Introgression of SbERD4 Gene Encodes an Early-Responsive Dehydration-Stress Protein That Confers Tolerance against Different Types of Abiotic Stresses in Transgenic Tobacco

Salicornia brachiata is an extreme halophyte that commonly grows on marsh conditions and is also considered a promising resource for drought and salt-responsive genes. To unveil a glimpse of stress endurance by plants, it is of the utmost importance to develop an understanding of stress tolerance mechanisms. ‘Early Responsive to Dehydration’ (ERD) genes are defined as a group of genes involved in stress tolerance and the development of plants. To increase this understanding, parallel to this expedited thought, a novel SbERD4 gene was cloned from S. brachiata, characterized, and functionally validated in the model plant tobacco. The study showed that SbERD4 is a plasma-membrane bound protein, and its overexpression in tobacco plants improved salinity and osmotic stress tolerance. Transgenic plants showed high relative water, chlorophylls, sugars, starch, polyphenols, proline, free amino acids, and low electrolyte leakage and H2O2 content compared to control plants (wild type and vector control) under different abiotic stress conditions. Furthermore, the transcript expression of antioxidant enzyme encoding genes NtCAT, NtSOD, NtGR, and NtAPX showed higher expression in transgenic compared to wild-type and vector controls under varying stress conditions. Overall, the overexpression of a novel early responsive to dehydration stress protein 4-encoding gene (SbERD4) enhanced the tolerance of the plant against multiple abiotic stresses. In conclusion, the overexpression of the SbERD4 gene mitigates plant physiology by enduring stress tolerance and might be considered as a promising key gene for engineering salinity and drought stress tolerance in crops.

CaPti1/CaERF4 module positively regulates pepper resistance to bacterial wilt disease through coupling enhanced immunity and dehydration tolerance

Bacterial wilt, a severe disease that affects over 250 plant species, is caused by Ralstonia solanacearum through vascular system blockade. Although both plant immunity and dehydration tolerance might contribute to disease resistance, whether and how they are related are still unclear. Herein, we provide evidence that immunity against R. solanacearum and dehydration tolerance are coupled and regulated by CaPti1-CaERF4 module. By expression profiling, virus-induced gene silencing in pepper and overexpression in Nicotiana benthamiana, both CaPti1 and CaERF4 were upregulated by R. solanacearum inoculation, dehydration stress and exogenously applied ABA. They in turn phenocopied with each other in promoting pepper resistance to bacterial wilt not only by activating HR cell death and SA-dependent CaPR1, but also by activating dehydration tolerance related CaOSM1 and CaOSR1, and stomata closure to reduce water loss in ABA signaling dependent manner. Yeast-two hybrid assay showed that CaERF4 interacts with CaPti1, which was confirmed by co-immunoprecipitation and pull-down assays. Chromatin immunoprecipitation and electrophoretic mobility shift assay showed that, upon R. solanacearum inoculation, CaPR1, CaOSM1 and CaOSR1 were directly targeted and positively regulated by CaERF4 via binding GCC-box or DRE-box, which was potentiated by CaPti1. In addition, CaPti1-CaERF4 complex might act downstream ABA signaling, since the exogenously ABA did not alter stomata aperture regulated by CaPti1-CaERF4 module. Importantly, CaPti1-CaERF4 module was found also acts positively in pepper growth and response to dehydration stress. Collectively, the results suggest that immunity and dehydration tolerance are coupled and positively regulated by CaPti1-CaERF4 in pepper plants to enhance resistance against R. solanacearum.

CIN-Like TCP13 is Essential For Plant Growth Regulation Under Dehydration Stress

Plants modulate their shape and growth in response to environmental stress. However, regulatory mechanisms underlying the changes in shape and growth under environmental stress remain elusive. The CINCINNATA (CIN)-like TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP) family of transcription factors (TFs) are key regulators for limiting the growth of leaves through negative effect of auxin response. Here, we report that stress-inducible CIN-like TCP13 plays a key role in inducing morphological changes in leaves and growth regulation in leaves and roots that confer dehydration stress tolerance in Arabidopsis thaliana. Transgenic Arabidopsis plants overexpressing TCP13 ( 35Spro ::TCP13OX ) exhibited leaf rolling, and reduced leaf growth under osmotic stress. The 35Spro:: TCP13OX transgenic leaves showed decreased water loss from leaves, and enhanced dehydration tolerance compared with their control counterparts. Plants overexpressing a chimeric repressor domain SRDX-fused TCP13 ( TCP13pro ::TCP13SRDX ) showed severely serrated leaves and enhanced root growth. Transcriptome analysis of TCP13pro ::TCP13SRDX transgenic plants revealed that TCP13 affects the expression of dehydration- and abscisic acid (ABA)-regulated genes. TCP13 is also required for the expression of dehydration-inducible auxin-regulated genes, INDOLE-3-ACETIC ACID5 ( IAA5 ) and LATERAL ORGAN BOUNDARIES ( LOB) DOMAIN 1 ( LBD1 ). Furthermore, tcp13 knockout mutant plants showed ABA-insensitive root growth and reduced dehydration-inducible gene expression. Our findings provide new insight into the molecular mechanism of CIN-like TCP that is involved in both auxin and ABA response under dehydration stress.

Genome-wide analysis of HSP70 gene superfamily in Pyropia yezoensis (Bangiales, Rhodophyta): identification, characterization and expression profiles in response to dehydration stress

Background Heat shock proteins (HSPs) perform a fundamental role in protecting plants against abiotic stresses. Individual family members have been analyzed in previous studies, but there has not yet been a comprehensive analysis of the HSP70 gene family in Pyropia yezoensis. Results We investigated 15 putative HSP70 genes in Py. yezoensis. These genes were classified into two sub-families, denoted as DnaK and Hsp110. In each sub-family, there was relative conservation of the gene structure and motif. Synteny-based analysis indicated that seven and three PyyHSP70 genes were orthologous to HSP70 genes in Pyropia haitanensis and Porphyra umbilicalis, respectively. Most PyyHSP70s showed up-regulated expression under different degrees of dehydration stress. PyyHSP70-1 and PyyHSP70-3 were expressed in higher degrees compared with other PyyHSP70s in dehydration treatments, and then expression degrees somewhat decreased in rehydration treatment. Subcellular localization showed PyyHSP70-1-GFP and PyyHSP70-3-GFP were in the cytoplasm and nucleus/cytoplasm, respectively. Similar expression patterns of paired orthologs in Py. yezoensis and Py. haitanensis suggest important roles for HSP70s in intertidal environmental adaptation during evolution. Conclusions These findings provide insight into the evolution and modification of the PyyHSP70 gene family and will help to determine the functions of the HSP70 genes in Py. yezoensis growth and development.

DNA methylation-mediated modulation of rapid desiccation tolerance acquisition and dehydration stress memory in the resurrection plant Boea hygrometrica

Pre-exposure of plants to various abiotic conditions confers improved tolerance to subsequent stress. Mild drought acclimation induces acquired rapid desiccation tolerance (RDT) in the resurrection plant Boea hygrometrica, but the mechanisms underlying the priming and memory processes remain unclear. In this study, we demonstrated that drought acclimation-induced RDT can be maintained for at least four weeks but was completely erased after 18 weeks based on a combination of the phenotypic and physiological parameters. Global transcriptome analysis identified several RDT-specific rapid dehydration-responsive genes related to cytokinin and phospholipid biosynthesis, nitrogen and carbon metabolism, and epidermal morphogenesis, most of which were pre-induced by drought acclimation. Comparison of whole-genome DNA methylation revealed dehydration stress-responsive hypomethylation in the CG, CHG, and CHH contexts and acclimation-induced hypermethylation in the CHH context of the B. hygrometrica genome, consistent with the transcriptional changes in methylation pathway genes. As expected, the global promoter and gene body methylation levels were negatively correlated with gene expression levels in both acclimated and dehydrated plants but showed no association with transcriptional divergence during the procedure. Nevertheless, the promoter methylation variations in the CG and CHG contexts were significantly associated with the differential expression of genes required for fundamental genetic processes of DNA conformation, RNA splicing, translation, and post-translational protein modification during acclimation, growth, and rapid dehydration stress response. It was also associated with the dehydration stress-induced upregulation of memory genes, including pre-mRNA-splicing factor 38A, vacuolar amino acid transporter 1-like, and UDP-sugar pyrophosphorylase, which may contribute directly or indirectly to the improvement of dehydration tolerance in B. hygrometrica plants. Altogether, our findings demonstrate the potential implications of DNA methylation in dehydration stress memory and, therefore, provide a molecular basis for enhanced dehydration tolerance in plants induced by drought acclimation.

Dissecting the Roles of Cuticular Wax in Plant Resistance to Shoot Dehydration and Low-Temperature Stress in Arabidopsis

Cuticular waxes are a mixture of hydrophobic very-long-chain fatty acids and their derivatives accumulated in the plant cuticle. Most studies define the role of cuticular wax largely based on reducing nonstomatal water loss. The present study investigated the role of cuticular wax in reducing both low-temperature and dehydration stress in plants using Arabidopsis thaliana mutants and transgenic genotypes altered in the formation of cuticular wax. cer3-6, a known Arabidopsis wax-deficient mutant (with distinct reduction in aldehydes, n-alkanes, secondary n-alcohols, and ketones compared to wild type (WT)), was most sensitive to water loss, while dewax, a known wax overproducer (greater alkanes and ketones compared to WT), was more resistant to dehydration compared to WT. Furthermore, cold-acclimated cer3-6 froze at warmer temperatures, while cold-acclimated dewax displayed freezing exotherms at colder temperatures compared to WT. Gas Chromatography-Mass Spectroscopy (GC-MS) analysis identified a characteristic decrease in the accumulation of certain waxes (e.g., alkanes, alcohols) in Arabidopsis cuticles under cold acclimation, which was additionally reduced in cer3-6. Conversely, the dewax mutant showed a greater ability to accumulate waxes under cold acclimation. Fourier Transform Infrared Spectroscopy (FTIR) also supported observations in cuticular wax deposition under cold acclimation. Our data indicate cuticular alkane waxes along with alcohols and fatty acids can facilitate avoidance of both ice formation and leaf water loss under dehydration stress and are promising genetic targets of interest.