Gibberellin (GA) 20-oxidase (GA 20-ox) and GA 3β-hydroxylase (GA 3β-hy) are enzymes that catalyze the late steps in the formation of active GAs, and are potential control points in the regulation of GA biosynthesis by light. We have investigated the photoregulation of the GA 20-ox and GA 3β-hy transcript levels in pea (Pisum sativum L.). The GA 20-ox transcript level was higher in light-grown seedlings than in etiolated seedlings, whereas GA 3β-hy mRNA accumulation was higher in etiolated seedlings. However, transfer of etiolated seedlings to light led to a 5-fold increase in the expression of both transcripts 4 h after transfer. GA 20-ox mRNA accumulation is regulated by both phytochromes A and B. Transfer to light also resulted in a 6-fold decrease in GA1 levels within 2 h. These results suggest that the light-induced drop in GA1 level is not achieved through regulation of GA 20-ox and GA 3β-hy mRNA accumulation. The application of exogenous GA1 to apical buds of etiolated seedlings prior to light treatments inhibited the light-induced accumulation of both GA 20-ox and GA 3β-hy mRNA, suggesting that negative feedback regulation is an important mechanism in the regulation of GA 20-ox and GA 3β-hy mRNA accumulation during de-etiolation of pea seedlings.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Plant biology
Research Field:	Plant physiology
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Horticultural crops
Objective Field:	Horticultural crops not elsewhere classified
UTAS Author:	Weller, JL (Associate Professor Jim Weller)
UTAS Author:	Reid, JB (Professor Jim Reid)
ID Code:	17802
Year Published:	1999
Web of Science® Times Cited:	56
Deposited By:	Plant Science
Deposited On:	1999-08-01
Last Modified:	2010-11-09
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