桤木为放线菌结瘤共生固氮植物，共生放线菌为Frankia菌，该菌有宿主植物广泛、固氮酶屏氧机制独特等特性，预示它在构建新的共生固氮体系方面有较大潜力。申请人从桤木根瘤鉴定2个3-戊醇糖苷，发现该类物质特异性地分布在根瘤。文献报道3-戊醇使植物产生抗性，然而桤木根瘤特异性地产生3-戊醇糖苷的生物功能是什么，它们在Frankia菌侵染植物形成根瘤过程中发挥怎样的关键作用，及作用通路是什么，有待研究。本项目将通过根瘤和Frankia菌中3-戊醇糖苷的分离分析鉴定,比较其在共生（根瘤）和独生（体外培养）状态下的积累差异；分析3-戊醇和不同种类的3-戊醇糖苷的时空表达差异，并对SA和JA防卫反应信号、结瘤因子信号途径相关基因表达进行实验解析，确认3-戊醇糖苷在桤木与Frankia菌共生固氮中的功能及作用通路。研究结果有望揭示根瘤产生3-戊醇糖苷的本质，对理解桤木与Frankia菌互作机制有重要意义。

Alnus cremastogyne, an alder actinorhizal plant, which is mutualistic symbiosis with Frankia. The host plants with Frankia are extensive, and nitrogen-fixing enzyme in actinorhizal nodules could escape from oxygen with unique mechanism. These traits of Frankia indicate that it has great potential in construction of new symbiosis system of nitrogen fixation. We have previously isolated two 3-pentanol glycosides from root nodules of alder, which are specifically distributed in nodules. It was reported 3-pentanol primed plant immunity against bacterial pathogen. However, the bio-function and pathway of 3-pentanol glycosides in symbiotic nitrogen fixation of A. cremastogyne and Frankia, have not yet been discovered. This project is designed to isolate and identify 3-pentanol glycosides from root nodules of alder, to find their difference in composition and content of 3-pentanol glycosides between symbiotic nodules and Frankia in vitro, and to analyze the function of 3-pentanol glycosides in symbiotic nitrogen fixation of alder and Frankia. The accomplishment of this project will generate understanding about why alder nodules produce 3-pentanol glycosides, and knowledge on the function of 3-pentanol glycosides in symbiotic process between A. cremastogyne and Frankia....The goal of my project is to discover the bio-function of 3-pentanol glycosides in symbiotic nitrogen fixation of A. cremastogyne and Frankia, as well as the function pathway. ..Hypothesis: Frankia infects alder plants, and alder recognizes alien signals and emitted 3-pentanol, which primes plant immunity to defend Frankia. Then, Frankia synthesizes 3-pentanol glycosides to make 3-pentanol into a bond state from a free state. Consequently, defense reaction is inactivated in alder, and Frankia successfully infects on alder root. Moreover, 3-pentanol glycosides may supply as carbon source in trophic exchanges during symbiosis.