PARENT SESSION
Posters P2B Light, redox and metabolic regulation: Light Reactions. Abstracts (444-478)

Redox state analysis of plastoquinone-pool in Arabidopsis reveals unexpected changes under different light conditions. Jerzy Kruk^*,1, Stanislaw Karpinski², ¹ Department of Plant Physiology and Biochemistry, Kraków, Poland² Department of Botany, Stockholm, Sweden

ABSTRACT- Using high-performance liquid chromatography, we were able to determine directly the total redox state of the plastoquinone (PQ), as well as the redox state of the plastoquinone-pool in Arabidopdis thaliana wild type (WT) leaves and in the chlorophyll a/b binding protein harvesting-organelle specific (designated gene CAO) mutant, named chaos, which has a reduced photosystem II antenna. The obtained results show that total level of PQ in chaos mutant was 5 times higher than in the WT in relation to foliar total chlorophyll content. The level of the photoactive PQ, i.e. PQ-pool, was 37% and in the chaos mutant only 15% of the total PQ present in leaves. The composition of the non-photoactive pool was also different in both plants; the reduction level was 50% in the WT and over 95% in the chaos mutant. The redox state of the PQ-pool was in darkness reduced in 63% and in the chaos mutant in 25%, and during the low-light (110 micromol s^-1m²) period the reduction of the PQ-pool increased to 95% and 63% in the WT and chaos mutant, respectively. Unexpectedly, in the course of excess-light treatment (20-fold increased irradiance) for a period of one hour, the PQ-pool was gradually oxidised for both plants and persisted during the next one hour of the recovery period under low-light conditions. The observed effects of differential light treatments are discussed in terms of the regulation of different molecular and physiological processes by the redox state of the PQ-pool.

KEY WORDS: Arabidopsis, chaos mutant, platoquinone, redox state