| Botrytis cinerea and Fusarium graminearum are two common pathogenic fungi,which result in great harm to crop production,processing and storage of foodstuffs.Therefore,it is of great significance to take effective measures to prevent crop diseases caused by B.cinerea and F.graminearum.Yeasts have always been the focus of biological control of plant diseases due to their unique advantages.The biocontrol mechanisms of yeasts include competiting,inducing host plants to develop resistance,directly parasiting pathogens and secreting toxins lethal to pathogenic fungus,resisting oxidative stress,forming biofilms in damaged tissues and producing inhibitory volatile organic compounds(VOCs)with inhibitory,etc..Among them,there are few reports on the biological controlof VOCs of yeasts,and the inhibitory mechanisms are unclear.It is significant to explore the inhibitory mechanisms of VOCs of yeasts on plant pathogenic fungus and to use yeast for biological control.Saccharomyces cerevisiae,as the most widely used food-grade yeast for fermentation production,has attracted much attention for its effectiveness on biological control against plant pathogens.In this study,we investigated the inhibitory effects of VOCs of S.cerevisiae on B.cinerea and F.graminearum,and explored the mechanism of the inhibition.The main results obtained can be divided into the following three parts:1.The VOCs of S.cerevisiae inhibit the growth and differentiation of B.cinerea and F.graminearumThe VOCs produced by budding yeast have inhibitory effects on two plant pathogenic fungus,B.cinerea and F.graminearum,and the strength of the inhibitory effect is positively related to the yeast inoculation concentration.With the action of VOCs of yeast,under the light microscope,the conidiogenesis of B.cinerea and F.graminearum was inhibited;the mycelium bifurcation was more severe;and the mycelium became shorter and stouter.In addition,vesicular swelling and curling appeared.Under the Cyro-Scanning Electron Microscope(SEM),the observations showed that the mycelia of the control group were full and densely intertwined,but the inhibited mycelia by the VOCs of yeast were sparse,decayed and shriveled,distorted and agglomerated,and deformed and enlarged at the top of the mycelium.The detection results on the YPD plates were consistent with those on the PDA plates.However,because YPD is a yeast growth medium and PDA is a pathogenic fungus growth medium,the same concentration of yeast on YPD plates has a better inhibitory effect on pathogenic fungus than on PDA plates.These results indicate that the VOCs of yeast can inhibit the growth and differentiation of B.cinerea and F.graminearum.2.Ethyl acetate,the main component of yeast VOCs,inhibits the growth and differentiation of B.cinerea and F.graminearumThe headspace solid phase microextraction with gas chromatography-mass spectrometry(HS-SPME-GC-MS)detection found that the main components of VOCs of wild-type S.cerevisiae were isoamyl acetate,ethyl acetate,ethyl decanoate,etc.,among which the content of ethyl acetate was the highest.Commercially analyzed pure ethyl acetate has a strong inhibitory effect on B.cinerea and F.graminearum,and the higher the concentration,the stronger the inhibitory effect.At the same concentration,the inhibitory effect of ethyl acetate on B.cinerea is significantly stronger than that on F.graminearum.Deletion of the key coding genes ATF1 and ATF2 encoding alcohol acetyltransferase required for ethyl acetate production in S.cerevisiae cannot significantly reduce the inhibitory effects of VOCs on B.cinerea and F.graminearum.Although over-expression of ATF1 in wild-type and mutant without IAH1,which encodes an esterase,enhanced ethyl acetate production,the main components became isoamyl acetate and phenethyl acetate by using HS-SPME-GC-MS detection.Meanwhile,the inhibitory effect of VOCs of ATF1 over-expressed strains on F.graminearum on PDA plates was not significantly enhanced in comparison to wild-type strain.However,the inhibitory effect of VOCs of ATF1 over-expressed strain without IAH1 on F.graminearum on YPD plates was slightly enhanced in comparison to wild-type strain.In addition,commercial analysis of pure phenethyl acetate has a very strong inhibitory effect on F.graminearum,and the inhibitory effect is stronger than ethyl acetate.These results indicate that the main components of VOCs of budding yeast can indeed inhibit the growth and differentiation of B.cinerea and F.graminearum.3.Expression levels of key genes of F.graminearum affected by VOCs of S.cerevisiaeTranscriptome analysis showed that the total number of genes expressed in the VOCs treated F.graminearum group(t-MIX)was higher than that in the F.graminearum without VOCs treatment control group(CK-MIX).Then the expression levels of the differential genes in the two samples were compared,and the result showed that 1,097 genes were up-regulated and 1,304 genes were down-regulated in the treatment group compared with the control group.GO enrichment analysis of differential genes showed that a large number of genes in the treatment group were significantly up-regulated in their expression levels,including these function in biological processes,cellular components and molecular functions.KEGG enrichment analysis of differential genes showed that the expression levels of important pathway genes in F.graminearum inhibited by VOCs were significantly down-regulated.These genes can be divided into 5 categories:pathways related to biochemical metabolism(such as sugar and amino acid metabolism),pathways related to cell process(such as intracellular catabolism and cell growth),pathways related to organismal systems(such as internal secretion),pathways related to genetic information processing(such as sorting and degradation)and pathways related to environmental information processing(such as signal transduction).These results indicate that VOCs of S.cerevisiae significantly affected the expression level of key genes of F.graminearum,which led to the inhibition of its growth and differentiation.The above results indicate that S.cerevisiae can affect the gene expression level of some key metabolic pathways of pathogenic fungi without direct contact to fungi to inhibit their growth,development and differentiation through yeast VOCs,especially the main component ethyl acetate.Therefore,we can try to use a single component or multiple components in combination to prevent the infection of pathogenic fungus under specific conditions such as storage and preservation of vegetables and fruits,grain storage or food processing in future. |
PDF Full Text Request