Regulation Of Methyl Jasmonate Treatment On CBF Signal Pathway Of Bell Pepper In Cold Stress

Bell pepper(Capsicum anuum.L)belongs to dicotyledonous Solanaceae pepper,alias sweet pepper.The birthplace of bell pepper is Central and South America and it is a cold sensitive plant.Bell pepper has a high nutritional value and has a variety of nutrients that are beneficial to human body.It is generally believed that low temperature storage technology has become an effective preservation technology for fruits and vegetables.Low temperature can inhibit the respiratory metabolism of fruits and vegetables to a certain extent,which is helpful for the preservation of nutrients in fruits and vegetables and creates favorable conditions for prolonging the quality guarantee period.However,during the process of production,transportation and low-temperature storage of bell peppers,bell peppers will rot and deteriorate,thus causing cold damage symptoms,seriously affecting the commodity quality and value of bell peppers.Methyl jasmonate is an effective regulator.It can have certain influence on plant stress response.It is helpful for the growth and development of plants and has been widely used in various fruits and vegetables.It is used to keep the fruit and vegetables fresh and prevent the occurrence of chilling injury,thus improving the chilling resistance of fruits and vegetables,reducing membrane lipid peroxidation and other chilling injury symptoms of fruits and vegetables at low temperature,and improving the quality of postharvest fruits at low temperature storage.CBF can be defined as a member of the AP2/ERF family,which is a typical transcription factor,and it is also called DREB,which plays an indispensable role in plant stress response in low temperature environment.At present,the most classical low temperature reaction pathway is ICE1-CBF-COR pathway.In this study,through the determination and analysis of physiological and biochemical indexes of bell pepper,the occurrence of chilling injury and the change of related indexes of bell pepper under low temperature stress were studied.Then,by transcriptome sequencing,analysis and screening of CBF/DREB differentially expressed genes and transcription factors of bell pepper fruits with and without cold injury were carried out.Real-time PCR was used to detect transcription regulation mechanism expression level of molecular biology technology key genes At the same time,the bell pepper stored at low temperature was treated with methyl jasmonate to explore the effect of methyl jasmonate treatment on the regulation of chilling injury and the effect of methyl jasmonate treatment on the change of CBF pathway gene expression in bell pepper,so as to explore the regulation technology to reduce the chilling injury of bell pepper and provide theoretical basis for the research and development of regulation technology of chilling injury of bell pepper.The main results of this paper are as follows:(1)With the extension of storage time,the chilling injury index of postharvest bell pepper increased,especially significantly at 4?.The relative conductivity,decay rate,proline content and malondialdehyde content all increased to different degrees,and the change trend was not of much difference.The changes of thesephysiological indexes were the same as those of many studies on chilling injury.This shows that bell pepper cells are seriously damaged and affected by cold stress,which all represent the collapse of membrane system,and the symptoms of cold injury are more obvious.Chlorophyll content was also on a downward trend during storage,indicating that chilling injury also leads to a decrease in chlorophyll content.The results showed that the bell pepper stored at 4? for 20 days had obvious sunken spots and folds,large water-stained cold damage spots,completely blurred pericarp and pulp tissues,obvious cell contraction and serious tissue damage.The bell pepper stored at 10? showed slight water loss and wilting,and there was no obvious cold damage symptom during the storage period.(2)When stored at4?,100mol/L methyl jasmonate treatment could reduce chilling injury,inhibit chlorophyll decomposition,hinder browning of fruits,facilitate storage of ascorbic acid,have certain influence on ripening of bell pepper,maintain the best quality of bell pepper,and enhance cold tolerance of bell pepper.At the same time,methyl jasmonate treatment could improve the comprehensive activities of antioxidant enzymes SOD,POD,APX and CAT,which was helpful to improve the expression level of coding genes.This provides effective storage technology for cold resistance of postharvest bell pepper.(3)The fruits of bell pepper treated with methyl jasmonate were stored at 4 ? for 25 days.The results showed that the expression of Ca DREB2 E and Ca COR413 genes was higher than that of the untreated group at 4 ?.The time for the occurrence of the peak of Ca ICE1 gene expression of the methyl jasmonate treatment group in 4? was delayed by 5 days compared with that of the untreated group in4? The results showed that the activities of other types of DREB/CBF cold response pathway genes,except for Ca DREB1 F and Ca DREB1 B,were improved after methyl jasmonate-related treatment in bell pepper fruits,which could be expressed as an early signal to further enhance the expression of DREB/CBF cold response pathway related genes in the middle and late storage period of bell pepper fruits,thus improving the cold resistance of bell pepper fruits.