Multiple Gibberellin Receptors Contribute to Phenotypic Stability under Changing Environments.

The pleiotropic and complex gibberellin (GA) response relies on targeted proteolysis of DELLA proteins mediated by a GA-activated GIBBERELLIN-INSENSITIVE DWARF1 (GID1) receptor. The tomato () genome encodes for a single DELLA protein, PROCERA (PRO), and three receptors, SlGID1a (GID1a), GID1b1, and GID1b2, that may guide specific GA responses. In this work, clustered regularly interspaced short palindromic repeats (CRISPR) /CRISPR associated protein 9-derived mutants were generated and their effect on GA responses was studied. The triple mutant was extremely dwarf and fully insensitive to GA. Under optimal growth conditions, the three receptors function redundantly and the single mutants exhibited very mild phenotypic changes. Among the three receptors, GID1a had the strongest effects on germination and growth. Yeast two-hybrid assays suggested that GID1a has the highest affinity to PRO. Analysis of lines with a single active receptor demonstrated a unique role for GID1a in protracted response to GA that was saturated only at high doses. When the mutants were grown in the field under ambient changing environments, they showed phenotypic instability, the high redundancy was lost, and exhibited dwarfism that was strongly exacerbated by the loss of another receptor gene. These results suggest that multiple GA receptors contribute to phenotypic stability under environmental extremes.