Effects and Regulatory Mechanism of Exogenous H2O2 on Amino Acid Metabolism in Post-harvest Broccoli: an Integrated Analysis of Transcriptomic and Metabolomic

An integrated transcriptome and metabolome profiling was used to investigate how exogenous H2O2 affects amino acid metabolism and its underlying regulatory mechanism involved in post-harvest broccoli’s yellowing and senescence processes. This approach found 86 differentially expressed genes (DEGs) and 28 differentially accumulated metabolites (DAMs) associated with amino acid metabolism during broccoli storage in the Control, H2O2, and DPI (diphenylene iodonium, an H2O2 inhibitor) treatments on 2 or 4 d. Furthermore, H2O2 treatment promoted the biosynthesis and accumulation of amino acids (e.g., tryptophan, valine, isoleucine, arginine, lysine, histidine, and glutamate) while inhibiting the degradation of seven amino acids (e.g., tyrosine, valine, leucine, isoleucine, β-alanine, glutamate, and proline) into tricarboxylic acid (TCA) cycle precursor (pyruvate) and intermediates (fumarate, acetyl-CoA, and 2-oxoglutarate). This inhibition alleviated metabolic disorders and ammonium-induced toxicity of post-harvest broccoli. Additionally, H2O2 treatment promoted the NH3 conversion into glutamine and the urea cycle, further mitigating ammonium-induced toxicity. H2O2 treatment also down-regulated the expressions of S-adenosylmethionine synthases (SAM), 1-aminocyclopropane-1-carboxylate synthases (ACS), and 1-aminocyclopropane-1-carboxylate oxidases (ACO), which reduced the S-adenosyl-L-methionine content, thereby inhibiting ethylene biosynthesis from methionine. Therefore, this study provides insights into the role and potential underlying regulatory mechanism of H2O2 on amino acid metabolism during broccoli senescence, thus offering a theoretical basis for delaying senescence in post-harvest horticultural products by regulating their amino acid metabolism.