The Analysis Of The Relationship Between CPPU With Sink Strength Regulation And Sugar Metabolism In Kiwifruit

Fruit size is the main factor affecting the quality and price of the kiwifruit.Forchlorfenuron(CPPU)is widely used to regulate the size of kiwifruit and other fruits in the production.CPPU treatment can promote the cell division and expansion and accelerate fruit expansion,which is also related to the improvement of the fruit sink strength.In order to explore the relationship between the regulation of the kiwifruit sink strength and the unloading and metabolism of fruit assimilates,the Actinidia deliciosa 'Hayward' kiwifruit was used as the test material in this paper,and water was used as control and young kiwifruits were dipped in 50 mg / L CPPU at 20 days after blooming.The effects of CPPU on the regulation of kiwifruit sink strength and sugar metabolism were studied,and the effects of CPPU treatment on the expression of related metabolic genes were analyzed by transcriptome analysis.At the same time,the overexpression and interference vectors of the key genes Md NINV1 and Ad SUSY1 regulated after sucrose unloading were constructed,and the corresponding kiwifruit transgenic lines were obtained by agrobacterium-mediated method.The sugar content and other indexes were measured,and the main results are as follows:1.Compared with the control,treated with 50 mg/L CPPU can effectively increase the single fruit weight of the Hayward kiwifruit and increase the vertical and horizontal diameter of the fruit.The largest increase of the fruit size was in the first and second weeks after CPPU treatment,which is not later than 35 days after blooming.The results showed that the content of fructose had no significant change in the first three weeks after CPPU treatment,and it was higher in the later stage of development than the control group,and the content of glucose and sucrose in the whole fruit development period were higher than the control group.The analysis of enzyme activity of genes related to sugar metabolism found that compared with the control,the activity of SPS(sucrose phosphate synthetase)in the fruit treated with CPPU was increased as a whole,Sucrose synthase(SUSY)and acid invertase(AINV)involved in sucrose cracking were higher than the control in the early stage of fruit development and lower in the later stage of fruit development.These results indicated that the CPPU treatment increased the fruit sink strength and increased CHO allocation.This may be related to accelerated sucrose cracking.In addition,the content of Vc in kiwifruit treated with CPPU was higher than the control group in the early stage of development,but lower than the control group in the later stage of development.The content of reduced Vc and total Vc increased first and then decreased in the whole fruit development period in both of the control group and CPPU treated group.2.In order to further explore the mechanism of CPPU treatment to improve the fruit sink strength and promote the fruit growth,RNA-seq technology was used to analyze the changes of fruit transcriptome in the first three weeks after CPPU treatment.The results showed that the CPPU treatment had an effect on the sugar metabolism pathway.In the carbohydrate metabolism transport pathway,CPPU treatment up-regulated starch metabolism genes such as ?-amylase and ?-glucan phosphorylase,and in the pathway of sucrose unloading,CPPU treatment up-regulated the expression levels of SUT,SPT,CWINV,SUSY,HXK and other genes,especially SUSY1 which is related to kiwifruit sink strength was significantly up-regulated on the 7th day after CPPU treatment.This may be directly related to the regulation of SUSY activity and sink strength by CPPU.At the same time,the analysis of hormone signals revealed that the differential genes mainly concentrated on cytokinin perception and signal transduction,ethylene biosynthesis,ethylene perception and signal transduction,gibberellin biosynthesis,gibberellin modification and degradation,and the changes of these hormone signals may be related to the changes of genes related to the regulation of sink strength,sucrose unloading capacity and cell division.3.In order to prove the role of sucrose cleavage method in sucrose unloading,the overexpression vector of Md NINV1 and the interference vector of Ad SUSY1 were constructed.The 'Hayward' kiwifruit resistant strains were obtained through agrobacterium-mediatedmethod and 3 positive strains with heterologous overexpression of Md NINV1 were obtained by DNA and RNA level molecular detection;3 strains interfered by Ad SUSY1 were also obtained.The measurement of the sugar content in Md NINV1 leaves found that both of the fructose and glucose content were lower than the wild type,and the fructose content was reduced by about 50% and the glucose content was reduced by about 30%,while the change in sucrose content was not significant.The sugar content of Ad SUSY1 leaves was measured and found that the sucrose content of the transgenic lines decreased significantly.