LRRK1, a receptor-like cytoplasmic kinase, regulates leaf rolling through modulating bulliform cell development in rice

Moderate leaf rolling is useful in improving photosynthetic efficiency and grain yields. Receptor-like cytoplasmic kinases (RLCKs) play important roles in plant growth and development. However, little is known about their functions in rice leaf morphogenesis. Here, we report the isolation and characterization of LRRK1 ( leaf rolling receptor-like cytoplasmic kinase 1 ), an RLCK gene involved in the regulation of leaf rolling. LRRK1 was mainly localized at the plasma membrane and was phosphorylated in vivo. Overexpression of LRRK1 in rice reduced the size of bulliform cells at the adaxial cell layers, which caused in turn adaxially rolled leaves. However, deficiency of LRRK1 in the lrrk1 mutant did not result in a detectable visual phenotype. LRRK1 could upregulate the expression of negative regulators but downregulate the expression of positive regulators of bulliform cell development. These results indicate that LRRK1 is a negative regulator involved in the bulliform cell development. Furthermore, the panicle numbers in LRRK1 -overexpressing plants increased significantly compared with the wild-type plants under a rational close planting condition. Taken together, these findings suggest that LRRK1 plays an important role in regulating leaf rolling and is a promising candidate gene for breeding rice with ideal plant architecture and improved grain yield.