RNAi-mediated Silencing of OsGEN-L (OsGEN-like), a New Member of the RAD2/XPG Nuclease Family, Causes Male Sterility by Defect of Microspore Development in Rice

We have cloned a new member of the RAD2/XPG nuclease family, OsGEN-L (OsGEN-like), from rice (Oryza sativa L.). OsGEN-L possesses two domains, the N- and I-regions, that are conserved in the RAD2/XPG nuclease family. Database searches and phylogenetic analyses revealed that OsGEN-L belongs to class 4 of the RAD2/XPG nuclease family, and OsGEN-L homologs were found in animals and higher plants. To elucidate the function of OsGEN-L, we generated rice OsGEN-L-RNAi transgenic plants in which OsGEN-L expression was silenced. Most of the OsGEN-L-RNAi plants displayed low fertility, and some of them were male-sterile. OsGEN-L-RNAi plants lacked mature pollen, resulting from a defect in early microspore development. A OsGEN-L-green fluorescent protein (GFP) fusion protein was localized in the nucleus, and the OsGEN-L promoter was specifically active in the anthers. Furthermore, a recombinant OsGEN-L protein possessed flap endonuclease activity and both single-stranded and double-stranded DNA-binding activities. Our results suggest that OsGEN-L plays an essential role in DNA metabolism required for early microspore development in rice.