Abstract
In a rice stay-green mutant, nyc1, degradation of LHCII, chlorophyll and carotenoid was suppressed during senescence. We hypothesized that NYC1 encodes chlorophyll b reductase. Although the product of NOL, a paralogue of NYC1, showed chlorophyll b reductase activity in vitro, we were not able to detect the activity of the NYC1 product so far. In order to further examine the function of NYC1, we analyzed a null mutant for the NYC1 ortholog, At-nyc1-1, in Arabidpsis. In At-nyc1-1, during senescence, degradation of LHCII and chlorophyll b was inhibited, but that of chlorophyll a was not inhibited. We also investigated the effect of At-nyc1-1 mutation on carotenoid composition, accumulation of LHC isoforms and the photosynthetic core complexs, photosynthetic activity and thylakoid formation. In addition, we report our attempt to measure the chlorophyll b reductase activity of AtNYC1 and AtNOL protein expressed in E. coli.
