Abstract
We isolated the pcb2 (pale-green and chlorophyll b reduced 2) mutant from the EMS mutant library of Arabidopsis. This mutant exhibits pale-green phenotype and contains only one third the amount of chlorophyll compared to wild-type. Especially the amount of chlorophyll b was reduced dramatically. Eelectron microscopic observation of pcb2 mutant mesophyll cells showed that their grana stacks were remarkably decreased, although both the size and the number of chloroplasts were almost the same as those of wild-type. The responsible gene was mapped to an area of 190kb length at the upper arm of the 5th chromosome, where 49 genes were found. Comparison of DNA sequences revealed a single nucleotide substitution causing nonsense mutation in one of the genes. This gene has similarity to genes for proteins from Oryza sativa and Chlorobium tepidum whose function has, however, not yet been determined.
