Abstract
The variegated phenotype in Arabidopsis var2 mutant is attributed to a defect of FtsH2, a metalloprotease localized in thylakoid membranes and critically involved in the quality control of photosystem II. We previously showed that the green sectors of var2 contain the same chloroplasts as wild-type except for accumulation of reactive oxygen species. The white sectors of var2 contain undifferentiated plastids with high accumulation of scavenging enzymes such as CSD2 and APX. To understand the physiological significance of variegated leaves, microarray analysis was performed using total RNA extracted separately from green and white sectors. We found that the gene expression profile of var2 green sectors was comparable to that of wild-type. On the other hand, we found that a significant number of genes were up- or down-regulated between var2 green and white sectors. Genes related to photosynthesis and chloroplasts were down-regulated, while genes related to stresses, especially oxidative stress, were up-regulated in white sectors. Among the up-regulated genes, we focused on CSD2, and based on these results, we propose a novel function for CSD2 as a copper buffer in white sectors.
