Laboratorio de Ecología Molecular y Evolución, Universidad Nacional Autónoma de México, FES Iztacala, Avenida de los Barrios 1, Los Reyes Iztacala, Tlalnepantla de Baz, 54090, Mexico.
Posgrado en Ciencias Biológicas, UNAM, Circuito de Posgrados, Ciudad Universitaria, Coyoacán, Ciudad de México, 04510, Mexico.
BMC Genomics. 2023 Aug 31;24(1):509. doi: 10.1186/s12864-023-09607-8.
Structural descriptions of complete genomes have elucidated evolutionary processes in angiosperms. In Cactaceae (Caryophyllales), a high structural diversity of the chloroplast genome has been identified within and among genera. In this study, we assembled the first mitochondrial genome (mtDNA) for the short-globose cactus Mammillaria huitzilopochtli. For comparative purposes, we used the published genomes of 19 different angiosperms and the gymnosperm Cycas taitungensis as an external group for phylogenetic issues.
The mtDNA of M. huitzilopochtli was assembled into one linear chromosome of 2,052,004 bp, in which 65 genes were annotated. These genes account for 57,606 bp including 34 protein-coding genes (PCGs), 27 tRNAs, and three rRNAs. In the non-coding sequences, repeats were abundant, with a total of 4,550 (179,215 bp). In addition, five complete genes (psaC and four tRNAs) of chloroplast origin were documented. Negative selection was estimated for most (23) of the PCGs. The phylogenetic tree showed a topology consistent with previous analyses based on the chloroplast genome.
The number and type of genes contained in the mtDNA of M. huitzilopochtli were similar to those reported in 19 other angiosperm species, regardless of their phylogenetic relationships. Although other Caryophyllids exhibit strong differences in structural arrangement and total size of mtDNA, these differences do not result in an increase in the typical number and types of genes found in M. huitzilopochtli. We concluded that the total size of mtDNA in angiosperms increases by the lengthening of the non-coding sequences rather than a significant gain of coding genes.
完整基因组的结构描述阐明了被子植物中的进化过程。在仙人掌科（石竹目）中，已经在属内和属间鉴定出叶绿体基因组的高度结构多样性。在这项研究中，我们组装了短球形仙人掌乳突球属 Mammillaria huitzilopochtli 的第一个线粒体基因组（mtDNA）。为了比较的目的，我们使用了已发表的 19 种被子植物和裸子植物苏铁 Cycas taitungensis 的基因组作为系统发育问题的外部群体。
M. huitzilopochtli 的 mtDNA 组装成一条线性染色体，长度为 2,052,004 bp，其中注释了 65 个基因。这些基因共占 57,606 bp，包括 34 个蛋白质编码基因（PCGs）、27 个 tRNA 和 3 个 rRNA。在非编码序列中，重复序列丰富，共有 4,550 个（179,215 bp）。此外，还记录了五个来自叶绿体的完整基因（psaC 和四个 tRNA）。大多数（23 个）PCGs 估计存在负选择。系统发育树显示的拓扑结构与基于叶绿体基因组的先前分析一致。
M. huitzilopochtli mtDNA 中包含的基因数量和类型与其他 19 种被子植物相似，无论其系统发育关系如何。尽管其他石竹目表现出 mtDNA 结构排列和总大小的强烈差异，但这些差异不会导致乳突球属中发现的典型基因数量和类型增加。我们得出的结论是，被子植物 mtDNA 的总大小通过非编码序列的延长而增加，而不是通过编码基因的显著增加。
