Abstract
Plants produce two chlorophyll species, chlorophyll a and chlorophyll b. These chlorophylls are enzymatically converted to each other within the chloroplast. The conversion of chlorophyll b to chlorophyll a is a two-step reaction, the first of which is catalyzed by chlorophyll b reductase. We have previously shown that this enzyme is essential in the breakdown of chlorophyll b, LHCII and thylakoid membranes during leaf senescence. Since the gene for this enzyme is highly expressed during seed maturation as well, we speculated that this enzyme also functions in maturing seeds. In this study, we investigated a role of this enzyme in seed maturation by analyzing an Arabidopsis mutant that lacks chlorophyll b reductase. We found that a large amount of chlorophyll remained in the mature seeds in this mutant. The germination rate of the mutant seeds decreased with increasing storage periods. The cotyledons of the mutants often variegated or went bleached, which is most likely due to a photodamage by excessive chlorophyll. These results suggest that chlorophyll b reductase plays an important role in the seed maturation process.
