Poster: Reproductive Development

Abs # 473: Regulation of the light-intensity-dependent promotion of flowering by glutathione in Arabidopsis thaliana

Presenter:	Hatano-Iwasaki, Aya , aya-i@bio-ribs.com
Authors	Hatano-Iwasaki, Aya  (A) (B)  Iwabuchi, Masaki  (A)   Ogawa, Ken'ichi  (A) (B)
Affiliations:	(A): Research Institute for Biological Sciences, Okayama (RIBS, Okayama) (B): Crest, JST

We have already reported that glutathione (GSH) is associated with flowering in Arabidopsis thaliana [Plant Cell Physiol. 42: 524, 2001]. GSH is a tripeptide that is synthesized from glutamate via two reactionsDThe key reaction of GSH biosynthesis is catalyzed by g-glutamylcysteine synthetase (g-ECS) and relies on the light intensity. The light-intensity-dependent promotion of flowering depends on the reaction that is catalyzed by g-ECS. In this study, we generated the transgenic Arabidopsis plants overexpressing g-ECS to evaluate the relationship of GSH with the light-intensity-dependent promotion of flowering. Flowering in the wild-type and transgenic plants was promoted in a light-intensity-dependent manner, but in weak-light conditions, the transgenics showed delayed flowering compared to the wild-type. As the light intensity increased, the difference in flowering time between the wild-type and transgenic plants reduced and, in strong-light conditions, almost disappeared. These indicate that GSH suppresses the light-intensity-dependent promotion of flowering. The expression levels of the flowering-time genes FT and AGL20/SOC1 in transgenic plants were not reduced compared to those in wild-type in both strong- and weak-light conditions. Thus, it is not by inhibiting the expression of these genes that GSH suppresses the light-intensity-dependent promotion of flowering. The wild-type and transgenic plants grown in strong light showed reduced expression levels of these genes compared to those in weak light. Flowering-promotional effects of light were also observed in the mutants defective in GI acting upstream of these genes. These suggest that the light-intensity-dependent promotion of flowering associated with GSH is independent of these flowering-regulating genes.