| China is one of the largest producers of apples worldwide.However,apple is susceptible to postharvest disease caused by fungal pathogens during storage.Especially,apple decay caused by Penicillium expansum has led to serious economic losses.Patulin which is one of the main mycotoxins produced by P.expansum threatens the health of human.In the past,chemical fungicides were the most commonly used agents to control fungal diseases.However,the negative effects of chemical fungicides on the environment and human health are increasingly apparent.Over the years,researchers have been actively looking for alternatives instead of chemical fungicide.Biological control has made breakthrough progress in recent years.It is considered to be the most promising alternative instead of chemical fungicide,most of the yeast,has become a reaearch hotspot.But some studies have indicated that the biocontrol efficacy of antagonistic yeasts,when used alone,is not comparable to that of chemical fungicide.Therefore,it is urgent to improve the biocontrol efficacy of antagonistic yeasts to promote the commercialization application process.β-glucan is not toxic and harmless.Currently,it is mainly used for the production of various foods,raw materials for medicines and raw materials for cosmetics.The present study aimed to determine the effect of β-glucan on the biological control activity of Cryptococcus podzolicus against blue mold decay which was isolated and identified by our laboratory.The physiological mechanism was studied by yeast physiology and fruit resistance.The molecular mechanism of biocontrol efficacy enhanced by β-glucan was further discussed by using proteomics and transcriptome technology.Results of this study were as follows:(1)β-glucan increased the biological control ability of C.podzolicus against blue mold decay of apples and the best concentration was 0.5%(w/v).Additionally,natural decay incidence of apples was decreased when apples were treated by C.podzolicus induced by0.5% β-glucan.The treatment did not have adverse effects on various storage quality parameters.(2)When induced by β-glucan,C.podzolicus grew better in apple wounds at either20°C or 4°C.The results of scanned electron microscope(SEM)showed that C.podzolicuswas able to parasitize P.expansum mycelia,resulting in the distortion of mycelia.After induction,there was no growth of mycelia in apple wounds.β-glucan improved the activities of catalase(CAT)and β-1,3-glucanase in C.podzolicus and reduced the accumulation of malondialdehyde(MDA).Our results also indicated that in treated apples,the activities of defense-related enzymes,including polyphenol oxidase(PPO),peroxidase(POD),phenylalanine ammonia-lyase(PAL),and CAT were increased,whereas MDA content was decreased.(3)Different proteins from C.podzolicus were identified using two-dimensional gel electrophoresis.The expression of proteins related to energy production including Cytochrome c oxidase and ATP synthase outside of sugar metabolism including Triosephosphate isomerase and Enolase was up-regulated when C.podzolicus was induced by β-glucan.Besides,the expression of some proteins was also up-regulated involved in synthesis of cell wall and skeleton including UDP-glucuronicacid decarboxylase,Xyloglucan galactosyltransferase and beta1-tubulin.(4)Gene expression of C.podzolicus was studied using transcriptome technology.A total of 666 differentially expressed genes(Fold Change≥2)were identified,among which613 were up-regulated and 53 were down-regulated.Results were analysed combined with proteomics,then 9 different genes were selected for verification,encoding Endochitinase,Cytochrome c oxidase,ATP synthase,ATP carrier protein,Polysaccharide monooxygenase,Catalase-peroxidase,Superoxide dismutase,Glutaredoxin-2 and β-galactosidase separately.The first 8 genes were up-regulated,related to synthesis of cell wall and energy,polysaccharide hydrolysis and oxidation,and the gene encoding β-galactosidase was down-regulated which was associated with cell aging. |
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