6.重力刺激および摘心処理による腋芽伸長の誘導機構の比較解析(口頭発表)

概要

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The leading shoot dominates the growth of the axillary buds. After decapitation of the shoot apex, outgrowth of axillary buds begins. This phenomenon is known as apical dominance. Auxin basipetally derived from apical bud has an inhibitory effect on the growth of axillary buds, whereas cytokinin promotes axillary bud outgrowth. It is also proposed that graviresponse is involved in apical dominance. When the upper part of main shoot of morning glory (Pharbitis nil) is bent down, an axillary bud situated on the uppermost node starts to elongate. Using an agravitropic mutant of morning glory, weeping, we previously demonstrated that this release from apical dominance requires graviresponse. However, the molecular mechanism of this phenomenon is unclear. In this report, we examined the involvement of cytokinin and auxin in gravity-regulated axillary bud growth in comparison with that induced by decapitation. The newly isolated cytokinin biosynthetic gene, PnIPT2, was up-regulated by decapitation, whereas it was suppressed by auxin exogenously treated to the stump. PnIAAl, an auxin inducible gene, was down-regulated by decapitation. In contrast, neither PnIPT2 nor PnIAAl expression changed with shoot bending treatment. These results suggest that mechanism for gravity-influenced release from apical dominance is independent of that of decapitation.
2007-10-05