RNAi-mediated silencing of OsRAD, a new member of the RAD2/XPG nuclease family, causes male sterility by defect of microspore development in rice

Abstract

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