Abstract
Brassinosteroids (BRs) are essential plant hormones that control many aspects of plant growth and development. Our previous works revealed that the levels of endogenous BRs, especially those of typhasterol and castasterone, in rice seedling shoots, but not in the roots, were increased under continuous white or blue light condition as compared with continues dark condition. However, no such effects were observed under far-red and red light conditions. In this study, we analyzed transcript levels of BR biosynthesis genes using quantitative RT-PCR technique, in order to address the possible contribution of light quality to altering BR levels in rice seedlings shoots. As the result we found that the transcript levels of CYP85A1, encoding a protein that catalyzes C-6 oxidation step in BR biosynthesis, were up-regulated under white or blue light, but not under far-red or red light conditions. These results suggest that the increased levels of endogenous BRs in shoots of white or blue light grown rice seedlings should be a consequence of blue light-mediated up-regulation of CYP85A1 gene.
