Control Of Patulin In Pear By Hannaella Sinensis And It’s Mechanisms Of Degration Of Patulin

Patulin(PAT)is a mycotoxin produced by diverse fungi such as Penicillium,Aspergillus spp and Byssochlamys.PAT contamination has been detected in many fruits and vegetables.PAT contamination threatens human health due to its teratogenic,carcinogenic and mutagenic effects.Biological methods of PAT control and degradation have received widespread attention from scholars due to their economical cost advantages and higher safety.However,most of the research mainly focuses on the physiological mechanisms of biological control and degradation of PAT,and the molecular mechanism has less understood and needs further in-depth analysis.In this thesis,we aimed to assess the effectiveness of Hannaella sinensis,a yeast with good postharvest control of apple,in controlling postharvest decay and PAT in pear fruit.The explored physiological and molecular mechanism of PAT degradation by H.sinensis in vitro using transcriptomics and proteomics.The results provide a theoretical reference for commercial application of antagonistic yeast for PAT degradation.The main findings of the thesis are as follows:1.H.sinensis effectively controlled postharvest decay of pear fruit and reduced the accumulation of PAT in pear wounds.H.sinensis reduced the amount of PAT in pear fruit by inhibiting the growth of P.expansum strains in pear wounds.2.The live cells of H.sinensis were involved in PAT degradation.The PAT elimination by H.sinensis was not a cell wall-mediated adsorption process or an extracellular metabolites-mediated degradation.PAT induction enhanced the ability of the intracellular material of H.sinensis to degrade PAT,and cycloheximide treatment reduced the ability of H.sinensis to degrade PAT.3.The differentially expressed genes between PAT-induced H.sinensis and H.sinensis alone were identified based on transcriptomics techniques.The results showed that the differentially up-regulated genes include:(1)genes related to protein processing,which help to maintain functional protein operation in H.sinensis cells;(2)genes encoding redox-related enzymes,which maintain redox homeostasis in H.sinensis cells;(3)genes related to DNA repair synthesis,which maintain the integrity of the H.sinensis cell genome;(4)genes encoding proteins associated with cell growth and reproduction to avoid the damage of H.sinensis cells caused by PAT stimulation;(5)genes encoding proteins associated with material transport to enhance cell viability while participating in vivo PAT transport in H.sinensis yeast cells;(6)genes related to the cell membrane and cell wall synthesis,to provide stable environmental conditions for H.sinensis cellular activities;(7)genes related to resistance to improve H.sinensis resistance to stress.4.Proteomics-based identification of differentially expressed proteins in PATinduced cultures of H.sinensis and H.sinensis alone revealed that the differentially upregulated proteins included:(1)proteins associated with protein processing to prevent PAT from disrupting protein function;(2)redox-related proteins involved in the scavenging of reactive oxygen species inside cells;(3)proteins associated with growth and reproduction,to maintain the normal life activities of yeast cells;(4)proteins related to transport,to improve the ability of yeast cells to transport substances;(5)proteins related to cell wall synthesis,to avoid external damage to the cell;(6)resistance-related proteins to enhance cellular defense mechanisms against adverse external environments.