Poster: Temperature Responses

Abs # 192: Upregulation of Glutathione Biosynthesis Promotes Bolting and Senescence of Rosette Plant Eustoma grandiflorum

Presenter:	Yanagida, Mototsugu , yanagida@bio-ribs.com
Authors	Yanagida, Mototsugu  (A) (B)  Mino, Masanobu  (A)   Iwabuchi, Masaki  (A)   Ogawa, Ken'ichi  (A) (B)
Affiliations:	(A): Research Institute for Biological Sciences, Okayama (RIBS Okayama) (B): Crest, JST

Some plants pass the winter with an expanded leaf rosette forming on the ground. Many of them require a certain period of chilling (vernalization) for initiating bolting and subsequent flowering. Chilling-responsive reductant glutathione (GSH) is an abundant and ubiquitous tripeptide in plant cells that is biosynthesized through two steps catalyzed by g-glutamylcysteine synthetase (g-ECS) and glutathione synthetase. We here report that upregulation of GSH synthesis is involved in the process of vernalization-induced bolting in the typical rosette type plant Eustoma grandiflorum that absolutely requires vernalization for bolting. GSH enhanced this vernalization effect, whereas the GSH biosynthesis inhibitor buthionine sulfoximine (BSO) nullified it without reducing the growth rate. GSH reversed the inhibition by BSO in a dose-dependent manner. The GSH level increased during the early vernalization period, and this increase was coupled with the activity of g-ECS, with little change in the levels of GSH precursors. The gene expression of g-ECS changed little during the vernalization period, indicating that vernalization stimulates de novo GSH biosynthesis with the activation of g-ECS protein, leading to bolting. GSH induced the bolting of E. grandiflorum without vernalization. Furthermore GSH unexpectedly hastened the senescence of E. grandiflorum leaves, although it is a general consensus that antioxidants such as GSH and ascorbic acid retard senescence. On the other hand, BSO kept the plant green and growing even 6 months after vernalization when the plant without BSO was completely senescent and no longer grew. These findings suggest that the crucial amount of GSH biosynthesized determines the bolting and senescence time of E. grandiflorum