Drought Stress-responsive Genes Research Articles

Development of Gene-Based InDel Markers on Putative Drought Stress-Responsive Genes and Genetic Diversity of Durian (Durio zibethinus).

Insertion-deletion (InDel) markers are co-dominant, relatively abundant and practical for agarose gel genotyping. InDel polymorphism usually affects gene functions. Nucleotide sequences of durian (Durio zibethinus) are available, but InDel makers have not been well established. This study aimed to develop drought-related gene-based InDel markers for durian through bioinformatic analysis of RNA-Seq datasets. The polymorphism of the markers was verified in 24 durian genotypes local to Thailand. Bioinformatic analysis indicated 496 InDel loci having lengths more than 9bp. To evaluate these InDel markers, 15 InDel loci were selected. Nine markers were successfully amplified a clear polymorphic band pattern on 2% agarose gel. The polymorphic information content (PIC) of these nine markers ranged from 0.1103 to 0.5808. The genetic distance between the 24 genotypes ranged from 0.222 to 0.889. The phylogeny based on the nine InDel loci distinguished the 24 genotypes and divided samples into four groups. This set of gene-based InDel markers on putative drought-responsive genes will be useful for genetic studies.

Exogenous melatonin induces salt and drought stress tolerance in rice by promoting plant growth and defense system

Due to global climate change, crops are certainly confronted with a lot of abiotic and biotic stress factors during their growth that cause a serious threat to their development and overall productivity. Among different abiotic stresses, salt and drought are considered the most devastating stressors with serious impact on crop’s yield stability. Here, the current study aimed to elucidate how melatonin works in regulating plant biomass, oxidative stress, antioxidant defense system, as well as the expression of genes related to salt and drought stress in rice plants. Eight groups of rice plants (3 replicates, 5 plants each) underwent varied treatments: control, melatonin, salt, drought, salt + drought, salt + melatonin, drought + melatonin, and salt + drought + melatonin. Melatonin (100 µM) was alternately applied a week before stress exposure; salt stress received 100 mM NaCl every 3 days for 3 weeks, and drought stress involved 10% PEG. Young leaves were randomly sampled from each group. The results showed that melatonin treatment markedly reduces salt and drought stress damage by promoting root, shoot length, fresh and dry weight, increasing chlorophyll contents, and inhibiting excessive production of oxidative stress markers. Salt and drought stress significantly decreased the water balance, and damaged cell membrane by reducing relative water contents and increasing electrolyte leakage. However, melatonin treated rice plants showed high relative water contents and low electrolyte leakage. Under salt and drought stress conditions, exogenous application of melatonin boosted the expression level of salt and drought stress responsive genes like OsSOS, OsNHX, OsHSF and OsDREB in rice plants. Taken together, our results reveal that melatonin treatment significantly increases salt and drought tolerance of rice plants, by increasing plant biomass, suppressing ROS accumulation, elevating antioxidants defense efficiency, and up-regulating the expression of salt and drought stress responsive genes.

Genome-Wide Identification of the Trihelix Transcription Factor Family and Functional Analysis of the Drought Stress-Responsive Genes in Melilotus albus.

The trihelix gene family is a plant-specific family of transcription factors that play an important role in many metabolic pathways, including plant growth and development and stress responses. Drought stress is a major factor limiting the distribution and yield of Melilotus albus. However, the distribution of this gene family in M. albus and its biological functions in response to drought stress have not been reported. To investigate the responses of functional genes to drought stress in M. albus, in this study, a total of 34 MaGTs were identified and characterized, of which 32 MaGT proteins were predicted to be nuclear-localized. Based on conserved motif and phylogenetic analyses, the MaGTs could be divided into five subgroups (GT-1, GT-2, SH4, GT-γ, SIP1). Seven potential candidate genes for drought tolerance were screened and identified via qRT-PCR based on a transcriptome data analysis of drought stress in M. albus. The results indicated that MaGT17 was not only significantly upregulated in the roots after 24 h of drought stress, but also showed a significant induction in the shoots. This finding further confirms that MaGT17 is capable of responding to drought stress in M. albus. Taken together, these results will offer essential insights for understanding the underlying molecular mechanisms of the trihelix proteins and useful data for further research on the growth, development and stress responses of trihelix proteins in M. albus.

OsCM regulates rice defence system in response to UV light supplemented with drought stress.

Studies on plant responses to combined abiotic stresses are very limited, especially in major crop plants. The current study evaluated the response of chorismate mutase overexpressor (OxCM) rice line to combined UV light and drought stress. The experiments were conducted in pots in a growth chamber, and data were assessed for gene expression, antioxidant and hormone regulation, flavonoid accumulation, phenotypic variation, and amino acid accumulation. Wild-type (WT) rice had reduced the growth and vigour, while transgenic rice maintained growth and vigour under combined UV light and drought stress. ROS and lipid peroxidation analysis revealed that chorismate mutase (OsCM) reduced oxidative stress mediated by ROS scavenging and reduced lipid peroxidation. The combined stresses reduced biosynthesis of total flavonoids, kaempferol and quercetin in WT plants, but increased significantly in plants with OxCM. Phytohormone analysis showed that SA was reduced by 50% in WT and 73% in transgenic plants, while ABA was reduced by 22% in WT plants but increased to 129% in transgenic plants. Expression of chorismate mutase regulates phenylalanine biosynthesis, UV light and drought stress-responsive genes, e.g., phenylalanine ammonia lyase (OsPAL), dehydrin (OsDHN), dehydration-responsive element-binding (OsDREB), ras-related protein 7 (OsRab7), ultraviolet-B resistance 8 (OsUVR8), WRKY transcription factor 89 (OsWRKY89) and tryptophan synthase alpha chain (OsTSA). Moreover, OsCM also increases accumulation of free amino acids (aspartic acid, glutamic acid, leucine, tyrosine, phenylalanine and proline) and sodium (Na), potassium (K), and calcium (Ca) ions in response to the combined stresses. Together, these results suggest that chorismate mutase expression induces physiological, biochemical and molecular changes that enhance rice tolerance to combined UV light and drought stresses.

DEAD-box RNA helicase 6 regulates drought and abscisic acid stress responses in rapeseed (Brassica napus)

DEAD-box RNA helicase is a major subfamily of RNA helicases with vital roles played in plant growth, development, and plant-environment interactions. RNA helicase 6 in rapeseed (Brassica napus) (BnRH6) is a member of DEAD-box RNA helicase. While previous research has demonstrated the role of BnRH6 in salt stress regulation, the involvement of BnRH6 in drought stress adaptation remains unknown. This report described a function of BnRH6 in drought stress response. BnRH6 was sufficiently induced by osmotic stress. Transgenic Brassica napus and Arabidopsis thaliana (Arabidopsis) overexpressing BnRH6 (OE) showed a drought tolerance phenotype, characterized by improved plant growth, increased survival rates, reduced water loss, leaf chlorosis and oxidative stress. Furthermore, BnRH6 was also induced by exogenous abscisic acid (ABA). BnRH6 overexpression plants exhibited ABA hypersensitivity with lagging seed germination, growth stunt and diminished stomatal opening in the presence of ABA, suggesting the involvement of ABA signal. Assessment of several well-identified drought stress responsive genes such as Calcium-dependent Protein Kinase 14 (BnCDPK14), Enhanced Response to ABA1 (BnERA1) and ABA Insensitive 1 (BnABI1) revealed that their expressions were accordingly changed in BnOE plants, possibly with interplays between BnRH6 and those genes. Our data highlighted the functional role of BnRH6, which plays a positive role in active regulation of drought stress response likely through an ABA-dependent manner in rapeseed plants.

The physiology of drought stress in two grapevine cultivars: Photosynthesis, antioxidant system, and osmotic regulation responses.

Drought stress impedes viticultural plant growth and development by modifying various metabolic pathways. However, the regulatory network response underlying drought stress is not yet clear. In this study, the leaves and roots of "Shine Muscat" ("SM," Vitis labruscana × Vitis vinifera) and "Thompson Seedless" ("TS," V. vinifera L. cv.) were subjected to drought stress to study the regulatory network used by drought stress. Morphophysiological results showed that the malondialdehyde content after 28 days of drought stress increased more significantly in "TS" than "SM."Furthermore, the multiomics analysis studies showed that a total of 3036-6714 differentially expressed genes and 379-385 differentially abundant metabolites were identified in "SM" and "TS" grapevine cultivars under drought stress. Furthermore, the retained intron was the major form of differential alternative splicing event under drought stress. The photosynthesis pathway, antioxidant system, plant hormone signal transduction, and osmotic adjustment were the primary response systems in the two grapevine cultivars under drought stress. We have identified GRIK1, RFS2, and LKR/SDH as the hub genes in the coexpression network of drought stress. In addition, the difference in the accumulation of pheophorbide-a reveals different drought resistance mechanisms in the two grapevine cultivars. Our study explained the difference in drought response between cultivars and tissues and identified drought stress-responsive genes, which provides reference data for further understanding the regulatory network of drought tolerance in grapevine.

A module centered on the transcription factor Msn2 from arbuscular mycorrhizal fungus Rhizophagus irregularis regulates drought stress tolerance in the host plant.

Arbuscular mycorrhizal (AM) fungi can form mutualistic endosymbiosis with > 70% of land plants for obtaining fatty acids and sugars, in return, AM fungi promote plant nutrients and water acquisition to enhance plant fitness. However, how AM fungi orchestrate its own signaling components in response to drought stress remains elusive. Here, we identify a transcription factor containing C2H2 zinc finger domains, RiMsn2 from Rhizophagus irregularis. To characterize the RiMsn2, we combined heterologous expression, subcellular localization in yeasts, and biochemical and molecular studies with reverse genetics approaches during the in planta phase. The results indicate that RiMsn2 is highly conserved across AM fungal species and induced during the early stages of symbiosis. It is significantly upregulated in mycorrhizal roots under severe drought conditions. The nucleus-localized RiMsn2 regulates osmotic homeostasis and trehalose contents of yeasts. Importantly, gene silencing analyses indicate that RiMsn2 is essential for arbuscule formation and enhances plant tolerance to drought stress. Results from yeasts and biochemical experiments suggest that the RiHog1-RiMsn2-STREs module controls the drought stress-responsive genes in AM fungal symbiont. In conclusion, our findings reveal that a module centered on the transcriptional activator RiMsn2 from AM fungus regulates drought stress tolerance in host plant.

Transcriptome Analysis of Pecan (Carya illinoinensis) Differentially Expressed Genes in Response to Drought Stress

Pecan (Carya illinoinensis) is an economically important nut tree that is greatly affected by drought, limiting its production and distribution. Although the complete genome of the pecan was published several years ago, the molecular basis of the pecan’s response to drought remains unclear. In this study, we analyzed the high-throughput transcriptome data for pecans under 3, 6, 9, 12, and 15 days of drought stress compared with the controls. A total of 12,893 differentially expressed genes (DEGs) were identified under drought stress, with 11,684 of them showing significant changes after 15 d of drought treatment. Among these, 4448 genes were up-regulated while 7226 were down-regulated. The trend analysis revealed that DEGs could be classified into 20 clusters. Surprisingly, the majority of genes (6148) showed a gradual down-regulation, and 3683 genes showed a gradual up-regulation in response to drought. Gene ontology enrichment analysis showed that the DEGs were mainly enriched in biological processes. The KEGG pathway enrichment results indicated that the DEGs were mainly enriched in several pathways, including metabolic pathways, the biosynthesis of secondary metabolites, and plant hormone signal transduction processes. Among the DEGs, 457 protein kinase and 734 transcription factor genes were shown to be drought-responsive and may play key roles in the response to drought, and the expression patterns of selected candidate genes were further validated using quantitative real-time PCR. Collectively, these findings highlighted the multiple processes in pecans under drought stress and provided valuable insights into the further investigation of the functions of drought stress-responsive genes and the molecular basis of the pecan drought stress response.

Transcriptome Identification of R2R3-MYB Gene Family Members in Pinus massoniana and PmMYB4 Response to Drought Stress

One of the largest families of transcription factors in plants, the MYB transcription factors family (Myeloblastosis, MYB TF), plays a vital role in regulating plant biochemical and physiological processes. The role of MYB TF in coping with stresses, such as drought, salt and cold, has been reported. Unfortunately, a comprehensive identification of R2R3-MYB TF in Masson pine (Pinus massoniana) has not been achieved. In this study, a total of 49 sequences were identified as R2R3-MYB TF. The structure, function and phylogenetic relationships of the conserved structural domains of Masson pine R2R3-MYB TF and Populus trichocarpa Torr. & A.Gray ex Hook. TFs were compared using bioinformatics tools. The results showed that Masson pine R2R3-MYB TF was divided into 24 groups, mainly located in the nucleus, and mostly lacking signal peptides and transmembrane structural domains with multiple phosphorylation sites. The drought stress-responsive R2R3-MYB gene, PmMYB4, was selected from the drought stress transcriptome based on analysis of the expression pattern and tissue specificity of PmMYB4 gene under abiotic stress using qPCR. The results showed that PmMYB4 can be involved in drought stress treatment through ABA signaling, as well as in multiple stress responses such as salt stress, and there were significant differences in the expression of PmMYB4 in the eight tissues. These results provide a reference scheme for the functional identification of R2R3-MYB transcription factors, which may be involved in plant responses to multiple stresses such as drought, and enrich our understanding of the functions of R2R3-MYB transcription factors in plants.

Analysis of G-Quadruplex-Forming Sequences in Drought Stress-Responsive Genes, and Synthesis Genes of Phenolic Compounds in Arabidopsis thaliana.

Sequences of nucleic acids with the potential to form four-stranded G-quadruplex structures are intensively studied mainly in the context of human diseases, pathogens, or extremophile organisms; nonetheless, the knowledge about their occurrence and putative role in plants is still limited. This work is focused on G-quadruplex-forming sites in two gene sets of interest: drought stress-responsive genes, and genes related to the production/biosynthesis of phenolic compounds in the model plant organism Arabidopsis thaliana. In addition, 20 housekeeping genes were analyzed as well, where the constitutive gene expression was expected (with no need for precise regulation depending on internal or external factors). The results have shown that none of the tested gene sets differed significantly in the content of G-quadruplex-forming sites, however, the highest frequency of G-quadruplex-forming sites was found in the 5'-UTR regions of phenolic compounds' biosynthesis genes, which indicates the possibility of their regulation at the mRNA level. In addition, mainly within the introns and 1000 bp flanks downstream gene regions, G-quadruplex-forming sites were highly underrepresented. Finally, cluster analysis allowed us to observe similarities between particular genes in terms of their PQS characteristics. We believe that the original approach used in this study may become useful for further and more comprehensive bioinformatic studies in the field of G-quadruplex genomics.

Assessment of drought stress responsive genes expression profiles and proline accumulation in a diverse set of grapevine rootstocks

In order to study plant responses to drought stress, it is important to have markers for such responses. This issue has been a challenge for decades and numerous traits have been used for this purpose. In the current study, the influence of drought stress on proline biosynthesis, leaf water potential, and also gene expression levels of 10 genes probably involved in drought stress response regulation pathways were investigated. Also, all experiments were performed in both root and leaf tissues of studied rootstocks to investigate the response of plant tissues which is more suitable for the assessment of possible markers. As a result of the study, the highest percentage of proline increase in leaf and root tissues was mostly observed in susceptible rootstocks. The leaf water potential (-MPa) measurements showed the most decrease in leaf water potential values in highly tolerant rootstocks, so the maximum differences between control and drought stress treated plants were determined in SO4, 140Ru, 1045, and 44-53M rootstocks, respectively. Gene expression levels of HAT5, RAP2-4, WRKY23, GRP, GDH, PRP2, GAS2, PD2, STPK, and genes were described in 18 different grapevine rootstocks and it was concluded that the root samples indicating more significant gene expression changes, could be more informative than leaf samples.

Heterologous expression of the TaPI-PLC1-2B gene enhanced drought and salt tolerance in transgenic rice seedlings.

Drought and salt stress are important factors that affect plant growth and development and cause crop yield reductions worldwide. Phospholipase C is a class of enzymes that can hydrolyze phospholipids, and it has been shown to play an important role in plant growth regulation and stress response. We used rice as a model to investigate the function of the wheat TaPI-PLC1-2B gene in salt and drought tolerance. For this purpose, we heterologously expressed the TaPI-PLC1-2B gene in rice and studied the transcriptional differences in transgenic and wide-type rice plants in the presence and absence of drought and salt stress. Our results showed that 2130 and 1759 genes expressed differentially in the TaPI-PLC1-2B overexpression rice line under salt and drought stress, respectively. Gene ontology enrichment results showed that differentially expressed genes (DEGs) were significantly enriched in cellular process, metabolic process, stimulus-response, cell, organelle, catalytic activity, and other functional processes under salt and drought stress. In addition, the Kyoto Encyclopedia of Genes and Genomes pathway analysis showed DEG enrichment in plant-pathogen interaction, phosphoinositol, plant hormones, and other signaling pathways under the two stress treatments. Furthermore, the chromosomal localization of salt and drought stress-responsive DEGs showed a clear distribution pattern on specific rice chromosomes. For instance, the greatest number of drought stress-responsive genes mapped to rice chromosomes 1 and 6. The current analysis has built the basis for future explorations to decipher the TaPI-PLC1-2B-mediated plant stress response mechanism in the relatively challenging wheat system.

Genome-Wide Identification of ERF Transcription Factor Family and Functional Analysis of the Drought Stress-Responsive Genes in Melilotus albus.

As an important forage legume with high values in feed and medicine, Melilotus albus has been widely cultivated. The AP2/ERF transcription factor has been shown to play an important regulatory role in plant drought resistance, but it has not been reported in the legume forage crop M. albus. To digger the genes of M. albus in response to drought stress, we identified and analyzed the ERF gene family of M. albus at the genome-wide level. A total of 100 MaERF genes containing a single AP2 domain sequence were identified in this study, named MaERF001 to MaERF100, and bioinformatics analysis was performed. Collinearity analysis indicated that segmental duplication may play a key role in the expansion of the M. albus ERF gene family. Cis-acting element predictions suggest that MaERF genes are involved in various hormonal responses and abiotic stresses. The expression patterns indicated that MaERFs responded to drought stress to varying degrees. Furthermore, four up-regulated ERFs (MaERF008, MaERF037, MaERF054 and MaERF058) under drought stress were overexpressed in yeast and indicated their biological functions to confer the tolerance to drought. This work will advance the understanding of the molecular mechanisms underlying the drought response in M. albus. Further study of the promising potential candidate genes identified in this study will provide a valuable resource as the next step in functional genomics studies and improve the possibility of improving drought tolerance in M. albus by transgenic approaches.

Production and characterization of a novel interspecific somatic hybrid combining drought tolerance and high quality of sweet potato and Ipomoea triloba L.

A novel interspecific somatic hybrid combining drought tolerance and high quality of sweet potato and Ipomoea triloba L. was obtained and its genetic and epigenetic variations were studied. Somatic hybridization can be used to overcome the cross-incompatibility between sweet potato (Ipomoea batatas (L.) Lam.) and its wild relatives and transfer useful and desirable genes from wild relatives to cultivated plants. However, most of the interspecific somatic hybrids obtained to date cannot produce storage roots and do not exhibit agronomic characters. In the present study, a novel interspecific somatic hybrid, named XT1, was obtained through protoplast fusion between sweet potato cv. Xushu 18 and its wild relative I. triloba. This somatic hybrid produced storage roots and exhibited significantly higher drought tolerance and quality compared with its cultivated parent Xushu 18. Transcriptome and real-time quantitative PCR (qRT-PCR) analyses revealed that the well-known drought stress-responsive genes in XT1 and I. triloba were significantly up-regulated under drought stress. The genomic structural reconstructions between the two genomes of the fusion parents in XT1 were confirmed using genomic in situ hybridization (GISH) and specific nuclear and cytoplasmic DNA markers. The DNA methylation variations were characterized by methylation-sensitive amplified polymorphism (MSAP). This study not only reveals the significance of somatic hybridization in the genetic improvement of sweet potato but also provides valuable materials and knowledge for further investigating the mechanism of storage root formation in sweet potato.

H3K36 demethylase JMJ710 negatively regulates drought tolerance by suppressing MYB48-1 expression in rice.

The homeostasis of histone methylation is maintained by histone methyltransferases and demethylases, which are important for the regulation of gene expression. Here, we report a histone demethylase from rice (Oryza sativa), Jumonji C domain-containing protein (JMJ710), which belongs to the JMJD6 group and plays an important role in the response to drought stress. Overexpression of JMJ710 causes a drought-sensitive phenotype, while RNAi and clustered regularly interspaced short palindromic repeats (CRISPR)-knockout mutant lines show drought tolerance. In vitro and in vivo assays showed that JMJ710 is a histone demethylase. It targets to MYB TRANSCRIPTION FACTOR 48 (MYB48-1) chromatin, demethylates H3K36me2, and negatively regulates the expression of MYB48-1, a positive regulator of drought tolerance. Under drought stress, JMJ710 is downregulated and the expression of MYB48-1 increases, and the subsequent activation of its downstream drought-responsive genes leads to drought tolerance. This research reports a negative regulator of drought stress-responsive genes, JMJ710, that ensures that the drought tolerance mechanism is not mis-activated under normal conditions but allows quick activation upon drought stress.

Plant growth-promoting rhizobacteria Shewanella putrefaciens and Cronobacter dublinensis enhance drought tolerance of pearl millet by modulating hormones and stress-responsive genes.

Drought is a major abiotic stress that affects crop productivity. Endophytic bacteria have been found to alleviate the adverse effects of drought on plants. In the present study, we evaluated the effects of two endophytic bacteria Shewanella putrefaciens strain MCL-1 and Cronobacter dublinensis strain MKS-1 on pearl millet (Pennisetum glaucum (L.) R. Br.) under drought stress conditions. Pearl millet plants were grown under three water levels: field capacity (FC), mild drought stress (MD), and severe drought stress (SD). The effects of inoculation on plant growth, physiological attributes, phytohormone content, and drought stress-responsive genes were assessed. The inoculation of pearl millet seeds with endophytes significantly improved shoot and root dry weight and root architecture of plants grown under FC and drought stress conditions. There was a significant increase in relative water content and proline accumulation in the inoculated plants. Among the phytohormones analyzed, the content of ABA and IAA was significantly higher in endophyte-treated plants under all moisture regimes than in uninoculated plants. C. dublinensis-inoculated plants had higher GA content than uninoculated plants under all moisture regimes. The expression level of genes involved in phytohormone biosynthesis (SbNCED, SbGA20oX, and SbYUC) and coding drought-responsive transcription factors (SbAP2, SbSNAC1 and PgDREB2A) was significantly higher under SD in endophyte-inoculated plants than in uninoculated plants. Thus, these endophytic bacteria presumably enhanced the tolerance of pearl millet to drought stress by modulating root growth, plant hormones, physiology and the expression of genes involved in drought tolerance.

Exogenous citric acid enhances drought tolerance in tobacco (Nicotiana tabacum).

Organic acids play a pivotal role in improving plant response to long-term drought stress. External application of organic acids has been reported to improve drought resistance in several species. However, whether organic acids have similar effects in tobacco remains unknown. A screening study of the protective function of organic acids in tobacco and understanding the underlying molecular mechanism would be useful in developing a strategy for drought tolerance. Several physiological and molecular adaptations to drought including abscisic acid, stomatal closure, reactive oxygen species homeostasis, amino acid accumulation, and drought-responsive gene expression were observed by exogenous citric acid in tobacco plants. Exogenous application of 50 mm citric acid to tobacco plants resulted in higher chlorophyll content, net photosynthesis, relative water content, abscisic acid content and lower stomatal conductance, transpiration and water loss under drought conditions. Moreover, reactive oxygen species homeostasis was better maintained through increasing activity of antioxidant enzymes and decreasing hydrogen peroxide content after citric acid pretreatment under drought. Amino acids involved in the TCA cycle accumulated after external application of citric acid under drought stress. Furthermore, several drought stress-responsive genes also dramatically changed after application of citric acid. These data support the idea that external application of citric acid enhances drought resistance by affecting physiological and molecular regulation in tobacco. This study provides clear insights into mechanistic details of regulation of amino acid and stress-responsive gene expression by citric acid in tobacco in response to drought, which is promising for minimizing growth inhibition in agricultural fields.

Gateway cloning and in-planta transformation of drought stress responsive Ecmyb1 gene isolated from Eleusine coracana var.PRM 6107

Drought is one of the key abiotic stress that critically influences the crops by restraining their growth and yield potential. Being sessile, plants tackle the detrimental effects of drought stress via modulating the cellular state by changing the gene expression. Such alteration of gene expression is essentially driven by the transcriptional syndicate. Transcription factors (TF) are the key regulatory protein that controls the expression of their target gene by binding to the cis-regulatory elements present in the promoter region. Myb-TFs ubiquitously present in all eukaryotes belong to one of the largest TF family, and play wide array of biological functions in plants including anthocyanin biosynthesis, vasculature system, cell signaling, seed maturation and abiotc stress responses. In the present study the full length Myb TF from Eleusine corocana was subcloned using Gateway cloning system and further transformed into Arabidopsis thaliana through floral dip method. Transgenic Arabidopsis thaliana plants harbouring Ecmyb1 gene were screened and grown in transgenic glasshouse under controlled conditions.

Overexpression of AtBBD1, Arabidopsis Bifunctional Nuclease, Confers Drought Tolerance by Enhancing the Expression of Regulatory Genes in ABA-Mediated Drought Stress Signaling.

Drought is the most serious abiotic stress, which significantly reduces crop productivity. The phytohormone ABA plays a pivotal role in regulating stomatal closing upon drought stress. Here, we characterized the physiological function of AtBBD1, which has bifunctional nuclease activity, on drought stress. We found that AtBBD1 localized to the nucleus and cytoplasm, and was expressed strongly in trichomes and stomatal guard cells of leaves, based on promoter:GUS constructs. Expression analyses revealed that AtBBD1 and AtBBD2 are induced early and strongly by ABA and drought, and that AtBBD1 is also strongly responsive to JA. We then compared phenotypes of two AtBBD1-overexpression lines (AtBBD1-OX), single knockout atbbd1, and double knockout atbbd1/atbbd2 plants under drought conditions. We did not observe any phenotypic difference among them under normal growth conditions, while OX lines had greatly enhanced drought tolerance, lower transpirational water loss, and higher proline content than the WT and KOs. Moreover, by measuring seed germination rate and the stomatal aperture after ABA treatment, we found that AtBBD1-OX and atbbd1 plants showed significantly higher and lower ABA-sensitivity, respectively, than the WT. RNA sequencing analysis of AtBBD1-OX and atbbd1 plants under PEG-induced drought stress showed that overexpression of AtBBD1 enhances the expression of key regulatory genes in the ABA-mediated drought signaling cascade, particularly by inducing genes related to ABA biosynthesis, downstream transcription factors, and other regulatory proteins, conferring AtBBD1-OXs with drought tolerance. Taken together, we suggest that AtBBD1 functions as a novel positive regulator of drought responses by enhancing the expression of ABA- and drought stress-responsive genes as well as by increasing proline content.

Molecular, chemical, and physiological analyses of sorghum leaf wax under post-flowering drought stress

Wax accumulation on the sorghum surface plays an important role in drought tolerance by preventing non-stomatal water loss. Thereby, the effect of post-flowering drought stress (PFDS) on the epicuticular wax (EW) amount, relative water content (RWC), chlorophyll, and grain yield in sorghum drought contrasting genotypes were investigated. The experiment was conducted as a split-plot based on randomized complete block design (RCBD) with two water treatments (normal watering and water holding after 50% flowering stage), and three genotypes (Kimia and KGS23 as drought-tolerant and Sepideh as drought-susceptible). Scanning electron microscopy and GC-MS analyses were used to determine the wax crystals density and its compositions, respectively. In addition, based on literature reviews and publicly available datasets, six wax biosynthesis drought stress-responsive genes were chosen for expression analysis. The results showed that the amounts of EW and wax crystals density were increased in Kimia and Sepideh genotypes and no changed in KGS23 genotype under drought stress. Chemical compositions of wax were classified into six major groups including alkanes, fatty acids, aldehydes, esters, alcohols, and cyclic compounds. Alkanes increment in drought-tolerant genotypes led to make an effective barrier against the drought stress to control water losses. In addition, the drought-tolerant genotypes had higher levels of RWC compared to the drought-susceptible ones, resulted in higher yield produced under drought condition. According to the results, SbWINL1, FATB, and CER1 genes play important roles in drought-induced wax biosynthesis. The results of the present study revealed a comprehensive view of the wax and its compositions and some involved genes in sorghum under drought stress.