Idnurm Alexander
School of BioSciences, The University of Melbourne, Melbourne, VIC 3010, Australia.
J Genet. 2018 Dec;97(5):1195-1204.
A DNA region in the mitochondrial genome of the fungus (Mucorales, Mucoromycota) was characterized in a population of wild-type strains. The region encodes a predicted protein similar to the reverse transcriptases encoded by mitochondrial retroplasmids of species and other Sordariomycetes (Ascomycota), but is uncommon in other fungi. DNA sequences of this element, named , are highly variable between the strains, having greater than 2.5% divergence, yet most of the nucleotide differences fall in codon positions that do not change the amino acid sequence. The high proportion of polymorphisms coupled to the rarity of nonsynonymous changes suggests that mystique is subject to counteracting forces of hypermutation and purifying selection. However, while evidence for negative selection may infer that the element provides a fitness benefit, some strains of do not have the element and grow equivalently well as those strains with it. A mechanism to explain the variability between the alleles is proposed, of error-prone replication through an RNA intermediate, reverse transcription and reintegration of the element into the mitochondrial genome.
在一组野生型菌株中对真菌（毛霉目，毛霉亚门）线粒体基因组中的一个DNA区域进行了表征。该区域编码一种预测蛋白，类似于由物种和其他粪壳菌纲（子囊菌门）的线粒体反转录质粒编码的反转录酶，但在其他真菌中并不常见。这个名为神秘元素的DNA序列在菌株之间高度可变，差异大于2.5%，然而大多数核苷酸差异位于不改变氨基酸序列的密码子位置。多态性的高比例加上非同义变化的罕见性表明，神秘元素受到高突变和纯化选择的对抗力量的影响。然而，虽然负选择的证据可能推断该元素提供了适应性益处，但一些菌株没有该元素，并且与有该元素的菌株生长得一样好。提出了一种解释神秘元素等位基因之间变异性的机制，即通过RNA中间体进行易出错的复制、反转录以及该元素重新整合到线粒体基因组中。
