Abstract
Hd6 encodes a casein kinaseII (CK II) α subunit and suppresses flowering under long-days in rice, a short-day plant. Since CKII has been shown to be a key component of the circadian clocks in several model organisms, we analyzed free-running rhythms of Cab1R::luc and diurnal mRNA rhythms of circadian clock-related genes, such as OsLHY, OsPRR1, OsGI and Hd1 using nonfunctional, functional and over- expressing lines of Hd6, but could not detect any significant differences of those expression patterns among them. In contrast, Hd3a and RFT gene expression were repressed in both Hd6 functional and Hd6ox lines. We further revealed that Hd6 suppress flowering only with Hd1 functional alleles. Therefore, we performed a phosphorylation assay by rHd6 after co-immunoprecipitation with FLAG - Hd1 protein, which was transiently expressed in rice Oc-cell. The result suggests Hd6 may phosphorylate a member in Hd1 complex, but not Hd1 itself in rice.
