Lectin receptor kinase OsLecRK-S.7 is required for pollen development and male fertility

Pollen grains are covered by exine that protects the pollen from stress and facilitates pollination. Here we isolated a male sterile mutant s13283 in rice exhibiting aborted pollen with abnormal exine and defective aperture. The mutant gene encodes a novel plasma membrane-localized legume-lectin receptor kinase that we named OsLecRK-S.7. OsLecRK-S.7 was expressed at different levels in all tested tissues and throughout anther development. In vitro kinase assay showed OsLecRK-S.7 capable of autophosporylation. Mutation in s13283 (E560K) and mutation of the conserved ATP binding site (K418E) both knocked out the kinase activity. Mass spectrometry showed Thr₃₇₆ , Ser₃₇₈ , Thr₃₈₆ , Thr₄₀₃ , and Thr₆₅₇ to be the autophosphorylation sites. Mutation of individual autophosphorylation site affected the in vitro kinase activity to different degrees, but did not abolish the gene function in fertility complementation. oslecrk-s.7 mutant plant overexpressing OsLecRK-S.7 recovered male fertility but showed severe growth retardation with reduced number of tillers, and these phenotypes were abolished by E560K or K418E mutation. The results indicated that OsLecRK-S.7 was a key regulator of pollen development.