Song Xinzheng, Geng Yuehua, Xu Chao, Li Jiaxin, Guo Yashuang, Shi Yan, Ma Qingzhou, Li Qiang, Zhang Meng
Department of Plant Pathology, Henan Agricultural University, Zhengzhou, Henan, China.
School of Food and Biological Engineering, Chengdu University, Chengdu, Sichuan, China.
IMA Fungus. 2024 Jun 11;15(1):15. doi: 10.1186/s43008-024-00149-6.
In the present study, three mitogenomes from the Bipolaris genus (Bipolaris maydis, B. zeicola, and B. oryzae) were assembled and compared with the other two reported Bipolaris mitogenomes (B. oryzae and B. sorokiniana). The five mitogenomes were all circular DNA molecules, with lengths ranging from 106,403 bp to 135,790 bp. The mitogenomes of the five Bipolaris species mainly comprised the same set of 13 core protein-coding genes (PCGs), two rRNAs, and a certain number of tRNAs and unidentified open reading frames (ORFs). The PCG length, AT skew and GC skew showed large variability among the 13 PCGs in the five mitogenomes. Across the 13 core PCGs tested, nad6 had the least genetic distance among the 16 Pleosporales species we investigated, indicating that this gene was highly conserved. In addition, the Ka/Ks values for all 12 core PCGs (excluding rps3) were < 1, suggesting that these genes were subject to purifying selection. Comparative mitogenomic analyses indicate that introns were the main factor contributing to the size variation of Bipolaris mitogenomes. The introns of the cox1 gene experienced frequent gain/loss events in Pleosporales species. The gene arrangement and collinearity in the mitogenomes of the five Bipolaris species were almost highly conserved within the genus. Phylogenetic analysis based on combined mitochondrial gene datasets showed that the five Bipolaris species formed well-supported topologies. This study is the first report on the mitogenomes of B. maydis and B. zeicola, as well as the first comparison of mitogenomes among Bipolaris species. The findings of this study will further advance investigations into the population genetics, evolution, and genomics of Bipolaris species.
在本研究中，组装了来自双极霉属（玉米大斑病菌、玉米小斑病菌和稻瘟病菌）的三个线粒体基因组，并与另外两个已报道的双极霉属线粒体基因组（稻瘟病菌和索氏双极霉）进行了比较。这五个线粒体基因组均为环状DNA分子，长度在106,403 bp至135,790 bp之间。五个双极霉物种的线粒体基因组主要由相同的一组13个核心蛋白质编码基因（PCG）、两个rRNA以及一定数量的tRNA和未鉴定的开放阅读框（ORF）组成。五个线粒体基因组中13个PCG的长度、AT偏斜度和GC偏斜度表现出很大的变异性。在所测试的13个核心PCG中，nad6在我们研究的16个格孢腔菌目物种中的遗传距离最小，表明该基因高度保守。此外，所有12个核心PCG（不包括rps3）的Ka/Ks值均<1，表明这些基因受到纯化选择。比较线粒体基因组分析表明，内含子是导致双极霉属线粒体基因组大小变异的主要因素。cox1基因的内含子在格孢腔菌目物种中经历了频繁的获得/丢失事件。五个双极霉物种线粒体基因组中的基因排列和共线性在该属内几乎高度保守。基于组合线粒体基因数据集的系统发育分析表明，五个双极霉物种形成了得到充分支持的拓扑结构。本研究是关于玉米大斑病菌和玉米小斑病菌线粒体基因组的首次报道，也是双极霉属物种线粒体基因组之间的首次比较。本研究结果将进一步推动对双极霉属物种群体遗传学、进化和基因组学的研究。
