Abstract
Cf9-interacting thioredoxin was originally identified as a protein interacting with the C-terminal cytosolic domain of Cf9, which confer resistance to Cladosprium fulvum that expresses Avr9. However, the gene structure and proteome analysis suggested that CITRX is a chloroplast-localized protein and is conserved among green algae and higher plants. In order to confirm the subcellular localization of CITRX, AtCITRX-GFP was transiently expressed in Arabidopsis protoplasts. AtCITRX-GFP was exclusively localized to chloroplasts. The T-DNA insertion mutant for citrx gene showed albino phenotype and decreased expression of plastid photosynthesis genes. It has been previously reported that CITRX was detected in plastid transcriptional active chromosome, pTAC in A. thaliana and S. alba. In addition, we found that AtCITRX likely interacts with one of pTAC proteins and a chloroplast protein that is involved in plastid differentiation. These data suggested that AtCITRX mainly functions in chloroplasts and is involved in plastid gene expression.
