Molecular mechanism for establishment of basic compatibility in plant infection of pathogens producing host-specific toxins

1.引起油菜黑斑病的病原菌brassicola仅在寄主叶片上产生一种名为AB-toxin的HST蛋白。我们发现一种诱导ab毒素产生的寡糖在孢子萌发后从寄主叶片中释放出来。寄主源性因子介导病原菌孢子萌发产生HST是首次报道。众所周知，引起芸苔属植物灰斑病的a .brassicae会产生destruxin B作为HST，但在本研究中，我们发现destruxin B的毒性是非特异性的，病原菌会产生不同于destruxin B.2的新蛋白HST。PatnogensA致病性分子分析。引起番茄茎秆溃疡病的番茄病菌，产生名为aal毒素的HST。我们分离出一个HST生物合成基因ALT1，其产物在病原体中催化aal毒素的产生。ALT1基因形成了参与病原菌aal毒素生物合成的基因簇。ALT1仅存在于病原体的条件可免除（CD）染色体上，表明其是通过水平基因转移获得的。植物致病菌可及性的分子分析引起苹果赤斑病的苹果病型，产生一种名为am毒素的HST。由于单一显性基因控制苹果品种对病原菌和am毒素的敏感性，我们试图检测与敏感性相关的分子。结果表明，苹果品种的易感性与叶绿体伴侣蛋白α-亚基（60α）同源物SA60密切相关，而SA60是通过苹果抗性品种叶绿体伴侣蛋白60α基因的点突变而出现的。am毒素在苹果易感品种的叶绿体中有一个主要作用位点。因此，SA60蛋白可能是am毒素的受体。另一方面，番茄病原菌A.alternata tomato pathotype和引起番茄Corynespora cassiicola的coynespora cassiicola分别产生名为AL-toxin和CCT toxin的HSTs。研究了两种病原菌对番茄中抗真菌物质α-番茄素的敏感性。结果表明，番茄病原菌在侵染过程中对α-番茄素进行了解毒作用，而解毒作用是病原菌在HSTs介导下向组织定植的必要条件。少

1.Detection of Pathogens Producing Host-Specific Toxins (HSTs) and Structure Determination of HSTsAlternaria brassicicola, the cause of black leaf spot of Brassica plants, produced a protein HST named AB-toxin only on host leaves. We found that an oligosaccharide for inducing AB-toxin production is released from host leaves after spore germination. Production of HST by germinating spores of pathogen mediated with host-derived factor is the first report. A.brassicae, the cause gray leaf spot of Brassica plants, is known to produce destruxin B as a HST, In this study, however, we found that toxicity of destruxin B is non-specific, and the pathogen produces new protein HST(s) different from destruxin B.2.Molecular Analysis of Pathogenicity in PatnogensA.alternata tomato pathotype, the cause Alternaria stem canker of tomato, produces HST named AAL-toxin. We isolated a HST biosynthesis gene, ALT1, whose product catalyzes the production of AAL-toxin in the pathogen. The ALT1 gene formed gene … More cluster involved in AAL-toxin biosynthesis of the pathogen. ALT1 was only present on the conditionally dispensable (CD) chromosomes in the pathogen suggesting acquisition by horizontal gene transfer.3.Molecular Analysis of Accessibility of Pathogens in PlantsA.alternata apple pathotype, the cause of Alternaria blotch of apple, produces a HST named AM-toxin. Because a single dominant gene controls susceptibility to the pathogen and AM-toxin in apple cultivars, we attempted to detect the susceptibility-related molecules. The results indicated that susceptibility of apple cultivars closely associates with SA60, a homolog of α-subunit (60α) of chloroplast chaperonin, and SA60 appears through a point mutation of chloroplast chaperonin 60α genes in resistant cultivars of apple. AM-toxin has a primary action site in chloroplasts of susceptible apple cultivars. Therefore, SA60 proteins may be a receptor for AM-toxin. On the other hand, tomato pathogens, A.alternata tomato pathotype and Corynespora cassiicola, the cause of Corynespora target spot of tomato, produce HSTs named AL-toxin and CCT toxin, respectively. Both pathogens were investigated for the sensitivity to α-tomatine, an antifungal substance in tomato. The results indicated that tomato pathogens detoxify α-tomatine in the infection process and that the detoxification is essential for colonization of the pathogens into tissues mediated by HSTs. Less