Effect of environmental factors on brassinosteroid biosynyhesis

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We investigated the effects of light and temperature on brassinosteroid (BR) biosynthesis as well as fluctuation of BR biosynthesis gene expression during seed growth.1. Effect of light on the biosynthesis of BR in rice,Blue light promoted the synthesis of castasterone and typhasterol in rice, At the same time blue light activated the expression of the OsD WARP gene involved in C6 oxidation responsible for the synthesis of castasterone and typhasterol. Red light and far-red light did not show such a pvomotive activity.2. Effect of temperature on the biosynthesis of BR in rice.The endogenous ERs in rice seedlings grown at 21, 28, 35 and 42℃ were quantified. Compared with 28℃, 35℃ promoted C2α-hydroxylation, while 42℃ suppressed C22-hydroxylation. No such effects were observe in the case of 21℃.3. Fluctuation of pea BR biosynthesis genes during pea seed growth.Pea genes homologous to Arcibidopsis ER biosynthesis genes were cloned and their fluctuation during pea seed growth was examined. We found that the P sDWARF gene is expressed in rapidly growing seeds and is responsible for the synthesis of active ERs such as brassinolide and castasterone. The PsCPD and PsDWF4 genes were found to be responsible for the synthesis of BR intermediates in the early to middle growth stages, In contrast, the level of PsCPD1 transcript was low at the early to middle growth stages but high at the maturing and mature stages, suggesting that 6-deoxocathasteonre accumulated in mature seeds is hydroxylated at C23 by PsCPD1 during early germination and the product is utilized for the synthesis of active BRs, The expression of the PsDET2 gene was found to be constant during seed growth.