Overexpression of the Transcription Factor GmbZIP60 Increases Salt and Drought Tolerance in Soybean (Glycine max)

The regulation of downstream responsive genes by transcription factors (TFs) is a critical step in the stress response system of plants. While bZIP transcription factors are known to play important roles in stress reactions, their functional characterization in soybeans remains limited. Here, we identified a soybean bZIP gene, <i>GmbZIP60</i>, which encodes a protein containing a typical bZIP domain with a basic region and a leucine zipper region. Subcellular localization studies confirmed that <i>GmbZIP60</i> is localized in the nucleus. Expression analysis demonstrated that <i>GmbZIP60</i> is induced by salt stress, drought stress, and various plant hormone treatments, including abscisic acid (ABA), ethylene (ETH), and methyl jasmonate acid (MeJA). Overexpressing <i>GmbZIP60</i> (<i>OE-GmbZIP60</i>) in transgenic soybean and rice enhanced tolerance to both salt and drought stresses. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that the expression levels of abiotic stress-responsive genes were significantly higher in transgenic plants than in wild-type (WT) plants under stress conditions. Chromatin immunoprecipitation-qPCR (ChIP-qPCR) analysis further confirmed that GmbZIP60 directly binds to the promoters of abiotic stress-related genes induced by ABA, ETH, JA, and salicylic acid (SA). Overall, these findings revealed <i>GmbZIP60</i> as a positive regulator of salt and drought stress tolerance.