An ATP-Binding Cassette Transporter WBC11Is Required For Pollen Formation In Rice

ATP-binding cassette (ABC) transporters are a large family of proteins, which are conserved from bacteria to animal. ABC family transporters were divided into eight sub-families, and plants are a rich source of ABC proteins.Pollen, the male gametophyte, is essential for plant reproduction. One pollen mother cell undergoes meiosis to form four haploid cells in a tetrad. Subsequently, microspores released from tetrad, and materials synthesized in tapetum transport to the anther locule to support the development of microspores. In this study, we identify a sterile mutant induced by EMS, which is normal in vegetable development but produce no seed. Through map-based cloning, we find that an ATP-binding cassette transporter gene WBC11on chromosome10, named as OsWBCll, is responsible for its sterile phenotype. Different from AtWBC11, OsWBCll is exclusively expressed in reproductive organ. No obvious defects are observed in the morphology of Oswbcll pollen mother cells prior to the formation of microspore. After releasing from tetrad, the microspores can not undergo normal development and degrade in the locule. Meanwhile, the inflation rather than degradation of tapetal cells is also observed in Oswbcll, which indicates that some cytoplasmic inclusions are accumulated abnormally in the tapetum. By transforming into rice protoplast, we find that OsWBC11localizes to the plasma membrane.As WBC11/ABCG11was thought to be essential for lipids transmembrane transport in plant, we assume that OsWBC11plays a crucial role in the transport of sporopollenin lipid precusors from tapetum to anther locules, which is essential for exine formation on the pollen surface.