Background: Understanding the mechanisms involved in climacteric fruit ripening is key to improve fruit harvest quality and postharvest performance. Kiwifruit (Actinidia deliciosa cv. 'Hayward') ripening involves a series of metabolic changes regulated by ethylene. Although 1-methylcyclopropene (1-MCP, inhibitor of ethylene action) or ozone (O) exposure suppresses ethylene-related kiwifruit ripening, how these molecules interact during ripening is unknown.
Results: Harvested 'Hayward' kiwifruits were treated with 1-MCP and exposed to ethylene-free cold storage (0 °C, RH 95%) with ambient atmosphere (control) or atmosphere enriched with O (0.3 μL L) for up to 6 months. Their subsequent ripening performance at 20 °C (90% RH) was characterized. Treatment with either 1-MCP or O inhibited endogenous ethylene biosynthesis and delayed fruit ripening at 20 °C. 1-MCP and O in combination severely inhibited kiwifruit ripening, significantly extending fruit storage potential. To characterize ethylene sensitivity of kiwifruit following 1-MCP and O treatments, fruit were exposed to exogenous ethylene (100 μL L, 24 h) upon transfer to 20 °C following 4 and 6 months of cold storage. Exogenous ethylene treatment restored ethylene biosynthesis in fruit previously exposed in an O-enriched atmosphere. Comparative proteomics analysis showed separate kiwifruit ripening responses, unraveled common 1-MCP- and O-dependent metabolic pathways and identified specific proteins associated with these different ripening behaviors. Protein components that were differentially expressed following exogenous ethylene exposure after 1-MCP or O treatment were identified and their protein-protein interaction networks were determined. The expression of several kiwifruit ripening related genes, such as 1-aminocyclopropane-1-carboxylic acid oxidase (ACO1), ethylene receptor (ETR1), lipoxygenase (LOX1), geranylgeranyl diphosphate synthase (GGP1), and expansin (EXP2), was strongly affected by O, 1-MCP, their combination, and exogenously applied ethylene.
Conclusions: Our findings suggest that the combination of 1-MCP and O functions as a robust repressive modulator of kiwifruit ripening and provide new insight into the metabolic events underlying ethylene-induced and ethylene-independent ripening outcomes.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6296049 | PMC |
http://dx.doi.org/10.1186/s12870-018-1584-y | DOI Listing |
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