Integrated Proteomic and Physiological Profiling of Phosphate Stress Response in Potato (Solanum tuberosum L.)

Inorganic phosphate (Pi) is an essential element for plant growth and development. To investigate the response of potatoes to Pi stress, five treatments of control (1.25 mM KH₂PO₄), low Pi treatments (0, 0.25, and 0.5 mM KH₂PO₄), and high Pi treatment (2.5 mM KH₂PO₄) were set up. The physiological results showed that both low and high Pi treatments inhibited the growth and development of potato plants. Low Pi treatments inhibited the yield and starch granule size of potato tubers, and there was no significant difference under the high Pi treatment. Two-dimensional gel electrophoresis (2-DE) and MALDI-TOF/TOF-MS mass spectrometry were used to identify 49 differentially expressed protein spots (p < 0.05, differential expression ≥ 2-fold) in potato leaves under different Pi treatments. Some primary carbon metabolism-related enzymes were up-regulated, and sufficient metabolic intermediates and energy were provided by low Pi treatments to enhance the resistance to Pi stress. Moreover, low Pi treatments induced more defense mechanisms than "high Pi treatments", resulting in enhanced resistance. Under Pi stress, although most photoreaction-related proteins were down-regulated, potato specifically induced the up-regulation of CO₂ fixation and assimilation-related enzymes to maintain growth and metabolism. Pi stress disrupted redox homeostasis, but potatoes achieved dynamic regulation of the antioxidant system by inducing synergistic up-regulation of some antioxidant enzymes. Finally, low Pi stress also activated the calcium signaling pathway, which may synergistically act with other signal transduction proteins to regulate Pi absorption, transport, and utilization in potatoes. These results provide important information on the response of potatoes to Pi stress.