Effects Of GA₃ And PBZ On Internode Lengthand Gene Expression Of Gibberellins Metabolism In Peach ?Prunus Persica L.?

Peach(Prunus persica)native to China,has a long history of artificial cultivation.The peach cultivars in china with strong vegetative growth need more pruning and the application of growth regulator,so make the control of tree size is critical for the optimization of productivity and for limiting the amount of labor and inputs needed for orchard management.Gibberellin is an important hormone regulating plant growth,KO,GA3-ox,GA20-ox are the key biosynthetic enzymes which involved in the biosynthetic pathway,and the degrading enzyme is GA2-ox.In addition,DELLA,GID1 c,SLY1 and ERF11 transcription factors play an important role in GA signaling pathway to regulate the internode length of plant.Currently,the enzymes and protein genes have been studied in many plants,while few in peach.In this study,31 peach cultivars as materials were selected for GA3 and PBZ treatment,and the sensitivity of different peach varieties to exogenous GA3 and PBZ were analyzed after measuring the growth and internode length after treatment.Moreover,the moderate sensitive cultivar ' huangshuimi' as the experimental material were selected to treat with GA3 and PBZ and mensurate the activity of GA synthesis and metabolism enzymes in the leaves.Then the expression of key genes in GA synthesis and metabolism pathway and signaling pathway were mensurated by using the QRT-PCR.The aim of this study could be provided fundamental basis for using genetic engineering technology to control the height of peach trees.The main results were as follows:1.The objective of the study was to determine the sensitivity of 31 peach germplasm resources to exogenous GA3 and PBZ,respectively.The growth indexes of the 31 peach germplasm resources were investigated after foliar application of PBZ and exogenous GA3.Moreover,the sensitivity indexes of the initial growth,the total growth and internode length of different treatments were analyzed by cluster analysis.The results showed that the average values of the three growth indexes were increased after exogenous GA3 treatment compared with control of spraying water,while the average value of the three growth indexes decreased after PBZ treatment.Clustering results showed three cultivars including ‘Tezaohong',‘Zhongtao 5' and ‘Beijing 9' were clustered into the group of high sensitivity to exogenous GA3.Twenty resources were clustered into the group of lower sensitivity.Fifteen resources were clustered into the group of high sensitivity to PBZ.Six resources were clustered into the group of lower sensitivity to PBZ.These results would be provided a theoretical foundation to regulate vegetative growth by using PBZ and exogenous GA3.2.Selected reference gene with stable expression in peach shoot and leaf tissue.After the treatment of exogenous GA3 and PBZ on the ‘Huangshuimi',QRT-PCR techniques were used to measure the expression of 10 commonly used reference genes in peach,the comprehensive analysis results showed that 18 s r RNA was the most suitable reference gene.3.Measured the shoot growth and internode length change of ‘huangshuimi' after exogenous GA3 and PBZ treatment.The shoot and internode length were measured after spraying of exogenous GA3 and PBZ separately,with spraying clear water as control,The results showed that exogenous GA3 treatment could effectively increase the amount of shoot growth and internode length,while PBZ treatment significantly inhibited the growth of shoot growth.In addition,exogenous GA3 could effectively restore the growth of shoot at 17 d after PBZ treatment.4.Measured the activity of GA synthesis and metabolism enzymes in the leaves of ‘Huangshuimi' after exogenous GA3 and PBZ treatment.The results showed that the activity of KO,GA20-ox and GA3-ox were decreased after the treatment of exogenous GA3 and then increased in the later stage.It indicated that these genes were involved in the negative feedback regulation.After PBZ treatment,the activity of KO enzyme was decreased at 5 d,and the activity of GA20-ox and GA3-ox showed a decreasing trend at 8 h after treatment.The enzyme activity of GA2-ox was completely consistent with the control after PBZ treatment.The results showed that PBZ inhibited the elongation of plant stems by inhibiting the key enzyme activities in the GA synthesis pathway.5.Measured the expression of the GA synthesis and metabolism,signaling pathway genes in ‘Huangshuimi' shoots and leaves with different treatments.The results showed that the expression of KO,GA20-ox,GA3-ox and GA2-ox gene were also involved in the regulation of GA feedback after exogenous GA3 treatment.After the exogenous GA3 treatment at different stages,the expression of DELLA and SLY1 genes in shoots and leaves showed inhibition at the early stage and rapidly increased in the later stage.The expression of GID1 c gene in the shoot and leaf tissue was different.In the different period of exogenous GA3 treatment,the expression trend of GID1 c gene in different tissues had a completely opposite change,which showed that the GID1 c gene was the key gene for the growth of peach shoot in GA signaling pathway.After PBZ treatment,the expression of KO and GA20-ox gene in different tissues decreased,especially in leaves,and the expression of GA3-ox gene was significantly down-regulated in the shoot tissue.In addition,the expression levels of GID1 c,SLY1 and ERF11 genes after PBZ treatment also showed a slight downward trend in different tissues.These results indicated that PBZ could be inhibitted the growth of plant growth mainly by reducing the expression of key genes in GA synthesis and metabolism pathway and signaling pathway in gene level.