PARENT SESSION
Posters P4B Sugar signalling: Photosynthesis, hormones and development. Abstracts (480-527)

Transcriptome analysis of an Arabidopsis mutant with perturbed photosynthetic carbohydrate metabolism and altered redox status. Robin Walters^*,1, Nicholas Kruger¹, ¹ Department of Plant Sciences, Oxford, UK

ABSTRACT- The tpt-1 (ape2) mutant of Arabidopsis is deficient in the chloroplast envelope triose-phosphate/phosphate translocator, which is the major route for carbohydrate export during photosynthesis. The mutation has a dramatic effect on photosynthetic metabolism, leading to greatly reduced accumulation of sucrose and a marked increase in starch synthesis. Furthermore, under high light growth conditions photosynthesis becomes phosphate limited, so that both plastoquinone and components of the chloroplast stroma become more reduced. To investigate the regulatory impact of such changes in carbohydrate and redox status, we have carried out a whole genome microarray analysis of wild type and tpt-1 plants each grown under both low light and high light. Approximately 1400 genes showed statistically significant changes in mRNA abundance, but of these only 100 showed changes greater than 2-fold under both growth conditions. Increased in the mutant were mRNAs encoding many proteins implicated in stress responses, including WRKY transcription factors, receptor protein kinases, and a respiratory burst oxidase; we suggest that these represent a coordinated response to reduced sugar levels in the leaf. However, the most pronounced increases (>5-fold) were in the expression of the TPS8 and TPS11 genes encoding members of the trehalose-6-phosphate (T6P) synthase family; analysis of other microarray data supports the hypothesis that the changes in expression of these TPS genes are as a result of altered carbohydrate leaf metabolism. Since manipulation of T6P levels affects photosynthetic capacity, and T6P is important in regulating glycolysis in yeast, we speculate that TPS8 and TPS11 form part of a regulatory network in which synthesis and sensing of T6P both influence and are influenced by primary carbohydrate metabolism.

KEY WORDS: trehalose, sugar sensing, microarray