Study on biosynthesis of the phytotoxins produced by the phytopathogens, with the aim for plant protection.

本课题组已经发现，Cochliobolus spicifer D-5菌株产生植物毒素，即辣椒酮A、B、C和辣椒酮，以及一种植物生长调节剂，即辣椒素。我们还澄清了这些代谢物是由常见的聚酮前体生物合成的。在寻找与结构相关的代谢物的过程中，我们发现了一个与辣椒酮相关的新代谢物，命名为Cochliospicin A，并确定了其结构。根据结构分析，推测该化合物是由辣椒酮和C3单元组成的。以前，我们从Bipolaris sorokiniana OB-25-1中分离到一种新的植物毒素，sorokinianin，该毒素被认为是由前寄生孢子酚、倍半萜和C3单元形成的。我们试图利用B.sorokiniana OB-25-1来阐明C3单位的生物起源。根据饲养实验和置换培养实验的结果，发现C3单位的生物起源是TCA循环中的成员草酸。新冠脉孢霉NHL 2298产生植物毒素、新新菌素和新呋喃酮。为了阐明这些植物毒素的生物合成途径，我们搜索了结构上相关的代谢物，并发现了新西吡啶酮类化合物。从新呋喃酮的结构确定，新呋喃酮的醛前体与烷基胺发生席夫碱反应，再经过希夫碱脱水反应，即可生物合成新呋喃酮。

It had been found by our research group that the D-5 strain of Cochliobolus spicifer produces phytotoxins, i.e.spiciferones A,B,C,and spiciferinone, and a plant growth regulator, i.e.spicifernin. We also clarified that these metabolites are biosynthesized from a common polyketide precursor. In the course of our search for the structurally-related metabolites, we found a new metabolite related to spiciferinone, named it cochliospicin A and determined its structure. From the structure elucidated, cochliospicin A was supposed to form from spiciferinone and a C3 unit. Previously, we isolated a new phytotoxin, sorokinianin from Bipolaris sorokiniana OB-25-1 and sorokinianin was supposed to be formed from prehelminthosporol, a sesquiterpene, and a C3 unit. We attempted to clarify the biogenetic origin of the C3 unit using B.sorokiniana OB-25-1. Based on the results from the feeding experiments and the replacement culture experiments, the biogenetic origin of the C3 unit was found to be oxaloacetic acid, a memeber of the TCA cycle.Neocosmospora vasinfecta NHL 2298 produces phytotoxins ; neovasinin and neovasifuranones. To clarify the biosynthetic pathway of these phytotoxins, we searched for the structurally related metabolites and found neovasipyridones. From the structure of neovasipyridones determined, neovasipyridones are biosynthesized through the Schiff base formation reaction of the aldehyde precursor of neovasifuranones with alkyl amines, followed by dehydration of the Schiff base.