Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 30, 2003
Publication Date: December 20, 2003
Citation: WU, G., ORT, D.R. MUTATION IN THE -SUBUNIT OF CHLOROPLAST ATP SYNTHASE IN ARABIDOPSIS ALTERS THE REDOX REGULATORY PROCESS AND PHOTOSYNTHESIS UNDER THE LIGHT. PLANT PHYSIOLOGY SUPPLEMENT. 2003. Abstract. p. 103.
The <gamma>-subunit of chloroplast ATP synthase contains a redox regulatory domain through which ATP synthase activity is regulated during diurnal cycles of light by dithiols and disulfide exchange between thioredoxin and the <gamma>-subunit. The cfq mutant has a point mutation in the downstream of <gamma>-subunit regulatory domain, in which the Glu244 is substituted by Lysine. In this experiment, the fresh chloroplasts were used to study the change of the mutant ATP synthase behaviors. The ATPase activity of cfq is slightly responsive to the light induction, but the wild-type ATPase activity increased to more than 2 folds under 50 <mu>mol m<sup>-2</sup> s<sup>-1</sup>. On the contrary, the ATP synthetic activity of cfq increased significantly under the light with a peak at 800 <mu>mol m<sup>-2</sup> s<sup>-1</sup> although it is much lower than that of wild-type and requires higher light intensity to reach the maximum value. These results indicate that the mutation in the <gamma>-subunit greatly impairs the redox regulation of ATP synthase. The result also shows that the saturate light for the hydrolytic activity is much lower than the saturate light required for the synthetic activity indicating the inconsistency between the two processes. The light induction of steady-state CO<sub>2</sub> exchange experiments show that the photosynthesis rate of cfq is about 20 percent lower than that of wild-type and it takes longer time to reach full induction.