The slender phenotype of pea is deficient in DELLA proteins

The recent cloning of the pea genes LA and CRY has historical implications, since the combined effect of null mutations in these genes is the elongated, gibberellin-insensitive "slender" phenotype, which gave rise to the theory that gibberellins (GAs) are inhibitors of inhibitors of growth. Interestingly, the duplication event that produced the second gene (LA or CRY) appears to have occurred more than 100 mya, and yet the two genes have retained essentially similar functions. They both encode DELLA proteins, which inhibit growth while at the same time promoting the synthesis of the growth-promoting hormone, gibberellin (GA). This duality of function is discussed in the context of recent suggestions that DELLAs integrate multiple hormone signals, rather than just the GA signal. We also present new data showing that LA and CRY play a major role in regulating fruit growth.