The Rice Wall-Associated Receptor-Like Kinase Gene OsDEES1 Plays a Role in Female Gametophyte Development

The wall-associated kinase (WAK) gene family is a unique subfamily of receptor-like kinases (RLKs) in plants. WAK-RLKs play roles in cell expansion, pathogen resistance, and metal tolerance in Arabidopsis (Arabidopsis thaliana). Rice (Oryza sativa) has far more WAK-RLK genes than Arabidopsis, but the functions of rice WAK-RLKs are poorly understood. In this study, we found that one rice WAK-RLK gene, DEFECT IN EARLY EMBRYO SAC1 (OsDEES1), is involved in the regulation of early embryo sac development. OsDEES1 silencing by RNA interference caused a high rate of female sterility. Crossing experiments showed that female reproductive organs lacking OsDEES1 carried a functional defect. A detailed investigation of the ovaries from OsDEES1 RNA interference plants indicated that the knockdown of OsDEES1 expression did not affect megasporogenesis but that it disturbed female gametophyte formation, resulting in a degenerated embryo sac and defective seed formation. OsDEES1 exhibited a tissue-specific expression pattern in flowers and seedlings. In the ovary, OsDEES1 was expressed in the megagametophyte region and surrounding nucellus cells in the ovule near the micropylar region. OsDEES1 was found to be a membrane-localized protein with a unique sequence compared with other WAK-RLKs. These data indicate that OsDEES1 plays a role in rice sexual reproduction by regulating female gametophyte development. This study offers new insight into the functions of the WAK-RLK family.