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The effects of l-arginine (Arg, 1 mM) and/or methyl salicylate (MeSA, 0.05 mM) treatment on gray mold caused by Botrytis cinerea in tomato fruit were studied. Results indicated that Arg or MeSA alleviated the incidence and severity of fruit disease caused by B. cinerea, and that both Arg and MeSA (Arg + MeSA) further inhibited the development of fruit decay. Treatment with Arg + MeSA not only enhanced the activities of superoxide dismutase, catalase, and peroxidase but also promoted the expression levels of pathogenesis-related protein 1 gene and the activities of defense-related enzymes of phenylalanine ammonia-lyase, polyphenol oxidase, β-1,3-glucanase, and chitinase during most of the storage periods, which were associated with lower disease incidence and disease index. In addition, the combined treatment elevated the levels of total phenolics, polyamines, especially putrescine, and nitric oxide. These observations suggest that treatment of fruit with Arg + MeSA is an effective and promising way to alleviate postharvest decays on a commercial scale.

Background: To understand whether arginine catabolism might be involved in hot air (HA)-induced chilling tolerance mechanism in tomato fruit, we investigated the effect of HA treatment on endogenous arginine catabolism in relation to chilling injury., Results: Tomato fruit were harvested at mature green stage and treated with HA at 38°C for 12 h and then stored at 2°C for 21 days. The effects of HA treatment on fruit chilling injury and gene expression levels or enzyme activity, and metabolites related to arginine catabolism were evaluated. HA treatment reduced the chilling injury symptoms of tomato fruit and enhanced the accumulation of endogenous polyamines, especially putrescine and proline. This accumulation is associated with the increased transcript levels of genes encoding arginase (LeARG1 and LeARG2), arginine decarboxylase (LeADC), ornithine decarboxylase (LeODC) and ornithine aminotransferase (LeOAT) at most sampling times. However, HA treatment had little effect on nitric oxide synthase activity and nitric oxide concentration., Conclusion: These results revealed that the reduction in chilling injury by HA treatment may be due to the accumulation of putrescine and proline induced primarily by activating the catabolism of endogenous arginine., (© 2013 Society of Chemical Industry.)

The effects of methyl salicylate (MeSA) on chilling injury (CI) and gene expression levels, enzyme activities, and metabolites related to arginine catabolism in cherry tomato fruit were investigated. Freshly harvested fruits were treated with 0.05 mM MeSA vapor at 20 °C for 12 h and then stored at 2 °C for up to 28 days. MeSA reduced CI and enhanced the accumulation of putrescine, spermidine, and spermine, which was associated with increased gene expression levels and activities of arginase, arginine decarboxylase, and ornithine decarboxylase at most sampling times. MeSA also increased nitric oxide synthase activity, which at least partly contributed to the increased nitric oxide content. The results indicate that MeSA activates the different pathways of arginine catabolism in cold-stored fruit and that the reduction in CI by MeSA may be due to the coordinated metabolism of arginine and the increase in polyamines and nitric oxide levels.

Basic helix-loop-helix (bHLH) transcription factors (TFs) are widely distributed in eukaryotes and play an important role in biological growth and development. The identification and functional analyses of bHLH genes/proteins in edible mushrooms (Agaricus bisporus) have yet to be reported. In the present study, we identified 10 putative bHLH members carrying the conserved bHLH domains. Phylogenetic analyses revealed that the 10 AbbHLHs were the closest to sequences of species belonging to 7 different fungal subgroups, which was supported by loop length, intron patterns, and key amino acid residues. The substantial increase after harvest and continuously elevated expression of AbbHLH1 during the development until the disruption of mushroom velum, and the preferential expression in cap and gill tissues suggest the important function of AbbHLH1 in postharvest development of A. bisporus. The relationship of arginine catabolism-related genes with the early stage of postharvest continuing development also was revealed by expression determination. Subcellular localization showed that AbbHLH1 could be localized in nucleus. Importantly, the electrophoretic mobility shift and dual-luciferase reporter assays showed that AbbHLH1 activated the promoters of AbOAT , AbSPDS , and AbSAMDC and suppressed the expression of AbARG , AbUREA , and AbODC , probably for the modulation of arginine catabolism and thus control of postharvest mushroom development. Taken together, the available data provide valuable functional insight into the role of AbbHLH proteins in postharvest mushrooms. • Ten bHLH genes were firstly identified in edible mushrooms (Agaricus bisporus). • AbbHLH1 was a potential regulator in the postharvest development of A. bisporus. • AbbHLH1 could be localized in nucleus. • AbbHLH1 directly bound to the promoters of arginine catabolism-related genes. • AbbHLH1 promoted/inhibited the promoters of arginine catabolism-related genes. [ABSTRACT FROM AUTHOR]

[Display omitted] • MeJA differentially regulated arginine catabolism–related genes and proteins. • MeJA tissue-specifically regulated arginine catabolism–related genes and proteins. • MeJA-upregulated AbASS expression most likely occurred at the translational level. • Both arginine and ornithine contents were reduced after exposure to MeJA. • MeJA-regulated arginine catabolism correlated with free polyamine accumulation. Methyl jasmonate (MeJA)-regulated postharvest quality retention of Agaricus bisporus fruiting bodies is associated with arginine catabolism. However, the mechanism of MeJA-regulated arginine catabolism in edible mushrooms is still unclear. This study aimed to investigate the regulatory modes of MeJA on the expression of arginine catabolism–related genes and proteins in intact and different tissues of A. bisporus mushrooms during storage. Results showed that exogenous MeJA treatment activated endogenous JA biosynthesis in A. bisporus mushrooms, and differentially and tissue-specifically regulated the expression of arginine catabolism–related genes (AbARG , AbODC , AbSPE-SDH , AbSPDS , AbSAMDC, and AbASL) and proteins (AbARG, AbSPE-SDH, AbASL, and AbASS). MeJA caused no significant change in AbASS expression but resulted in a dramatic increase in AbASS protein level. Neither the expression of the AbSAMS gene nor the AbSAMS protein was conspicuously altered upon MeJA treatment. Additionally, MeJA reduced the contents of arginine and ornithine and induced the accumulation of free putrescine and spermidine, which was closely correlated with MeJA-regulated arginine catabolism–related genes and proteins. Hence, the results suggested that the differential and tissue-specific regulation of arginine catabolism–related genes and proteins by MeJA contributed to their selective involvement in the postharvest continuing development and quality retention of button mushrooms. [ABSTRACT FROM AUTHOR]

Abstract: The influence of methyl jasmonate (MeJA) on levels of gene transcripts, enzyme activities and metabolites related to arginine catabolism and chilling injury (CI) was studied in cherry tomato (Solanum lycopersicum L. cv. Messina) fruit stored at 2°C for 21 days. The CI index of fruit pretreated with 0.05mM MeJA vapor for 12h at 20°C was reduced compared with that of untreated fruit. The reduction was associated with up-regulated arginine catabolism. The mRNA levels and activities of arginase, arginine decarboxylase (ADC) and ornithine aminotransferase (OAT) in treated fruit were higher than in control fruit, while those of ornithine decarboxylase (ODC) increased transiently in response to MeJA treatment during the early days of cold storage. Free putrescine (Put) and proline accumulated in MeJA-treated fruit, while levels of other arginine-related amino acids were affected by MeJA. Spermidine (Spd) and spermine (Spm) contents remained unchanged in response to MeJA treatment over most of the storage time. The results indicate that MeJA becomes involved in coordinated catabolism of arginine, and helps to improve chilling tolerance in cherry tomato fruit. [Copyright &y& Elsevier]