Study On The Mechanism Of Lanolin-induced ’Zaosu’ Pear Fruit Coloring

Anthocyanin contributes to the coloration of pear fruit and enhances plant defenses.In this study,based on the discovery that green-skinned pear fruit turned red after the lanolin treatment,the mechanisms of the skin coloration in ‘Zaosu’ pear induced by this substance were investigated.We analyzed the physiological mechanism of lanolin-induced red fruit of ‘Zaosu’ pear.Metabolic pathways and ERFs that responded to the lanolin-induced anthocyanin synthesis were screened from RNA sequencing(RNA-Seq)data.PbERF22 and PbERF19 regulating anthocyanin biosynthesis were demonstrated by experiments of transient transformation,yeast one-hybrid assays and dual luciferase assay.The main results are as followed:1.Lanolin affected the levels of flavonoid components and several hormones in ‘Zaosu’ pear fruit.The content of catechin,procyanin B2,epicatechin,chlorogenic acid,quercetin 3-galactoside and quercetin-3-xyloside after the lanolin treatment was significantly increased,and the content of cyanidin 3-galactoside especially remarkable.We measured the contents of several hormones in lanolin-treated ‘Zaosu’ pear fruit and found that the jasmonate contents were significantly increased and the abscisic acid contents were significantly decreased.The phenotype of fruits treated with DIECA(the inhibitor of JA biosynthesis)+ lanolin,1-MCP(the inhibitor of ethylene biosynthesis)+ lanolin and ABA + lanolin showed that JA,ABA,and ethylene were not the key factor for lanolin-induced anthocyanin synthesis.2.Multiple metabolic pathways and transcription factor family were involved in lanolin-induced anthocyanin biosynthesis.A gene expression analysis showed that lanolin promoted anthocyanin biosynthesis by inducing the up-regulation of Pb MYB10、Pb MYB10b、Pb DFR、Pb ANS and Pb UFGT.We selected two stages of lanolin-induced ‘Zaosu’ fruit coloration for the transcriptome analysis,748 DEGs were identified in both stages using a comparative transcriptome data.The KEGG enrichment analysis and a gene ontology(GO)annotation and enrichment analysis indicated that the DEGs were significantly enriched in the biosynthesis of flavonoids,plant hormone signal transduction,as well as plant–pathogen interactions and oxidation-reduction process.An q RT-PCR analysis showed that the jasmonate synthetic genes and the ethylene synthetic genes were significantly up-regulated.Transcription factor family analysis showed that ERFs and WRKYs were highly enriched.3.Hormone signal-regulated PbERF22 and PbERF19 promoted lanolin-induced anthocyanin biosynthesis.PbERF22,PbERF19,PbERF27 and PbERF114 were screened from RNA sequencing(RNA-Seq)data.a phylogenetic analysis found that each of the PbERFs was closely related with the ERFs associated with anthocyanin accumulation from other plant species Correlation analysis showed that four ERFs were significantly correlated with Pb MYB10,PbERF22 and PbERF114 were significantly correlated with Pb UFGT,PbERF19,PbERF27 and PbERF114 were significantly correlated with Pb ANS.The experiments of transient transformation indicated that the overexpression of PbERF22 and PbERF19 promoted anthocyanin biosynthesis by up-regulating the expression levels of anthocyanin structural and regulatory genes in ‘Zaosu’ pear fruit,the anthocyanin content after PbERF22 RNAi was no significant change.Me JA treatment promoted the expression of PbERF22 and PbERF19,1-MCP significantly reduced the PbERF22 expression induced by lanolin,but the PbERF19 expression did not.One-hybrid assays and dual luciferase assay indicated that PbERF22 or PbERF19 enhances the activation effect of Pb MYB10 or Pb MYB10 b on the Pb UFGT promoter,and were involved in the regulation of anthocyanin biosynthesis.