In addition, through the GUS staining of 1-week-old pGmbZIP15:GUS transgenic Arabidopsis seedlings grown on media supplemented with 100 mM NaCl or 200 mM mannitol, GmbZIP15 promoter activity was observed to be significantly decreased in cotyledons and true leaves under NaCl and mannitol conditions compared to normal conditions ( Figure S2C), which was consistent with the results of qRT-PCR ( Figure S1A,B). Under normal conditions, GmbZIP15 expression level in OX-GmbZIP15 plants was clearly higher than that in WT however, GmbZIP15 expression in OX-GmbZIP15 plants treated with NaCl and mannitol sharply decreased, but was higher than WT plants by 12 h and was nearly undetectable by 24 h post-treatment ( Figure S2A,B). The qRT-PCR analysis was used to determine GmbZIP15 expression patterns in 2-week-old wild-type (WT) and two overexpression lines under salt and drought treatments. To validate the response of GmbZIP15 to abiotic-stress conditions, we generated soybean plants overexpressing GmbZIP15 ( OX-GmbZIP15), and two lines (OE-8, OE-16) with higher expression level were selected for further research ( Figure S1). Among these genes, the expression of GmbZIP15 was suppressed by drought and flooding stress and it was therefore selected for further investigation. We previously identified 160 bZIP genes from soybean and characterized their expression in response to abiotic stress. Three DREB homologues, namely, GmDREBa, GmDREBb, and GmDREBc, have been identified in the soybean genome and the transcript levels of GmDREBa and GmDREBb in the leaves of soybean seedlings were shown to increase following salt-, drought-, and cold-stress treatment. Among the DREB2 genes in Arabidopsis, DREB2A is largely induced by drought, salinity, and cold stress. DREB2 proteins are members of the AP2/ERF family of plant-specific TFs and function in an ABA-independent manner. ABF1 has also been shown to function in drought-stress responses, despite its lower expression level compared to other abiotic-stress-induced AREB/ABFs, and thus areb1areb2abf3abf1 plants display decreased drought resistance compared to areb1areb2abf3 plants regarding primary root growth. Abiotic stress and ABA has also been shown to induce the expression of AREB1/ ABF2, AREB2/ ABF4, and ABF3, and an increased abundance of these AREB/ABFs in turn increases ABA sensitivity and abiotic-stress resistance. In Arabidopsis under abiotic-stress conditions, ABA enacts responses primarily through four bZIP TFs, namely, ABF1, AREB1/ABF2, AREB2/ABF4, and ABF3, the expression of which is activated by SnRK2s. Recent studies have found that plants respond to abiotic-stress conditions mainly through ABA-dependent and ABA-independent signaling pathways, which are regulated by AREB/ABFs and DREB2A transcription factors (TFs), respectively. Cellular ABA levels in plants increase in response to abiotic stress, leading to the expression of stress-responsive genes, the regulation of metabolic processes, and the quenching of ROS, thereby maintaining plant cell homeostasis under stress conditions. Overall, these data indicate that GmbZIP15 functions as a negative regulator in response to salt and drought stresses.ĪBA is one of the most important stress-related phytohormones and plays a pivotal role in signal transduction during abiotic-stress responses. RNA-seq and qRT-PCR analyses revealed that GmbZIP15 positively regulates GmSAHH1 expression and negatively regulates GmWRKY12 and GmABF1 expression in response to abiotic stress. Furthermore, plants expressing a functional repressor form of GmbZIP15 exhibited drought-stress resistance similar to WT. Overexpression of GmbZIP15 in soybean resulted in hypersensitivity to abiotic stress compared with wild-type (WT) plants, which was associated with lower transcript levels of stress-responsive genes involved in both abscisic acid (ABA)-dependent and ABA-independent pathways, defective stomatal aperture regulation, and reduced antioxidant enzyme activities. The transcript level of GmbZIP15 was suppressed under salt- and drought-stress conditions. Here, we characterized the roles of soybean transcription factor GmbZIP15 in response to abiotic stresses. bZIP transcription factors (TFs) are one of the largest TF families and have been shown to be associated with various environmental-stress tolerances among species however, their function in abiotic-stress response in soybean remains poorly understood. Soybean ( Glycine max), as an important oilseed crop, is constantly threatened by abiotic stress, including that caused by salinity and drought.

Srdx transcription