Effect Of N-butanol Treatment On Inducing Cold Resistance In Postharvest Hami Melon Fruit

Hami melon has a unique flavor,sweet as honey,thick and thin flesh and other excellent characteristics,It has won the favor of consumers at home and abroad and the reputation of "the king of melons",and has become the backbone of Xinjiang’s characteristic forest and fruit industry.one.Due to the high temperature and climacteric fruit characteristics of Hami melon at harvest,storage at room temperature after harvest is very easy to senesce and soften,which seriously reduces the commercial value of the fruit.Low-temperature storage can significantly slow down the fruit senescence process.Because Hami melon is cold-sensitive,the fruit is prone to chilling damage,limiting the practical application of cold chain circulation technology and refrigeration in Hami melon fruit.Although different treatment methods have been discussed on the chilling injury of Hami melon.However,n-butanol,as a specific inhibitor of phospholipase D,has not been thoroughly investigated for its antagonism to low temperature after fruit harvest.Therefore,in this experiment,n-butanol was used to treat postharvest Hami melon,and RNA-Seq technology was used to explore The effects of alcohol on the storage,antioxidant capacity,membrane lipid metabolism,and proline metabolism of Hami melon fruit at low temperature after harvest reveal that n-butanol enhances the postharvest cold tolerance of Hami melon and alleviates the postharvest chilling injury of the fruit and gene cloning of PLD-β.The main findings are as follows:(1)"Xizhoumi No.25" Hami melon as the test material,screen the appropriate concentration of n-butanol solution(0.0%、0.5%、1.0%、1.5%).The test results showed that compared with the control,different concentrations of n-butanol had different effects,among which the treatment with a concentration of 1.0% n-butanol could significantly reduce the chilling injury index,symptoms of Hami melon fruit and inhibit the peel titratable to a certain extent compared with other treatments.Acid content,pulp firmness,ascorbic acid,and peel soluble protein content decreased,and peel soluble sugar content increased during refrigeration.Therefore,1% n-butanol solution was the best treatment concentration for alleviating chilling injury of Hami melon.(2)After the Hami melon was harvested and treated with 1.0% n-butanol solution,the antioxidant system of the peel was studied.The results showed that n-butanol treatment could reduce the hydrogen peroxide content(except 0-14 d)and inhibit the generation of superoxide anions;Antioxidant enzymes SOD,CAT,POD(except 0-7 d),APX and GR have obvious activities.The contents of reduced ASA,reduced GSH,and DHA in the Hami melon fruit of the n-butanol treatment group were higher than those of the control group,and the activity of antioxidant enzymes and the content of ASA-GSH cycle substrates in the fruit were increased,thereby eliminating Excessive active oxygen free radicals can alleviate the occurrence of chilling damage in Hami melon.(3)1.0% n-butanol treatment reduced the cell membrane permeability and malondialdehyde content of pericarp,and increased the content of phosphatidyl alcohol and the unsaturated fatty acids linoleic acid,linolenic acid,oleic acid(except 14 d),erucic acid(28-42 d)equal content,reduce the content of saturated fatty acid stearic acid(0-28 d)and phosphatidic acid(except 21 d),as well as the activities of PLD and lipoxygenase,key enzymes of membrane lipid metabolism,down-regulate the expression of Cm PLD-β and Cm LOX(42 d)d)Expression.The gene cloning of the key gene of Hami melon membrane lipid PLD,found that the relationship between Hami melon Cm PLD-β and cucumber(Cs XP5)is the closest,with a homology of 100%,followed by pumpkin,with a homology of 87%,indicating that the Hami melon Cm PLD-β gene is functional Similar to cucumber above,through the double alignment analysis of the base sequences of Cm PLD-β and Cs XP5,the first segment of the promoter region of Cm PLD-β was obtained by experimental amplification,and it was found that the base sequences of the two promoter regions were inconsistent.It indicated that n-butanol treatment reduced the content of saturated fatty acids and the degradation of membrane lipid components and unsaturated fatty acids by reducing the activities of key enzymes lipoxygenase and PLD in the membrane lipid pathway and the expression of Cm PLD-β,thereby alleviating the content of malondialdehyde and unsaturated fatty acids.The increase of cell membrane permeability reduces the chilling injury index.(4)1.0% n-butanol treatment can increase proline content,ornithine transferase activity,P5 CS acid synthase activity and Cm P5 CS expression,and can reduce the rate-limiting enzyme proline dehydrogenase activity.It has a significant effect on the expression of Cm Pro DH in its later stage.It is speculated that n-butanol can increase the activities of P5 CS and OAT,the key enzymes of proline synthesis,and the expression of Cm P5 CS,and reduce the key of proline degradation.The activity of the enzyme proline dehydrogenase and the expression of Cm Pro DH in the later stage further maintained the high proline content and alleviated the chilling injury of Hami melon.