乙烯和细胞分裂素对苹果砧木耐盐性均具有重要调控作用。利用八棱海棠×M.9杂交群体，在后代耐盐性的QTL区间上发现了一个细胞分裂素合成酶基因LOG5b。其启动子上DRE元件（ERF结合元件之一）的串联重复数目在两亲本间存在差异。本项目拟以乙烯响应因子ERF4在酵母单杂交系统中能够结合LOG5b启动子为突破口，利用EMSA、ChIP-qPCR和VIGS等技术手段，明确ERF4如何作用于LOG5b启动子DRE元件来影响苹果砧木耐盐性。利用GFP/GUS双标签瞬时表达、LUC/REN双荧光素酶活性等检测手段，确认DRE元件串联重复变异如何影响LOG5b的转录效率。通过获得不同基因型启动子驱动的LOG5b转基因苹果愈伤，明晰LOG5b及其启动子变异对苹果砧木耐盐性的影响，为苹果砧木的分子辅助育种提供抗性基因储备和理论依据。

Both ethylene and cytokinin could regulate the salt tolerance of apple rootstocks. Using robusta × M.9 hybrid population, we found a cytokinin synthetase gene LOG5b in the QTL interval of salt tolerance. The number of tandem repeats of the DRE element (a binding site of the ERF) on LOG5b promoter differs between the two parents. This project intends to take ERF4 combining with LOG5b promoter as the breakthrough point. We will find out whether ERF4 directly acts on the DRE element of LOG5b promoter to affect the salt tolerance of apple rootstocks, using EMSA, ChIP-qPCR and VIGS assay. The detection of GFP/GUS dual-label transient expression and LUC/REN dual-luciferase activity will be used to confirm whether the variable number of tandem repeats of DRE element affect the transcriptional efficiency of LOG5b in apple rootstock. We will finally clarify the effects of LOG5b and its promoter variation on the salt tolerance of apple rootstocks by obtaining a series of different genotype promoter-driven LOG5b transgenic apple callus. These will provide resistance genetic resources and theoretical basis for molecular-assisted breeding of apple rootstocks.