By contrast with a plenty of our

By methylphenidate hcl mg with a plenty of our understanding on arginine metabolism in animals and higher plants, very little thus far is known on the specific function of arginase that acts as a key control point for keeping arginine balance in edible mushrooms and neither for its physiological role in postharvest mushroom development and senescence. There is some indication that MeJA effects may be, in part, mediated by increased arginase levels. For example, the expression of the arginase encoding gene of Arabidopsis, ARGAH2, was strongly stimulated upon MeJA treatment and transcripts of the pathogenesis-related proteins were expressed differentially in the presence or absence of ARGAH2 (Brownfield et al., 2008). Similarly, levels of the tomato leave arginase gene (LeARG2) transcripts and the arginase activity were also found to be able to respond to MeJA treatment (Chen et al., 2004). Other than these significant achievements, our previous study also found that the mRNA level and activity of arginase were positively correlated with ADC and ornithine aminotransferase (OAT) activities and pretreatment with MeJA significantly elevated the contents of putrescine and proline in tomato fruit during cold storage, indicating that the increased arginase activity induced by MeJA participates in controlling chilling tolerance (Zhang et al., 2012). Considering all these evidences, it was easily concluded that arginase pathway involves in various physiological processes and stress responses under MeJA induction. Duo to all these facts, we reasonably hypothesize that arginase participates in the MeJA-regulated quality maintenance of postharvest A. bisporus fruit bodies. The objective of this study was for the first time to examine the influence of postharvest MeJA on arginase gene expression and activity when combined with or without an arginase inhibitor, Nω-hydroxy-nor-l-arginine (nor-NOHA) and the role of MeJA-induced arginase activity on quality retention of A. bisporus mushroom when stored at 4°C.
Materials and methods
Results
Discussion Arginase in plants and mammals has perceived a great deal of attention for its potential function in various biotic and abiotic stress conditions (Brauc et al., 2012, Gravot et al., 2012, Morris, 2009, Zhang et al., 2010). However, the role of arginase has received scarce attention in edible mushrooms. In 2005, the A. bisporus arginase gene AbARG was first cloned and found be closely related to urea accumulation in fruit bodies (Wagemaker et al., 2005). Other than this limited information, investigation about its physiological roles in postharvest mushroom development and senescence remains elusive so far. Our research focuses on the involvement of arginase in the MeJA-regulated postharvest quality maintenance of A. bisporus during storage at 4°C. As far as we know, this is the first study showing that the quality retention of postharvest mushrooms by MeJA treatment may partially depend on arginase induction. Our present study found that, as reflected in many organisms e.g. Arabidopsis (Brownfield et al., 2008) and tomato (Chen et al., 2004, Zhang et al., 2012), MeJA induced increased AbARG mRNA level (Fig. 1A), which directly promoted arginase activity in fruiting bodies of A. bisporus during the entire storage (Fig. 1B). For A. bisporus, one interesting phenomena was that MeJA led to an opposite trend between arginase activity and AbARG expression level from day 0 to day 3, indicating that more than one gene encoding arginase may exist in A. bisporus. To assess the participation of arginase in MeJA-regulated quality retention of A. bisporus mushroom, a more potent arginase inhibitor called nor-NOHA (Custot et al., 1997) rather than NOHA which can act as a substrate for NO production (Tenu et al., 1999), was used before the imposition of MeJA. As expected, the addition of nor-NOHA suppressed the effect of MeJA to induce the elevation of arginase mRNA and activity in mushrooms, thus demonstrating the role of MeJA in boosting arginase activity in mushroom.