PARENT SESSION
Posters P6C Photosynthesis, respiration and alternative electron sinks. Abstracts (660-680)

Investigations into the role of IMMUTANS gene product as an alternative electron sink in Arabidopsis thaliana. Dominic Rosso ^*,1, Alexander Ivanov¹, Steve Rodermel ², Denis Maxwell¹, Norman Huner¹, ¹ Department of Biology, London, Ontario, Canada² Department of Botany, Ames, Iowa, USA

ABSTRACT- Chlororespiration has been defined as a chloroplastic respiratory electron transport chain (ETC) that interacts with the photosynthetic ETC. A component of the chlororespiratory pathway is believed to be encoded by the IMMUTANS gene, the presumed plastid terminal oxidase (PTOX). We hypothesize that plants in which IMMUTANS has been over-expressed (OVEX) should exhibit increased capacity to act as a sink for photosynthetic ETC compared to WT and a plant which lacks the IMMUTANS gene (CS 3157). To assess potential functional differences in photosynthetic intersystem electron transport between WT, OVEX, and knockout mutant, we used the absorbance change at 820 nm (A₈₂₀/A₈₂₀) as a measure of the oxidation-reduction state of P700. We found that plants in which the IMMUTANS gene has been over-expressed (OVEX) had 50% greater oxidation-reduction of P700 compared to WT. Interestingly, the extent of photo-oxidation of P700 for the knockout mutant exhibited an even greater extent of photo-oxidation of P700. Overall, these data indicate that IMMUTANS does not play a significant role as a competitive alternative electron sink to photosynthetic electron transport.

KEY WORDS: Chlororespiration, IMMUTANS, Alternative electron sink, Plastid terminal oxidase