Response of Wheat DREB Transcription Factor to Osmotic Stress Based on DNA Methylation

Dehydration-responsive element-binding protein (DREB) plays an important role in response to osmotic stress. In this study, DREB2, DREB6 and Wdreb2 are isolated from wheat AK58, yet they belong to different types of DREB transcription factors. Under osmotic stress, the transcript expression of DREB2, DREB6 and Wdreb2 has tissue specificity and is generally higher in leaves, but their expression trends are different along with the increase of osmotic stress. Furthermore, some elements related to stresses are found in their promoters, promoters of DREB2 and Wdreb2 are slightly methylated, but DREB6’s promoter is moderately methylated. Compared with the control, the level of promoter methylation in Wdreb2 is significantly lower under osmotic stress and is also lower at CG site in DREB2, yet is significantly higher at CHG and CHH sites in DREB2, which is also found at a CHG site in DREB6. The status of promoter methylation in DREB2, DREB6 and Wdreb2 also undergoes significant changes under osmotic stress; further analysis showed that promoter methylation of Wdreb2 is negatively correlated with their expression. Therefore, the results of this research suggest the different functions of DREB2, DREB6 and Wdreb2 in response to osmotic stress and demonstrate the effects of promoter methylation on the expression regulation of Wdreb2.

Orchestration of plant development and defense by indirect crosstalk of SA and BR signaling through a transcription factor GhTINY2

Salicylic acid (SA) and brassinosteroids (BRs) are well known to regulate diverse processes of plant development and stress responses, but the mechanisms by which these phytohormones mediate the growth-defense trade-off is largely unclear. In addition, little is known about the roles of DEHYDRATION RESPONSIVE ELEMENT BINDING (DREB) transcription factors, especially in biotic stress and plant growth. Here, we identified a cotton (Gossypium hirsutum) APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) gene GhTINY2 which is strongly induced by Verticillium dahliae. Overexpression of GhTINY2 in cotton and Arabidopsis (Arabidopsis thaliana) enhanced tolerance to V. dahliae, while knockdown of GhTINY2 expression increased cotton susceptibility to the pathogen. By directly activating WRKY51 expression, GhTINY2 promoted SA accumulation and SA signaling transduction. Moreover, GhTINY2-overexpressing cotton and Arabidopsis showed growth retardation, increased sensitivity to inhibitors of BR biosynthesis and downregulation of several BR-induced genes and upregulation of BR-repressed genes, while GhTINY2-RNAi cotton showed the opposite results. We further demonstrate that GhTINY2 negatively regulates BR signaling by interacting with BRASSINAZOLE-RESISTANT 1 (BZR1) and restraining its transcriptional activation of the expression of INDOLE-3-ACETIC ACID INDUCIBLE 19 (IAA19). These findings indicate that GhTINY2 fine-tunes the immunity-growth trade-off via an indirect crosstalk between WRKY51-mediated SA biosynthesis and BZR1-IAA19-regulated BR signaling.

OsPP2C09 Is a Bifunctional Regulator in Both ABA-Dependent and Independent Abiotic Stress Signaling Pathways

Clade A Type 2C protein phosphatases (PP2CAs) negatively regulate abscisic acid (ABA) signaling and have diverse functions in plant development and in response to various stresses. In this study, we showed that overexpression of the rice ABA receptor OsPYL/RCAR3 reduces the growth retardation observed in plants exposed to osmotic stress. By contrast, overexpression of the OsPYL/RCAR3-interacting protein OsPP2C09 rendered plant growth more sensitive to osmotic stress. We tested whether OsPP2CAs activate an ABA-independent signaling cascade by transfecting rice protoplasts with luciferase reporters containing the drought-responsive element (DRE) or ABA-responsive element (ABRE). We observed that OsPP2CAs activated gene expression via the cis-acting drought-responsive element. In agreement with this observation, transcriptome analysis of plants overexpressing OsPP2C09 indicated that OsPP2C09 induces the expression of genes whose promoters contain DREs. Further analysis showed that OsPP2C09 interacts with DRE-binding (DREB) transcription factors and activates reporters containing DRE. We conclude that, through activating DRE-containing promoters, OsPP2C09 positively regulates the drought response regulon and activates an ABA-independent signaling pathway.

Analysis of Soybean DREB Transcription Factors Family and DREB Time Expression Profile under Drought Stress

Background: DREB transcription factors regulate the expression of stress-responsive genes, and thus play an important role in plant stress response to abiotic stresses. To obtain a global expression profile of soybean DREB genes under drought stress, we first explored the soybean genome to identify DREB family genes, and then analyzed a set of transcriptome data of drought stress to verify their involvement in stress response. Results: We identified 73 DREB family genes from the soybean genome. These DREB genes were further divided into six subgroups basing on the phylogenetic analysis. Gene structure analysis showed that most DREB genes have a single exon. Soybean DREB genes were unevenly distributed on 19 chromosomes. We further identified 186 putative target genes of soybean DREB proteins and found that these targeted genes were significantly enriched in metabolism pathways of fructose and mannose. The analysis of transcriptome data after 4 hours, 8 hours, and 12 hours of drought, the expression of DREB genes were constantly increased, indicating that the DREB family genes responded to drought stress. Conclusion: We identified 73 DREB genes from soybean genome and analyzed their features including gene structures, protein motifs, and putative target genes.