Abstract
To investigate regulation of the photoperiodic control of flowering in rice, we employed the night break (NB) experiment. Although effects of NB have been studied in a few short day plants, little is known about the molecular basis of NB.
We investigated mRNA expression patterns of OsGI, Hd1 and Hd3a after a single NB. We found that Hd3a was dramatically suppressed by NB. However, strong Hd3a suppression was not observed in plants exposed to the light early or late in darkness. No difference in CAB1R expression suggests that NB does not cause the phase shift of circadian rhythm. Next, NB on the se5 mutants, which has the defect in the phytochrome pathway, exhibited no influence on Hd3a expression, indicating Se5 is essential for Hd3a suppression by NB in wild type. These results suggest that flowering in rice is mediated by the interaction with the internal rhythm and direct light signal.
