Comparative Transcriptomic Analysis of Chlorophyll Metabolism in Broccoli Under Preharvest 1-MCP Application Versus Pre-Cooling Combined with Cold Chain Storage

Broccoli (Brassica oleracea var. italica) is highly nutritious, rich in vitamin C, glucosinolates, and minerals. However, its high postharvest respiratory rate leads to rapid quality deterioration, particularly chlorophyll degradation and yellowing under ambient conditions. In China, the lack of timely pre-cooling facilities exacerbates postharvest losses. Therefore, developing safe, effective and low-cost preservation methods for broccoli during transportation is of great practical importance. In this study, RNA sequencing was employed to analyze the effects of preharvest 1-methylcyclopropene (1-MCP) and postharvest pre-cooling combined with cold treatments on gene expression in broccoli. Transcriptome analysis revealed that both treatments significantly upregulated or maintained key genes involved in chlorophyll biosynthesis (e.g., Glutamyl-tRNA reductase (GluTR), porphobilinogen deaminase (PBGD), magnesium chelatase (MgCh)) and downregulated chlorophyll degradation-related genes (e.g., Chlorophyllase (CLH), pheophytinase (PPH), pheophorbide a oxygenase (PaO)), resulting in enhanced chlorophyll retention. Furthermore, chlorophyllide a oxygenase (CAO) was upregulated, while chlorophyll b reductase (CBR) was downregulated, suggesting modulation of the chlorophyll cycle. These findings elucidate the molecular mechanisms by which 1-MCP and pre-cooling combined with cold regulate chlorophyll metabolism, providing new insights into the gene regulatory network underlying the postharvest quality maintenance in broccoli.