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

本课题组研究发现，D-5株穗状旋孢霉产生植物毒素（spiciferones A、B、C和spiciferinone）和植物生长调节剂（spicifernin）。我们还阐明了这些代谢物是由一种常见的聚酮前体生物合成的。在寻找结构相关代谢物的过程中，我们发现了一个新的与spiciferinone相关的代谢物，命名为cochliospicin A，并确定了其结构。从结构解析，cochliospicin A被认为是由spiciferinone和C3单元形成的。以前，我们分离到一个新的植物毒素，sorokinianin从平脐蠕孢OB-25-1和sorokinianin被认为是由prehelminthosporol，倍半萜，和C3单元。我们试图用B.sorokiniana OB-25-1来阐明C3单元的生物起源。根据饲养实验和替换培养实验的结果，C_3单位的生物起源是TCA循环的成员草酰乙酸，新cosmospora vasinfecta NHL 2298产生植物毒素：新瓦松素和新瓦松呋喃酮。为了阐明这些植物毒素的生物合成途径，我们寻找了结构相关的代谢产物，并发现了新伐西吡啶酮。从确定的结构的neovasipridones，neovasipridones是生物合成通过希夫碱形成反应的醛前体的neovasifuranones与烷基胺，然后通过脱水的希夫碱。

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.