| China is the country with the largest apple production in the world.However,apples are more likely to be infected by the pathogen Penicillium expansum during post-harvest transportation,storage,and sales,which causes the blue mold decay.At present,most of the post-harvest diseases of apples are controlled by chemical fungicides,but they are unsafe to some extent.Biological control has gradually become a new method to control apple post-harvest diseases because of its green and harmless advantages.In recent years,some antagonistic yeasts have been studied to control apple post-harvest disease,but the research on the molecular mechanism of antagonistic yeast controlling apple postharvest disease is not comprehensive enough.In this paper,an antagonistic yeast strain with significant control effect on the blue mold decays of apples was obtained through screening and isolation,and its control effect on apple natural rot was explored.The physiological mechanism of controlling apple post-harvest disease was analyzed,and the molecular mechanism of controlling apple post-harvest disease was revealed through transcriptomics and proteomics,which provided a theoretical reference for the subsequent commercial application of this antagonistic yeast.The main findings of this paper are as follows:1.An antagonistic yeast strain was screened from the orchard soil,which has a significant control effect on the blue mold decays of apples.It was identified as Hannaella sinensis by morphological observation and molecular biological analysis.Through the 14-day oral acute toxicity test in mice,it was proved that H.sinensis is a safe and non-toxic yeast.2.H.sinensis could effectively reduce the rot rate and rot diameter of the blue mold decays of apples.The control effect increased with the increase of H.sinensis concentration,and the best control effect was achieved when the concentration of H.sinensis was 1×10~8 cells/m L.In addition,H.sinensis also significantly reduced the natural decay rate of apples,and had no adverse effect on storage quality.3.The physiological mechanisms of H.sinensis controlling apple postharvest diseases include:H.sinensis inhibited the spore germination and germ tube growth of P.expansum by competing for nutrients and space;H.sinensis could stably colonize apple wounds and surfaces;H.sinensis induced the activities of resistance-related enzymes(PPO,POD,APX,SOD and PAL)in apples,increased the expression of resistance enzyme genes,increased the content of total phenols and flavonoids,and reduced the degree of peroxidative damage to the membrane.4.Using transcriptomic techniques to analyze the differentially expressed genes in apples of H.sinensis-treated and control groups,it was found that many genes encoding different defense-related pathways were induced by H.sinensis.(1)The up-regulated expression of genes encoding related regulatory factors in the immune system improved the defense of apples;(2)The expression of some genes in the biosynthetic pathways of resistance-related substances such as salicylic acid,anthocyanins,and flavonoids were up-regulated to improve apple resistance;(3)The expression of genes encoding enzymes responsible for scavenging reactive oxygen species were up-regulated to maintain cell redox homeostasis;(4)The expression of receptor protein-encoding genes responsible for signal transduction were up-regulated,improving apple’s response to stress environments.(5)The expression of genes encoding transporters responsible for material transport were up-regulated to improves the ability of apple material transport.5.Proteomics analysis of H.sinensis-induced differentially expressed proteins in apple based on TMT technology showed that the defense mechanisms involved in differentially expressed proteins mainly included reactive oxygen species scavenging,improvement of plant resistance and synthesis of resistant substances,improvement of plant disease resistance,the degradation of pathogen cell wall,cell signaling,antibacterial activity,transport of defense-related substances and protein processing. |
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