Abstract
To identify Arabidopsis nuclear genes responsible for chloroplast development, we have identified a large number of albino and pale-green (apg) mutants by screening of Ds-tagged lines. One of the apg mutants, apg6, has Ds insertion in a gene encoding a Hsp101 homolog of heat shock protein. We have isolated its revertants, and also identified three alleles of apg6. All these three alleles showed same phenotype, pale-green. These results suggest a role of the Hsp101 homolog in chloroplast development. The APG6 protein contains a transit peptide that function chloroplast localization, but no transmembrane domain. Based on electron micrographic observation of chloroplasts of apg6 cells, apg6 plastids were smaller than those of wild type, and contained undeveloped thylakoid membrane. The expression of APG6 is strongly increased by heat stress. These results suggest that the APG6 protein may function as a chaperon in chloroplast stroma.
