He C, Nourse J P, Kelemu S, Irwin J A, Manners J M
Cooperative Research Centre for Tropical Plant Pathology, University of Queensland, Brisbane, Australia.
Mol Gen Genet. 1996 Sep 13;252(3):320-31. doi: 10.1007/BF02173778.
Two genetically distinct biotypes (A and B) of Colletotrichum gloeosporioides that cause different anthracnose diseases on the legumes Stylosanthes spp. have been identified in Australia. A DNA sequence that was present in biotype B and absent in biotype A was isolated by differential hybridisation of a genomic library using total genomic DNA of each biotype as hybridisation probes. This sequence also failed to hybridise to DNA of three biotypes of C. gloeosporioides from other host species and to DNA of three other species of Colletotrichum. This clone was used to isolate two cosmid clones of biotype B. Sequence analysis of these clones revealed a repetitive element of approximately 5.7 kb in length. This element, termed CgT1, was dispersed in the genome and present in about 30 copies. The element contained open reading frames encoding deduced sequence motifs homologous to gag-like proteins, reverse transcriptase and RNase H domains of non-LTR retrotransposons. The termini of CgT1 lacked long terminal repeats (LTRs) but contained a 3' A-rich domain. The insertion site of one copy of the element was flanked by short 13-bp direct repeats. These characteristics of the termini, taken together with the overall structure and sequence homologies, indicate that CgT1 belongs to the non-LTR, LINE-like retrotransposon class of elements that are present in many eukaryotes. PCR primers designed to amplify regions of CgT1 can be used to distinguish biotypes A and B in Australia. DNA fingerprinting analysis of genomic DNA using hybridisation probes derived from the terminal regions of CgT1 revealed that Australian isolates of biotype B are monomorphic. CgT1 was not detected in some isolates causing Type B disease from other countries and when CgT1 was present there was considerable polymorphism in CgT1 organisation in the genome. CgT1 is the first transposon-like element to be identified in the genus Colletotrichum and has considerable potential as a tool for the study of population structure, genome dynamics and evolution in C. gloeosporioides.
在澳大利亚已鉴定出两种遗传上不同的胶孢炭疽菌生物型（A和B），它们在豆科植物柱花草属上引起不同的炭疽病。通过使用每种生物型的总基因组DNA作为杂交探针，对基因组文库进行差异杂交，分离出了生物型B中存在而生物型A中不存在的一段DNA序列。该序列也未能与来自其他寄主物种的三种胶孢炭疽菌生物型的DNA以及炭疽菌属的其他三个物种的DNA杂交。这个克隆被用于分离生物型B的两个黏粒克隆。对这些克隆的序列分析揭示了一个长度约为5.7 kb的重复元件。这个元件被命名为CgT1，它分散在基因组中，约有30个拷贝。该元件包含开放阅读框，编码与非LTR反转录转座子的gag样蛋白、逆转录酶和RNase H结构域同源的推导序列基序。CgT1的末端缺乏长末端重复序列（LTRs），但含有一个富含A的3'结构域。该元件一个拷贝的插入位点两侧是短的13 bp直接重复序列。这些末端特征，连同整体结构和序列同源性，表明CgT1属于许多真核生物中存在的非LTR、类LINE反转录转座子元件类别。设计用于扩增CgT1区域的PCR引物可用于区分澳大利亚的生物型A和B。使用源自CgT1末端区域的杂交探针对基因组DNA进行DNA指纹分析表明，澳大利亚生物型B的分离株是单态的。在来自其他国家的一些引起B型疾病的分离株中未检测到CgT1，而当存在CgT1时，基因组中CgT1的组织存在相当大的多态性。CgT1是在炭疽菌属中鉴定出的第一个类似转座子的元件，作为研究胶孢炭疽菌种群结构、基因组动态和进化的工具具有相当大的潜力。
