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

1.产生寄主特异性毒素（HSTs）的病原菌的检测及HSTs的结构鉴定芸苔黑斑病病原链格孢（Alternaria brassicicicola）仅在寄主叶片上产生一种HST蛋白，命名为AB-毒素。我们发现，诱导AB毒素生产的寡糖释放从寄主叶片孢子萌发后。利用寄主衍生因子介导的病原菌孢子萌发产生HST尚属首次报道。芸苔灰斑病菌（A.brassicae）产生的HST称为destruxin B，但本研究发现destruxin B的毒性是非特异性的，而且病原菌产生了不同于destruxin B的新蛋白HST（s）。我们分离了HST生物合成基因，ALT 1，其产物催化病原体中AAL毒素的产生。ALT 1基因形成基因 关于我们 参与病原体的AAL-毒素生物合成的簇。ALT 1仅存在于病原菌的条件致病性染色体上，表明其是通过基因水平转移获得的。3.植物病原菌可及性的分子分析苹果链格孢菌（A.alternata）致病型产生一种HST，命名为AM毒素。由于苹果品种对病原菌和AM毒素的感病性由一个显性基因控制，因此我们试图检测感病性相关分子。结果表明，苹果品种的感病性与叶绿体伴侣蛋白α亚基（60α）的同源物SA 60密切相关，SA 60在抗病品种中是通过叶绿体伴侣蛋白60α基因的点突变而产生的。AM毒素在感病品种的叶绿体中具有主要作用部位。因此，SA 60蛋白可能是AM毒素的受体。另一方面，番茄病原菌互隔孢霉（A.alternata tomato pathotype）和引起番茄棒孢菌靶斑的病原菌Corynespora damicola分别产生HST，称为AL毒素和CCT毒素。研究了两种病原菌对番茄中抗真菌物质α-番茄碱的敏感性。结果表明，番茄病原菌在侵染过程中对α-番茄碱进行解毒，并且解毒是HSTs介导的病原菌在组织中定殖所必需的。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