Hydrogen Sulfide Regulating Grape Storage And Preservation And Its Mechanisms

Due to the rich in nutrition,delicious and juicy,grapes are widly popular with consumers.Thus,it is very important to maintain the nutritive quality and commodity quality of postharvest grapes.It has been proved that hydrogen sulfide,as a new type of gas signal molecule,is involved in a variety of physiological and biochemical processes in plants.However,the effect of hydrogen sulfide on postharvest grape freshness preservation and its mechanism have not been reported to now.In present research,the changes of physiological,biochemical,transcriptional and metabolic levels of postharvest grape after H₂S treatment were investagted,with exogenous sodium thiohydride as the donor to treat postharvest grape fruits.Furthermore,the mechanism of H₂S treatment to the synthesis of resveratrol and anthocyanin in postharvest grapes was clarified by transcriptional-metabolic methods.The results of present thesis provide theoretical basis for the development of the hydrogen sulfide as antistaling agent to fresh grape forever,clarify the anti-aging mechanism of hydrogen sulfide control plants and the signal transduction mechanism of regulation of the synthesis of secondary metabolites.The results were showed as follow:1.The Physiological and biochemical changes of postharvest grapes after H₂S treatment.The optimal concentration of exogenous hydrogen sulfide was 1.0mmol L^-1 in grape fruits treated with NaHS solution with H₂S donor.H₂S treatment reduce the stem’s browning index,rotting rate and weight loss rate of grape,and delay the decline of grape fruit hardness.The treatment slow down the decrease of soluble solids,reducing sugars,soluble proteins and titrable acids in fruits in different degrees.It also inhibits the decomposition of chlorophyll in the stem and grapes,keep the contents of carotenoids at a stable level,which in turn keeps the grape stem fresh green and prevents the fruit from yellowing in appearance.In addition,H₂S treatment could slow down the decrease in the contents of natural antioxida nts（Vc,total phenols,and flavonoids）in postharvest grapes,induce the increase of the activity of POD,CAT,APX and other reactive oxygen scavenging enzyme system,and decrease the activity of LOX and PPO.The above results indicate that hydrogen sulfide can enhance the anti-aging ability of fruits and play its anti-oxidation effect by mobilizing the metabolic activities of these storage substances,and thus,delaying the aging of postharvest grapes.H₂S signaling molecule is involved in plant cells,physiological and biochemical processes related to the oxidative metabolism,enhance the activity of antioxidant enzyme system by the accumulation of active oxygen product,which finally delay the aging of postharvest grapes.2.The changes of transcriptional profile of postharvest grapes after H₂S treatment.The number os differentially expressed genes of grape after hydrogen sulfide treatment varies with the times,which was determined using the transcriptome sequencing method.Comparated the untreated grapes,1038 genes were found differentially expressed in the combined samples treated with H2S after two,four and six days.The differentially expressed genes after two,four and six days of H₂S treatment were 2445,2020and 2345,respectively.Combined the samples of treatment for two,four and six days,the most influented pathways by H₂S were the anthocyanin synthesis pathway,flavonoid and flavonol biosynthesis and taurine and taurine metabolic pathways.After treatment for two days,the most influented pathways by H₂S were photosynthetic trigger protein,taurine and taurine metabolism,and flavone and flavonol biosynthesis pathways.After treatment for four days,the most influented pathways by H₂S were linoleic acid metabolism,flavone and flavonol biosynthesis,taurine and taurine metabolic pathways.After treatment for six days,the most influented pathways by H₂S were anthocyanin synthesis,taurine and taurine metabolism,flavone and flavonol biosynthesis pathways.The above results demonstrated that hydrogen sulfide can relulate the variety processes in postharvest grape cells,including of complex physiological metabolism,regulation effect of secondary metabolites synthesis,different hormones,and photosynthesis and pathogen interaction,etc.,which clarify the mechanism of anti-aging and anti-oxidation of postharvest grape by H₂S in gene transcriptional level.3.The changes of metabolic profile of postharvest grapes after H₂S treatment.Using the method of HPLC-MS,the metabolic profile of postharvest grapes after H₂S treatment changed significantly.After hydrogen sulfide treatment,300 and 304 different metabolites were detected under positive ion mode and negative ion mode,respectively.After enrichment through the KEGG pathway,19 different metabolites positive ion mode and 34 different metabolites positive ion mode were screened as markers for the changes of grape metabolism after H₂S treatment,respectively.The pathway of differential metabolite enrichment changed with the time of H₂S treatment.In the overall level,the most five influenced pathways under positive ion mode after H₂S treatment were phenol,xylene and ginger diol biosynthesis pathway,naphthalene degradation,the degradation of aromatic compounds,metabolic pathway,secondary metabolites synthesis pathway;under negative ion mode,the five influenced pathways were phenylalanine metabolism,toluene degradation,benzoic acid degradation,2-carbonyl carboxylic acid metabolism,diphenol,xylene and gingerol biosynthesis pathways.4.The mechanis m of H₂S treatment on the regulation of the synthesis of resveratrol and anthocyanin in postharvest grape.After hydrogen sulfide treatment,the contents of flavonoids,resveratrol and anthocyanins in grapes increased significantly.The expression of 16 resveratrol synthesis related genes changed significantly in postharvest grape after H₂S treatment;and the phenylalanine,phenylalanine,p-coumaric acid and resveratrol contents also increased with H₂S treatment significantly.After treatment with H₂S,the expression of 10 anthocyanin synthesis related genes changed in different level;the dihydroxenol,naringin,white fish pelargonium aglucone and cornflower,3-O-3’,6’-O-2 formyl glycosidase increased in a significant level in postharvest grape.Hydrogen sulphide after processing,the grapes of resveratrol synthesis all have different degrees of 10 key genes expression changes,and the difference of metabolites synthesis mainly phenyl alanine biosynthesis,benzene propane biosynthesis and stilbene compounds biosynthesis pathway of phenylalanine,P coumaric acid and the increase of the end-products of resveratrol.The above results reveal the response mechanism of postharvest grape to hydrogen sulfide in apparent level,physical and chemical properties,gene level and metabolic level,which provides the data base for explaining the mechnasim of hydrogen sulfide treatment on the regulation of the accumulation of metabolites in cell and supplies the theoretical basis for exploring the mechanism of delayed fruit senescence by hydrogen sulfide treatment.