儿茶素和表儿茶素对植物抗病具有重要作用。前人研究表明，一般植物中表儿茶素是以花青素为底物进行生物合成的，而我们的前期研究表明，海棠中应该还存在一条未在其他植物中报导过的表儿茶素合成新途径：以儿茶素为底物合成表儿茶素。本研究拟通过在转录水平对比花青素合成酶基因干扰后的塞维斯海棠及其野生型，结合进一步的基因干扰实验，获得编码儿茶素差向异构酶的基因片段，然后通过RACE-PCR克隆基因全长，酵母表达和离体酶促反应对其基因功能进行验证，进而阐明海棠中由儿茶素差向异构酶催化的表儿茶素合成途径，完善植物中表儿茶素代谢途径，为植物抗病育种提供理论支持。

Catechin and epicatechin were very important for pant disease resistant. Privious reports domenstrated that epicatechin was biosynthsized through catalyzing of anthocyanidin in plants. Privious study of applicant showed that there is a new epicatechin biosynthesis pathway in crab apple, which using catechin as subatrate. In this project, wild type and ANS-RNA interference trasgenic Malus sieversii var. niedzwetzkyana were used as experimental materials. The catechin isomerase coded gene was obtained using of expression profiling analysis, protein purification and separation, agrobacterium mediated genitic transformation and RACE-PCR. The function of gene was characterized by yeast expression and enzym assay.The research results could improve the epicatechin metabolic pathways in plants, and provide theoretical support for the concept of highly disease resistant plant breeding.