抗病油桐根木质部三萜化合物阻断枯萎病菌侵染的调控机制

枯萎病给油桐产业造成毁灭性灾害，目前尚无有效防治手段，亟待加强抗病机制重大基础科学问题的探索。前期研究发现油桐枯萎病菌（Fof1）在抗病油桐根木质部被阻断，根木质部提取物抑制Fof1生长；同时抗病油桐根木质部3个三萜化合物含量和三萜糖基化修饰酶（GT1）基因表达水平均显著高于感病油桐。关于Fof1侵染后抗病油桐根木质部中3个化合物是否被GT1修饰产生抑菌活性，从而抵御Fof1侵染的调控机制还不清楚。为此，本研究以感、抗病油桐为材料，首先评价3个化合物对Fof1的抑制作用及Fof1侵染前后活性差异；进一步研究GT1在感、抗病油桐细胞、组织和器官水平的表达模式；基于油桐全基因组数据研究感、抗油桐GT1的基因结构差异；最后通过油桐根木质部原生质体细胞瞬时过表达GT1，鉴定其修饰3个化合物的能力。研究结果最终解析抗病油桐根木质部三萜化合物阻断Fof1侵染的调控机理，为油桐抗枯萎病育种提供新思路。

Tung tree wilt disease (also referred to the tung plague), caused by F. oxysporum f. sp. fordii (Fof1), resulted in the disaster of tung tree plantation. Our previous work found that the pathogen Fof1 could invade the root epidermis, cortex and phloem both in susceptible and resistant tung trees. However, Fof1 could further penetrate into the xylem of the susceptible tung tree but not the xylem of resistant tung trees. Meanwhile, the crude extract from the root xylem of the resistant tung trees was shown inhibition abilities to the pathogen Fof1, and the three compounds of triterpenoids were exhibited significant higher level in resistant tung trees. Moreover, Glycosyltransferase family protein 1 (GT1), which has been reported to modify triterpenoids, had higher expression level in resistant tung trees. However, it is still elusive that whether and how GT1 modify the three compounds of triterpenoids in the root xylem of resistant tung tree and finally help the host resist the pathogen Fof1. To answer the question, we first aimed to isolate and identify the three compound of triterpenoids from the root of resistant tung trees, and evaluate its ability to inhibit pathogen Fof1. Secondly, we will characterize the expression profile at cellular, tissue and organ level. Third, we will further investigate the gene structure of GT1 based on the whole genome sequencing data of the tung tree. Finally, to validate the modification abilities of GT1 on triterpenoids in root xylem of resistant tung tree, we will develop a transient expression system for GT1 overexpression using root xylem protoplast cells of resistant tung tree. The study will shed light on how the transmission of the pathogen Fof1 was chemically blocked in the root xylem of resistant tung tree. Taken together, the work will provide an alternative strategy for the Fusarium wilt resistance breeding of tung tree.