Abstract
An Arabidopsis mutants yellow variegated 1 (var1) and var2 exhibit a leaf-variegated phenotype. The responsible genes encode different FtsH metalloproteases (FtsH5 and FtsH2, respectively) involved in the quality control of photosystems. To understand the mechanisms leading to leaf variegation, we isolated the suppressor of var2. Interestingly, it also suppresses the variegation of var1 and var1/var2. The mutation was found in a gene encoding a chloroplastic translation initiation factor 2 (cpIF2). We showed that this protein indeed acts as a cpIF2 in vivo. The suppression of leaf variegation caused by the loss of FtsHs was most likely attributed to reduced protein synthesis in chloroplasts. This hypothesis was further supported by the observation that chloroplast translation elongation factor G mutant also suppressed the leaf variegation of var2. Based on these results, we propose that the balance between protein synthesis and degradation in chloroplasts is crucial for variegation formation.
