Study On Expressions Of Ripening-related Genes In Fruit Of Jackfruit And Cloning And Sequence Analysis Of β-galactosidase Gene

Fruit ripening is a complex physiological process, and is closely related to thetexture and storage performance of the fruit. In this thesis, by using reference genesselected in this study, espressions of genes for polygalacturonase, pectin methylesterase, pectin methyl esterase inhibitor, cellulase, ɑ-galactosidase, β-galactosidase,arabinofuranosidase, ɑ-mannosidase, β-mannosidase, ɑ-amylase, β-amylase and theacid invertase during fruit ripening of different genetypes of soft flesh jackfruit(GHsj12As and GHsj12Cs) and hard flesh jackfruit (GHsj12D and GHsj12G.) wereinvestigated, and a cDNA sequence of β-galactosidase gene was obtained by RACEtechnique and analysised in bioinformatic ways. Main results showed as following:1) Expression stabilities of five reference genes in different tissues of jackfruitwere analysed. The results showed that, the most stable reference genes among thosein fruit were UBQ, GAPDH and18S rRNA, and in leaves were UBQ, GAPDH andβ-tubulin, and in florescences were UBQ, GAPDH and ɑ-tubulin.2) Investigations on gene expressions showed that, ɑ-mannosidase,β-mannosidase and ɑ-amylase may play an important role in the fruit softening ofjackfruit, the polygalacturonase, pectin methyl esterase, pectin methyl esteraseinhibitor, cellulase, ɑ-galactosidase, β-galactosidase, arabinofuranosidase, β-amylaseand acid invertase were not major genes that lead to softening of jackfruit fruit.ɑ-amylase gene and β-amylase gene may be associated with the formation of textureand quality of jackfruit fruit.3) A cDNA sequence of β-galactosidase gene was obtained from fruit of jackfruit.It was3264bp in length and contained a2574bp ORF encoding857amino acidresidues, and encoding a protein with predicted molecular weight of95.4538KD, anda theoretical isoelectric point of8.88. This protein belonged to the family35glycosylhydrolases, and had glycosyl hydrolases and galactose lectin conserved domains andcould bind carbohydrate and hydrolyzed O-glycosyl compound. The encoded proteinsubcellularly located in the mitochondria,and was a hydrophilic protein. It had asignal peptide and some helical transmembrane regions, which might be a transmembrane protein or membrane prptein. The protein had19functional sites and27phospjorylation sites. The secondary structure consisted of ɑ-helix, β-fold,extended chains and irregular curls. The tertiary structure showed high similarity withbeta-galactosidase4of tomato.