Expression Analysis Of XIP Gene In Postharvest Browning And Breakdown Of Longan

Longan is an important characteristic fruit in south China,because of its vigorous physiological metabolism when it ripening and it often infected by a variety of pathogenic fungi,so its quality is likely to deteriorate after harvest.Therefore,controlling postharvest diseases of longan can effectively control the rot and deterioration of postharvest fruits of longan,which is of great significance for the preservation of postharvest fruits of longan.Many studies have shown that plants secrete cell wall degrading enzyme inhibitory proteins when they are infected by pathogenic fungi.It is believed that these inhibitory proteins play an important role in plant disease resistance and defense.At present,the well-studied cell wall degrading enzyme inhibitory proteins in plant mainly include polygalacturonase inhibitory protein(P GIP),xyloglucan-specific endo-glucanase inhibitory protein(XEGIP)and xylanase inhibitory protein(XIP),but the study on these inhibitory proteins in longan has not been reported yet.Therefore,the study of cell wall degrading enzyme inhibitory protein gene in longan is very helpful for understand the disease resistance mechanism of longan and control the postharvest disease of longan.In this experiment,two varieties of longan fruits,"Shixia" and "Dongbi",were used as materials to compare the differences of pericarp browning and aril breakdown characteristics between the two varieties under normal temperature and low temperature storage.Based on the early transcriptome sequencing data in the laboratory,according to the protein of wheat xylanase inhibiting protein domain structure,find the longan class XIP gene families.Among the differentially expressed genes in transcriptome data,six XIP genes,two β-1,3-glucanase GLU genes and two chitinase CHI genes with significant differences in expression were found,and their expression patterns were verified and analyzed.The main research results are as follows:1)Low temperature storage can delay postharvest pericarp browning and aril breakdown of longan,and germicidal treatment before storage can obviously delay pericarp browning and aril breakdown of longan fruits.2)A total of 59 XIP genes have been identified from the longan genome,and the expression patterns of these genes were greatly different in the pericarp and pulp of fruits at normal and low temperatures,.Among them,20 to 30 XIP genes were not expressed or expressed at very low levels during storage.According to the level of transcriptional expression and the trend of changes in gene transcriptional expression,the transcriptional expression patterns of the remaining genes during storage were basically divided into three or four types.3)The XIP gene of longan may be involved in the defense response in the early stage of storage,and the effect was more obvious during normal temperature storage.The difference of XIP gene expression between the two varieties might be related to the difference of disease resistance between ?Shixia? and ?Dongbi?.The role of XIP gene in the pericarp and pulp of longan was different during low temperature storage.Pathogen infection in control treatment may induced the expression of XIP gene.4)Four disease-resistant related genes were also involved in the disease resistance and defense of longan.CHI gene may play a more important role in the pulp of ?Dongbi?.Low temperature significantly inhibited the expression of the four disease-resistant genes,and pathogen infection also induced the expression of GLU and CHI genes.