Setaria italica SiWRKY89 enhances drought tolerance in Arabidopsis

Foxtail millet ( Setaria italica ), a drought-tolerant plant, is grown in drylands all over the world. However, the molecular basis of drought tolerance in S. italica is not yet understood. Previously, we comprehensively characterised the SiWRKY genes and discovered that SiWRKY89 , a homologue of AtWRKY57 , had a noticeably higher expression level during dry conditions. In this study, a transgenic experiment was carried out in Arabidopsis to investigate the function of SiWRKY89 in conferring drought tolerance. Phenotypic analysis showed that the root length of seedlings and the survival rates of mature transgenic Arabidopsis were greater than those of the control plants under drought conditions. Additionally, compared to the control plants, the transgenic plants had higher proline content and antioxidant activity. Furthermore, qRT-PCR investigation for abiotic stress-responsive genes revealed that SiWRKY89 -overexpressing plants had higher expression levels than their control counterparts. Additionally, the yeast one-hybrid experiment demonstrated that SiWRKY89 could bind to the W-box elements of AtNCED3 . By upregulating the downstream gene AtNCED3 and activating the reactive oxygen species scavenging mechanisms, SiWRKY89 overexpression improved Arabidopsis drought tolerance. Thus, we provide a molecular and biochemical basis for drought tolerance and a candidate gene for crop breeding for drought tolerance.