苹果酸在苹果果实风味和加工品质中起重要作用，也是重要的营养品质指标，因此研究苹果果实苹果酸积累的分子调控机制对苹果优质育种具有重要作用。申请人前期在苹果的苹果酸含量主效QTLs内鉴定到一个关键候选基因MdMYB44，通过超表达和干扰研究证实MdMYB44负向调控苹果酸的积累，其机理可能与该基因与苹果酸转运蛋白基因Ma1、Ma10、MdVHA-A3和MdVHA-D2的启动子互作有关；基因型分析表明MdMYB44启动子变异位点SNP T/−和SNP A/G与果实苹果酸含量紧密关联。本项目拟进一步明晰MdMYB44在苹果酸积累中的调控模式和作用机理，研究变异位点SNP T/−和SNP A/G及其不同组合对启动子活性的影响，并鉴定与SNP T和SNP A特异性结合的转录因子。本项目的实施为深入研究苹果果实苹果酸积累的分子调控网络，开发苹果酸含量高效的分子标记，保障苹果产业可持续发展具有重要意义。

Malate plays an important role in the flavour and palatability of apple fruit, which is also an essential indicator of nutrition quality. Therefore, deciphering the mechanism of malate accumulation in apple fruits can contribute to the improvement of high-quality breeding. Our previous study indicated that MdMYB44 was a candidate gene in the major QTLs of malate content in apple fruit. MdMYB44 functions as a repressor and negatively regulates malate accumulation by over-expressing and repressing analysis, the mechanism of which may be relevant to the binding of the MdMYB44 to the promoter of the malate transporter genes Ma1, Ma10, MdVHA-A3 and MdVHA-D2. Furthermore, the allelic variations of SNP T/− and SNP A/G in the MdMYB44 promoter are closely associated with apple fruit malate content using genotype analysis. The present project will focus on revealing the regulation pattern and the mechanism of MdMYB44 in malate accumulation. Furthermore, the effects of the allelic variations SNP T/−, SNP A/G and their combinations to the MdMYB44 promoter activity will be verified, and the transcription factors specific binding the SNP T and SNP A will be identified. The project will be important for understanding the complex molecular mechanisms that regulate malate accumulation in apple fruit and developing efficient molecular markers for malate content, and also will be valuable to the apple industry.