U. S. -Japan joint research on the molecular pathology of host-specific-toxin-depending fungal infection to plants

L.一种产生ACT毒素的链格孢菌AM毒素在北美的发生情况：通过生物测定和HPLC分析，发现北卡罗来纳州苹果园Delicious品系上的新链格孢病病原菌产生AM毒素I，属于苹果链格孢菌致病型.生化分析表明，尽管AK-、ACT-、AM-、ACR-和HMT-毒素在感病基因型中的主要作用靶点不同，但它们都具有通过破坏植物细胞的动态防御机制来诱导寄主特异性的入侵者进入的能力.稻瘟病菌在萌发过程中产生一种侵染诱导因子，这可能与稻瘟病菌与水稻之间基本亲和性的建立有关.毒素受体的检测与分离：（1）用多克隆抗体检测了Victorin（HV-毒素）在燕麦叶片组织中的共价结合位点：在体内，Victorin与100和45 Kd蛋白的结合位点分别为： ...更多信息 在感病和抗病燕麦品种中均观察到了与100、55和45 Kd的结合。(2)AK-毒素被发现绑定到质膜纯化的感病品种，而不是那些从抗性，日本梨。为了证实，多克隆抗AK毒素抗体在兔子中产生。Cochliobolus carbonum race 1具有两个多功能酶HTS-1和HTS-2，这两个酶是合成HC-毒素环肽所必需的，它们通过ATP/PPI交换来激活某些成员氨基酸。使用特异性多克隆抗HTS-1抗体并通过与对应于酶的胰蛋白酶肽的氨基酸序列的合成寡核苷酸杂交来鉴定编码HTS-1（220 kd）的部分cDNA克隆。HTS-1基因是一个连续的22 kb DNA的一部分，该DNA存在于产生HC毒素的真菌分离株中，而不产生HC毒素的真菌分离株中则缺乏该基因。以烟草赤星病菌（Alternaria alternata）为研究对象，利用质粒载体PDH 25和高重复核糖体RNA基因簇（rDNA）构建了烟草赤星病菌（Alternaria alternata）的高效整合转化体系PDH 25 rla。交替转化是通过质粒携带的rDNA片段与其在染色体中的同源物之间的单交换进行的同源重组。HC-毒素还原酶使HC-毒素在必需羰基上失活，仅在抗C.碳离子小种1（基因型Hm/Hm或Hm/hm）。少

l. Occurrence of AM-toxin an ACT-toxin producing Alternaria Alternata in North America : The pathogen for new alternariosis on Delicious lines in North Carolina apple orchards was found to produce AM-toxin I by bioassay and HPLC analysis, and to fall into the apple pathotype of Alternaria alternate.2. Biochemical analysis revealed that although AK-, ACT-, AM-, ACR- and HMT-toxins have different primary targets in susceptibility genotypes, they exert in common an ability to induce host-specifically the accessibility to invader by nullifying dynamic defense mechanisms in plant cells.3. Pyricularia oryzae causing rice blast produced an infection-inducing factor on germination, which may involve in establishment of the basic compatability between rice plants and the fungus.4. Detection and isolation of toxin receptors : (1) Covalent binding sites of victorin (HV-toxin) in oat leaf tissues were detected by polyclonal, antibodies : in vivo binding of victorin to proteins of 100 and 45 Kd was … More observed in both susceptible and resistanit cultivars of oats, and also, in vitro binding to 100, 55 and 45 Kd in both genotypes. (2) AK-toxin was found to bind to plasma membranes purified from susceptible cultivar, but not those from resistant, of Japanese pear. To confirm, polyclonal anti-AK-toxin antibodies are raising in rabbits.5. Cochliobolus carbonum race 1 possesses two multifunctional enzymes required for HC-toxin cyclic peptide synthesis, HTS-1 & HTS-2, which activate-certain member amino acids by ATP/PPI exchange. A partial CDNA clone, encoding HTS-1 (220 kd) was identified using a specific polyclonal anti-HTS-1 antibody and by hybridization, to a synthetic oligonucleotide corresponding to the amino acid sequence of a tryptic peptide of the enzyme. The gene for HTS-1 is part of a contiguous 22 kb of DNA that is present in isolates of the fungus that make HC-toxin and is lacking in those that do not.6. An efficient integrative transformation system (PDH25rla) for Alternaria alternata was established by using a plasmid vector PDH25 and a highly repetitive ribosomalRNA gene cluster (rDNA) of A. alternata. The transformation occurred by homologous recombination as a single crossover between the plasmid-borne RDNA segment and its homologue in the chromosome.7. HC-toxin reductase that inactivates HC-toxin at the essential carbonyl group, is detectable only in extracts of maize that are resistant to C. carbonium race 1 (genotype Hm/Hm or Hm/hm). Less