GW5 preferentially express in developing panicles and the highest levels of GW5 expression were found in young panicles. OsGW5 might be involved in the ubiquitin-proteasome pathway to regulate grain width and weight. GW5 acts upstream of GSK2 to control of grain size and lamina bending. GW5 acts as positive regulator of brassinosterpoid signalling by physically interacting with GSK2 and inhibits its kinase activity towards OsBZR1 and DLT, leading to accumulation of unphosphorylated OsBZR1 and DLT proteins in the nucleus, and influences BR-responsive gene expression, grain size and weight in rice (Liu et al., 2017). Significant negative correlation between grain width and the expression level of GW5 was observed by Liu et al., 2017, which suggest that the expression level of GW5, but not the change in its coding sequence, regulates grain width.