Study On The Mechanism Of Plant Growth Regulator On Fruit Coloring Of Ziziphus Jujuba Mill

Jujube fruit mainly occurs during the period of fruit coloring.It is an effective way and method to control the ‘Hupingzao’ jujube fruit cracking by adjusting the fruit coloring period so as to avoid the local rainy season and reduce the loss caused by post-rain cracking.In this experiment,Ziziphus jujube ‘Hupingzao’ was used as material.Based on the screening of plant growth regulators gibberellin（GA₃）and Paclobutrazol(PP₃₃₃),which can effectively regulate the ‘Hupingzao’ fruit coloring period,combined with RNA-seq analysis,we studied the effects of GA₃ and PP₃₃₃ treatment on on the metabolism ofsubstances closely related to the fruit coloring process,including pigment,endogenous hormone and soluble sugar during the period of fruit development.This study explored the regulation mechanism of ‘Hupingzao’ development and provided a basis for more effective prevention of jujube cracking.The main findings are as follows:1.GA₃ treatment significantly reduced the content of total phenols and flavonoids in jujube pericarp,Increased the ratio of chlorophyll to carotenoid;GA₃ treatment reduced the content of endogenous GAs,IAA and ZR in fruit of jujube jube were reduced,and increased the content of endogenous ABA in ‘Hupingzao’;GA₃ treatment significantly increased the total soluble sugar content in at the later period of ‘Hupingzao’ fruit development but had little effect on starch content.The net activity of sucrose metabolizing enzymes played an important role in the accumulation of total sugar in ‘Hupingzao’ fruit.By transcriptome sequencing analysis,Compared with the control,the total number of differentially expressed genes of GA₃ treatment was 1,565,and the number of up-regulated genes and down-regulated genes were 860 and 705 respectively.DEG annotated by KEGG pathway mainly focuses on the starch and sugar metabolism,the signal transduction of plant hormones and phenylpropanoid biosynthesis pathway of related to anthocyanin synthesis.The number of DEG involved in the mentioned metabolism pathways above was 19,13,and 6,respectively,accounting for 7.28 %,4.98 %,and 2.3 %.GA₃ could downregulate the key genes in the synthesis pathway of flavonoids and anthocyanins.2.After the first spraying,chlorophyll b,carotenoid,the total phenol and flavonoid contents in ‘Hupingzao’ pericarp were significantly increased.PP₃₃₃ treatment significantly reduced the contents of IAA,GA and ABA in ‘Hupingzao’ fruit and the different concentration of PP₃₃₃ treatment had a great change on the content of ZR.PP₃₃₃ treatment significantly increased the soluble sugar content of ‘Hupingzao’ fruit in the middle stage of fruit coloration.After treatment with PP₃₃₃,the activities of sucrose metabolizing enzymes SS,SPS and NI still play an important role in regulating the accumulation of soluble sugar in ‘Hupingzao’ fruit.By transcriptome sequencing analysis,the total number of differentially expressed genes of PP₃₃₃ treatment and the control was 2,169,including 820 up-regulated genes and 1,349 down-regulated genes.Compared with the control,the different genes annotated by KEGG metabolic pathway were main expressed in plant hormone signal transduction（19）,starch and sucrose metabolism（19）,phenylpropanoid synthesis（17）,flavonoid biosynthesis（13）and terpenoids.biosynthesis（10）pathways,accounting for5.25%,5.25%,4.70 %,3.59 %,and 2.76 % respectively.PP₃₃₃ couldupregulate the key genes in the synthesis pathway of flavonoids and anthocyanins.3.There is difference between the PP₃₃₃ and GA₃ treatment in regulating the coloring of jujube fruit.The control pathway of PP₃₃₃ is mainly reflected in the biosynthesis pathway of flavonoids,while GA₃ treatment is the starch and sugar metabolism pathway.treatment by transcriptome sequencing analysis,in which 860 were up-regulated genes and 705 were down-regulated.DEGs annotated by KEGG pathway were mainly detected on the starch and sugar metabolic processes,the signal transduction process of plant hormones,and phenylpropanoid biosynthesis pathway related to anthocyanin synthesis with the involved number of DEGs at 19,13,and 6,respectively,and accounting for 7.28 %,4.98 %,and 2.3 % of total DEGs.All key genes in the synthesis pathway of flavonoids and anthocyanins were down regulated by GA₃.2.The contents of chlorophyll b,carotenoid,the total phenol and flavonoids in ‘Hupingzao’ pericarp were significantly enhanced by the first time application of PP₃₃₃,while the contents of IAA,GA,and ABA in fruits were significantly reduced and the different treatments of PP₃₃₃ at different concentrations displayed different effects on ZR content.PP₃₃₃ significantly increased the soluble sugar content of ‘Hupingzao’ fruit in the middle stage of fruit coloration.When plants were treated with PP₃₃₃,the activities of sucrose metabolizing enzymes SS,SPS,and NI played important roles in regulating of soluble sugar accumulation in ‘Hupingzao’ fruits.A total of 2,169 DEGs in PP₃₃₃ treatment were discovered by transcriptome sequencing analysis,including 820 up-regulated and 1,349 down-regulated genes.Compared to the control,the different genes annotated by KEGG metabolic pathway were main expressed in plant hormone signal transduction（19 genes）,starch and sucrose metabolism（19 genes）,phenylpropanoid synthesis（17 genes）,flavonoid biosynthesis（13 genes）,and terpenoids biosynthesis（10 genes）pathways,accounting for 5.25%,5.25%,4.70 %,3.59 %,and 2.76 % of total DEGs,respectively.PP₃₃₃ could upregulate the key genes in the synthesis pathway of flavonoids and anthocyanins.3.Present studies demonstrated that PP₃₃₃ and GA₃ conducted different functions in regulating the date fruit coloring process.PP₃₃₃ mainly impacted the biosynthesis pathway of flavonoids,while GA₃ affected the starch and sugar metabolic pathway.