Expression Patterns and Molecular Mechanisms Regulating Drought Tolerance of Soybean [Glycine max (L.) Merr.] Conferred by Transcription Factor Gene GmNAC19

Abstract

NAC transcription factors are commonly involved in the plant response to drought stress. A transcriptome analysis of root samples of the soybean variety 'Jiyu47' under drought stress revealed the evidently up-regulated expression of <i>GmNAC19</i>, consistent with the expression pattern revealed by quantitative real-time PCR analysis. The overexpression of <i>GmNAC19</i> enhanced drought tolerance in <i>Saccharomyces cerevisiae</i> INVSc1. The seed germination percentage and root growth of transgenic <i>Arabidopsis thaliana</i> were improved in comparison with those of the wild type, while the transgenic soybean composite line showed improved chlorophyll content. The altered contents of physiological and biochemical indices (i.e., soluble protein, soluble sugar, proline, and malondialdehyde) related to drought stress and the activities of three antioxidant enzymes (i.e., superoxide dismutase, peroxidase, and catalase) revealed enhanced drought tolerance in both transgenic <i>Arabidopsis</i> and soybean. The expressions of three genes (i.e., <i>P5CS</i>, <i>OAT</i>, and <i>P5CR</i>) involved in proline synthesis were decreased in the transgenic soybean hairy roots, while the expression of <i>ProDH</i> involved in the breakdown of proline was increased. This study revealed the molecular mechanisms underlying drought tolerance enhanced by <i>GmNAC19</i> via regulation of the contents of soluble protein and soluble sugar and the activities of antioxidant enzymes, providing a candidate gene for the molecular breeding of drought-tolerant crop plants.