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Asahina, Masashi [1], Satoh, Shinobu [1], Kamada, Hiroshi [1], Yamauchi, Yukika [2], Hanada, Atsushi [2], Kamiya, Yuji [2], Yamaguchi, Shinjiro [2].

Analysis of tissue-reunion process in the cut hypocotyl and gibberellin biosynthesis in cucumber and tomato.

CUCUMBER and tomato hypocotyls were cut to half of its diameter transversely, and morphological and histochemical analyses of the process of tissue-reunion in the cortex were performed. Cell division in the cortex commenced 3 d after cutting, and the cortex was nearly fully united within 7 d. Cell division during tissue-reunion was strongly inhibited when the cotyledon was removed. This inhibition was reversed by applying gibberellin (GA) to the apical tip of the cotyledon-less plant. Supporting this observation, cell division in the cortex was inhibited by treatment of the cotyledon with uniconazole-P (an inhibitor of GA biosynthesis), and this inhibition was also reversed by simultaneous application of GA. In contrast to the essential role of cotyledon, normal tissue-reunion in cut hypocotyls was still observed when the shoot apex was removed. The requirement of GA for tissue-reunion in cut hypocotyls was also evident in gib-1, the GA-deficient mutant of tomato. These results suggest GA is required for the cell division during tissue-reunion in the cortex of cut hypocotyls in cucumber and tomato seedlings, and that cotyledons are necessary for the tissue-reunion in hypocotyls. To study the involvement of cotyledons in GA content in the hypocotyl directly, cotyledons were removed from 7-d-old cucumber seedlings, and endogenous GA levels in the hypocotyls were determined. Compared with 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.


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1 - University of Tsukuba, Graduate School of Life and Environmental Sciences, 304 Gene Research Center, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8572, Japan
2 - RIKEN (The Institute of Chemical and Physical Research), Plant Science Center, Suehirocho1-7-22, Tsurumi-ku, Yokohama, Kanagawa, 230, Japan

Keywords:
gibberellin
tissue-reunion
cotyledon
hypocotyl.


Session: Poster-90
Location: Ballroom CD/Monona Terrace
Date: Tuesday, July 25th, 2006
Time: 8:00 AM
Abstract ID:125


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