30 オーキシンによって発現が抑制される PsIPT5 の解析

概要

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Apical dominance is a phenomenon that apical shoot inhibits the outgrowth of axillary buds. It is thought that auxin inhibits the growth of axillary buds, whereas cytokinin promotes it. However, auxin does not act directly for axillary buds and it is important for basipetal auxin transport in stem. Therefore, we screened genes that were specifically expressed in the 2nd node before and after decapitation in pea. As a result, we have isolated cDNA for adenylate isopentenyltransferase, PsIPT5,which encodes the key enzyme in cytokinin biosynthesis. PsIPT5 was expressed in the 2nd node and neighbor stem 1h after decapitation at the 1cm of upper parts of the 2nd node, suggesting that auxin is involved in PsIPT5 expression since auxin transport basipetally at about 1 cm/hour. In order to elucidate this possibility, we analyzed the effect of exogenous auxin on the expression of PsIPT5. PsIPT5 was expressed in the segments that incubated in auxin free medium, but not in the auxin treated segments. Cytokinin contents in stem and axillary buds were increased 6h after decapitation. PsIPT5 was not expressed in axillary buds after decapitation, suggesting that cytokinin was derived from stem. These results suggest that auxin represses the expression of PsIPT5 and cytokinin is biosynthesized in stem after decapitation.
植物化学調節学会の論文
2002-10-31