GmWRKY49, a Salt-Responsive Nuclear Protein, Improved Root Length and Governed Better Salinity Tolerance in Transgenic Arabidopsis

Plant WRKY transcription factors (TFs) are active guardians against pathogens' insurgency, key components in developmental processes, contributors in signal transduction pathways, and regulators of diverse biotic and abiotic stress responses. In this research, we isolated, cloned, and functionally characterized a new WRKY TF GmWRKY49 from soybean. GmWRKY49 is a nuclear protein which contains two highly conserved WRKY domains and a C2H2-type zinc-finger structure. The normalized expression (log(2) ratio) of GmWRKY49 was 2.75- and 1.90-fold in salt-tolerant and salt-susceptible soybean genotypes, respectively. The transcripts of GmWRKY49 could be detected in roots, stems, leaves, flowers, and almost no expression in pod tissues. The salinity-tolerance response of this gene was studied through overexpression in soybean composite seedlings and transgenic Arabidopsis. The effect of GmWRKY49 overexpression on root length of transgenic Arabidopsis was also investigated. Under salt stress, several parameters including germination rate, survival rate, root length, rosette diameter, relative electrolyte leakage, and proline content were significantly higher in composite seedlings and transgenic Arabidopsis than those in wild-type. Moreover, GmWRKY49 enhanced salinity tolerance in soybean mosaic seedlings and transgenic Arabidopsis. These results suggest that GmWRKY49 is a positive regulator of salinity tolerance in soybean and has high potential utilization for crop improvement.