Study On The Regulatory Mechanism Of Trans-2-hexenal And Hydrogen Molecules On Postharvest Tomato Color Change

Color is an important quality attribute of consumers’ acceptance of fruits and vegetables,and the change of tomato color is an important sign of tomato maturity and senescence.This article takes tomato as the experimental object,and uses tomato endogenous gaseous substances trans-2-hexenal((E)-2-hexenal)and hydrogen molecules(H2)to carry out exogenous treatment of post-harvest tomato fruits.Methods such as biochemical determination,electron microscopy observation and transcriptomics have studied the regulation mechanism of these two gas substances on the postharvest color conversion of tomatoes,in order to provide theoretical support for the adjustment of postharvest color conversion of tomatoes,and provide better color for the production of tomatoes.Theoretical basis.The main findings are as follows:1.(E)-2-Hexenal(E2H)treatment inhibited the color change during tomato postharvest ripening,and the degree of inhibition was concentration-dependent.By analyzing the sequential and combined treatment results of E2 H and ethylene(ET),it is inferred E2 H acts downstream of ET.It was observed by transmission electron microscopy(TEM)that E2 H treatment reduced the number of plastid globules(pg)than the control group.The result of the pigment measurement also corresponds to the inhibition of color change.Soluble solids(SSC)and titratable acid(TA)are not affected by E2 H treatment.In the middle of storage(6-36 h),the levels of ascorbic acid and malondialdehyde(MDA)were up-regulated.The measurement results of gas phase ion mobility spectroscopy(GC-IMS)showed that the volatile matter pattern after E2 H treatment was similar to that of the control group.Two genes related to carotenoid synthesis(OR and OR-l)were down-regulated during the pre-storage stage.Two key genes(LOX and HPL)in the E2 H synthesis pathway are up-regulated and downregulated respectively during storage.Therefore,this study speculates the following regulatory relationship: ET→carotenoid biosynthesis→E2H signal transduction→internal membrane structure(IMS)transformation→increase carotenoid accumulation.In view of the results of these experiments and observations,it is speculated that when carotenoids are not yet fully synthesized and accumulated,the fruit can start the conversion of IMS through E2 H treatment,so that the number of pg is insufficient and the color change of tomatoes is inhibited.2.Transcriptome sequencing of E2H-treated tomatoes,GO enrichment and GO and KEGG annotation of differential genes were performed to obtain different differential gene annotation pathways.Three pathways with more differential genes: α-linolenic acid metabolism pathway,ethylene biosynthesis pathway and carotenoid biosynthesis pathway were verified by PCR(AOS、ACO1、ACS2、ACS4、PSY1、PDS and LCY-β).The verification results are consistent with the sequencing results,indicating the accuracy of transcriptome sequencing.From the transcriptomics analysis results,it can be known that E2 H treatment has no significant effect on the ethylene biosynthetic pathway.E2 H accelerates the decomposition of α-linolenic acid and reduces the expression of key genes in the carotenoids biosynthesis pathway,which is consistent with our hypothesis on the regulation mechanism of E2 H on tomato color conversion.3.Hydrogen molecule(carrier is hydrogen-rich water,HRW)treatment inhibited the color change of cherry tomatoes during the postharvest ripening period,and the inhibitory effect of high concentration was more significant.Transcriptomics sequencing of HRW-treated tomatoes showed that the different genes were mainly upregulated.The expression clustering heat map analysis of pathways with more differential genes showed that HRW treatment reduced the expression of genes related to the chlorophyll metabolism pathway and carotenoid biosynthesis pathway,and inhibited the color change of cherry tomatoes during the ripening process.At the same time,the pathways related to antioxidant activity are enhanced.Among them,the biosynthetic pathway of flavonoids and the pathway of peroxisome synthesis are more obvious.Flavonoids and peroxisomes enhance the antioxidant capacity of fruits,and better The redox dynamic balance is maintained,thereby maintaining the quality of the fruit,delaying senescence,and inhibiting the color change during the ripening process of the fruit.In summary,the two gas substances can inhibit the color change of tomatoes during the postharvest ripening period,but the regulation mechanism is different.E2 H treatment accelerated the conversion of IMS when the carotenoids were not fully accumulated,resulting in a decrease in the number of plastid globules and carotenoid content,and inhibition of tomato color change;HRW treatment enhanced tomato antioxidant capacity and inhibited chlorophyll metabolism and The synthesis of carotenoids delays fruit ripening and inhibits the color change of tomatoes.