Abstract

Leaf inclination is one of the most important components of the ideal architecture, which effects yield gain. Leaf inclination was shown that is mainly regulated by brassinosteroid (BR) and auxin signaling. Here, we reveal a novel regulator of leaf inclination, auxin transporter OsPIN1b. Two CRISPR-Cas9 homozygous mutants,ospin1b-1andospin1b-2,with smaller leaf inclination compared to the wild-type,Nipponbare(WT/NIP), while overexpression lines,OE-OsPIN1b-1andOE-OsPIN1b-2have opposite phenotype. Further cell biological observation showed that in the adaxial region,OE-OsPIN1b-1has significant bulge compared to WT/NIP andospin1b-1, indicating that the increase in the adaxial cell division results in the enlarging of the leaf inclination inOE-OsPIN1b-1. The OsPIN1b was localized on the plasma membrane, and the free IAA contents in the lamina joint ofospin1bmutants were significantly increased while they were decreased inOE-OsPIN1blines, suggesting that OsPIN1b might action an auxin transporter such as AtPIN1 to alter IAA content and leaf inclination. Furthermore, theOsPIN1bexpression was induced by exogenous epibrassinolide (24-eBL) and IAA, andospin1bmutants are insensitive to BR or IAA treatment, indicating that the effecting leaf inclination is regulated byOsPIN1b. This study contributes a new gene resource for molecular design breeding of rice architecture.Keywords:auxin;auxin transporter;BR;leaf inclination;OsPIN1b;rice