Arginase participates in the methyl jasmonate-regulated quality maintenance of postharvest Agaricus bisporus fruit bodies

It has been demonstrated that Agaricus bisporus (J.E. Kange) Imbach fruit body exerts enhanced postharvest quality retention when treated with 100 mu mol L-1 exogenous methyl jasmonate (MeJA) vapor. In this study, fruit bodies of A. bisporus were treated with 100 mu mol L-1 MeJA vapor or the combination of 100 mu mol L-1 MeJA and 20 mu mol L-1 N-omega-hydroxy-nor-L-arginine (nor-NOHA, an inhibitor of arginase), respectively, before they were stored for 21 d at 4 degrees C. Our data showed that treatment with MeJA alone indeed induced the increased transcription and activity of arginase whereas this effect was largely inhibited by pretreatment with nor-NOHA. In correspondence to this observation, nor-NOHA suppressed the ability of MeJA to decrease open caps and to down-regulate malondialdehyde (MDA) production and polyphenol oxidase (PPO) and lipoxygenase (LOX) activities. Biochemical analysis further demonstrated that nor-NOHA counteracted the MeJA in stimulating antioxidant enzyme activities of catalase (CAT) and superoxide dismutase (SOD) and accumulating total phenolics and flavonoids. In addition, the effect of MeJA in slowing the decline rate of soluble protein and total sugar contents was also partially impaired by nor-NOHA. Taken together, our findings firmly showed that arginase acts as an important regulatory factor in maintaining the MeJA-induced mushroom quality retention during postharvest storage.