抄録
It has reported that the Brassinosteroids (BRs) function as a positive regulator of photomorphogenesis unexpectedly. To understand true functions of BRs, we analyzed expression levels of BR-related 4 genes (DWF4,BR6ox2,BR6ox1and SAUR-AC1) by real-time-quantitative (RTQ)-PCR in Arabidopsis etiolated seedlings. An etiolated seedling of Arabidopsis thaliana. consists of a long hypocotyl, a hook, and closed cotyledons. When the seedlings were exposed to light, the hypocotyl elongation was inhibited. At the same time, the hook started to unfold and cotyledons started to develop 3-6 hours after the treatment. Prior to the hook unfolding, expressions of all the four genes were strongly induced. In cotyledons, the expression of BR6ox2, DWF4, SAUR-AC1 were activated throughout 24hours. These results suggested that the hook opening and cotyledon development were induced by the BRs synthesized de novo. On the other hand, hypocotyls elongation may be controlled in more complex regulatory manners.
