Proteomic analysis of cold stress responses in tobacco seedlings
Cold stress is one of the major abiotic stresses limiting the productivity and the geographical distribution of many important crops. To gain a better understanding of cold stress responses in tobacco (Nicotiana tabacum), we carried out a comparative proteomic analysis. Five-week-old tobacco seedlings were treated at 4°C for 4 h. Cold treatment resulted in stress phenotypes of smoothing and shallowing leaves and increased relative electrolyte leakage. The expression changes of total proteins in tobacco leaves were examined using two-dimensional electrophoresis. Quantitative image analysis revealed a total of 101 protein spots that changed their intensities significantly, 21 protein spots were down-regulated, eight were up-regulated after the cold treatment, 50 protein spots only expressed in the control sample, while 22 protein spots were only present in the cold treatment sample. Mass spectrometry analysis allowed the identification of 73 differentially expressed proteins, including well known and novel cold-responsive proteins. The identified proteins are involved in several processes such as photosynthesis, protein processing, redox homeostasis, ribonucleic acid (RNA) processing, signal transduction, translation, cell division/cycle, and metabolisms of carbon and energy. Several types of proteins showed enhanced degradation during chilling stress, especially the photosynthetic proteins. Gene expression analysis of 25 different proteins by reverse transcriptase- polymerase chain reaction (RT-PCR) showed that the messenger RNA (mRNA) levels of 18 genes correlated well with the protein levels. In conclusion, our study provides new insights into cold stress responses in tobacco and needs to be further studied in future.
Key words: Proteomics, cold stress, tobacco (Nicotiana tabacum).