| Sugar is the basic raw material for the formation of fruit quality and flavor substances and the synthesis of other nutrients.Sugar content is not only an important factor in determining fruit quality,but also participates in other important physiological functions and metabolism.Therefore,It is of great significance for the improvement of jujube varieties and the development of jujube industry to study the sugar metabolism pathway of jujube fruit from the level of molecular biology.This study determined the changes in sugar content and the expression patterns of genes related to sugar metabolism in the current main varieties of Xinjiang jujube(Junzao,Huizao,and Dongzao)during the critical period of fruit sugar accumulation;(Dabailing,Beibeixiaozao,Heigeda and Jinai-2)and high-sugar cultivars(Dahuizao,Gedacui,Guangyangzao and Xinzhenghong-2)fruit sugar content changes and the secondary branches of jujube sugar metabolism-related genes at different developmental stages The expression levels of phloem,jujube hanging phloem,jujube leaves and fruit were determined;transcriptome sequencing was performed on jujube fruits of low-sugar and low-acid varieties(Jing-39)and high-sugar and low-acid varieties(Fucuimi)at different developmental stages.Bioinformatics analysis;the main research results are as follows:(1)In this study,8 sugar components of sucrose,glucose,fructose,galactose,rhamnose,mannose and xylose were detected from jujube fruits.Among them,sucrose,glucose,and fructose were the main sugar components.The accumulation of fructose and glucose dominates,and sucrose dominates in the later period.At the fruit ripening stage,the low-sugar varieties were reducing sugar accumulation type,and the high-sugar varieties were sucrose accumulation type.The difference in sugar accumulation mode between low-sugar and high-sugar varieties was that the low-sugar varieties occur during the development process from the crisp ripening stage to the full-ripening stage.The transition from sucrose accumulation to glucose accumulation.(2)The differences in the expression of Zj SUC2 gene and Zj SWEET2 gene in jujube fruits,as well as the expression of Zj SS1 gene,Zj SS2 gene and Zj SS3 gene in the phloem of jujube hanging resulted in the difference in sugar accumulation patterns between low-sugar and high-sugar fruits.The expression of Zj SPS1,Zj SPS2,Zj SS2 and Zj SWEET2 genes in fruits promotes the accumulation of fruit sucrose,and the expression of Zj SS3,Zj v INV2 and Zj SUC3 genes in fruits promotes the conversion of fruit sucrose;Zj SS1 and Zj SS3 genes may It promotes the conversion of fructose,glucose,and sucrose in leaves,phloem of jujube hanging and secondary branch phloem into other metabolic substrates.The expression of Zj v INV2 gene in the phloem of jujube hanging has the effect of increasing the accumulation of fructose and glucose.(3)In this study,the Illumina Hi Seq 2500 sequencing platform was used to conduct transcriptome(RNA-Seq)research on the five stages of fruit development in ’Fucuimi’ and ’Jing-39’.In Fa vs Ja(Fucuimi honey young fruit stage vs Jing-39 young fruit stage),Fb vs Jb(Fucuimi honey swelling stage vs Jing-39 swelling stage),Fc vs Jc(Fucuimi honey white maturing stage vs Jing-39 white ripening stage),Fd vs Jd(Fucuimi honey crisp mature period vs Jing-39 crisp mature period)and Fe vs Je(Fucuimi honey complete mature period vs Jing-39 complete mature period)3 436,3 492,3 398,3 509 and 3 694 were counted in.In terms of enrichment,the differential genes were 132 775,141 505,139 212,140 663,and 160 619,respectively;there were 2 422 in Fa vs Ja,Fb vs Jb,Fc vs Jc,Fd vs Jd,and Fe vs Je,respectively.2 422,2594,2 647,2 615 and 3 116 differential genes were mapped to 114,117,119,120 and 119 KEGG pathways respectively.Using |log2(foldchang)|>1 and qvalue<0.005 as the screening conditions,38 differentially expressed genes were screened out of the pathways with significant enrichment of differentially expressed genes,which participated in 3 pathways related to sugar metabolism,namely glycosylase Resolve the pathways of glycogenogenesis,galactose metabolism,starch and sucrose metabolism.(4)Through the analysis of the differential genes enriched in sugar metabolism in ’Jing-39’ and ’Fucuimi’fruits,PGM,HK1,HK2,HK3,PK were screened out from the sugar metabolism related pathways enriched by 3 differential genes,SUC2,INV,SS1,SS5,SS7,FK4,FK5,FK6 and FK7 had 14 key genes that cause differences in sugar accumulation between ’Fucuimi’ and ’jing-39’.Among them,the differential expression of Zj SS1,Zj SS5,and Zj SS7 genes are the key genes leading to the accumulation of sucrose in the fruits of’Jing-39’ and ’Fucuimi’.Zj FK4-7 gene may play a key regulatory role in the process of jujube fruit changing from sucrose accumulation type to glucose accumulation type.In the study,the Zj SUC2 gene converts sucrose into galactose,glucose and fructose in the galactose metabolism pathway,and plays a role in promoting the catabolism of sucrose. |
