Search

Superficial scald is a significant physiological disorder causing economic loss to the apple and pear fruit industry. Despite treatments to prevent the scald, fundamental biochemical knowledge about the injury is not completely known. To investigate the protein changes in association with scald development during storage and in response to treatments of diphenylamine and 1-MCP, two quantitative proteomic experiments employing stable isotope labeling by peptide dimethylation were conducted on two scald susceptible cultivars ‘Cortland’ and ‘Red Delicious’. Apples were untreated or treated with 2 g L −1 DPA or with/without 1 μL L −1 1-MCP, then stored at CA (3.0 kPa O 2 + 1.0 kPa CO 2 ) at 0–1 °C for up to 7 months. Among the quantified proteins, 428 proteins were common to both cultivars and 110 increased in abundance and 48 decreased during the onset of scald development. Fifty seven and 67 proteins changed significantly in abundance in response to DPA and 1-MCP treatments after 4 and 7 months storage, respectively. When combining the results from both cultivars, 14 proteins increased in abundances and 4 proteins decreased in abundance with scald development but inhibited and enhanced by both DPA and 1-MCP treatments, respectively, which were proposed to be in association with scald development of apples. Our results reveal and confirm that antioxidant and redox system, phenylpropanoid metabolism, ethylene biosynthesis, allergens, sulfur amino acids containing proteins and program cell death have direct link to the scald development. [ABSTRACT FROM AUTHOR]

Abstract: 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 36μLL−1 ethylene for 24h or inhibited by 1-MCP treatment (1.0μLL−1 for 24h), respectively. Postharvest physiological indices including respiration and ethylene production were monitored for 22d for ethylene treatment and 47d 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. [Copyright &y& Elsevier]

The effects of ethylene and 1-methylcyclopropene (1-MCP) on apple fruit volatile biosynthesis and gene expression were investigated. Statistical analysis identified 17 genes that changed significantly in response to ethylene and 1-MCP treatments. Genes encoding branched-chain amino acid aminotransferase ( BCAT ), aromatic amino acid aminotransferase (ArAT) and amino acid decarboxylases ( AADC ) were up-regulated during ripening and further enhanced by ethylene treatment. Genes related to fatty acid synthesis and metabolism, including acyl-carrier-proteins ( ACPs ), malonyl-CoA:ACP transacylase ( MCAT ), acyl-ACP-desaturase ( ACPD ), lipoxygenase ( LOX ), hydroperoxide lyase ( HPL ), alcohol dehydrogenase (ADH), pyruvate decarboxylase (PDC2), β-oxidation, acyl-CoA synthetase (ACS), enoyl-CoA hydratase (ECHD), acyl-CoA dehydrogenase (ACAD), and alcohol acyltransferases (AATs) also increased during ripening and in response to ethylene treatment. Allene oxide synthase (AOS), alcohol dehydrogenase 1 (ADH1), 3-ketoacyl-CoA thiolase and branched-chain amino acid aminotransferase 2 (BCAT2) decreased in ethylene-treated fruit. Treatment with 1-MCP and ethylene generally produced opposite effects on related genes, which provides evidence that regulation of these genes is ethylene dependent. [ABSTRACT FROM AUTHOR]