Poster: Temperature responses

Abs # 145: Differential regulation in response to environmental stresses and functional characterization of trehalose biosynthesis genes from rice.

Presenter:	Imai, Ryozo , rzi@affrc.go.jp
Authors	Imai, Ryozo  (A)   Shima, Shuhei  (A) (B)  M. Habibur, Pramanik R (A)   Satoshi, Tahara  (B)
Affiliations:	(A): National Agricultural Research Center for Hokkaido Region (B): Hokkaido University
Web Site:	http://cse.naro.affrc.go.jp/rzi/index.html

Trehalose is a non-reducing disaccharide of glucose and commonly serves as a stress protectant and/or reserve carbohydrate in a variety of organisms including bacteria, fungi, yeast and invertebrates. Recently, genes for trehalose biosynthesis and minute occurrence of trehalose in higher plants have been demonstrated. However, the function of trehalose in higher plants remains to be explored. Trehalose is synthesized from UDP-glucose and glucose-6-phosphate in a two-step process by trehalose-6-phophate synthase (TPS) and trehalsoe-6-phosphate phosphatase (TPP). We have reported that a TPP gene of rice (OsTPP1) is transiently induced upon chilling stress (12C), which was followed by concomitant transient increases in total cellular TPP activity and trehalose levels in roots (Pramanik and Imai, Plant Biology 2003 p67). Four putative TPP genes were found in the rice genome sequence. RT-PCR using specific primers indicated OsTPP1 and OsTPP2 mRNAs are present in root and shoot of young seedlings while OsTPP3 and OsTPP4 mRNAs were undetectable either in root and shoot tissues. OsTPP2 was functionally characterized in vivo and in vitro utilizing yeast mutant and purified recombinant protein, respectively. Expression of OsTPP2 was induced transiently by chilling (12C) but the response was delayed and reduced as compared with OsTPP1. Drought and salt as well as exogenous ABA treatment induced the OsTPP2 expression in a manner different from OsTPP1.