Abiotic Stress Response Pathways Research Articles

Whole-Genome Analysis of ZF-HD Genes among Three Dendrobium Species and Expression Patterns in Dendrobium chrysotoxum

ZF-HD transcription factors, which are unique to land plants, are involved in the regulation of abiotic stress response and related signaling pathways, and play a crucial role in plant growth and development. Dendrobium is one of the largest genera of orchids, with a high ornamental and ecological value. However, the specific functions of the ZF-HDs in Dendrobium remain unknown. In this study, we identified a total of 53 ZF-HDs from D. chrysotoxum (17), D. catenatum (23), and D. huoshanense (13), and analyzed their physicochemical properties, phylogenetic relationships, chromosomal locations, protein structures, conserved motifs, and expression patterns. The phylogenetic relationships revealed that 53 ZF-HDs were classified into six subfamilies (ZHDI–V and MIF), and all ZF-HD proteins contained motif 1 and motif 4 conserved domains, while a minority of these proteins had exons. The analysis of cis-elements in the promoters of ZF-HDs from three Dendrobium species showed that growth- and development-related elements were the most prevalent, followed by hormone response and abiotic stress response elements. Through collinearity analysis, 14 DchZF-HDs were found to be collinear with DhuZF-HDs, and 12 DchZF-HDs were found to be collinear with DcaZF-HDs. Furthermore, RT-qPCR analysis revealed that DchZF-HDs play a regulatory role in the development of lateral organs during the flowering process. The results indicated that DchZHD2 plays a role in the unpigmented bud stage, while DchMIF8 and DchZHD16 play significant roles during the pigmented bud and initial bloom stages. Hence, this study provides a crucial basis for further exploring ZF-HDs functions in regulating the floral organs of orchids.

Genome-wide transcriptional profiling and physiological investigation elucidating the molecular mechanism of multiple abiotic stress response in Stevia rebaudiana Bertoni

Considering the major source of plant-derived low/non-calorie steviol glycosides (SGs), comprehensive physiological, biochemical, and deep transcriptional investigations were conducted to explicit deeper insight into multiple abiotic stress responses in Stevia rebaudiana. The physiological indicators including photosynthesis, chlorophyll, relative water content, shoot growth, electrolyte leakage, and SG biosynthesis were negatively impacted under drought (DS), followed by salinity (SS) and waterlogging (WS). Global transcriptional analysis revealed significant upregulated expression of the genes encoding for ROS detoxification (GST, SOD, APX, glutathione peroxidase), osmotic adjustment (alpha-trehalose-phosphate and S-adenosylmethionine decarboxylase), ion transporters (CAX, NHX, CNGS, VPPase, VATPase), water channel (PIP1, TIP) and abiotic stress-responsive candidate genes (LEA, HSPs, and Dehydrins) regulating abiotic stress response in S. rebaudiana. These inferences were complemented with predicted interactome network that revealed regulation of energy metabolism by key stress-responsive genes (GST, HKT1, MAPKs, P5CSs, PIP), transcription factors (HSFA2, DREB1A, DREB2A), and abiotic stress responsive pathways (ABA, ethylene, ion stress). This is the first detailed study to comprehend the molecular regulation of stress response and their interplay under DS, SS, and WS. The key genes and regulators can be functionally validated, and will facilitate targeted gene editing for genetic improvement of crop sustainability under changing environmental conditions in S. rebaudiana.

Transcriptome Analysis Reveals Association of Photosynthesis and Phytohormone Pathways with Leaf Color in Chinese Cabbage

Chinese cabbage (Brassica rapa L. ssp. Pekinensis) in the genus Brassica of the family Brassicaceae (Cruciferae) originates from China and is one of the most consumed leafy vegetables in East Asian countries. The leaf color is tightly linked with its growth, development, and yield. By screening an EMS mutagenized population of Chinese cabbage inbred line A03, we identified a yellowgreen leaf mutant ygl. This mutant developed abnormal ultrastructure in chloroplasts. Transcriptome and Gene Ontology (GO) analyses unveiled that abiotic stress response and glucan metabolism pathways were enriched in ygl compared to A03. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis reveals that differentially expressed genes were mainly associated with plant hormone signal transduction, photosynthesis, and starch and sucrose metabolism. In ygl, the expression of some photosynthetic pathway genes was significantly up-regulated, while the transcription of key genes related to carbon fixation, starch syntheses, and sugar metabolism pathways, such as RBCS1A, APS1, APL3, and SUS1, was markedly down-regulated. We also found a similar reduction trend in mRNA levels of IAA19, IAA29, and ARR4 associated with auxin and cytokinin pathways. Taken together, we uncovered transcriptional profiles for some important genes that may be responsible for leaf color development, and such gene expression repertoire may be useful for further investigation into the phenotype-to-genotype link in the ygl mutant Chinese cabbage.

Understanding the cross-talk of major abiotic-stress-responsive genes in rice: A computational biology approach

This study aims to identify key abiotic-stress-responsive genes in Oryza sativa and investigate their expression profiles, protein–protein interactions, and co-expression patterns to better understand the molecular mechanisms underlying stress response in rice. The ultimate goal is to employ these findings in the development of gene-based molecular markers to breed rice cultivars with enhanced resistance to challenging environmental conditions. A total of 14 abiotic-stress-responsive genes in O. sativa were identified through literature mining. These genes were analyzed for their chromosomal distribution, transcript length, CDS length, and translated amino acid length. Pairwise similarity matrix, phylogenetic analysis, and protein–protein interaction networks were employed to understand the evolutionary relationships and functional interactions among these genes. Expression profiles of six key genes (AOX1a, AOX1b, ALDH2a, ALDH2b, OsNAC6, OsDHN1) were investigated using the electronic fluorescent pictogram (eFP) program. KEGG pathway analysis and co-expression studies were also conducted to further understand the roles of these genes in abiotic stress response pathways. The 14 abiotic-stress-responsive genes were distributed across different chromosomes of O. sativa, suggesting the presence of interconnected cascades regulating abiotic-stress-response. Phylogenetic analysis revealed four clusters of genes, indicating their potential shared ancestry. Protein-protein interaction analysis identified three prominent clusters of interactions, with the strongest interactions occurring among Aldh2a, Aldh2b, OS07T0188800-01, and OsJ_04113 in one cluster, and between AOX1a and AOX1b in another cluster. Expression profiles of the six key genes varied across different stages of the rice life cycle. KEGG pathway analysis showed that ALDH2a and ALDH2b participated in almost all pathways except propanoate metabolism.The study demonstrated that the six key genes play significant regulatory roles in abiotic stress responses in O. sativa. The expression profiles, phylogenetic analysis, protein–protein interactions, and gene co-expression studies revealed interconnected cascades and cross-talk in response mechanisms of these genes. These findings can be employed to develop gene-based molecular markers for breeding rice cultivars with enhanced resistance to abiotic stresses, and contribute to the successful application of computational biology in plant breeding towards sustainable development goal.

Cross-species predictive modeling reveals conserved drought responses between maize and sorghum

Drought tolerance is a highly complex trait controlled by numerous interconnected pathways with substantial variation within and across plant species. This complexity makes it difficult to distill individual genetic loci underlying tolerance, and to identify core or conserved drought-responsive pathways. Here, we collected drought physiology and gene expression datasets across diverse genotypes of the C4 cereals sorghum and maize and searched for signatures defining water-deficit responses. Differential gene expression identified few overlapping drought-associated genes across sorghum genotypes, but using a predictive modeling approach, we found a shared core drought response across development, genotype, and stress severity. Our model had similar robustness when applied to datasets in maize, reflecting a conserved drought response between sorghum and maize. The top predictors are enriched in functions associated with various abiotic stress-responsive pathways as well as core cellular functions. These conserved drought response genes were less likely to contain deleterious mutations than other gene sets, suggesting that core drought-responsive genes are under evolutionary and functional constraints. Our findings support a broad evolutionary conservation of drought responses in C4 grasses regardless of innate stress tolerance, which could have important implications for developing climate resilient cereals.

Genome-Wide Characterization and Anthocyanin-Related Expression Analysis of the B-BOX Gene Family in Capsicum annuum L.

The transcription factors, B-box (BBX), belong to a subfamily of the zinc finger family of proteins and exhibit multiple biological functions in plant growth, development, and abiotic stress response pathways. In this study, a total of 23 CaBBX members were identified using the pepper reference genome database. According to the gene structure, conserved domains, and the phylogenetic tree, 23 CaBBX genes were divided into four groups, wherein the analysis of the promoter region indicated the presence of cis-acting elements related to plant development, hormones, and stress response. Interspecies collinearity analysis showed that the CaBBXs had three duplicated gene pairs, and the highest gene density was found on chromosomes 2 and 7. Transcriptome RNA-seq data and quantitative polymerase chain reaction (qRT-PCR) analysis of pepper plants spanning the entire period showed that more than half of the CaBBX genes were widely expressed in diversity tissues of pepper. Co-expression network analysis indicated that the CaBBXs and the anthocyanin structural genes had a close co-expression relationship. Thus, it was reasonably speculated that the CaBBX genes may be involved in the regulation of anthocyanin biosynthesis. Overall, this study involved the genome-wide characterization of the CaBBX family and may serve as a solid foundation for further investigations on CaBBX genes involved in the anthocyanin synthesis mechanisms and development in pepper.

The molecular characteristics of soybean ARR-B transcription factors

The Type-B authentic response regulator (ARR-Bs) gene family is one of the important plant-specific transcription factor families involved in variety of physiological processes. However, study of ARR-Bs gene family in soybean is limited. Genome-wide analysis and expression profiling of the ARR-Bs gene family were performed in the soybean genome. 31 ARR-Bs genes (namely GmARR-B1-31) were identified, containing conserved catalytic domains with protein lengths and molecular weights ranging from 246 to 699 amino acids (aa) and 28.30 to 76.86 kDa, respectively. Phylogenetic analysis grouped ARR-Bs genes into three clusters—Cluster I, Cluster II, and Cluster III—which included 15, 12, and 4 genes, respectively, and were asymmetrically distributed on 17 chromosomes. Tissue specific expression analysis of GmARR-Bs family revealed a high transcription level in flowers, roots and seeds. The subcellular localization of GmARR5, GmARR14 were observed in the nucleus, and the promoter region of them included low-temperature responsive element (LTR), the C-repeat/dehydration responsive element (DRE), MBS, ABRE, MYB, MEJA and TCA-elements, which possibly participate in abiotic stress and hormones responses. qRT-PCR analysis showed that the expression of GmARR-B genes were affected by different abiotic stresses, especially cold stress and salt stress, and GmARR-B5 and GmARR-B14 were significantly induced by cold stress. This suggested that ARR-Bs genes were involved in multiple abiotic stress response pathways and acted as a positive factor under cold stress.

Identification of bHLH genes through genome-wide association study and antisense expression of ZjbHLH076/ZjICE1 influence tolerance to low temperature and salinity in Zoysia japonica

Abiotic stress greatly affects plant growth and developmental processes, resulting in poor productivity. A variety of basic helix-loop-helix (bHLH) transcription factors (TFs) that play important roles in plant abiotic stress response pathways have been identified. However, bHLH proteins of Zoysia japonica, one of the warm-season turfgrasses, have not been widely studied. In this study, 141 bHLH genes (ZjbHLHs) were identified and classified into 22 subfamilies. The ZjbHLHs were mapped on 19 chromosomes except for Chr17 and one pair of the tandemly arrayed genes was identified on Chr06. Also, the co-linearity of ZjbHLHs was found to have been driven mostly by segmental duplication events. The subfamily IIIb genes of our present interest, possessed various stress responsive cis-elements in their promoters. ZjbHLH076/ZjICE1, a MYC-type bHLH TF in subfamily IIIb was analyzed by overexpression and its loss-of-function via overexpressing a short ZjbHLH076/ZjICE1 fragment in the antisense direction. The overexpression of ZjbHLH076/ZjICE1 enhanced the tolerance to cold and salinity stress in the transgenic Z. japonica plants. However, the anti-sense expression of ZjbHLH076/ZjICE1 showed sensitive to these abiotic stresses. These results suggest that ZjbHLH076/ZjICE1 would be a promising candidate for the molecular breeding program to improve the abiotic stress tolerance of Z. japonica.

Transcriptome-wide analysis of AP2/ERF transcription factors involved in regulating Taxol biosynthesis in Taxus × media

The AP2/ERF transcription factor (TF) family plays a key role in response to plant growth and development, biotic and abiotic stresses, but there are few studies on the regulation of Taxol biosynthesis. In this study, approximately 49 genes containing a complete AP2/ERF domain were identified from the Taxus × media (Yew tree) transcriptome database. Amino acid sequences, gene structures, phylogeny, and putative conserved motifs in these 49 TmAP2/ERF (APETALA2/Ethylene-Responsive factor of Taxus × media) proteins were analyzed, and compared with those AP2/ERF of Arabidopsis thaliana. All 49 TmAP2/ERF TFs contained at least one AP2/ERF domain and were divided into four subfamilies (AP2, RAV, DREB, and ERF). Expression analysis showed that nine TmERF genes belonging to DREB and ERF subfamilies can respond to low temperature and hormone treatment, suggesting their involvement in cross-talk between abiotic stress-responsive signaling pathways. Furthermore, the expression pattern of seven TmERF genes was measured using qRT-PCR in response to gibberellin acid (GA3). The results indicated that TmERF5, TmERF14, and TmERF36 are highly expressed under gibberellin acid exposure, consistent with the predictions based on transcriptome analysis. These findings will be helpful in understanding AP2/ERF gene-related secondary metabolic and stress response signaling and pathways in Taxus spp. with the aim of improving Taxol yields.

VaCBL6 from Vitis amurensis Involved in Abiotic Stress Response and ABA-mediated Pathway

VaCBL6 from Vitis amurensis Involved in Abiotic Stress Response and ABA-mediated Pathway

Morphological and Proteomic Evaluation of Zea Mays in Response to Osmotic Stress

Introduction: Drought is the main abiotic stress responsible for crop loss worldwide. Maize (Zea mays L.) is a widely grown drought-sensitive crop used as a staple food by the growing population. Therefore, it is imperative to assess the molecular mechanisms behind drought response and tolerance in maize. Transcriptomic profiling of abiotic stress responsive pathways in various crops appeared to be an unreliable approach due to post-transcriptional modifications, while there is limited published data on molecular mechanisms of osmotic-stress response in maize. Hence our study aimed at profiling osmotic stress responsive proteins augmented by their associated morphological features in Z. mays. Materials and Methods: In this regard, morphological and proteomic investigations were carried out on 16-day maize seedlings exposed to 5% (w/v) and 10% (w/v) polyethylene glycol(PEG) to induce osmotic-stress. Proteomics approach (one-dimensional (1D) and two-dimensional (2D) gel electrophoresis) compared differential protein abundance between controls and the osmotic stressed maize plants. Results: Morphological parameters such as plant growth, height, shoot diameter, leaf area, and colour were highly affected with PEG treatment as compared to the untreated ones. Molecular evaluation by 1D gel electrophoresis revealed that the separated protein patterns were highly expressed in the experiments than the controls. Using 2D gel electrophoresis, a total of seven and eight protein spots were revealed in experimental plants under 5% (w/v) and 10% (w/v) PEG treatment respectively while the control plants only expressed one protein. Increased drought stress resulted in a greater number of proteins with differential abundance. Conclusion: This study has successfully profiled the total osmotic stress responsive proteins and revealed the efficiency of proteomic tools in the qualitative detection of differential proteins from maize.

Genome-wide identification, characterisation, and evolution of ABF/AREB subfamily in nine Rosaceae species and expression analysis in mei (Prunus mume).

Rosaceae is an important family containing some of the highly evolved fruit and ornamental plants. Abiotic stress responses play key roles in the seasonal growth and development of plants. However, the molecular basis of stress responses remains largely unknown in Rosaceae. Abscisic acid (ABA) is a stress hormone involving abiotic stress response pathways. The ABRE-binding factor/ABA-responsive element-binding protein (ABF/AREB) is a subfamily of the basic domain/leucine zipper (bZIP) transcription factor family. It plays an important role in the ABA-mediated signaling pathway. Here, we analyzed the ABF/AREB subfamily genes in nine Rosaceae species. A total of 64 ABF/AREB genes were identified, including 18, 28, and 18 genes in the Rosoideae, Amygdaloideae, and Maloideae traditional subfamilies, respectively. The evolutionary relationship of the ABF/AREB subfamily genes was studied through the phylogenetic analysis, the gene structure and conserved motif composition, Ka/Ks values, and interspecies colinearity. These gene sets were clustered into four groups. In the Prunus ABF/AREB (PmABF) promoters, several cis-elements related to light, hormone, and abiotic stress response were predicted. PmABFs expressed in five different tissues, except PmABF5, which expressed only in buds. In the dormancy stages, PmABF1, 2, 5 and 7 showed differential expression. The expression of PmABF3, 4 and 6 was positively correlated with the ABA concentration. Except for PmABF5, all the PmABFs were sensitive to ABA. Several ABRE elements were contained in the promoters of PmABF1, 3, 6, 7. Based on the findings of our study, we speculate that PmABFs may play a role in flower bud dormancy in P. mume.

Transcriptome profiling reveals the effects of drought tolerance in Giant Juncao

BackgroundGiant Juncao is often used as feed for livestock because of its huge biomass. However, drought stress reduces forage production by affecting the normal growth and development of plants. Therefore, investigating the molecular mechanisms of drought tolerance will provide important information for the improvement of drought tolerance in this grass.ResultsA total of 144.96 Gb of clean data was generated and assembled into 144,806 transcripts and 93,907 unigenes. After 7 and 14 days of drought stress, a total of 16,726 and 46,492 differentially expressed genes (DEGs) were observed, respectively. Compared with normal irrigation, 16,247, 23,503, and 11,598 DEGs were observed in 1, 5, and 9 days following rehydration, respectively. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed abiotic stress-responsive genes and pathways related to catalytic activity, methyltransferase activity, transferase activity, and superoxide metabolic process. We also identified transcription factors belonging to several families, including basic helix-loop-helix (bHLH), WRKY, NAM (no apical meristem), ATAF1/2 and CUC2 (cup-shaped cotyledon) (NAC), fatty acyl-CoA reductase (FAR1), B3, myeloblastosis (MYB)-related, and basic leucine zipper (bZIP) families, which are important drought-rehydration-responsive proteins. Weighted gene co-expression network analysis was also used to analyze the RNA-seq data to predict the interrelationship between genes. Twenty modules were obtained, and four of these modules may be involved in photosynthesis and plant hormone signal transduction that respond to drought and rehydration conditions.ConclusionsOur research is the first to provide a more comprehensive understanding of DEGs involved in drought stress at the transcriptome level in Giant Juncao with different drought and recovery conditions. These results may reveal insights into the molecular mechanisms of drought tolerance in Giant Juncao and provide diverse genetic resources involved in drought tolerance research.

Protein Phosphorylation Response to Abiotic Stress in Plants.

Plants are an important part of nature because as photoautotrophs, they provide a nutrient source for many other living organisms. Due to their sessile nature, to overcome both biotic and abiotic stresses, plants have developed intricate mechanisms for perception of and reaction to these stresses, both on an external level (perception) and on an internal level (reaction). Specific proteins found within cells play crucial roles in stress mitigation by enhancing cellular processes that facilitate the plants survival during the unfavorable conditions. Well before plants are able to synthesize nascent proteins in response to stress, proteins which already exist in the cell can be subjected to an array of posttranslation modifications (PTMs) that permit a rapid response. These activated proteins can, in turn, aid in further stress responses. Different PTMs have different functions in growth and development of plants. Protein phosphorylation, a reversible form of modification has been well elucidated, and its role in signaling cascades is well documented. In this mini-review, we discuss the integration of protein phosphorylation with other components of abiotic stress-responsive pathways including phytohormones and ion homeostasis. Overall, this review demonstrates the high interconnectivity of the stress response system in plants and how readily plants are able to toggle between various signaling pathways in order to survive harsh conditions. Most notably, fluctuations of the cytosolic calcium levels seem to be a linking component of the various signaling pathways.

Identification of histone deacetylase genes in Dendrobium officinale and their expression profiles under phytohormone and abiotic stress treatments.

The deacetylation of core histones controlled by the action of histone deacetylases (HDACs) plays an important role in the epigenetic regulation of plant gene transcription. However, no systematic analysis of HDAC genes in Dendrobium officinale, a medicinal orchid, has been performed. In the current study, a total of 14 histone deacetylases in D. officinale were identified and characterized using bioinformatics-based methods. These genes were classified into RPD3/HDA1, SIR2, and HD2 subfamilies. Most DoHDAC genes in the same subfamily shared similar structures, and their encoded proteins contained similar motifs, suggesting that the HDAC family members are highly conserved and might have similar functions. Different cis-acting elements in promoters were related to abiotic stresses and exogenous plant hormones. A transient expression assay in onion epidermal cells by Agrobacterium-mediated transformation indicated that all of the detected histone deacetylases such as DoHDA7, DoHDA9, DoHDA10, DoHDT3, DoHDT4, DoSRT1 and DoSRT2, were localized in the nucleus. A tissue-specific analysis based on RNA-seq suggested that DoHDAC genes play a role in growth and development in D. officinale. The expression profiles of selected DoHDAC genes under abiotic stresses and plant hormone treatments were analyzed by qRT-PCR. DoHDA3, DoHDA8, DoHDA10 and DoHDT4 were modulated by multiple abiotic stresses and phytohormones, indicating that these genes were involved in abiotic stress response and phytohormone signaling pathways. These results provide valuable information for molecular studies to further elucidate the function of DoHDAC genes.

A Rice Immunophilin Homolog, OsFKBP12, Is a Negative Regulator of Both Biotic and Abiotic Stress Responses.

A class of proteins that were discovered to bind the immunosuppressant drug FK506, called FK506-binding proteins (FKBPs), are members of a sub-family of immunophilins. Although they were first identified in human, FKBPs exist in all three domains of life. In this report, a rice FKBP12 homolog was first identified as a biotic stress-related gene through suppression subtractive hybridization screening. By ectopically expressing OsFKBP12 in the heterologous model plant system, Arabidopsis thaliana, for functional characterization, OsFKBP12 was found to increase susceptibility of the plant to the pathogen, Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). This negative regulatory role of FKBP12 in biotic stress responses was also demonstrated in the AtFKBP12-knockout mutant, which exhibited higher resistance towards Pst DC3000. Furthermore, this higher-plant FKBP12 homolog was also shown to be a negative regulator of salt tolerance. Using yeast two-hybrid tests, an ancient unconventional G-protein, OsYchF1, was identified as an interacting partner of OsFKBP12. OsYchF1 was previously reported as a negative regulator of both biotic and abiotic stresses. Therefore, OsFKBP12 probably also plays negative regulatory roles at the convergence of biotic and abiotic stress response pathways in higher plants.

Global profiling of alternative splicing landscape responsive to salt stress in wheat (Triticum aestivum L.)

Alternative splicing (AS) plays crucial roles during plant development especially in stress responses. Although many studies have been performed on AS, the function of which participating in abiotic stress responses is still not well known. To assess the interplay between AS and salt stress, genome-wide analyses of AS were performed. Totally, 11,141 genes were found exhibiting significant AS changes after salt stress treatment, and more AS events were identified in Chinese Spring (CS, salt-sensitive) (21,203) than in Qing Mai 6 (QM, salt-tolerant) (19,742). Meanwhile, wheat homeologous genes displayed differential AS responses under salt stress treatment, and 7235, 8143 and 7407 AS events were identified on subgenome A, B and D respectively. Comparison of AS events at different time after salt stress showed that 4747 and 4129 salt stress responsive AS events were characterized in CS and QM, respectively, and most AS events were induced at 48 h after salt stress (HAS) compared with the other three stages. Functional enrichment analysis found that abiotic stress responsive pathways tended to be enriched in partitioned differentially spliced genes (DSGs) between CS and QM after salt stress treatment, and Pfam classification showed that many stress related proteins were also enriched under salt stress condition. Thus, these results demonstrated that AS regulation may play key roles in response to salt stress, which, together with transcriptional regulation, contributes to abiotic stress tolerance in wheat.

Epigenetic regulation in plant abiotic stress responses.

In eukaryotic cells, gene expression is greatly influenced by the dynamic chromatin environment. Epigenetic mechanisms, including covalent modifications to DNA and histone tails and the accessibility of chromatin, create various chromatin states for stress-responsive gene expression that is important for adaptation to harsh environmental conditions. Recent studies have revealed that many epigenetic factors participate in abiotic stress responses, and various chromatin modifications are changed when plants are exposed to stressful environments. In this review, we summarize recent progress on the cross-talk between abiotic stress response pathways and epigenetic regulatory pathways in plants. Our review focuses on epigenetic regulation of plant responses to extreme temperatures, drought, salinity, the stress hormone abscisic acid, nutrient limitations and ultraviolet stress, and on epigenetic mechanisms of stress memory.

Differential physiological, transcriptomic and metabolomic responses of Arabidopsis leaves under prolonged warming and heat shock

BackgroundElevated temperature as a result of global climate warming, either in form of sudden heatwave (heat shock) or prolonged warming, has profound effects on the growth and development of plants. However, how plants differentially respond to these two forms of elevated temperatures is largely unknown. Here we have therefore performed a comprehensive comparison of multi-level responses of Arabidopsis leaves to heat shock and prolonged warming.ResultsThe plant responded to prolonged warming through decreased stomatal conductance, and to heat shock by increased transpiration. In carbon metabolism, the glycolysis pathway was enhanced while the tricarboxylic acid (TCA) cycle was inhibited under prolonged warming, and heat shock significantly limited the conversion of pyruvate into acetyl coenzyme A. The cellular concentration of hydrogen peroxide (H2O2) and the activities of antioxidant enzymes were increased under both conditions but exhibited a higher induction under heat shock. Interestingly, the transcription factors, class A1 heat shock factors (HSFA1s) and dehydration responsive element-binding proteins (DREBs), were up-regulated under heat shock, whereas with prolonged warming, other abiotic stress response pathways, especially basic leucine zipper factors (bZIPs) were up-regulated instead.ConclusionsOur findings reveal that Arabidopsis exhibits different response patterns under heat shock versus prolonged warming, and plants employ distinctly different response strategies to combat these two types of thermal stress.

Xanthomonas translucens commandeers the host rate-limiting step in ABA biosynthesis for disease susceptibility

Plants are vulnerable to disease through pathogen manipulation of phytohormone levels, which otherwise regulate development, abiotic, and biotic responses. Here, we show that the wheat pathogen Xanthomonas translucens pv. undulosa elevates expression of the host gene encoding 9-cis-epoxycarotenoid dioxygenase (TaNCED-5BS), which catalyzes the rate-limiting step in the biosynthesis of the phytohormone abscisic acid and a component of a major abiotic stress-response pathway, to promote disease susceptibility. Gene induction is mediated by a type III transcription activator-like effector. The induction of TaNCED-5BS results in elevated abscisic acid levels, reduced host transpiration and water loss, enhanced spread of bacteria in infected leaves, and decreased expression of the central defense gene TaNPR1 The results represent an appropriation of host physiology by a bacterial virulence effector.