D-39 タバコホメオボックス遺伝子NTH15の過剰発現はジベレリン生合成系を直ちに阻害する

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We have previously reported that over-expression of a tobacco homeobox gene, NTH15, (Nicotiana tabacum homeobox 15) in transgenic tobacco led abnormal morphologies with drastic decrease in the content of active gibberellin, GA_1. RNA gel blot analysis and supplementary experiments revealed that the over-expression of NTH15 specitically inhibits the activity of GA 20-oxidase. In this study, we generate a glucocorticoid-inducible system to elucidate the kinetics underlying between the over-production of homeodomain protein and the inhibition of gibberellin biosynthetic pathway. The expression of GA 20-oxidase gene was down-regulated until 6 hours after induction of the NTH15 function. The content of GA_<20> also decreased after 6 hours from the induction and was not detected after 12 hours. While, the expression of 3β-hydroxylase gene has doubled until 24 hours after the induction. Because the content of GA_1 has also been decreased at this time, up-regulation of the 3β-hydroxylase gene is probably due to the feed-back regulation of the gibberellin biosynthetic pathway. These results clearly suggest that the overproduction of homeodomain protein immediately down-regulates the expression of GA 20-oxidase gene and inhibits the biosynthesis of GA_1 in transgenic plants.
植物化学調節学会の論文
1998-10-01