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

The function of the PsbS protein in relation to non-photochemical energy dependent quenching in rice plants. Hee-Young Koo^*,1, Ismayil Zulfugarov¹, Min-Hyuk Oh¹, Sun Ho Kim¹, Yong-Hwan Moon¹, Chin Bum Lee², Stefan Jansson³, Gynheung An⁴, ¹ Department of Molecular Biology, Pusan National University, Busan, Republic of Korea^{2 3 4}

ABSTRACT- A 22 kDa chlorophyll-binding protein of the photosystem II, PsbS, was found in Arabidopsis thaliana as a specific protein necessary for energy-dependent component of non-photochemical quenching (NPQ) that protects plants under photoinhibition and photooxidative stress by dissipating excessive light energy as heat (Li et al., Nature, 403: 391-395, 2000). In this research, we selected a rice knock-out mutant of PsbS from a T-DNA tagging line pool, and among the segregated 15 plants in its T2 generation all 4 homozygous plants showed a clear phenotype of lacking NPQ. Western blotting using a PsbS specific antibody also proved that all the 4 plants were unable to make PsbS proteins. Although homozygous plants did not show apparent phenotypes different from wild types, their grain filling capacities were less than other segregating plants. This result proves the function of PsbS in relation to the fitness in the field with varying light intensity in rice as reported in Arabidopsis (Kulheim et al., Science, 297: 91-93, 2002). The role of NPQ and the function of PsbS in relation to the generation of reactive oxygen species will be discussed.

KEY WORDS: PsbS, NPQ, ROS, Photosystem II