Proteomics study on the changes in amino acid metabolism during broccoli senescence induced by elevated O₂ storage

To better understand the global changes of amino acid catabolism and anabolism in broccoli in response to high O₂ stress, iTRAQ-based proteomics combined with amino acid analysis was used to investigate the broccoli proteome at 0 and 4 d after treatment with different O₂ concentrations (5% O₂ + 5% CO₂, 20% O₂ + 5% CO₂ and 40% O₂ + 5% CO₂) at 20℃. A total of 106 proteins with changes ≥ 1.2-fold in abundance were observed. Amino acid anabolism was significantly suppressed by high O₂ stress, while catabolism was enhanced. High O₂ stress-induced amino acid metabolism promoted the conversion of Met to ethylene and the degradation of amino acids to intermediate metabolites of the TCA cycle, thereby suppressing glucosinolate biosynthesis. However, the up-regulation of arginase and urease induced by high O₂ stress aggravated ammonium toxicity. These findings enhance our understanding of high O₂ stress-induced amino acid metabolism, as well as the effects of amino acid metabolism on broccoli senescence.