A subtilisin-like serine protease specifically expressed in reproductive organs in rice

Abstract 

To identify genes specifically expressed in flowering pistils and that are related to reproductive phenomena, simplified differential display was performed with cDNA obtained from pistils and ovaries at several stages. One clone preferentially expressed in pistils at flowering and 1 day before flowering was identified as a rice subtilisin-like serine protease (RSP1). Sequence comparisons revealed that RSP1 has several characteristics in common with preproproteins. RT-PCR, northern blot, and in situ hybridization analysis revealed that RSP1 mRNA accumulates in pistils and in the filaments of stamens, whereas mRNA was undetectable in tissue from leaves, roots, panicles, and embryos. The mRNA levels in pistils increased slightly at flowering and decreased afterwards. Possible roles of the subtilisin-like serine protease in plant reproduction are discussed.