Abstract
Poor seedling emergence is a challenge for direct seeding of rice under deep-sowing field conditions. Here we reveal that UDP-glucosyltransferase OsUGT75A promotes rice seedling emergence under deep-sowing conditions by increasing shoot length. Expression of OsUGT75A was higher in the middle regions of the shoot and in shoots under deep-sowing conditions. Levels of free abscisic acid (ABA) and jasmonates (JA) were higher in shoots of OsUGT75A mutants than in those of wild-type plants, and OsUGT75A mutants were more sensitive to ABA and JA treatments. Reduced shoot length was attributed to higher ABA INSENSITIVE 3 (OsABI3) expression and lower JASMONATE-ZIM domain protein (OsJAZ) expression in shoots. Shoot extension by OsUGT75A is achieved mainly by promotion of cell elongation. An elite haplotype of OsUGT75A associated with increased shoot length was identified among indica rice accessions. OsUGT75A acts to increase seedling emergence under deep-sowing conditions.
