The Effects Of TDZ And Fruit Load On Aroma Components And Contents In ’Shine Muscat’ Grapes And Functional Analysis Of DXS Gene

In this paper,’Shine Muscat’ grape were used as experimental materials to study the effect of GA3、TDZ and different fruit load per cluster on grape fruit quality and aroma compounds and contents,the DXS gene was cloned from grape tissue,subcellular localization analysis and specific expression analysis also was performed.The main results are as follows:1.’Shine Muscat’ grape cluster was treated with GA3 and TDZ:25 mg·L-1 GA3 at full boom,25mg·L-1GA3 at two weeks after full boom(CK);25 mg·L-1 GA3 at full boom,25 mg·L-1 GA3+5 mg·L-1 TDZ at two weeks after full boom(T1);25 mg·L-1 GA3+2mg·L-1 TDZ at full boom，25 mg·L-1G A3+3 mg·L-1 TDZ at two weeks after full boom(T2);25 mg·L-1 GA3+3mg-L-1 TDZ at full boom,25 mg·L-1 GA3+2 mg·L-1 TDZ at two weeks after full boom(T3);25 mg·L-1 GA3+5 mg·L-1 TDZ at full boom,25 mg·L-1 GA3 at two weeks after full boom(T4).The treatment of TDZ significantly promoted fruit enlargement and decreased fruit shape index when compared with CK,TDZ had a significant effect on nutrient contents which fruit displayed lower total phenolic and flavonoid contents.The effect on fruit nutrient contents treated by T2、T3 was more obvious than those treated by T1 and T4,in which the contents of total phenolic and flavonoid were significantly lower.TDZ significantly reduced the content of total soluble sugars and sweetness values compared with treatment CK.Compared with treatment T1,T2 and T3,treatment T4 displayed lowest total acid and tartaric acid content.Similarly,TDZ significantly changed the aromatic composition and concentration.The contents of Hexanal and(E)-2-Hexenal were significantly improved by treated with TDZ.The terpene synthesis was obviously inhibited by TDZ which decreased the species and the contents of terpenoids such as linalool,geraniol and nerol.In four TDZ treatments,treatment T4 displayed highest proportion of terpenoids,the more intense rose fragrance and the lighter grass fragrance.2.There was significantly difference on grape fruit quality between different treatments.The cluster with 40 was superior with graceful shape、full fruit and uniform color;60 performed with smaller berries and sparse cluster;80 reached ripe inconsistency and mixed with different size fruit.No significant difference was found in the fruit soluble solids content between different treatments,but the soluble solid content of 40 was significantly higher.At the maturity stage,the cluster with 40 showed higher contents of terpenes in response to other treatments;the C6 compounds content of 60 was higher.And during fruit development,comparing with other treatments,terpene compounds of 40 dropped more slowly,and several trace terpenes such as cis-linaloloxide、citronellol disappeared later.Transcriptional analysis revealed that the expression of VvDXS was significantly affected by the treatment of different fruit load,and significant correlated with the total content of terpenes.Overall the expression of VvDXS in 40 was higher than others.3.The DXS gene was cloned from different tissues of ’Shine Muscat’ grape.The open reading frame(ORF)of VvDXSl and VvDXS3 were 2151 bp and 2160 bp;encoding 716 and 719 amino acids,respectively.Both DXS1 and DXS3 had three conserved functional domains of DXP_synthase_N、Transket_pyr and Transketolase_C,and EI subunit similar to DXP_synthase_N was also predicted in DXS1.Amino acid sequence homology alignment showed that the DXS protein of grape was highly conserved,and the C-terminal domain is more conserved than the N-terminal domain.Phylogenetic analysis indicates that DXS1 protein had a closed relationship with Catharanthus roseus and Citrus sinensis,while DXS3 was closed to Aquilaria sinensis,Arabidopsis thaliana and Artemisia annua.Subcellular localization indicated that the two proteins were localized in the chloroplast.Transcriptional level analysis showed that VvDXS1 and VvDXS3 were expressed in different tissues and different developmental stages of grape,and the expression level of DXS1 was significantly higher than DXS3.Therefore,it is speculated that both VvDXS1 and VvDXS3 are involved in the regulation of MEP metabolic pathway,and DXS1 exerts an enormous function,while DXS3 plays a minor role in regulating.