Bidochka Michael J, Leger Raymond J St, Stuart Alison, Gowanlock Karen
Department of Biology, Trent University, Peterborough, Ontario, Canada K9J 7B8.
Department of Entomology, University of Maryland, College Park, MD 20742, USA.
Microbiology (Reading). 1999 Apr;145 ( Pt 4):955-963. doi: 10.1099/13500872-145-4-955.
Phylogenetic relationships among 18 isolates in the genus Verticillium, representing 13 species of diverse econutritional groups (pathogens of insects, plants, mushrooms, nematodes and spiders, and saprobes), were examined by using sequences from the internal transcribed spacer (ITS) and small nuclear (NS) rRNA regions. The isolates were also assessed for their abilities to infect insect larvae (Galleria mellonella) and to cause necrosis in alfalfa (Medicago sativa), and for their proteolytic, chitinolytic and pectinolytic activities. The phylogenetic data suggested that Verticillium is polyphyletic in origin and is therefore a form genus. However, the phylogenetic tree supported the plant pathogens (V. dahliae, V. albo-atrum and V. nigrescens) as a clade. The alfalfa isolate of V. albo-atrum (isolate 595) was an interesting outlier to the main body of plant pathogens as it clustered with the insect pathogen V. indicum. Strains of V. lecanii and V. indicum were able to infect insects and are present in divergent groups in the consensus tree, suggesting that the ability to infect insects may have evolved independently many times. Similarly, the nematophagous Verticillium species appear to have evolved independently along several different routes and one isolate, V. chlamydosporium, was able to infect insects. V. albo-atrum, V. nigrescens and V. dahliae all produced high levels of enzymes capable of degrading pectin, a major component of plant cell walls. The ability to excrete pectinase was a broad indicator of the ability to produce lesions on alfalfa. In the plant pathogens, the functions of a broad-spectrum protease were assumed by trypsins which degrade Bz-AA-AA-Arg-NA substrates (Bz, benzoyl; AA, various amino acids; NA, p-nitroanilide). The insect pathogens and mushroom pathogen (V. fungicola) were characterized by production of high levels of subtilisin-like proteases active against a chymotrypsin substrate (succinyl-Ala2-Pro-Phe-NA) and the inability to clear pectin. The insect and mushroom pathogens, and several nematode pathogens, were distinguishable from the plant pathogens in their ability to produce chitinases.
利用来自内部转录间隔区（ITS）和小核（NS）rRNA区域的序列，研究了黄萎病菌属中18个分离株之间的系统发育关系，这些分离株代表了13个不同经济营养类群的物种（昆虫、植物、蘑菇、线虫和蜘蛛的病原体以及腐生菌）。还评估了这些分离株感染昆虫幼虫（大蜡螟）和在苜蓿（紫花苜蓿）中引起坏死的能力，以及它们的蛋白水解、几丁质分解和果胶分解活性。系统发育数据表明，黄萎病菌属起源于多系，因此是一个形态属。然而，系统发育树支持植物病原体（大丽轮枝菌、黑白轮枝菌和变黑轮枝菌）作为一个进化枝。黑白轮枝菌的苜蓿分离株（分离株595）是植物病原体主体的一个有趣的异常值，因为它与昆虫病原体印度轮枝菌聚类在一起。蜡蚧轮枝菌和印度轮枝菌的菌株能够感染昆虫，并且在共识树中处于不同的类群，这表明感染昆虫的能力可能已经独立进化了很多次。同样，捕食线虫的黄萎病菌物种似乎沿着几条不同的路线独立进化，并且一个分离株，厚垣轮枝菌，能够感染昆虫。黑白轮枝菌、变黑轮枝菌和大丽轮枝菌都产生了高水平的能够降解果胶的酶，果胶是植物细胞壁的主要成分。分泌果胶酶的能力是在苜蓿上产生病斑能力的一个广泛指标。在植物病原体中，可以降解Bz-AA-AA-Arg-NA底物（Bz，苯甲酰基；AA，各种氨基酸；NA，对硝基苯胺）的胰蛋白酶承担了广谱蛋白酶的功能。昆虫病原体和蘑菇病原体（食菌轮枝菌）的特征是产生高水平的对胰凝乳蛋白酶底物（琥珀酰-Ala2-Pro-Phe-NA）有活性的枯草杆菌蛋白酶样蛋白酶，并且不能分解果胶。昆虫和蘑菇病原体以及几种线虫病原体在产生几丁质酶的能力方面与植物病原体不同。
