Gibberellin regulates arabidopsis floral development via suppression of DELLA protein function

Abstract

AbstractFlower development, especially petals and stamens development, was severely arrested in Arabidopsis GA-deficient mutant plants, suggesting that gibberellin (GA) is a regulator of flower development. Although previous analysis have shown that GA promotes stem elongation by opposing DELLA proteins functions, it is not clear if these proteins are involved in the regulation of stamen development. We showed here that GA regulates cell elongation rather than cell division during Arabidopsis stamen filament elongation. GA also regulates pollen development from microspore to mature pollen grain. Genetic analysis showed that Arabidopsis DELLA proteins RGA, RGL2 and RGL1 synergistically repressed petal and stamen development in GA-deficient plants. Comparison of the global gene expression patterns in unopened flower buds of the ga1-3 mutant with wild type and ga1-3 gai-t6 rga-t2 rgl1-1 rgl2-1 mutant identified GA-regulated transcriptomes. We found that half of these genes were regulated in a DELLA-dependent manner. These genes were likely responsible for GA-mediated floral development. Genetic studies showed that three DELLA down regulated MYBs, AtMYB21, AtMYB24 and AtMYB57, were necessary for normal stamen development. They may act downstream of DELLA proteins in controlling stamen development. Recent reports showed that JA is required for the expression of AtMYB21 and AtMYB24. Our results indicated that DELLA proteins may modulate JA production through the JA biosynthesis gene DAD1 to repress the expression of AtMYB21, AtMYB24 and AtMYB57.