Author:

Abstract:

Trehalose functions as a reserve carbohydrate and a stress protectant in a large variety of microorganisms, insects and invertebrates. The major pathway for trehalose synthesis is a two-step reaction, involving a trehalose-6-phophate (T6P) synthase, which synthesizes T6P from UDP-glucose and glucose-6-phosphate, and a T6P-phosphatase (TPP). Trehalose synthesis has long been thought to be absent in most vascular plants, but its significance began to dawn when ectopic expression of microbial trehalose metabolism genes resulted in dramatic phenotypes affecting plant carbohydrate partitioning, growth, development and stress resistance. Arabidopsis thaliana encodes a remarkably large family of putative trehalose biosynthesis enzymes, consistent with rigid level control and important regulatory functions of T6P, emerging as a novel sugar “signal” in coordinating carbon supply with plant growth, developmental signaling and morphogenesis. We are focussing at the Class III (AtTPPA-AtTPPJ) enzymes, which only have the conserved phosphatase boxes in common with yeast Tps2 TPP. The growth phenotype of the yeast tps2 mutant can be complemented by any of the 10 TPP genes, suggesting that these Class III proteins all have in vivo TPP activity, in contrast to the classII (TPS5-TPS11) enzymes, which do not show any activity. We will present detailed in vitro kinetic analysis for the classIII genes. For a comprehensive expression analysis, we have made promoter GUS/GFP constructs for all genes. Preliminary analysis displays remarkable tissue- and developmental stage-specific expression patterns. Our results suggest important novel functions of trehalose metabolism in plant growth and development.