Abstract
Phytochrome photoreceptors regulate various physiological light responses in plants. In Arabidopsis, phytochrome interacting factors (PIFs) directly bind to both phytochromes and specific DNA elements in vitro, and regulate phytochrome-dependent gene expression to control seed germination, chlorophyl biosynthesis, and possibly, flowering time. Arabidopsis PIFs contain a phytochrome-interacting domain termed APB at N-terminus and a bHLH domain at C-terminus. Here, we identified 10 PIF-like genes based on this structure in rice genome. Interestingly, some rice PIF-like genes have only the APB, but no bHLH domain. Detailed motif analysis further revealed that several novel protein motifs were conserved in PIF-like proteins between rice and Arabidopsis, suggesting their evolutional relationship. Quantitative RT-PCR analysis indicated that some PIF like genes including the solo-APB proteins, showed distinct diurnal expression patterns between wild-type and se5, a phytochorme- deficient mutant of rice. This indicated that some PIF-like genes are regulated by phytochrome signaling in rice.
