Proteomic analysis of pakchoi leaves and roots under glycine–nitrogen conditions

The physiological and differential proteomic responses of pakchoi leaves and roots to glycine–nitrogen (Gly–N) treatments were determined. Two pakchoi (Brassica campestris ssp. chinensis L. Makino. var. communis Tsen et Lee) cultivars, ‘Huawang’ and ‘Wuyueman’, were grown under sterile hydroponic conditions with different N forms (Gly–N and nitrate–N). Gly–N-treated pakchoi exhibited decreased fresh weights, total N uptake, leaf areas, and net photosynthetic rates than those treated with nitrate–N. Differentially regulated proteins were selected after image analysis and identified using MALDI-TOF MS. A total of 23 proteins was up- or down-regulated following Gly–N treatment. These spots are involved in several processes, such as energy synthesis, N metabolism, photosynthesis, and active antioxidant defense mechanisms, that could enhance plant adaptation to Gly–N. The superior Gly tolerance of ‘Huawang’ was predominantly associated with a less severe down-regulation of proteins that are involved in the electron transport chain and N metabolism. Other factors could include less ribulose-1,5-bisphosphate carboxylase/oxygenase turnover or a higher up-regulation of stress defense proteins. These characteristics demonstrated that maintaining ATP synthesis, N metabolism, photosynthesis, and active defense mechanisms play a critical role in pakchoi adaptation to Gly–N.