土生空团菌(Cenococcum geophilum Fr.)18S rDNA中的I型内含子

Group-I introns in 18S rDNA of Cenococcum geophilum Fr．

摘要:

摘要:【目的】分析土生空团菌［Cenococcum geophilum Fr． (Cg)］18S rDNA 中I 型内含子的核苷酸序列和二级结构特征，探讨影响土生空团菌遗传多样性的因素。【方法】对23个Cg菌株18S rDNA的3'端进行PCR扩增，对其中14个菌株的扩增片段测序。利用MAGE version 4.0软件构建Neighbor-Joining系统发育树，利用Mfold 预测内含子的二级结构。【结果】序列分析表明，19个中国菌株中14个在18S rDNA中有I型内含子。结合GenBank中的相关数据，可知Cg菌株18S rDNA中内含子的序列长度为488－590nt，显示出92.3%－100%的同源性。在其5'端序列比较保守，在3'端序列差异较大。二级结构分析表明Cg菌株18S rDNA 中的内含子都有10个配对区(P1－P10)，在P5区域由P5，P5a，P5b，P5c，P5d组成，在P9的3'端有2个配对区(P9.1、P9.2)。【结论】来源于不同寄主及地域的Cg菌株有丰富的遗传多样性，本文没发现地理因素和寄主来源对Cg的遗传分化有影响。

Abstract:

Abstract:［Objective］To analyze the sequences and secondary structure of group-I introns in 18S rDNA of Cenococcum geophilum，and to study the factors effecting Cg genetic diversity． ［Method］The 3' end region of 18S rDNA were amplified from twenty-three Cg isolates，and the PCR fragments from thirteen isolates were sequenced． The Neighbor-Joining phylogenetic analyses were performed using MAGE version 4. 0，and the secondary structures of the Cg introns were predicted using Mfold． ［Result］The results showed that fourteen out of nineteen Cg isolates originated in China had group-I introns in 18S rDNA． Their sequences，ranging in size from 488 to 590 nucleotides，were from 92. 3% to 100% similar to each other from our data and GenBank data． The 5' end sequences of the introns were conserved，while the 3' end sequences were variable． The analysis of secondary structure indicated all the introns from forty-five Cg isolates contained ten pairing regions (P1－P10)． The P5 region was composed of P5，P5a，P5b，P5c and P5d，and there were two extra pairing stems (P9. 1、P9. 2) besides the 3' end of P9． ［Conclusion］It was suggested that Cg had rich genetic diversity，and we did not found the relationship between Cg genetic variation and its geographical and host origination．