Ariizumi T, Lawrence PK, Steber CM

The SLEEPY1 (SLY1) F-box gene is a positive regulator of gibberellin (GA) signaling. Loss of SLY1 results in GA-insensitive phenotypes including dwarfism, reduced fertility, delayed flowering, and increased seed dormancy. These sly1 phenotypes are partially rescued by overexpression of the SLY1 homolog, SNEEZY (SNE)/SLEEPY2 suggesting that SNE can functionally replace ...

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SLY1. GA responses are repressed by DELLA family proteins. GA relieves DELLA repression when the SCF-SLY1 (Skp1, cullin, F-box) ubiquitin ligase ubiquitinates DELLA protein thereby targeting it for proteolysis. 35S:HA-SLY1 and 35S:HA-SNE translational fusions were constitutively expressed in sly1-10 lines to determine whether SNE behaves like SLY1 in GA signaling. Both HA-SLY1 and HA-SNE interacted with the CUL1 (cullin) subunit of the SCF complex in co-immunoprecipitation assays, and this interaction required the F-box domain. Both HA-SLY1 and HA-SNE co-immunoprecipitated with the DELLA RGA, and this interaction required the C-terminal domain. Whereas HA-SLY1 overexpression resulted in decreased expression of both DELLA RGA and RGL2, HA-SNE caused a decrease in DELLA RGA but not in RGL2 protein levels. This suggests that one reason HA-SLY1 is able to effect a stronger rescue of sly1-10 phenotypes than HA-SNE is because SLY1 interacts with a broader spectrum of DELLA proteins. The FLAG-SLY1 protein was found to co-immunoprecipitate with the GA receptor HA-GID1b supporting the model that SLY1 regulates DELLA through interaction with the DELLA-GA-GID1 complex.

Date: Dec. 16, 2010

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