Abstract
We have previously shown that gibberellin (GA) is required for tissue-reunion in the cortex of cut hypocotyls in cucumber and tomato 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 hypocotyls. Quantitative RT-PCR analysis 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 tomato seedlings. 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. These results suggest that cotyledons play a role in determining GA content in cucumber and tomato hypocotyls.
