肺囊康定产生菌Glarea lozoyensis线粒体基因组序列的再分析

Reanalysis of the mitochondrial genome of the pneumocandin- producing fungus Glarea lozoyensis

摘要:

[目的] Glarea lozoyensis是抗真菌药物卡泊芬净的产生菌，其突变菌株ATCC 74030的线粒体基因组已被报道。我们此前的研究发现诱变剂能引起该菌某些细胞核基因的突变，但诱变剂是否也能引起线粒体DNA序列的改变并不清楚。[方法] 组装野生型菌株ATCC 20868的线粒体基因组，并与发表的突变型菌株ATCC 74030的线粒体基因组进行比较。通过PCR验证野生和突变菌株线粒体基因组间表现差异之处，并利用正确的线粒体基因组序列进行新的分析。[结果] 我们成功组装出野生型菌株ATCC 20868的线粒体基因组，通过比较其与发表的ATCC 74030的线粒体基因组序列，发现存在6处单核苷酸变异位点和2处具有长度差异的区域。然而，随后的PCR验证和序列比较并没有发现2个菌株间存在这些差异。最初观察到的碱基差异是因为发表的ATCC 74030线粒体基因组存在序列错误。有趣的是，在Glarea lozoyensis的线粒体基因组中，我们发现存在3个具有内含子的tRNA基因和1个rnpB基因。同时，该菌线粒体基因组中存在多种重复序列，在其线粒体和细胞核基因组间也存在明显的DNA片段重复事件。[结论] 诱变剂没有引起G. lozoyensis线粒体DNA的任何改变；发表的ATCC 74030的线粒体基因组存在序列错误。我们报道G. lozoyensis正确的线粒体基因组序列，并且发现该菌线粒体和细胞核基因组间频繁的基因交流。

Abstract:

[Objective] Glarea lozoyensis is a filamentous fungus used for industrial production of the antifungal drug caspofungin. Previously, the mitochondrial genome (mitogenome) of a mutant strain ATCC 74030 was reported. The purpose of the current study is to test if mutagen treatments have caused changes on the mitogenome of the fungus. [Methods] The mitogenome of the wild strain ATCC 20868 was assembled and compared with the published mitogenome of ATCC 74030. PCR assays were done for both strains. Additional analyses were done using correct mitogenome sequences. [Results] We successfully assembled the mitogenome of the wild strain ATCC 20868. Initial comparison of the mitogenomes of the wild and mutant strains indicated six variable nucleotide sites and two regions with length variations. PCR assays and subsequent sequencing, however, showed no difference between the two strains. The differences observed from initial comparison were due to sequence errors present in the published mitogenome of ATCC 74030. Interestingly, three intron-containing tRNAs and a rnpB gene were detected in the mitogenome of the fungus. Obvious repetitive elements were identified within the G. lozoyensis mitogenome, and duplication events were identified between its mitochondrial and nuclear genomes. [Conclusion] We verified that there existed erroneous sequences in the published mitogenome of ATCC 74030; mutagens did not cause variations on the mitogenome of G. lozoyensis. We reported the authentic mitogenome sequence of G. lozoyensis and found frequent gene transfer between mitochondrial and nuclear genomes in the fungus.