Genetic and molecular dissection of DELLA related GA-signaling pathway in regulating arabidopsis seed germination

CAO DONGNI

Publication

Genetic and molecular dissection of DELLA related GA-signaling pathway in regulating arabidopsis seed germination

CAO DONGNI

Abstract

GA regulates plant growth through a group of negative regulators named DELLA proteins. There are five DELLA proteins in Arabidopsis, GAI, RGA, RGL1, RGL2 and RGL3. Previous studies suggest that RGA, RGL1 and RGL2 synergistically repress flower development and RGL2 also represses seed germination. In this thesis, I showed that GAI, RGA and RGL2 together control seed germination. Loss-of-function of four DELLA proteins, GAI, RGA, RGL1 and RGL2, results in GA-independent seed germination and flower development. By comparing global gene expression patterns in imbibed seed and unopened flower bud of ga1-3 mutant with that of wild type and the ga1-3 gai-t6 rga-t2 rgl1-1 rgl2-1 mutant, we found that about half the total GA-regulated genes may be regulated in a DELLA-dependent fashion. A cross-comparison based on gene identity revealed that the GA-regulated DELLA-dependent transcriptomes in imbibed seeds and flower buds are distinct from each other. Several candidate DELLA-regulated genes were chosen for further study. Mutant alleles of these genes were obtained from TAIR and genetic characterization is in progress. Previous studies have shown that GA attenuates the repressive function of DELLA proteins by triggering their degradation. Our studies in BY2 cells suggested that stabilization of RGL2 protein is not the only pathway for regulating its bioactivity.