Zhiyuan He, Ting Zou, Qiao Xiao, Guoqiang Yuan, Miaomiao Liu, Yang Tao, Dan Zhou, Xu Zhang, Qiming Deng, Shiquan Wang, Aiping Zheng, Jun Zhu, Yueyang Liang, Xiumei Yu, Aijun Wang, Huainian Liu, Lingxia Wang, Ping Li*, Shuangcheng Li*
Starch accumulation is key for the maturity of rice pollen grains; however, the regulatory mechanism underlying this process remains unknown. Here, we have isolated a male-sterile rice mutant, abnormal pollen 1 (ap1), which produces nonviable pollen grains with defective starch accumulation. Functional analysis revealed that AP1 encodes an active L-type lectin receptor-like kinase (L-LecRLK). AP1 is localized to the plasma membrane and its transcript is highly accumulated in pollen during the starch synthesis phase. RNA-seq and phosphoproteomic analysis revealed that the expression/phosphorylation levels of numerous genes/proteins involved in starch and sucrose metabolism pathway were significantly altered in the mutant pollen, including a known rice UDP-glucose pyrophosphorylase (OsUGP2). We further found that AP1 physically interacts with OsUGP2 to elevate its enzymatic activity, likely through targeted phosphorylation. These findings revealed a novel role of L-LecRLK in controlling pollen maturity via modulating sucrose and starch metabolism.