RNase ZS1-mediated UbL40 mRNA decay controls thermo-sensitive genic male sterility in rice.

Male sterility is an important trait in hybrid crop breeding. Thermo-sensitive genic male sterility (TGMS) lines, which are male-sterile at restrictive (high) temperatures but convert to male-fertile at permissive (low) temperatures, have been widely utilized in two-line hybrid rice breeding3. However, the molecular mechanism underlying TGMS remains unclear. Here we show that the rice (Oryza sativa L.) thermo-sensitive genic male sterile gene 5 (tms5) locus, which in 2010 was present in cultivars occupying more than 70% (2.4 million hectares) of two-line hybrid rice-growing land in China, confers the TGMS trait through a loss-of-function mutation of RNase ZS1, resulting in failure to mediate mRNA decay of three temperature-responsive ubiquitin fusion ribosomal protein L40 genes (UbL40). TMS5 encodes an evolutionarily conserved endonuclease, RNase ZS1. RNase ZS1 can process tRNAs in vitro, but does not do so in vivo due to its localization in the cytoplasm. Defective RNase ZS1 in tms5 plants leads to over-accumulation of UbL401, UbL402 and UbL404 mRNAs at restrictive but not permissive temperatures. Furthermore, over-expression of UbL401 and UbL404 in wild-type plants causes male sterility, while knockdown of UbL401 and UbL404 in tms5 partially restores its fertility. Our results uncover a novel mechanism of RNase ZS1-mediated UbL40 mRNA decay which controls TGMS in rice and has potential applications in hybrid breeding not only of rice but also of other crops. Overall design: Examination of differences in mRNA accumulation between 93-11, NIL5 and NIL8.

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Zhou H, Zhou M, Yang Y, Li J, Zhu L, Jiang D, Dong J, Liu Q, Gu L, Zhou L, Feng M, Qin P, Hu X, Song C, Shi J, Song X, Ni E, Wu X, Deng Q, Liu Z, Chen M, Liu YG, Cao X, Zhuang C