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]

‘Ambrosia’ apple is one of the emerging apple cultivars that have been gaining popularity in North America due to its superior eating quality. An effective postharvest storage regime has been established for optimal storage and quality maintenance. Unfortunately, a postharvest physiological disorder has often been reported, which shows symptoms similar to low temperature induced soft scald in ‘Honeycrisp’. Therefore, a delayed cooling strategy prior to storage has been developed and implemented as a successful and economical method to prevent this disorder. In order to reveal the molecular mechanism of soft scald development and delayed cooling in combating this low temperature induced disorder, a quantitative proteomic investigation employing stable isotope dimethylation labeling by peptides was conducted on ‘Ambrosia’ apples from three commercial orchards in BC, Canada. Quantitative changes in protein abundance in association with disorder development and in response to delayed cooling treatment after one and three month storage were found. Among the quantified proteins, 495 and 575 proteins were commonly presented in three biological replicates after one and three month storage; respectively. Among them, the abundance of 78 and 88 proteins were found to be significantly changed in response to delayed cooling as compared with normal cold storage for one and three months, respectively. These identified proteins were functionally annotated using MAPMAN software, which identified glycolysis, lipid metabolism, amino acids (including GABA shunt), hormone response, stress and signaling, redox and glutathione metabolism as the major pathways influenced by the delayed cooling treatment. A principal component analysis (PCA) revealed groups of proteins that play a major role in response to disorder development and a negative response to delayed cooling. In addition, an ABC transporter protein F family is correlated to the delayed cooling treatment. This study demonstrates the potential mechanism of the biological effect of delayed cooling on apple fruit at the proteomic level. It also provides in-depth insight on molecular mechanisms of the delayed cooling treatment in apples. [ABSTRACT FROM AUTHOR]

1-Methylcyclopropene (1-MCP) is a well-known ethylene action inhibitor that has been applied to fruit after harvest to maintain fruit quality and extend storage life. Recently, the preharvest application of 1-MCP in a sprayable form has been developed and has demonstrated some beneficial effects to prolong harvest window and improve fruit quality. To gain understanding of molecular mechanisms for 1-MCP treatment, as both pre- and postharvest applications on apples, we conducted a quantitative proteomic experiment employing stable isotope labeling by peptide dimethylation on 'Honeycrisp' apples to reveal the significantly changed protein abundance in relationship to fruit quality after preharvest 1-MCP (Harvista™), postharvest 1-MCP treatments as well as their combination. We revealed the treatment affected fruit internal ethylene concentration, fruit quality indices and storage disorders incidence after 7 months of storage at 3 °C. Our quantitative proteomic study identified and quantified more than 600 proteins. Among the identified proteins, 312 proteins were found in common from all treatments, while 141 proteins abundance were changed with regards to preharvest, postharvest and the combination treatments of 1-MCP. We identified a few proteins that were only shown as result of preharvest 1-MCP treatment, while postharvest 1-MCP and in combination with preharvest treatment led to larger number proteins with reduced abundance. These results revealed and confirmed that postharvest 1-MCP and in combination with preharvest 1-MCP treatment affected ethylene biosynthesis, stress resistance, amino acid biosynthesis, antioxidant and redox system metabolisms. Potential metabolic changes resulting from 1-MCP treatment were found, and the efficacy of preharvest 1-MCP treatment was also discussed. [Display omitted] • Pre and postharvest 1-MCP treatments affect fruit quality after storage. • Pre and postharvest 1-MCP treatments affect proteomic changes after storage. • Preharvest 1-MCP treatment had no effect on ethylene biosynthesis and metabolism. • Preharvest 1-MCP treatment enhanced abundance of a few groups of proteins. • Proteomic networks in response to 1-MCP treatments is demonstrated and discussed. [ABSTRACT FROM AUTHOR]

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]