Effect of ethylene and 1-MCP on expression of genes involved in ethylene biosynthesis and perception during ripening of apple fruit

Ethylene plays an important role in regulating fruit ripening and senescence and directly influences the development of the eating quality of fresh apples, including appearance, color, texture, and flavor. Apple fruit (Malus domestica Borkh.) is a well-known climacteric fruit and a good model system to study fruit ripening and senescence. To better understand fruit ripening and the role of ethylene perception and signal transduction, apples harvested at a pre-climacteric stage were allowed to naturally ripen, or ripening was either stimulated by treatment with 36 mu L L-1 ethylene for 24 h or inhibited by 1-MCP treatment (1.0 mu L L-1 for 24 h), respectively. Postharvest physiological indices including respiration and ethylene production were monitored for 22 d for ethylene treatment and 47 d for 1-MCP treatment. Based on an efficiency test, 20 genes in relation to ethylene biosynthesis and perception were investigated using real-time qPCR during the post-treatment period. The ETR2, ETR5, ERSs, EIL4, ERFs genes together with ACS1 and ACO1 genes were significantly up-regulated in fruit during ripening. Ethylene treatment further enhanced the expression of ACO2, ETR1, CTR1s and EIN2A genes, while the ACS3 and ACO3, and EIN2B genes were only slightly affected. 1-MCP treatment significantly inhibited expression of ACS1, ACO1 and ACO2 ethylene biosynthesis genes, which coincided with ethylene production. 1-MCP treatment also reduced expression of ETR1, ETR2, ETR5, ERSs, CTR1 EIN2A, EIL4 and ERFs genes, while having a limited effect on ACS3, ACO3, and EIN2B. This study demonstrated the complexity and dynamic changes of transcriptional profiles of ethylene perception and biosynthesis in response to fruit ripening, ethylene, and 1-MCP treatment. Understanding of the significant changes of these genes and their function may help to explore the mechanisms controlling apple fruit ripening and its response to exogenous ethylene stimuli and action inhibition at the receptor level during ripening and senescence. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.