Park Yunjung, Chen Xiaobang, Punja Zamir K
Department of Biological Sciences, Centre for Environmental Biology, Simon Fraser University, 888 University Drive, Burnaby, BC, V5A 1S6, Canada.
Mycol Res. 2006 Jun;110(Pt 6):697-704. doi: 10.1016/j.mycres.2006.03.007. Epub 2006 Jun 9.
Double-stranded (ds) RNA banding patterns were determined in 21 wild-type strains of the soilborne plant pathogen Chalara elegans originating from different geographic regions worldwide. Five strains, each with a unique dsRNA pattern, were selected for cDNA cloning, northern blot analysis and dsRNA transmission experiments. Four strains contained multiple (up to 6) dsRNA elements (2.0kbp to 12kbp in size) and one strain contained a single 2.8kbp fragment. These five strains were distinguished from one another by their unique RAPD-PCR patterns. Seven partial cDNA clones were derived from the predominant 2.8, 5.3, and 12kbp dsRNA elements. Nucleotide sequence analysis and northern blot hybridizations revealed a high degree of genetic dissimilarity among the different molecular-size dsRNA elements, even those found within a single strain. Four clones from the 5.3kbp dsRNA fragment showed a 23-43 % amino acid identity to either the coat protein or RNA-dependent RNA polymerase regions of viruses in the Totiviridae. One clone from the 2.8kbp dsRNA fragment had a 55-57 % amino acid identity to the RdRp region of viruses in the Narnaviridae. Two clones from the 12kbp dsRNA fragment showed no significant homology to any known virus group. Colonies derived from 100 single-conidia isolates of C. elegans strains with the 2.8, 5.3 and 12kbp elements all contained the corresponding dsRNA element, indicating that dsRNA transmission through conidia was highly efficient, regardless of molecular size. However, transmission of dsRNA between the mycelium of strains of C. elegans could not be achieved in this study. Genetically unique strains carrying diverse dsRNA elements appear to have evolved within populations of C. elegans. Based on our findings, there are at least 3 groups of viruses present in C. elegans.
对来自世界各地不同地理区域的21株土传植物病原菌优雅弯孢霉（Chalara elegans）的野生型菌株进行了双链（ds）RNA条带模式分析。选择了5株具有独特dsRNA模式的菌株进行cDNA克隆、Northern印迹分析和dsRNA传播实验。4株菌株含有多个（多达6个）dsRNA元件（大小为2.0kbp至12kbp），1株菌株含有一个2.8kbp的片段。这5株菌株通过其独特的RAPD-PCR模式相互区分。从主要的2.8、5.3和12kbp dsRNA元件中获得了7个部分cDNA克隆。核苷酸序列分析和Northern印迹杂交显示，不同分子大小的dsRNA元件之间存在高度的遗传差异，即使是在单个菌株中发现的那些元件。来自5.3kbp dsRNA片段的4个克隆与Totiviridae病毒的外壳蛋白或RNA依赖性RNA聚合酶区域的氨基酸同一性为23%-43%。来自2.8kbp dsRNA片段的1个克隆与Narnaviridae病毒的RdRp区域的氨基酸同一性为55%-57%。来自12kbp dsRNA片段的2个克隆与任何已知病毒组均无明显同源性。来自具有2.8、5.3和12kbp元件的优雅弯孢霉菌株的100个单分生孢子分离物形成的菌落均含有相应的dsRNA元件，这表明dsRNA通过分生孢子的传播效率很高，与分子大小无关。然而，在本研究中未能实现dsRNA在优雅弯孢霉菌株菌丝体之间的传播。携带不同dsRNA元件的遗传独特菌株似乎已在优雅弯孢霉种群中进化。根据我们的发现，优雅弯孢霉中至少存在3组病毒。
