Feed-Forward Regulation of Gibberellin Deactivation in Pea

Multiple lines of evidence suggest that the genes involved in gibberellin (GA) biosynthesis are regulated by bioactive GA levels. With the recent cloning of GA 2-oxidase genes from pea, we investigated whether this homeostatic regulation extends to the genes controlling GA deactivation in this species, utilizing two well-characterized GA-deficient mutants, ls and na and a GA-accumulating mutant, sln. The pea GA 2-oxidases showed feed-forward effects at the mRNA level, while the endogenous levels of GA 20, GA 29, GA 1, and GA 8 showed no evidence of feed-forward regulation. Analyses of genomic Southern blots and expressed sequenced tag (EST) databases suggest that other GA 2-oxidases could possibly account for this lack of feed-forward on GA levels.