Poster: Transcription Regulation

Abs # 1066: Arabidopsis bZIP proteins that are early-responsible to sugars in an ABA-independent-manner

Presenter:	Yoshida, Yoshimasa
Authors	Yoshida, Yoshimasa  (A)   Maeo, Kenichiro  (A)   Kojima, Hisae  (A)   Kato, Takenori  (A)   Yoine, Masato  (A)   Nakamura, Kenzo  (A)
Affiliations:	(A): Lab Of Biochem, Sch Of Bioagricultural Sc, Nagoya U.

Sugar-dependent regulation of expression of various plant genes occurs by multiple signal-perception and -transduction pathways. Exogenous sugar causes elevation of the endogenous level of ABA in Arabidopsis, and some of the sugar-regulated genes are also regulated by ABA. Several ABRE-binding bZIP proteins, such as ABF1, ABF3 and GBF4, were identified among many sugar-regulated genes of Arabidopsis (SRG), and these bZIP proteins were also responsible to ABA. In contrast to these ABA-responsible bZIP proteins, mRNA for SRG-Y16 coding for a group D bZIP protein was found to be induced within 1 hr after exogenous application of sucrose. The induction of SRG-Y16 mRNA was also observed with glucose, fructose or 2-deoxy glucose, but not with mannitol or 3-O-methyl glucose. Furthermore, the SRG-Y16 mRNA was not induced by ABA. These expression property of SRG-Y16 was not shared with other members of the group D bZIP proteins. Unlike many other sugar-responsible mRNAs, the sugar-induced increase in the level of SRG-Y16 mRNA was not abolished by cycloheximide. We also found that mRNA for SRG-Y24 coding for a group C bZIP protein rapidly decreased within 1 hr after treatment with sucrose, glucose or fructose. Mannitol or ABA did not cause significant decrease in the level of SRG-Y24 mRNA compared to these metabolizable sugars. The rapid decrease in the level of SRG-Y24 mRNA after treatment with sucrose was not abolished by cycloheximide. These results suggest that SRG-Y16 and SRG-Y24 genes are early-responsible to sugars and they are involved in the early stages of sugar signal response.