Regulation Function Of Nitric Oxide On Lipoxygenase In Fruit Of Peach

Fragrance endows a special flavour sense for the fruit and becomes a typical ‘flavour characteristic spectrum' or ‘flavour fingerprint',playing an decisive role in the composition of the fruit flavour.The flavour components in the peach are very complicated,including lot of volatile substances such as aldehydes,alcohol,esters,lactones,terpene and ketone.Aliphatic acid is a main precursor in the formation of the fruit flavour.Aliphatic acid is the main source for the most plant fragrance and the important way to synthesize the characteristic fragrance substances of peach.Alcohol,aldehyde,ester and lactone can be formed in this way.The main synthetic route of aliphatic acid is lipoxygenase(LOX),which is formed hydroperoxide by reacting with linoleic Acid and linolenic Acid,and then formed hexanal or hexene aldehyde by reacting with hydroperoxidelyase(HPL).The obtained aldehydes react with alcohol dehydrogenase(ADH)to achieve the corresponding alcohol.Finally,the alcohol reacts with alcohol acyltransferases(AAT)to get the corresponding lipid.In order to investigate the influence of nitric oxide(NO)on the synthesis of the fruit flavour substances during storage,we studied the regulating effect of NO to the LOX which is the important enzyme to the LOX pathway.Our experiment is based on the picked Feicheng peach.NO solution with different concentration was used to handle the peaches at the physiological maturity stage.The change of the LOX activity was observed under different treatment at room temperature and 0 ?.It is observed that the LOX activity in peaches has a trend of rise both at room temperature and 0 ?.Compared with the control experiment,it can be seen that the treatment of NO restrains the LOX activity and the LOX activity with the treatment of 15 ?mol L-1 NO is less active than that of 5 ?mol L-1 NO and 30 ?mol L-1 NO.Four mRNA sequences of the LOX family gene were received from National Center for Biotechnology Information(NCBI).Total RNA was extracted and cloned to get cDNA from Feicheng peaches by the qPCR degenerate primer designed through this conserved sequence.TUB was used as an internal reference,we calculated the relative ratio of the copy number between LOX-1,LOX-2,LOX-3 and LOX-4 to analyze the level of the gene expression.It can be concluded that NO suppresses the expression of LOX-1,LOX-2,LOX-3 genes before promotes while promotes the expression of LOX-4 gene before suppresses.The treatment effect with 15 ?mol L-1 NO is more obvious than that of 5 ?mol L-1 NO and 30 ?mol L-1 NO.LOX-2-pET-30 a and LOX-3-pET-30 arecombinant vectors were built to import the e.coli Transetta(DE3)for protein expression.After protein simulation analysis,it is found that four LOX proteins are easier to have the Glutathione reaction than nitrozation reaction.NO reacts with the active center of LOX-1,LOX-2,LOX-3 and LOX-4 proteins is by the hydrogen bond.NO controls the activity of lipoxygenase by regulating the expression of LOX gene in peaches to further influence the synthesis of aromatic volatiles in peaches.