Expression Profiling of Rice Chloroplast Proteins During Growth and Development

In plants, chloroplast is the key organelle for the photosynthesis, the knowledge about biological processes in chloroplast has been accumulated. However, limited information exists on the expression of chloroplast proteins. To investigate the expression profiling of rice chloroplast proteins in different growth and developmental stages and provide a pilot experiment for rice antibody-based proteomics. To address this questions, ten rice chloroplast genes were chosen and antibodies were generated using proteins expressed in E. coli or epitope peptides synthesized in vitro as immunogen, protein expression profiling were investigated by Western blotting for root, stem, leaf and panicles at five developmental stages. The results indicated that all chloroplast proteins tested were expressed in leaf, but not detectable in root. The photosynthesis primary reaction protein CAB1 and CAB2, the electron transport protein OEE1, and the ROS scavenging-related proteins 2-CysP and Trx were expressed in stem, but four carbon fixation proteins RCA, GAPDH, FBPA and SBPase, which involved in Calvin cycle, were not detected in stem. In panicle, the chloroplast proteins showed different expression patterns, CAB2 and 2-CysP were expressed at all stages during panicle growth and development, CAB1 and OEE1 were expressed at late stage, and the four proteins involved in Calvin cycle were expressed only in the middle stage. Interestingly, four proteins in Calvin cycle showed the same expression patterns, supporting their cohesive relationship. In addition, the data revealed possible clues of post-translational modification, dimer and different forms of transcripts. Comparison analysis between the profiling of gene transcription and translation revealed parallel phenomena; however, they are quite different at least in some instances. Taking together, this experiment revealed the expression patterns of rice chloroplast proteins in a direct and relative quantitative way, provided helpful information for better understanding their function and also provided a preliminary proof for the concept of a rice antibody-based proteomics strategy.