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Showing papers in "Journal of Integrative Plant Biology in 2010"


Journal ArticleDOI
TL;DR: In this paper, a review focuses on recent literature reporting on the main types of abiotic and biotic stresses that alter the biosynthesis of lignin in plants and how a stressor modulates expression of the genes related with ligninsynthesis.
Abstract: Lignin is a polymer of phenylpropanoid compounds formed through a complex biosynthesis route, represented by a metabolic grid for which most of the genes involved have been sequenced in several plants, mainly in the model-plants Arabidopsis thaliana and Populus. Plants are exposed to different stresses, which may change lignin content and composition. In many cases, particularly for plant-microbe interactions, this has been suggested as defence responses of plants to the stress. Thus, understanding how a stressor modulates expression of the genes related with lignin biosynthesis may allow us to develop study-models to increase our knowledge on the metabolic control of lignin deposition in the cell wall. This review focuses on recent literature reporting on the main types of abiotic and biotic stresses that alter the biosynthesis of lignin in plants.

761 citations


Journal ArticleDOI
TL;DR: Recent advances in flavonoid research are covered, deficiencies in the understanding of the physiological processes are discussed, and approaches to identify the cellular targets of flavonoids are suggested.
Abstract: Flavonoids are ubiquitous in the plant kingdom and have many diverse functions including defense, UV protection, auxin transport inhibition, allelopathy, and flower coloring. Interestingly, these compounds also have considerable biological activity in plant, animal and bacterial systems - such broad activity is accomplished by few compounds. Yet, for all the research over the last three decades, many of the cellular targets of these secondary metabolites are unknown. The many mutants available in model plant species such as Arabidopsis thaliana and Medicago truncatula are enabling the intricacies of the physiology of these compounds to be deduced. In the present review, we cover recent advances in flavonoid research, discuss deficiencies in our understanding of the physiological processes, and suggest approaches to identify the cellular targets of flavonoids.

578 citations


Journal ArticleDOI
TL;DR: The root-shoot-to-root signaling loop called autoregulation of nodulation (AON) as mentioned in this paper has been shown to be an important step in the formation of a new root organ.
Abstract: Legumes are highly important food, feed and biofuel crops. With few exceptions, they can enter into an intricate symbiotic relationship with specific soil bacteria called rhizobia. This interaction results in the formation of a new root organ called the nodule in which the rhizobia convert atmospheric nitrogen gas into forms of nitrogen that are useable by the plant. The plant tightly controls the number of nodules it forms, via a complex root-to-shoot-to-root signaling loop called autoregulation of nodulation (AON). This regulatory process involves peptide hormones, receptor kinases and small metabolites. Using modern genetic and genomic techniques, many of the components required for nodule formation and AON have now been isolated. This review addresses these recent findings, presents detailed models of the nodulation and AON processes, and identifies gaps in our understanding of these process that have yet to be fully explained.

535 citations


Journal ArticleDOI
TL;DR: This review presents the current knowledge on the ROS signals and their role during plant-microorganism interactions and reports the characterisation of ROS producing and scavenging systems from plants and from microorganisms during interactions.
Abstract: Reactive Oxygen Species (ROS) are continuously produced as a result of aerobic metabolism or in response to biotic and abiotic stresses. ROS are not only toxic by-products of aerobic metabolism, but are also signalling molecules involved in several developmental processes in all organisms. Previous studies have clearly shown that an oxidative burst often takes place at the site of attempted invasion during the early stages of most plant-pathogen interactions. Moreover, a second ROS production can be observed during certain types of plant-pathogen interactions, which triggers hypersensitive cell death (HR). This second ROS wave seems absent during symbiotic interactions. This difference between these two responses is thought to play an important signalling role leading to the establishment of plant defense. In order to cope with the deleterious effects of ROS, plants are fitted with a large panel of enzymatic and non-enzymatic antioxidant mechanisms. Thus, increasing numbers of publications report the characterisation of ROS producing and scavenging systems from plants and from microorganisms during interactions. In this review, we present the current knowledge on the ROS signals and their role during plant-microorganism interactions.

277 citations


Journal ArticleDOI
TL;DR: In this paper, the constitutive and induced oleoresin terpenoids for conifer defense accumulate in preformed cortical resin ducts and in xylem trauma-associated resin duct.
Abstract: Defense-related terpenoid biosynthesis in conifers is a dynamic process closely associated with specialized anatomical structures that allows conifers to cope with attack from many potential pests and pathogens. The constitutive and inducible terpenoid defense of conifers involves several hundred different monoterpenes, sesquiterpenes and diterpenes. Changing arrays of these many compounds are formed from the general isoprenoid pathway by activities of large gene families for two classes of enzymes, the terpene synthases and the cytochrome P450-dependent monooxygenases of the CYP720B group. Extensive studies have been conducted on the genomics, proteomics and molecular biochemical characterization of these enzymes. Many of the conifer terpene synthases are multi-product enzymes, and the P450 enzymes of the CYP720B group are promiscuous in catalyzing multiple oxidations, along homologous series of diterpenoids, from a broad spectrum of substrates. The terpene synthases and CYP720B genes respond to authentic or simulated insect attack with increased transcript levels, protein abundance and enzyme activity. The constitutive and induced oleoresin terpenoids for conifer defense accumulate in preformed cortical resin ducts and in xylem trauma-associated resin ducts. Formation of these resin ducts de novo in the cambium zone and developing xylem, following insect attack or treatment of trees with methyl jasmonate, is a unique feature of the induced defense of long-lived conifer trees.

253 citations


Journal ArticleDOI
TL;DR: Current models of biosynthesis, trans-membrane transport, and long-distance translocation of cytokinins in higher plants are summarized to gain insight into this elaborate signaling system.
Abstract: During plant development, distantly-located organs must communicate in order to adapt morphological and physiological features in response to environmental inputs. Among the recognized signaling molecules, a class of phytohormones known as the cytokinins functions as both local and long-distance regulatory signals for the coordination of plant development. This cytokinin-dependent communication system consists of orchestrated regulation of the metabolism, translocation, and signal transduction of this phytohormone class. Here, to gain insight into this elaborate signaling system, we summarize current models of biosynthesis, trans-membrane transport, and long-distance translocation of cytokinins in higher plants.

252 citations


Journal ArticleDOI
TL;DR: A concise review on the most recent progress in the regulatory mechanisms associated with plant SPL transcription factors, especially in relation to miRNAs, and the potential application in agriculture is briefly discussed.
Abstract: SQUAMOSA Promoter-Binding Protein-Like (SPL) genes encode plant-specific transcription factors that play important roles in plant phase transition, flower and fruit development, plant architecture, gibberellins signaling, sporogenesis, and response to copper and fungal toxins. In Arabidopsis, many SPL genes are post-transcriptionally regulated by the microRNA (miRNA) miR156, among which AtSPL9 in turn positively regulates the expression of the second miRNA miR172. This miR156-AtSPL9-miR172 regulatory pathway plays critical roles during juvenile to adult leaf development and the miR156-SPLs feedback interaction persists all through the plant development, which may be conserved in other plants. In the present paper, we provide a concise review on the most recent progress in the regulatory mechanisms associated with plant SPL transcription factors, especially in relation to miRNAs. The potential application of these discoveries in agriculture is briefly discussed.

210 citations


Journal ArticleDOI
TL;DR: Results suggest that H(2)S could increase antioxidant capability in wheat seeds leading to the alleviation of Al(3+) stress.
Abstract: Protective role of hydrogen sulfide (H2S) on seed germination and seedling growth was studied in wheat (Triticum) seeds subjected to aluminum (Al3+) stress. We show that germination and seedling growth of wheat is inhibited by high concentrations of AlCl3. At 30 mmol/L AlCl3 germination is reduced by about 50% and seedling growth is more dramatically inhibited by this treatment. Pre-incubation of wheat seeds in the H2S donor NaHS alleviates AlCl3-induced stress in a dose-dependant manner at an optimal concentration of 0.3 mmol/L. We verified that the role of NaHS in alleviating Al3+ stress could be attributed to H2S/HS− by showing that the level of endogenous H2S increased following NaHS treatment. Furthermore, other sodium salts containing sulfur were ineffective in alleviating Al3+ stress. NaHS pretreatment significantly increased the activities of amylases and esterases and sustained much lower levels of MDA and H2O2 in germinating seeds under Al3+ stress. Moreover, NaHS pretreatment increased the activities of guaiacol peroxidase, ascorbate peroxidase, superoxide dismutase and catalase and decreased that of lipoxygenase. NaHS pretreatment also decreased the uptake of Al3+ in AlCl3-treated seed. Taken together these results suggest that H2S could increase antioxidant capability in wheat seeds leading to the alleviation of Al3+ stress.

189 citations


Journal ArticleDOI
TL;DR: The different steps required for cellulose formation and crystallization are discussed, and the most important specific aspects that are supported by solid experimental data are highlighted.
Abstract: Cellulose biosynthesis is one of the most important biochemical processes in plant biology. Despite the considerable progress made during the last decade, numerous fundamental questions related to this key process in plant development are outstanding. Numerous models have been proposed through the years to explain the detailed molecular events of cellulose biosynthesis. Almost all models integrate solid experimental data with hypotheses on several of the steps involved in the process. Speculative models are most useful to stimulate further research investigations and bring new exciting ideas to the field. However, it is important to keep their hypothetical nature in mind and be aware of the risk that some undemonstrated hypotheses may progressively become admitted. In this review, we discuss the different steps required for cellulose formation and crystallization, and highlight the most important specific aspects that are supported by solid experimental data.

181 citations


Journal ArticleDOI
TL;DR: This study showed that the genetic control of yield and its components in common wheat involved the important genes such as Rht and Vrn, and several significant MQTLs were found in the chromosomal regions corresponding to several rice genomic locations containing important QTLs for yield related traits.
Abstract: A major objective of quantitative trait locus (QTL) studies is to find genes/markers that can be used in breeding programs via marker assisted selection (MAS). We surveyed the QTLs for yield and yield-related traits and their genomic distributions in common wheat (Triticum aestivum L.) in the available published reports. We then carried out a meta-QTL (MQTL) analysis to identify the major and consistent QTLs for these traits. In total, 55 MQTLs were identified, of which 12 significant MQTLs were located on wheat chromosomes 1A, 1B, 2A, 2D, 3B, 4A, 4B, 4D and 5A. Our study showed that the genetic control of yield and its components in common wheat involved the important genes such as Rht and Vrn. Furthermore, several significant MQTLs were found in the chromosomal regions corresponding to several rice genomic locations containing important QTLs for yield related traits. Our results demonstrate that meta-QTL analysis is a powerful tool for confirming the major and stable QTLs and refining their chromosomal positions in common wheat, which may be useful for improving the MAS efficiency of yield related traits.

163 citations


Journal ArticleDOI
TL;DR: Several lines of evidence support the existence of significant cyclic electron flow at high temperature and it is hypothesized that these changes allow for adenosine tri-phosphate homeostasis and maintenance of an energy gradient across the thylakoid membrane, helping to keep it from suffering irreversible damage at highTemperature.
Abstract: Photosynthesis is sensitive to high temperature with reversible declines during moderate stress and irreversible damage with more severe stress. While many studies have focused on the irreversible damage, the reversible changes can tell how photosynthesis tolerates high temperature. Knowing how high temperature is tolerated could lead to ways of extending high temperature tolerance. New analytical methods have been used to probe electron and proton circuits of intact leaves at high temperature. Combined with previous work with isolated systems, it appears that there is a large change in redox distribution among thylakoid components. Photosystem I becomes more reduced but photosystem II and the stroma become more oxidized. Several lines of evidence support the existence of significant cyclic electron flow at high temperature. It is hypothesized that these changes allow for adenosine tri-phosphate homeostasis and maintenance of an energy gradient across the thylakoid membrane, helping to keep it from suffering irreversible damage at high temperature.

Journal ArticleDOI
TL;DR: In this paper, a chimeric construct consisting of the double CaMV35S promoter fused to the Myc-dhar gene was introduced into Arabidopsis thaliana.
Abstract: Vitamin C (L-ascorbic acid, AsA) has important antioxidant and metabolic functions in both plants and animals. Once used, ascorbic acid can be regenerated from its oxidized form in a reaction catalyzed by dehydroascorbate reductase (DHAR, EC 1.8.5.1). To analyze the physiological role of DHAR catalyzing the reduction of DHA to ascorbate in environmental stress adaptation, we examined whether increasing the level of AsA through enhanced AsA recycling would limit the deleterious effects of oxidative stress. A chimeric construct consisting of the double CaMV35S promoter fused to the Myc-dhar gene was introduced into Arabidopsis thaliana. Transgenic plants were biochemically characterized and tested for responses to oxidative stress. Western blot indicated that the dhar-transgene was successfully expressed. In homozygous T4 transgenic seedlings, DHAR overexpression was increased up to 1.5 to 5.4 fold, which enhanced foliar ascorbic acid levels 2- to 4.25-fold and ratio of AsA/DHA about 3- to 16-fold relative to wild type. In addition, the level of glutathione, the reductant used by DHAR, also increased as did its redox state. When whole plants were treated with high light and high temperature stress or in vitro leaf discs were subjected to 10 μM paraquat, transgenic plants showed a larger AsA pool size, lower membrane damage, and a higher level of chlorophyll compared with controls. These data suggested that increasing the plant vitamin C content through enhanced ascorbate recycling could limit the deleterious effects of environmental oxidative stress.

Journal ArticleDOI
TL;DR: The study proves the feasibility of prolonging the leaf life of woody cassava and also sheds light on the control of cytokinin homeostasis in cassava leaves.
Abstract: Cassava (Manihot esculenta Crantz) sheds its leaves during growth, especially within the tropical dry season. With the production of SAG12-IPT transgenic cassava we want to test the level of leaf retention and altered cytokinin metabolism of transgenic plants via the autoregulatory senescence inhibition system. After confirmation of transgene expression by molecular analysis and phenotype examination in greenhouse plants, two transgenic plant lines, 529-28 and 529-48, were chosen for further investigation. Detached mature leaves of 529-28 plants retained high levels of chlorophyll compared with wild-type leaves after dark-induced senescence treatment. Line 529-28 showed significant drought tolerance as indicated by stay-green capacity after drought stress treatment. Field experiments proved that leaf senescence syndrome was significantly delayed in 529-28 plants in comparison with wild-type and 529-48 plants. Physiological and agronomical characterizations of these plants also revealed that the induced expression of IPT had effects on photosynthesis, sugar allocation and nitrogen partitioning. Importantly, the 529-28 plants accumulated a high level of trans-zeatin-type cytokinins particularly of corresponding storage O-glucosides to maintain cytokinin homeostasis. Our study proves the feasibility of prolonging the leaf life of woody cassava and also sheds light on the control of cytokinin homeostasis in cassava leaves.

Journal ArticleDOI
Fushun Hao1, Shiling Zhao1, Huan Dong1, Huan Zhang1, Lirong Sun1, Chen Miao1 
TL;DR: In this article, the effects of exogenous salicylic acid (SA) on stomatal closure and NO generation in Arabidopsis guard cells based on genetic and physiological data were demonstrated.
Abstract: Phytohormone salicylic acid (SA) plays important roles in plant responses to environmental stress. However, knowledge about the molecular mechanisms for SA affecting the stomatal movements is limited. In this paper, we demonstrated that exogenous SA significantly induced stomatal closure and nitric oxide (NO) generation in Arabidopsis guard cells based on genetic and physiological data. These effects were significantly inhibited by the NO scavenger c-PTIO, NO synthase (NOS) inhibitor L-NAME or nitrate reductase suppressor tungstate respectively, implying that NOS and nitrate reductase (NR) participate in SA-evoked stomatal closing. Furthermore, the effects of SA promotion of stomatal closure and NO synthesis are significantly suppressed in NR single mutants of nia1, nia2 or double mutant nia1/nia2, compared with the wild type plants. This suggests that both Nia1 and Nia2 are involved in SA-stimulated stomatal closure. In addition, pharmacological experiments showed that protein kinases, cGMP and cADPR are involved in SA-mediated NO accumulation and stomatal closure induced by SA in Arabidopsis.

Journal ArticleDOI
TL;DR: Different factors, which either respond to the wall or are present in the wall, and usually generate elevated [Ca(2+)] in the cytoplasm, provide evidence for a rich and multifaceted system of communication between the cy toplast and cell wall, with Ca(2+) as a carrier of information.
Abstract: Attention is given to the role of Ca(2+) at the interface between the cell wall and the cytoplast, especially as seen in pollen tubes. While the cytoplasm directs the synthesis and deposition of the wall, it is less well appreciated that the wall exerts considerable self control and influences activities of the cytoplasm. Ca(2+) participates as a crucial factor in this two way communication. In the cytoplasm, a [Ca(2+)] above 0.1 microM, regulates myriad processes, including secretion of cell wall components. In the cell wall Ca(2+), at 10 microM to 10 mM, binds negative charges on pectins and imparts structural rigidity to the wall. The plasma membrane occupies a pivotal position between these two compartments, where selective channels regulate influx of Ca(2+), and specific carriers pump the ion back into the wall. In addition we draw attention to different factors, which either respond to the wall or are present in the wall, and usually generate elevated [Ca(2+)] in the cytoplasm. These factors include: (i) stretch activated channels; (ii) calmodulin; (iii) annexins; (iv) wall associated kinases; (v) oligogalacturonides; and (vi) extracellular adenosine 5'-triphosphate. Together they provide evidence for a rich and multifaceted system of communication between the cytoplast and cell wall, with Ca(2+) as a carrier of information.

Journal ArticleDOI
TL;DR: It is shown that ABA and H2O2 induced a significant increase in the ZmMPK3 activity using immunoprecipitation and in-gel kinase assay, and the results showed that the ZpMK3 protein is localized mainly to the nucleus, suggesting that it may play an important role in response to environmental stresses.
Abstract: In search for components of mitogen-activated protein kinase (MAPK) cascades in maize (Zea mays) involved in response to abscisic acid (ABA) stimulus, a novel MAPK gene, ZmMPK3, from ABA-treated maize leaves cDNA was isolated and characterized. The full length of the ZmMPK3 gene is 1 520 bp and encodes a 376 amino acid protein with a predicted molecular mass of 43.5 kD and a pI of 5.83. ZmMPK3 contains all 11 MAPK conserved subdomains and the phosphorylation motif TEY. Amino acid sequence alignment revealed that ZmMPK3 shared high identity with group-A MAPK in plants. A time course (30-360 min) experiment using a variety of signal molecules and stresses revealed that the transcripts level of ZmMPK3 accumulated markedly and rapidly when maize seedlings were subjected to exogenous signaling molecules: ABA, H2O2, jasmonic acid and salicylic acid, various abiotic stimuli such as cold, drought, ultraviolet light, salinity, heavy metal and mechanical wounding. Its transcription was also found to be tissue-specific regulated. Here, we show that ABA and H2O2 induced a significant increase in the ZmMPK3 activity using immunoprecipitation and in-gel kinase assay. Furthermore, the results showed that the ZmMPK3 protein is localized mainly to the nucleus. These results suggest that the ZmMPK3 may play an important role in response to environmental stresses.

Journal ArticleDOI
TL;DR: Comparative analysis of expression patterns of Wox genes in rice and Arabidopsis suggest that the WOX genes play conserved and various roles in plants.
Abstract: WUSCHEL-related homeobox (WOX) genes form a large gene family specifically expressed in plants. They are known to play important roles in regulating the development of plant tissues and organs by determining cell fate. Recent available whole genome sequences allow us to do more comprehensive phylogenetic analysis of the WOX genes in plants. In the present study, we identified 11 and 21 WOXs from sorghum (Sorghum bicolor) and maize (Zea mays), respectively. The 72 WOX genes from rice (Oryza sativa), sorghum, maize, Arabidopsis (Arabidopsis thaliana) and poplar (Populus trichocarpa) were grouped into three well supported clades with nine subgroups according to the amino acid sequences of their homodomains. Their phylogenetic relationship was also supported by the observation of the motifs outside the homodomain. We observed the variation of duplication events among the nine sub-groups between monocots and eudicots, for instance, more gene duplication events of WOXs within subgroup A for monocots, while, less for dicots in this subgroup. Furthermore, we observed the conserved intron/exon structural patterns of WOX genes in rice, sorghum and Arabidopsis. In addition, WUS (Wuschel)-box and EAR (the ERF-associated amphiphilic repression)-like motif were observed to be conserved among several WOX subgroups in these five plants. Comparative analysis of expression patterns of WOX genes in rice and Arabidopsis suggest that the WOX genes play conserved and various roles in plants. This work provides insights into the evolution of the WOX gene family and is useful for future research.

Journal ArticleDOI
TL;DR: This study supports the feasibility of producing large quantities of biomass from marginal land sources, and suggests that some 380,000 tons of dry biomass could be produced each year from annual pruning of mulberry trees.
Abstract: Fast economic development in China has resulted in a significant increase in energy demand. Coal accounts for 70% of China's primary energy consumption and its combustion has caused many environmental and health problems. Energy security and environmental protection requirements are the main drivers for renewable energy development in China. Small farmland and food security make bioenergy derived from corn or sugarcane unacceptable to China: the focus should be on generating bioenergy from ligno-cellulosic feedstock sources. As China cannot afford biomass energy production from its croplands, marginal lands may play an important role in biomass energy production. Although on a small scale, marginal land has already been used for various purposes. It is estimated that some 45 million hm2 of marginal land could be brought into high potential biomass energy production. For the success of such an initiative, it will likely be necessary to develop multipurpose plants. A case study, carried out on marginal land in Ningnan County, Sichuan Province with per capita cropland of 0.07 ha, indicated that some 380 000 tons of dry biomass could be produced each year from annual pruning of mulberry trees. This study supports the feasibility of producing large quantities of biomass from marginal land sources.

Journal ArticleDOI
TL;DR: This review focuses on studies where the use of plant tissue cultures has been advantageous in structural and biosynthesis studies of lignin, and discusses the validity of tissue cultures as models for lignIn biosynthesis.
Abstract: Lignin, a phenolic polymer abundant in cell walls of certain cell types, has given challenges to scientists studying its structure or biosynthesis. In plants lignified tissues are distributed between other, non-lignified tissues. Characterization of native lignin in the cell wall has been difficult due to the highly cross-linked nature of the wall components. Model systems, like plant tissue cultures with tracheary element differentiation or extracellular lignin formation, have provided useful information related to lignin structure and several aspects of lignin formation. For example, many enzyme activities in the phenylpropanoid pathway have been first identified in tissue cultures. This review focuses on studies where the use of plant tissue cultures has been advantageous in structural and biosynthesis studies of lignin, and discusses the validity of tissue cultures as models for lignin biosynthesis.

Journal ArticleDOI
TL;DR: The importance of transcriptional regulation is illustrated by the correlation of expression of specific classes of genes with related biological processes occurring at specific stages of secondary growth, including cell division, cell expansion, and cell differentiation as mentioned in this paper.
Abstract: Secondary growth and wood formation are products of the vascular cambium, a lateral meristem. Although the mechanisms have only recently begun to be uncovered, transcriptional regulation appears increasingly central to the regulation of secondary growth. The importance of transcriptional regulation is illustrated by the correlation of expression of specific classes of genes with related biological processes occurring at specific stages of secondary growth, including cell division, cell expansion, and cell differentiation. At the same time, transcription factors have been characterized that affect specific aspects of secondary growth, including regulation of the cambium and differentiation of cambial daughter cells. In the present review, we summarize evidence pointing to transcription as a major mechanism for regulation of secondary growth, and outline future approaches for comprehensively describing transcriptional networks underlying secondary growth.

Journal ArticleDOI
TL;DR: It is shown that specific peroxidases catalyze lignin polymerization in the apoplastic space of Norway spruce xylem.
Abstract: Class III secretable plant peroxidases occur as a large family of genes in plants with many functions and probable redundancy. In this review we are concentrating on the evidence we have on the catalysis of lignin polymerization by class III plant peroxidases present in the apoplastic space in the xylem of trees. Some evidence exists on the specificity of peroxidase isozymes in lignin polymerization through substrate specificity studies, from antisense mutants in tobacco and poplar and from tissue and cell culture lines of Norway spruce (Picea abies) and Zinnia elegans. In addition, real time (RT-)PCR results have pointed out that many peroxidases have tissue specific expression patterns in Norway spruce. Through combining information on catalytic properties of the enzymes, on the expression patterns of the corresponding genes, and on the presence of monolignols and hydrogen peroxide in the apoplastic space, we can show that specific peroxidases catalyze lignin polymerization in the apoplastic space of Norway spruce xylem.

Journal ArticleDOI
TL;DR: Results indicate that tropical seagrass Thalassia hemprichii may respond positively to CO₂ -induced acidification of the coastal ocean, and the CO⁂ -stimulated improvement of photosynthesis and NSC content may partially offset negative effects of severe environmental disturbance such as underwater light reduction.
Abstract: The effects of CO2 enrichment on various ecophysiological parameters of tropical seagrass Thalassia hemprichii (Ehrenb.) Aschers were tested. T. hemprichii, collected from a seagrass bed in Xincun Bay, Hainan island of Southern China, was cultured at 4 CO2(aq) concentrations in flow-through seawater aquaria bubbled with CO2. CO2 enrichment considerably enhanced the relative maximum electron transport rate (RETRmax) and minimum saturating irradiance (E-k) of T. hemprichii. Leaf growth rate of CO2-enriched plants was significantly higher than that in unenriched treatment. Nonstructural carbohydrates (NSC) of T. hemprichii, especially in belowground tissues, increased strongly with elevated CO2(aq), suggesting a translocation of photosynthate from aboveground to belowground tissues. Carbon content in belowground tissues showed a similar response with NSC, while in aboveground tissues, carbon content was not affected by CO2 treatments. In contrast, with increasing CO2(aq), nitrogen content in aboveground tissues markedly decreased, but nitrogen content in belowground was nearly constant. Carbon: nitrogen ratio in both tissues were obviously enhanced by increasing CO2(aq). Thus, these results indicate that T. hemprichii may respond positively to CO2-induced acidification of the coastal ocean. Moreover, the CO2-stimulated improvement of photosynthesis and NSC content may partially offset negative effects of severe environmental disturbance such as underwater light reduction.

Journal ArticleDOI
TL;DR: Gen expression patterns of some genes in several stress response-associated pathways, including abscisic acid, jasmonic acid and phenylalanine ammonia-lyase, were examined, and these specific genes were responsive to drought stress positively.
Abstract: Preharvest aflatoxin contamination of grain grown on the US southeastern Coast Plain is provoked and aggravated by abiotic stress. The primary abiotic stress is drought along with high temperatures. The objectives of the present study were to monitor gene expression in developing kernels in response to drought stress and to identify drought-responsive genes for possible use in germplasm assessment. The maize breeding line Tex6 was used, and gene expression profiles were analyzed in developing kernels under drought stress verses well-watered conditions at the stages of 25, 30, 35, 40, 45 d after pollination (DAP) using the 70 mer maize oligo-arrays. A total of 9 573 positive array spots were detected with unique gene IDs, and 7 988 were common in both stressed and well-watered samples. Expression patterns of some genes in several stress response-associated pathways, including abscisic acid, jasmonic acid and phenylalanine ammonia-lyase, were examined, and these specific genes were responsive to drought stress positively. Real-time quantitative polymerase chain reaction validated microarray expression data. The comparison between Tex6 and B73 revealed that there were significant differences in specific gene expression, patterns and levels. Several defense-related genes had been downregulated, even though some defense-related or drought responsive genes were upregulated at the later stages.

Journal ArticleDOI
TL;DR: In this paper, a new allele gamyb-4 with a C base deletion in the second exon (+2308) caused a frame shift and premature translational termination.
Abstract: In higher plants, male reproductive development is a complex biological process that includes cell division and differentiation, cell to cell communication etc., while the mechanism underlying plant male reproductive development remains less understood. GAMYB encodes a gibberellins acid (GA) inducible transcription factor that is required for the early anther development in rice (Oryza sativa L.). Here, we report the isolation and characterization of a new allele gamyb-4 with a C base deletion in the second exon (+2308), causing a frame shift and premature translational termination. Histological analysis showed that gamyb-4 developed abnormal enlarged tapetum and could not undergo normal meiosis. To understand the regulatory role of GAMYB, we carried out quantitative reverse transcription-polymerase chain reaction analysis and comparison of microarray data. These results revealed that the expression of TDR (TAPETUM DEGENERATION RETARDATION), a tapetal cell death regulator, was downregulated in gamyb-4 and udt1 (undeveloped tapetum1). While the GAMYB expression was not obviously changed in tdr and udt1-1, and no apparent expression fold change of UDT1 in tdr and gamyb-4, suggesting that TDR may act downstream of GAMYB and UDT1, and GAMYB and UDT1 work in parallel to regulate rice early anther development. This work is helpful in understanding the regulatory network in rice anther development.

Journal ArticleDOI
TL;DR: Cumulatively, the data show that the xylem of arabidopsis provides the best model for secondary wall cellulose synthesis in cotton fiber and CesA genes within a "cell wall toolbox" are used in diverse ways for the construction of particular specialized cell walls.
Abstract: Through exploring potential analogies between cotton seed trichomes (or cotton fiber) and arabidopsis shoot trichomes we discovered that CesAs from either the primary or secondary wall phylogenetic clades can support secondary wall thickening. CesA genes that typically support primary wall synthesis, AtCesA1,2,3,5, and 6, underpin expansion and secondary wall thickening of arabidopsis shoot trichomes. In contrast, apparent orthologs of CesA genes that support secondary wall synthesis in arabidopsis xylem, AtCesA4,7, and 8, are up-regulated for cotton fiber secondary wall deposition. These conclusions arose from: (a) analyzing the expression of CesA genes in arabidopsis shoot trichomes; (b) observing birefringent secondary walls in arabidopsis shoot trichomes with mutations in AtCesA4, 7, or 8; (c) assaying up-regulated genes during different stages of cotton fiber development; and (d) comparing genes that were co-expressed with primary or secondary wall CesAs in arabidopsis with genes up-regulated in arabidopsis trichomes, arabidopsis secondary xylem, or cotton fiber during primary or secondary wall deposition. Cumulatively, the data show that: (a) the xylem of arabidopsis provides the best model for secondary wall cellulose synthesis in cotton fiber; and (b) CesA genes within a “cell wall toolbox” are used in diverse ways for the construction of particular specialized cell walls.

Journal ArticleDOI
TL;DR: A threshold model is proposed in which the formation of chloroplasts is due to the presence of activities/processes that are able to compensate for a lack of VAR2, and is proposed to explain the mechanism of var2 variegation.
Abstract: Variegation mutants are ideal model systems to study chloroplast biogenesis. We are interested in variegations whose green and white-sectored leaves arise as a consequence of the action of nuclear recessive genes. In this review, we focus on the Arabidopsis var2 variegation mutant, and discuss recent progress toward understanding the function of VAR2 and the mechanism of var2-mediated variegation. VAR2 is a subunit of the chloroplast FtsH complex, which is involved in turnover of the Photosystem II reaction center D1 protein, as well as in other processes required for the development and maintenance of the photosynthetic apparatus. The cells in green sectors of var2 have normal-appearing chloroplasts whereas cells in the white sectors have abnormal plastids that lack pigments and organized lamellae. To explain the mechanism of var2 variegation, we have proposed a threshold model in which the formation of chloroplasts is due to the presence of activities/processes that are able to compensate for a lack of VAR2. To gain insight into these activities, second-site suppressor screens have been carried out to obtain mutants with non-variegation phenotypes. Cloning and characterization of several var2 suppressor lines have uncovered several mechanisms of variegation suppression, including an unexpected link between var2 variegation and chloroplast translation.

Journal ArticleDOI
TL;DR: In this paper, the authors showed that the 3' untranslated regions of the StBEL5 mRNA are involved in mediating its long-distance transport and in controlling translation.
Abstract: BEL1-like transcription factors are ubiquitous in plants and interact with KNOTTED1-types to regulate numerous developmental processes. In potato, the RNA of several BEL1-like transcription factors has been identified in phloem cells. One of these, StBEL5, and its Knox protein partner regulate tuber formation by targeting genes that control growth. RNA detection methods and grafting experiments demonstrated that StBEL5 transcripts move across a graft union to localize in stolon tips, the site of tuber induction. This movement of RNA originates in source leaf veins and petioles and is induced by a short-day photoperiod, regulated by the untranslated regions, and correlated with enhanced tuber production. Addition of the StBEL5 untranslated regions to another BEL1-like mRNA resulted in its preferential transport to stolon tips leading to increased tuber production. Upon fusion of the untranslated regions of StBEL5 to a beta-glucuronidase marker, translation in tobacco protoplasts was repressed by those constructs containing the 3' untranslated sequence. The untranslated regions of the StBEL5 mRNA are involved in mediating its long-distance transport and in controlling translation. The 3' untranslated sequence contains an abundance of conserved motifs that may serve as binding motifs for RNA-binding proteins. Because of their presence in the phloem sieve tube system, their unique untranslated region sequences and their diverse RNA accumulation patterns, the family of BEL1-like RNAs from potato represents a valuable model for studying the long-distance transport of full-length mRNAs and their role in development.

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Hai-yan Liu1, Jin-Ran Dai1, Dongru Feng1, Bing Liu1, Hong-Bin Wang1, Jinfa Wang1 
TL;DR: Results suggest that MpAsr might be involved in plant responses to both abiotic stress and pathogen attack, and transgenic Arabidopsis plants overexpressing M pAsr exhibited higher drought tolerance, but showed no significant decreased sensitivity to F. cubense.
Abstract: Asr (abscisic acid, stress, ripening induced) genes are typically upregulated by a wide range of factors, including drought, cold, salt, abscisic acid (ABA) and injury; in addition to plant responses to developmental and environmental signals. We isolated an Asr gene, MpAsr, from a suppression subtractive hybridization (SSH) cDNA library of cold induced plantain (Musa paradisiaca) leaves. MpAsr expression was upregulated in Fusarium oxysporum f. sp. cubense infected plantain leaves, peels and roots, suggesting that MpAsr plays a role in plantain pathogen response. In addition, a 581-bp putative promoter region of MpAsr was isolated via genome walking and cis-elements involved in abiotic stress and pathogen-related responses were detected in this same region. Furthermore, the MpAsr promoter demonstrated positive activity and inducibility in tobacco under F. oxysporum f. sp. cubense infection and ABA, cold, dehydration and high salt concentration treatments. Interestingly, transgenic Arabidopsis plants overexpressing MpAsr exhibited higher drought tolerance, but showed no significant decreased sensitivity to F. oxysporum f. sp. cubense. These results suggest that MpAsr might be involved in plant responses to both abiotic stress and pathogen attack.

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TL;DR: In this article, the authors summarized recent advances in CLE signaling governing vascular development and showed that TDIF produced in and secreted from phloem cells is perceived by TDR/PXY, a leucine-rich repeat receptor kinase located in the plasma membrane of procambial cells.
Abstract: Cell division and differentiation of stem cells are controlled by non-cell-autonomous signals in higher organisms. The plant vascular meristem is a stem-cell tissue comprising procambial cells that produce xylem cells on one side and phloem cells on the other side. Recent studies have revealed that TDIF (tracheary element differentiation inhibitory factor)/CLE41/CLE44 peptide signal controls the procambial cell fate in a non-cell-autonomous manner. TDIF produced in and secreted from phloem cells is perceived by TDR/PXY, a leucine-rich repeat receptor kinase located in the plasma membrane of procambial cells. This signal suppresses xylem cell differentiation of procambial cells and promotes their proliferation. In addition to TDIF, some other CLE peptides play roles in vascular development. Here, we summarize recent advances in CLE signaling governing vascular development.

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TL;DR: This review will focus on recent progress that has been made towards understanding the rapid reprogramming of the transcriptome that occurs in response to stress as well as emerging mechanisms underpinning the reprograming of gene expression in Response to stress.
Abstract: As sessile organisms plants must cope with ever changing environmental conditions. To survive plants have evolved elaborate mechanisms to perceive and rapidly respond to a diverse range of abiotic and biotic stresses. Central to this response is the ability to modulate gene expression at both the transcriptional and post-transcriptional levels. This review will focus on recent progress that has been made towards understanding the rapid reprogramming of the transcriptome that occurs in response to stress as well as emerging mechanisms underpinning the reprogramming of gene expression in response to stress.