Comprehensive insight into the chlorophyll degradation mechanism of postharvest broccoli heads under elevated O2 controlled atmosphere

Postharvest broccoli heads undergo yellowing quickly in unsuitable conditions, which diminishes their quality and commercial value. We investigated the pattern and molecular regulatory mechanism of chlorophyll (Chl) degradation in broccoli under elevated O-2 controlled atmosphere. As results, the 40% O-2 + 5% CO2 treatment accelerated the Chl degradation and the change in color of postharvest broccoli heads, while the 5% O-2 + 5% CO2 treatment delayed the yellowing. The results indicated that Chl degradation pattern of postharvest broccoli heads concurrently involved the Pheide a oxygenase (PAO)/phyllobilin and oxidative degradation pathways, and the latter might be the dominant pathway of Chl degradation. The regulatory mechanism of elevated O-2 on Chl degradation may be related to its ability to accelerate cell damage and death, destroy the light-harvesting complex II, and promote up-regulation of genes in the PAO/phyllobilin and oxidative degradation pathways. In contrast, low O-2 treatment may down-regulate the expression of Chl degradation-related genes by increasing H2O2 content, thus delaying the yellowing of broccoli heads.

Automated summary

Elevated O-2 levels accelerate chlorophyll degradation and color change in postharvest broccoli heads, while low O-2 levels delay yellowing, possibly through down-regulation of chlorophyll degradation-related genes by increasing H2O2 content.