Abstract
An Arabidopsis leaf-variegated mutant var2 results from the loss of FtsH2, an ATP-dependent metalloprotease in thylakoid membranes. Here, we report physiological and biochemical characterization of the white sectors of var2. We successfully visualized plastids in the white sectors by expressing chloroplast-targeted GFP, suggesting that those plastids retain protein transport machinery. Observation of plastid DNAs by a DNA-specific fluorescent dye DAPI showed that plastid DNAs in the white tissues were organized as nucleoids typically detected in undifferentiated plastids. RT-PCR and immuno-blot analyses also showed that chloroplast genes as well as nuclear genes were expressed in the white tissues, although the levels of photosynthetic proteins appeared to decrease. These results collectively suggested that the white sector is an active tissue formed by viable cells. We currently examine if there are any changes in protein composition between the white and green sectors by proteomic analysis.
