Poster: Intracellular Signaling

Abs # 813: Trehalose metabolism and signaling in Arabidopsis thaliana links up with the abscisic acid and glucose response network

Presenter:	Ramon, Matthew O, matthew.ramon@bio.kuleuven.ac.be
Authors	Ramon, Matthew O (A)   Thevelein, Johan M (A)   Leyman, Barbara  (A)
Affiliations:	(A): Lab of Mol. Cell Biol.,K. Univ. Leuven & Dep. of Mol. Microbiol., Fl. Inst. of Biotech., VIB, kasteelpark Arenberg 31,3001 Leuven, Belgium

The non-reducing disaccharide trehalose acts as a stress protectant in a range of organisms such as resurrection plants and many micro-organisms. Only small amounts can be detected in Arabidopsis thaliana which implies a regulatory function for trehalose rather than a function as a stress protectant. In the yeast Saccharomyces cerevisiae, trehalose is synthesized in two reactions from UDP-glucose and glucose-6-phosphate by trehalose-6-phosphate (Tre6P) synthase (encoded by TPS1) and Tre6P phosphatase (encoded by TPS2). Both TPS1 and Tre6P are indispensable for the regulation of glucose influx into the glycolysis. In theArabidopsis genome, 11 Tps-like genes (AtTPS) have been detected. They can be grouped in two subfamilies, displaying most similarity either to yeast TPS1 or TPS2. AtTPS1 is functionally interchangeable with TPS1 in yeast with regard to its catalytic as well as its signaling function, which implies an equally important regulatory role for AtTPS1 in plant carbon metabolism. Indeed, AtTPS1 appears to be essential for the regulation of sugar metabolism during plant embryo-development. Low concentrations of exogenous applied trehalose interfere with carbon partitioning through the induction of the ApL3 starch biosynthesis gene and accumulation of starch in the source organs resulting in reduced root elongation (Wingler et al., (2000) Plant Physiol. 124:105-114). Here we show that the transcription factor ABI4 is necessary to transmit this trehalose effect. ABI4 is a key component in the abscisic acid and sugar signal transduction pathway. In addition, we measured a small increase in the internal trehalose levels in response to external ABA. It is the first time that a link has been established between the trehalose response and abscisic acid response.