Quantitative Proteomics Reveals SOS2-related Proteins in Arabidopsis under Salt Stress

Background: Soil salinity is a major issue that seriously affects plant growth and cultivated land utilization. Salt tolerance is one of the most fundamental biological processes that ensures plants survival. SOS2 is one of the most important components of the Salt Overly Sensitive (SOS) signaling pathway, which maintains plant ion homeostasis under salt stress. The SOS2-related signaling pathways remain incompletely exploited especially at the proteomics level. Objective: In this paper, proteins potentially interacting with and regulated by SOS2 in Arabidopsis were identified. Methods: The proteomes of Arabidopsis Wild Type (WT) and SOS2-deficient mutant (sos2-2) exposed to 100 mM NaCl for 6 h were compared, proteins were identified using data-independent acquisition-based quantitative proteomics strategy. Results: A total of 7470 proteins were identified and quantified, 372 Differentially Expressed Proteins (DEP) were detected between WT and sos2-2 mutant under normal condition and 179 DEPs were identified under salt treatment. Functional analysis showed that the DEPs were mainly involved in protein binding and catalytic activity. Among the DEPs under salt stress, the protein expressions of AVP1, Photosystem II reaction center protein A, B, C, and stress-responsive protein (KIN2) were significantly up-regulated. LHCA1, LHCA2, LHCA4, ATPD and ATPE were significantly down-regulated. These proteins were involved in biological processes including: stress response, photosynthesis, transport and heat shock. Conclusion: These results revealed complexity of the functions of SOS2 in maintaining intracellular homeostasis, in addition to its function in sodium homeostasis. Plant salt resistance is not independent but closely related to metabolic processes including photosystem, ATP synthase, transport and other stress resistances.