Poster: Hormones
Abs #
570: Endogenous Gibberellins Required for Tissue-Reunion in Cucumber and Tomato Hypocotyls
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Presenter: |
Asahina, Masashi , asahina@sakura.cc.tsukuba.ac.jp |
Authors | Asahina, Masashi (A) (B) Satoh, Shinobu (A) Kamada, Hiroshi (A) Yamauchi, Yukika (B) Hanada, Atsushi (B) Kamiya, Yuji (B) Yamaguchi, Shinjiro (B) | | Affiliations: |
(A): Institute of Biological Sciences, University of Tsukuba
(B): Plant Science Center, The Institute of Physical and Chemical Research (RIKEN)
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We have previously shown that gibberellin (GA) is required for the cell division during tissue-reunion in the cortex of cut hypocotyls in cucumber (Cucumis sativus L.) and tomato (Lycopersicon esculentum Mill.) seedlings, and that cotyledons are necessary for the tissue-reunion in hypocotyls. In this study, we analyzed expression of GA biosynthesis genes and endogenous GA contents to examine the contribution of cotyledons to providing GAs for the tissue-reunion in the cut hypocotyls.
To predict whether cotyledons produce GAs, expression of GA biosynthesis gene in each organ of tomato seedling was analyzed by quantitative RT-PCR. The result indicated that transcripts of LeGA20ox1 and LeGA3ox2 genes (encoding GA 20-oxidase and GA 3-oxidase, respectively) accumulate at relatively high levels in cotyledons in 10-day-old tomato seedlings. These results suggest the occurrence of GA biosynthesis in cotyledons, which is consistent with our hypothesis that cotyledons are involved in the production of GAs that are necessary for tissue-reunion in the hypocotyl. Our quantitative RT-PCR analysis also indicated that expression of GA biosynthesis genes in cotyledons does not change dramatically after cutting the hypocotyls.
To study the role of cotyledons in GA content in the hypocotyl directly, cotyledons were removed from 7-day-old cucumber seedlings, and endogenous GA levels in the hypocotyls were determined. Relative to intact seedlings, those without cotyledons contained reduced amounts of bioactive GA4 and its precursors in the hypocotyls. These results suggest that cotyledons are necessary for maintaining normal GA levels in cucumber and tomato hypocotyls.
