Study On Effects Of Nitric Oxide Fumigation On Lignin Metabolism Of Postharvest Wax Apple

In this paper,the effects of nitric oxide(NO)treatment on the physiological quality and lignin metabolism of postharvest rum fruit were studied by using the fruit of Syzygium samarangense Merr.et Perry as the experimental material.Two MYB genes were choosed and cloned from wax apple transcriptomics.And then,the function of MYB transcription factor was identified by the expression pattern analysis and functional analysis in Arabidopsis thaliana.The aim of this study is to provide a theoretical basis for the molecular regulation of lignin metabolism in postharvest wax apple.The main results of this study are as follows:1.In this study,we treated with the concentration of 10 and 0 ?l/L(control)NO on the postharvest wax apple.The effects of different concentrations of NO on the cottony softening index,weight loss rate,hardness,lignin and its phenolic hydroxyl content and the key enzymes activity.The results showed that the cottony softening index and weight loss rate increased gradually during the storage period,and the hardness decreased gradually and the cottony softening process continued increasing.Compared with the control group,NO treatment could delay the cottony softening process.In addition,the lignin content of postharvest wax apple increased,and NO treatment could delay the lignin metabolism and inhibit the increase of lignin content,but it did not affect the content of phenolic hydroxyl groups in lignin.The activity of phenylalanine ammonia lyase(PAL),peroxidase(POD)and 4-coumaric acid-coenzyme A ligase(4CL)increased during the storage in control group.In contrast,NO inhibited the increase in PAL,POD and 4CL activity.2.In order to study the effect of 10 ?l/L NO treatment on the key enzyme genes in the lignin metabolism pathway of postharvest wax apple,the key enzyme genes in the lignin synthesis pathway were selected and the bona fide gene involved in lignin biosynthesis was identified.The expression of PAL3,C4H1,4CL3,HCT2,C3H2,CCoAOMT1,CCR,F5H2,COMT1 and CAD1,which influence lignin biosynthesis in 10 ?l/L NO treatments,were determined by the expression of bona fide gene.In addition to CAD,the expression of the remaining 9 genes increased during storage,and the trend of the NO treatment group was slower than that of the control group.It is suggested that NO may regulate the biosynthesis of lignin by inhibiting the expression of key enzyme genes in lignin synthesis pathway.Most of the key genes affecting lignin biosynthesis under NO treatment are regulated by MYB transcription factors.3.Screening and cloning of the MYB transcription factor genes SsMYB4 and SsMYB330 from the transcriptome.MEME analysis showed that both genes contained the MYB domain,and the amino acid sequence analysis showed that both genes belonged to MYB transcription factors associated with lignin synthesis.Gene expression analysis showed that the expression of SsMYB4 decreased during storage,and up-regulated by NO.The expression of SsMYB330 increased during storage,while NO treatment inhibited the increase.The results show that SsMYB4 may be involved in the biosynthesis of lignin as a suppressor,and SsMYB330 may be involved in the synthesis of anthocyanins in the phenylpropane metabolic pathway and has limited effect on lignin biosynthesis.4.In order to verify the regulation of lignin synthesis in the MYB gene,two plant overexpression vectors were constructed and analyzed by Agrobacterium tumefaciens to Arabidopsis thaliana.The results showed that the overexpression of SsMYB4 resulted in the phenotypic changes of the transgenic plants,the thinning of the cell walls,the decrease of the lignin,cellulose and hemicellulose content in Arabidopsis thaliana,and confirmed that the lignin synthesis related gene.The results showed that SsMYB4 had a negative effect on the lignin biosynthesis of Arabidopsis thaliana.The overexpression of SsMYB330 did not significantly affect the phenotypic and cell wall changes of transgenic plants.The results showed that SsMYB330 had negative effect on lignin biosynthesis,but its effect was limited.The results showed that SsMYB330 had little effect on lignin,cellulose and hemicellulose content and lignin synthesis.