[Preliminary screening of target genes of rice transcription factor OsBP-73]

Previous data showed that a 31-bp (from -840 bp to -810 bp) DNA fragment located at the 5' upstream region of rice waxy gene could interact with nuclear protein extracted from developing endosperm of rice. When this 31 bp DNA sequence was used as a bait to screen a rice cDNA library with a yeast one-hybrid system, three groups of cDNA clones were isolated. One of them is pC73, the correspondent rice gene of pC73 was named as OsBP-73 (Oryza sativa binding protein). A pull-down assay was made to identify the target genes of transcription factor by using genomic DNA and recombinant p73 protein. The cDNA fragment containing DNA-binding domain of OsBP-73 was cloned into expression vector pET28-c(+) (Fig.1) to produce protein p73, fused with a his(6)-tag, from E. coli BL21 (DE3) (Fig.2). The p73 was purified with Ni-NTA under native condition (Fig.3). The target genes of p73 were identified in rice genome-wide by using a pull-down assay, and 22 candidate genes were obtained (Figs.4 and 5, and Table 1). The obtained results show that putative light-repressible receptor protein kinase and GAMYB-binding protein could serve as targets of the OsBP-73, suggesting that OsBP-73 might be involved in light signal transduction.