Proteomic changes induced by potassium deficiency and potassium substitution by sodium in sugar beet

In this study, sugar beets (Beta vulgaris L.) were grown at different K+/Na+ concentrations: mmol/L, 3/0 (control); 0.03/2.97 (K–Na replacement group; Trep); 0.03/0 (K de ciency group; Tdef) in order to investigate the effects of K+ de ciency and replacement of K+ by Na+ on plant proteomics, and to explore the physiologi- cal processes in uenced by Na+ to compensate for a lack of K+. After 22 days, fresh and dry weight as well as the Na+ and K+ concentration were measured and changes in proteomics were tested by 2D gel electrophoresis. Interest- ingly, Na+ showed stimulation in growth of seedlings and hindrance of K+ assimilation in Trep. Signi cant changes were also observed in 27 protein spots among the treat- ments. These are proteins involved in photosynthesis, cellular respiration, protein folding and degradation, stress and defense, other metabolisms, transcription related, and protein synthesis. A wide range of physiological processes, including light reaction, CO2 assimilation, glycolysis, and tricaboxylic acid cycle, was impaired owing to K+ star- vation. Compensating for the effect of K+ starvation, an increase in photosynthesis was also observed in Trep. How- ever, we also found a limitation of cellular respiration by Na+. Na+ is therefore in some ways able to recover damage due to K de ciency at protein level, but cannot functionally replace K as an essential nutrient.