PARENT SESSION
Posters P1B Photo-oxidative stress, photoinhibition. Abstracts (394-443)

The involvement of proteases in the protection of Synechocystis sp. PCC 6803 from environmental stresses. Myles Barker^*,1, Remco De Vries¹, Marko Boehm¹, Josef Komenda², Peter Nixon¹, ¹ Department of Biological Sciences, Imperial College London, South Kensington Campus, London, UK² Laboratory of Photosynthesis, Institute of Microbiology, Opatovicky mlyn, Trebon, Czechia

ABSTRACT- In oxygenic photosynthetic organisms the photosystem II (PSII) D1 subunit is damaged by light. In order to alleviate this problem, a repair cycle removes and replaces D1. It is only when there is an increase in the rate of damage to D1 in comparison to its resynthesis and replacement that a loss of PSII activity is observed. It is thought that D1 turnover in chloroplasts involves both the DegP/HtrA and FtsH proteases. This has therefore prompted research into cyanobacterial DegP/HtrA and FtsH homologues. Synechocystis 6803 harbours three putative DegP/HtrA protease homologues termed slr1204, sll1427 and sll1679. A triple mutant of all three genes was constructed and was found to be sensitive to high-light and other stresses. However, PSII repair and D1 turnover was normal. These findings suggest that the DegP/HtrA proteases are not required for D1 turnover, but may have auxiliary roles under light and other stresses. Synechocystis 6803 also contains four FtsH homologues termed slr0228, slr1390, slr1604 and sll1463. All four are putative AAA+ membrane associated proteins with Walker ATPase motifs, a zinc binding active site and a possible carboxy-terminal leucine zipper motif. An insertion mutant of slr0228 has previously shown that slr0228 is important for D1 turnover in Synechocystis 6803 (Silva et al., 2003. Plant cell 15, 2152-2164). In order to clarify the expression, location and interacting partners of slr0228 we have produced an epitope tagged Synechocystis 6803 strain.

KEY WORDS: HtrA, DegP, FtsH, Photosystem II