Proteomics dissection of cold responsive proteins based on PEG fractionation in Arabidopsis

Proteome profiling was performed on Arabidopsis plant exposed to cold stress at 4 °C for 24 h in an attempt to explore the mechanisms of plant climate adaptation. The polyethylene glycol(PEG) fractionation protocol developed in this lab was used to identify as many differentially expressed low-abundance proteins as possible. In comparison with those of the biological controls, 67 protein spots with at least two-fold difference in expression were identified for the plant exposed to cold temperatures; and from these spots, 50 proteins were successfully identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry(MALDI-TOF MS). Bioinformatics studies on these proteins show that 57.8% of these proteins were localized in the chloroplast. Of these proteins, 8 ones have functions in photosynthesis, including glycine hydroxymethyltransferase, Rubisco large subunit, Rubisco activase, PSBO2, fructose-1,6-bisphosphate aldolase, NADP-dependent malate dehydrogenase, sedoheptulose bisphosphatase and photosystem II reaction center PsbP family protein, suggesting that photosynthesis is greatly affected by cold stress. The identified proteins were validated by quantitative real-time polymerase chain reaction(qPCR). Taken together, our results suggest that the chloroplast might also act as a cold stress sensor and that photosynthesis-related proteins may play important roles in cold acclimation for Arabidopsis .