OsSPL11 positively regulates grain size by activating the expression of GW5L in rice.

Key message: Rice OsSPL11 activates the expression of GW5L through binding to its promoter and positively regulates grain size. Grain size (GS) is an important determinant of grain weight and yield potential in cereal. Here, we report the functional analysis of OsSPL11 in grain length (GL), grain width (GW), and 1000-grain weight (TGW). OsSPL11 mutant plants, osspl11 lines, exhibited a decrease in GL, GW, and TGW, and OsSPL11-OE lines showed an increase in GL and TGW. Expression analysis revealed that OsSPL11 was located in the nucleus and highly expressed in spikelet hull and young development grains, consistent with its function in determining GS. Further analysis confirmed that OsSPL11 directly activates the expression of GW5L to regulate GS, meanwhile OsSPL11 expression is negatively regulated by OsGBP3. Taken together, our findings demonstrate that OsSPL11 could be a key regulator of affecting GS during the spikelet hull development and facilitate the process of improving grain yield by GS modification in rice.