Study On The Biocontrol Efficacy Of Pichia Caribbica Enhanced By Induction Culture With Ascorbic Acid Under The Oxidative Stress And The Mechanisms Involved

The decay of post-harvest fruits caused by pathogen infection resulted in great economic losses.One of the main postharvest diseases of apples is the blue mold decay by Penicillium expansum.The biological control of blue mold decay of postharvest apples by antagonistic yeast has broad application prospect and development potential.However,the biocontrol efficacy of antagonistic yeast is often decreased by oxidative stress in the application process.Therefore,how to improve the tolerance of antagonistic yeast to oxidative stress is one of the key issues for improving its biocontrol efficacy.Ascorbic acid?vitamin C?is a good reducing agent,which can remove reactive oxygen species?ROS?to protect yeast under oxidative stress.In this paper,P.caribbica was cultured in the medium with ascorbic acid to improve its tolerance to oxidative stress caused by H₂O₂,and improve its biocontrol efficacy for blue mold decay of apples.The physiological mechanisms involved in the enhanced biocontrol efficacy of P.caribbica by induction culture with ascorbic acid under oxidative stress are clarified by investigate the colonization ability of this antagonistic yeast on the surface of apples,ROS accumulation and antioxidases activity.And the molecular mechanisms involved are revealed by proteome and transcriptome analysis.The results would provide theoretical guidance and new ideas for improving the biocontrol efficacy of antagonistic yeast in practical application,and promote the commercialization process of antagonistic yeast.The main research results of this paper are as follows:?1?The effects of treatment with H₂O₂,induction culture with ascorbic acid and treatment with H₂O₂ after induction culture with ascorbic acid on the control efficacy of P.caribbica for blue mold decay of apples were investigated.The results showed that treatment with H₂O₂ significantly decreased the control eccicacy of P.caribbica,and the control eccicacy of this antagonistic yeast decreased with the increase of H₂O₂concentration.The control eccicacy of P.caribbica was significantly improved by induction culture with ascorbic acid,and the optimal concentration of ascorbic acid was 250?g/mL.The control efficacy of P.caribbica under oxidative stress?H₂O₂treatment?was improved by induction culture with 250?g/mL of ascorbic acid.?2?The physiological mechanisms involved in the enhanced biocontrol efficacy of P.caribbica by induction culture with ascorbic acid under oxidative stress were carified by investigating the colonization ability,intracellular ROS accumulation and antioxidases activity.The results showed that colonization ability of P.caribbica under oxidative stress?H₂O₂ treatment?was increased,MDA content and ROS accumulation were significantly decreased,the activities of CAT,PPO and POD were significantly increased by induction culture with 250?g/mL of ascorbic acid,which improved the tolerance of P.caribbica to oxidative stress and improved its control efficacy for blue mold decay of apples.?3?Analyzing the effect of ascorbic acid on the protein expression of yeast under oxidative stress by proteomics technology.The results showed that,in the energy metabolism and glucose metabolism,fructose-diphosphate aldolase and malate dehydrogenase,alpha-glucoside enzyme and the related to the ribosome of yeast U-snRNP protein and mitochondrial aldehyde dehydrogenase related to the direct action of antioxidant enzymes were up-regulated.?4?Studying on the differentially expressed genes of P.caribbica induced by ascorbic acid at 250?g/mL under oxidative stress by transcriptome techniques.A total of 68 differentially expressed genes?Fold Change 2?were identified with transcriptome,including 38 up-regulated genes and 30 down-regulated genes.These genes were up-regulated,which were related to cell wall and energy synthesis,polysaccharide hydrolysis and antioxidant activity.