LAUSR

Heading date, panicle architecture and grain size are essential traits that affect rice yield. We identified a new gene OsGATA6, whose product regulates rice heading date. Overexpression of OsGATA6 results in delayed heading, increased grain number, and decreased grain size. Knock-down lines generated by artificial microRNA (amiRNA) and CRISPR genome-edited lines of OsGATA6 show earlier heading, decreased grain number, and increased grain size. These results suggest that OsGATA6 negatively regulates heading date, positively regulates panicle development, and affects grain size. OsGATA6 is constitutively expressed in rice, and strongly expressed in young leaves and panicles. In situ hybridization analyses showed that OsGATA6 specifically localizes in superficial cells of the panicle primordium. Overexpression lines show decreased expression of RFT1 and Hd3a, which promote heading. OsMFT1, which positively regulates heading date and grain number, is down-regulated in amiRNA lines. Further analyses showed that OsGATA6 can bind to the promoter of OsMFT1 and induce its expression, thereby regulating heading date and panicle development. Overexpression of OsGATA6 in Arabidopsis results in repressed expression of AtFT and late flowering, suggesting that its function is similar. Taken together, we have identified a new GATA regulator that influences rice heading date and grain number, which potentially increases rice yield.