Control Of Patulin In Pears By Meyerozyma Guilliermondii And Its Degradation Mechanisms Of Patulin

Patulin(PAT)is a highly toxic secondary metabolite produced by fungi of the genus Penicillium sp.and Aspergillus,which is likely to cause serious pollution to fruits and their products worldwide and endanger human health.Control and degradation of patulin in fruits and fruit products using antagonistic yeasts has a promising future.However,researches to control patulin biosynthesis using antagonistic yeasts are still at the rudimentary stage especially with the mechanisms involved in the control and/or degradation.This has seriously affected the application of antagonistic yeast in the control and degradation of mycotoxins.In this paper,Meyerozyma guilliermondii which has a good control on postharvest disease caused by Penicillium expansum on pear fruit was isolated by our research team.The mechanism of controlling PAT in pears and the physiological PAT degradation mechanism of M.guilliermondii in vitro are preliminarily explored.At the same time,the use of transcriptomics and proteomics techniques to explore the changes in gene and protein expression during the degradation of PAT by M.guilliermondii to reveal:1.M.guilliermondii can effectively control the PAT content in the wound of pear fruit,and the control effect is best when the concentration is 1×10~8 cells/m L.At 20°C and 4°C,M.guilliermondii can effectively control the PAT content in the pear wound and the whole fruit.M.guilliermondii has poor control effect of PAT on the wounds of fragrant pear and dangshan pear.2.The extracellular metabolites produced by M.guilliermondii stimulated by PAT or not have no degradation effect on PAT.M.guilliermondii active cells can degrade PAT in vitro.The intracellular enzymes produced by M.guilliermondii can reduce PAT to the detection limit.After PAT stimulation,the intracellular enzymes produced by M.guilliermondii have a better effect on PAT degradation.Cycloheximide treatment on M.guilliermondii slowed down the degradation of PAT.3.Whether PAT stimulated or not,the transcriptomics analysis of M.guilliermondii showed that 215 genes were up-regulated and 133 genes were down-regulated.The molecular mechanisms of M.guilliermondii’s regulation of PAT response mainly include:(1)Up-regulation of the expression of resistance-related genes to enhance PAT tolerance;(2)Up-regulation of the expression of transporter-related genes,which may be involved in the intracellular transport of PAT;(3)Up-regulate the expression of growth and reproduction-related genes to enhance cell viability and resist PAT toxicity;(4)Up-regulate the expression of transcription-and translation-related genes to prevent PAT from inhibiting transcription and translation;(5)Up-regulate the expression of genes related to DNA damage repair to repair PAT;(6)Up-regulated expression of anti-oxidative stress-related genes,eliminating the accumulation of ROS caused by PAT,and avoiding cell damage;(7)Up-regulating expression of possible PAT degradation-related genes,participating in the PAT degradation process.4.Whether PAT stimulated or not,compatative proteomic analysis results of M.guilliermondii showed that a total of 136 proteins were up-regulated and 122 proteins were down-regulated.The molecular mechanisms of M.guilliermondii’s regulation of PAT response mainly include:(1)Up-regulation of growth and reproduction-related protein expression,which promotes metabolism,and enhances cell viability;(2)Up-regulation of transcription and translation-related protein expression to ensure the progress of transcription and translation under PAT stress;(3)Up-regulation of the expression of resistance-related proteins to enhance the tolerance of M.guilliermondii under PAT stress;(4)Up-regulation of the expression of multidrug transporters,which may be related to PAT transport and pumping out of cells;(5)Resistance the expression of oxidative stress-related proteins is up-regulated to relieve the oxidative stress caused by PAT;(6)Cell wall and cell membrane production-related proteins are also up-regulated to enhance cell wall strength and resist the damage caused by PAT;(7)PAT degradation-related protein up-regulates expression,may be directly invovled in PAT degradation.