A role for the ubiquitin-26S-proteasome pathway in gibberellin signaling.

The gibberellin (GA) signaling pathway, like auxin and jasmonate signaling, uses the ubiquitin-proteasome pathway to control expression through protein degradation. A conserved F-box protein of an SCF E3 ubiquitin ligase is a positive regulator of GA signaling in Arabidopsis and rice. GA apparently stimulates stem elongation by causing this SCF complex to regulate negatively a family of negative regulators of GA response (the DELLA family of putative transcription factors). The DELLA family members AtRGA or (Repressor of ga1-3) and OsSLR1 (SLENDER RICE1) proteins both appear to be subject to GA-induced proteolysis. The need to have the F-box genes AtSLY1 and OsGID2 for this proteolysis suggests that GA causes proteolysis of AtRGA/OsSLR1 via the SCF(AtSLY1/OsGID2) ubiquitin ligase.