Department of Biological Sciences, Wayne State University, Detroit, MI, USA.
Environ Microbiol. 2019 Nov;21(11):4233-4240. doi: 10.1111/1462-2920.14783. Epub 2019 Sep 1.
Mitochondrial recombination in yeast is well recognized, yet the underlying genetic mechanisms are not well understood. Recent progress has suggested that mobile introns in mitochondrial genomes (mitogenomes) can facilitate the recombination of their corresponding intron-containing genes through a mechanism known as intron homing. As many mitochondrial genes lack introns, there is a critical need to determine the extent of recombination and underlying mechanism of intron-lacking genes. This study leverages yeast mitogenomes to address these questions. In Saccharomyces cerevisiae, the 3'-end sequences of at least three intron-lacking mitochondrial genes exhibit elevated nucleotide diversity and recombination hotspots. Each of these 3'-end sequences is immediately adjacent to or even fused as overlapping genes with a stand-alone endonuclease. Our findings suggest that SAEs are responsible for recombination and elevated diversity of adjacent intron-lacking genes. SAEs were also evident to drive recombination of intron-lacking genes in Lachancea kluyveri, a yeast species that diverged from S. cerevisiae more than 100 million years ago. These results suggest SAEs as a common driver in recombination of intron-lacking genes during mitogenome evolution. We postulate that the linkage between intron-lacking gene and its adjacent endonuclease gene is the result of co-evolution.
酵母中的线粒体重组是众所周知的，但潜在的遗传机制尚不清楚。最近的研究进展表明，线粒体基因组（线粒体基因组）中的移动内含子可以通过一种称为内含子归巢的机制促进其内含子基因的重组。由于许多线粒体基因缺乏内含子，因此迫切需要确定缺乏内含子的基因的重组程度和潜在机制。本研究利用酵母线粒体基因组来解决这些问题。在酿酒酵母中，至少三个缺乏内含子的线粒体基因的 3'-末端序列表现出升高的核苷酸多样性和重组热点。这些 3'-末端序列中的每一个都紧邻或甚至融合为与独立内切酶重叠的基因。我们的研究结果表明，SAEs 负责重组和相邻缺乏内含子基因的多样性增加。SAEs 也明显可以驱动在酿酒酵母分化超过 1 亿年前的酵母物种拉曼酵母中缺乏内含子的基因的重组。这些结果表明，SAEs 是线粒体基因组进化过程中缺乏内含子的基因重组的一个共同驱动因素。我们推测，缺乏内含子的基因与其相邻内切酶基因之间的联系是共同进化的结果。
