Research Center for Parasites & Vectors, College of Veterinary Medicine, Hunan Agricultural University, Changsha, 410128, China.
College of Biotechnology, Hunan University of Environment and Biology, Hengyang, 421001, China.
BMC Genomics. 2024 Nov 14;25(1):1084. doi: 10.1186/s12864-024-11005-7.
The over 4,100 species of bird lice are classified into 214 genera in the parvorders Amblycera and Ischnocera. Congeneric species of bird lice usually share much similarity in morphology and in mitochondrial (mt) genome organization. Two recent studies, however, reported substantial intra-genus variation in mt genome organization in bird lice. Both the ancestral single-chromosome mt genome and a fragmented mt genome with two or three minichromosomes were observed in the genera Austromenopon and Laemobothrion. To better understand intra-genus variation in mt genome organization, we sequenced the complete mt genome of the white spoonbill louse Ibidoecus plataleae and compared it with that of the glossy ibis feather louse Ibidoecus bisignatus reported previously. We found that I. plataleae had a fragmented mt genome with 12 minichromosomes; each minichromosome was 2,798 to 3,628 bp in size and had 2 to 6 genes. This is in stark contrast to the mt genome of I. bisignatus, which has all genes on a single chromosome, 14,909 bp in size. This is the most drastic intra-genus variation in mt genome organization observed to date in animals, indicating an unprecedented rapid process of mt genome fragmentation in the genus Ibidoecus. The divergence time between I. plataleae and I. bisignatus is currently unknown but is estimated to be less than 23 million years. Either many minichromosal split events occurred after I. plataleae diverged from I. bisignatus, or one minichromosome splits into multiple minichromosomes in a single event. Sequencing and comparing more Ibidoecusi species will help understand the unusual mt genome fragmentation in this genus.
超过 4100 种的鸟类虱被分类为 Amblycera 和 Ischnocera 亚目中的 214 个属。同属的鸟类虱在形态和线粒体（mt）基因组结构上通常具有很大的相似性。然而，最近的两项研究报告称，鸟类虱的 mt 基因组结构在属内存在大量变异。在 Austromenopon 和 Laemobothrion 属中观察到了祖先的单染色体 mt 基因组和具有两个或三个小染色体的碎片化 mt 基因组。为了更好地理解 mt 基因组结构在属内的变异，我们对白琵鹭虱 Ibidoecus plataleae 的完整 mt 基因组进行了测序，并将其与之前报道的光滑朱鹮羽虱 Ibidoecus bisignatus 的 mt 基因组进行了比较。我们发现 I. plataleae 具有碎片化的 mt 基因组，包含 12 个小染色体；每个小染色体大小为 2798 到 3628bp，包含 2 到 6 个基因。这与 Ibidoecus bisignatus 的 mt 基因组形成鲜明对比，后者所有基因都位于一个大小为 14909bp 的单一染色体上。这是迄今为止在动物中观察到的 mt 基因组结构在属内最剧烈的变异，表明 Ibidoecus 属的 mt 基因组碎片化经历了前所未有的快速过程。I. plataleae 和 I. bisignatus 之间的分化时间目前尚不清楚，但估计不到 2300 万年。要么是在 I. plataleae 与 I. bisignatus 分化后发生了许多小染色体分裂事件，要么是一个小染色体在一个事件中分裂成多个小染色体。对更多的 Ibidoecusi 物种进行测序和比较将有助于理解该属中异常的 mt 基因组碎片化。
