PARENT SESSION

Symposium S4B Sugar signalling: Photosynthesis, hormones and development
Tuesday August 31st, 2004 2:40 PM-4:40 PM Room 210A
Chair: Dan Bush
Co-Chair: Mathew Paul

Comparison of transcript profiles following short term exposure of Arabidopsis to elevated CO₂ or glucose. Sylva Donaldson^*,1, John Coleman¹, ¹ Department of Botany/University of Toronto, Toronto, Ontario, Canada

ABSTRACT- The impact of elevated CO2 concentrations on photosynthetic gene expression in a number of plant species has been well documented. There is considerable evidence to support the hypothesis that high CO generated, in planta levels of carbohydrates and/or the flux of specific sugars through metabolite pools initiate the signaling systems by which gene expression is modulated. Attempts to use the growth of Arabidopsis mutants on high external concentrations of glucose or sucrose as a mechanism to genetically dissect this signaling pathway, however, often identify genes in various hormone signaling pathways, principally those involving ABA. Although there is significant cross-talk between signaling pathways, a direct link between the genes identified in such screens, and the photosynthetic response of the plant to high CO, is not readily apparent. In an attempt to reconcile these results, we have used microarray analysis of the Arabidopsis transcriptome to examine patterns of gene expression in 9-day old seedlings exposed to 1500 ppm CO2 over an extended time course of 72 hours. We have compared these patterns of gene expressions with those generated by Arabidopsis seedlings grown continuously on glucose, or exposed to glucose for 48 hours following 9 days of growth on MS media alone. Transcript profiles of seedlings germinated and grown on glucose were significantly different from those generated by high CO2 exposure, and reflected the impact of a mixotrophic environment on developmental and abiotic stress responses. Limited, post germination exposure to high levels of external glucose more closely resembled the high CO2 transcriptome response but still impacts on a variety of other plant response pathways not initially affected by high CO2. The data are discussed with respect to the efficacy of screening protocols for mutants in photosynthetic gene expression.

KEY WORDS: high CO2, transcriptome, Arabidopsis, glucose