in plants, a trait that has potential biotechnological applications in agriculture.

Journal ArticleDOI
TL;DR: The combined effect of water stress and infection with plant-parasitic nematodes on the nutritional quality of tomato was investigated and the levels of phenolic compounds, carotenoids, and sugars in fruits were analyzed.
Abstract: Induction of abiotic stress in tomato plants has been proposed as a mechanism for improving the nutritional quality of fruits. However, the occurrence of biotic stress can interfere with normal abiotic stress responses. In this study, the combined effect of water stress and infection with plant-parasitic nematodes on the nutritional quality of tomato was investigated. Plants were exposed to one or both stresses, and the levels of phenolic compounds, carotenoids, and sugars in fruits were analyzed as well as physiological responses. Levels of carotenoids lycopene and β-carotene were lower in water-stressed tomatoes but exhibited a different response pattern under combined stress. Nematode stress was associated with increased flavonoid levels, albeit with reduced yields, while chlorogenic acid was increased by nematodes, water stress, and the combined stress. Sugar levels were higher only in tomatoes exposed to both stresses. These results emphasize the importance of studying plant stress factors in combina...

Journal ArticleDOI
TL;DR: A genome-wide survey of this gene family in 10 plant genomes showed that tandem duplication has been regarded as the major expansion mechanism and both monocot and dicot plants may have practiced different expansion and evolutionary history.
Abstract: Glutathione S-transferases (GSTs) exist in various eukaryotes and function in detoxification of xenobiotics and in response to abiotic and biotic stresses. We have carried out a genome-wide survey of this gene family in 10 plant genomes. Our data show that tandem duplication has been regarded as the major expansion mechanism and both monocot and dicot plants may have practiced different expansion and evolutionary history. Non-synonymous substitutions per site (Ka) and synonymous substitutions per site (Ks) analyses showed that N- and C-terminal functional domains of GSTs (GST_N and GST_C) seem to have evolved under a strong purifying selection (Ka/Ks < 1) under different selective pressures. Differential evolutionary rates between GST_N and GST_C and high degree of expression divergence have been regarded as the major drivers for the retention of duplicated genes and the adaptability to various stresses. Expression profiling also indicated that the gene family plays a role not only in stress-related biological processes but also in the sugar-signalling pathway. Our survey provides additional annotation of the plant GST gene family and advance the understanding of plant GSTs in lineage-specific expansion and species diversification.