| Prunus persica ’Jinxiangyu’ is a new yellow peach variety newly bred by Hunan Academy of Forestry.It has the characteristics of rich aroma,sweet taste,unique flavor and beautiful appearance with early fruit ripening time.Due to the different sweetness and taste of different varieties of peach fruit,fruit flavor and quality are different.Therefore,in-depth research on the fruit characteristics of ’Jinxiangyu’ and the discovery of key genes in the formation of fruit sugar quality can accelerate the promotion and application process of Jinxiangyu’,which has important theoretical significance for the regulation of sugar quality of yellow peach fruit.In this study,the phenological changes of ’Jinxiangyu’ were observed regularly,and physical indexes such as fruit weight and exocarp color difference were determined to observe the morphological changes of fruit development.The changes of soluble sugar content and related enzyme activities were determined by anthrone colorimetric method,and the correlation between them was analyzed.According to the law of soluble sugar accumulation,RNA-seq transcriptomic sequencing was conducted on the fruits of ’Jingxiangyu’ at three key stages(young fruit expansion period(20 d),slowly growing period(60 d)and maturation period(90 d))to analyze the expression patterns of key genes of carbohydrate biosynthesis during fruit development and the regulation rules on fruit sugar quality.Screening key genes regulating fruit soluble sugar formation.The main research results are as follows:1.The main characteristics of ’Jinxiangyu’ peach fruit are:The ripening time is early,the fruit development days are about 85 d,the rapid expansion of fruit development is 20-40 d and 60-85 d after anthesis,and the fruit development is slow at 40-60 d after anthesis,the fruit weight is about 130 g after ripening,the fruit shape is oval,the exocarp is yellow with high color,bright and beautiful color.2.The key stage of fruit quality formation was from 60-85 d after flowering.The contents of soluble sugar,fructose and sucrose in fruits increased significantly during this period.Fructose and sucrose were the main sugars in mature fruits,which were 42.71 mg·g-1 and 6.45 mg·g-1,respectively.At the early stage of fruit development,SS and SPS activities were lower,while AI and NI activities were higher.During the whole fruit development process,SS and SPS were positively correlated with sucrose and fructose content,but negatively correlated with glucose content.There was no significant correlation between AI activity and sugar components during the whole development process.NI is significantly positively correlated with glucose content and is a key enzyme in the direction of sucrose decomposition.3.The transcriptome sequencing results of the three key stages of fruit development showed that the differential expressed genes were mainly enriched in the biosynthesis pathway of secondary metabolites.The main differential genes for starch and sucrose metabolism were enriched during young fruit expansion versus slow growth period,indicating that sucrose and starch metabolism was more active in the early stage of fruit development.4.A total of 143 differentially expressed gene were involved in fructose and mannose metabolism,glycolysis/gluconogenesis,pentoses and glucuronate interconversion,galactose metabolism,and starch and sucrose metabolism during fruit development.33 key enzyme genes were significantly differentially involved in starch and sucrose metabolism,fructose and mannose metabolism.Among them,higher expression levels and sustained upregulation of SDH genes promote the accumulation of fructose content in later stages of fruit development.The gene expression levels of spsl,SS and SS1 were consistently up-regulated and showed a key role in sucrose regulation.The higher expression levels of SUS3 and INVA genes in early fruit development promoted the degradation of sucrose,and these genes jointly regulated and affected the changes of carbohydrate content in ’Jinxiangyu’ fruit. |
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