Poster: Photosynthesis

Abs # 359: Isolation of Arabidopsis mutants that have defects in the regulation of non-photochemical quenching under high light

Presenter:	Kurosawa, Mari , marikrsw@hotmail.com
Authors	Kurosawa, Mari  (A)   Sonoike, Kintake  (A)   Kudo, Hideki  (A)   Higuchi, Mieko  (A)
Affiliations:	(A): The University of Tokyo Graduate School of Frontier Sciences

To understand the regulatory mechanism of non-photochemical quenching under high-light condition, T-DNA tagged Arabidopsis thaliana mutants were screened by two-dimensional chlorophyll fluorescence video imaging system. Two mutants having altered kinetics of the chlorophyll fluorescence compared with that of the wild type have been isolated out of 2250 seedlings. These were designated as cfa1 and cfa2 mutants, mutants with chlorophyll fluorescence alteration. The cfa1 mutant was distinguishable from wild-type plants by slightly delayed appearance of the peak of the chlorophyll fluorescence. Further characterization of the cfa1 mutant by pulse amplitude modulation (PAM) fluorometer showed that non-photochemical quenching (NPQ) decreased to 76% of the wild-type plants, whereas other photosynthetic parameters did not show significant differences. The induction of the NPQ of the cfa1 mutant upon light illumination was slower, but the relaxation was about the same, compared with the wild-type plants, suggesting that the defect may not be related to the breaking off of DpH across thylakoid membranes, but may be the mechanisms responsible for the induction of NPQ under high light. It was shown that the T-DNA in this mutant was inserted on the site on chromosome 4 coding for a putative protein of unknown function. Amino acid sequence of this protein is highly conserved in Oryza sativa, though its function is also unknown. Further characterization of cfa1 may lead to the new insight into the regulation of non-photochemical quenching.