Arginine induces the resistance of postharvest jujube fruit against Alternaria rot

In order to explore the effects of arginine(Arg)treatment on postharvest rot of jujube caused by Alternaria alternata(A.alternata),winter jujube was treated with different concentrations of Arg(0,20,200,and 1000μmol/L).Results showed that Arg treatment substantially inhibited the expansion of lesion diameter,and jujubes treated with 200μmol/L Arg had the smallest lesion diameter.In vitro experiments demonstrated that Arg could not inhibit spore germination and mycelial growth of A.alternata.Further experimental results showed that Arg treatment reduced the production rate of O_(2)^(-) and H_(2)O_(2) content and improved the activities of superoxide dismutase,catalase,peroxidase,and ascorbate peroxidase in comparison with the control;Arg treatment enhanced the activities of chitinase andβ-1,3-glucanase.Furthermore,Arg treatment significantly increased the activity of phenylalamine ammonia lyase and the contents of flavonoids,phenolics,and lignin.Results indicated that,although Arg could not directly inhibit the growth of pathogenic fungi as a fungicide,it can induce resistance to Alternaria rot by maintaining the balance of reactive oxygen species,increasing the activities of pathogenesis-related protein,and promoting the phenylpropane metabolism in jujube fruit tissue.Therefore,Arg treatment can be a novel measure for inducing the resistance of jujube to postharvest Alternaria rot.

Heme oxygenase-1/carbon monoxide signaling participates in the accumulation of triterpenoids of Ganoderma lucidum

Ganoderic triterpenoids(GTs)are the primary bioactive constituents of the Basidiomycotina fungus,Ganoderma lucidum.These compounds exhibit antitumor,anti-hyperlipidemic,and immune-modulatory pharmacological activities.This study focused on GT accumulation in mycelia of G.lucidum mediated by the heme oxygenase-1(HO-1)/carbon monoxide(CO)signaling.Compared with the control,hemin(10μmol/L)induced an increase of 60.1%in GT content and 57.1%in HO-1 activity.Moreover,carbon monoxide-releasing molecule-2(CORM-2),CO donor,increased GT content by 56.0%and HO-1 activity by 18.1%.Zn protoporphyrin IX(ZnPPIX),a specific HO-1 inhibitor,significantly reduced GT content by 26.0%and HO-1 activity by 15.8%,while hemin supplementation reversed these effects.Transcriptome sequencing showed that HO-1/CO could function directly as a regulator involved in promoting GT accumulation by regulating gene expression in the mevalonate pathway,and modulating the reactive oxygen species(ROS)and Ca2+pathways.The results of this study may help enhance large-scale GT production and support further exploration of GT metabolic networks and relevant signaling cross-talk.