Palmer Droguett Daniela H, Fletcher Micah, Alston Ben T, Kocher Sarah, Cabral-de-Mello Diogo C, Wright Alison E
Ecology and Evolutionary Biology, School of Biosciences, The University of Sheffield, Sheffield, UK.
Ecology, Evolution, and Behavior Program, Michigan State University, East Lansing, MI, USA.
Genome Biol Evol. 2024 Dec 4;16(12). doi: 10.1093/gbe/evae264.
Sex chromosomes follow distinct evolutionary trajectories compared to the rest of the genome. In many cases, sex chromosomes (X and Y or Z and W) significantly differentiate from one another resulting in heteromorphic sex chromosome systems. Such heteromorphic systems are thought to act as an evolutionary trap that prevents subsequent turnover of the sex chromosome system. For old, degenerated sex chromosome systems, chromosomal fusion with an autosome may be one way that sex chromosomes can "refresh" their sequence content. We investigated these dynamics using treehoppers (hemipteran insects of the family Membracidae), which ancestrally have XX/X0 sex chromosomes. We assembled the most complete reference assembly for treehoppers to date for Umbonia crassicornis and employed comparative genomic analyses of 12 additional treehopper species to analyze X chromosome variation across different evolutionary timescales. We find that the X chromosome is largely conserved, with one exception being an X-autosome fusion in Calloconophora caliginosa. We also compare the ancestral treehopper X with other X chromosomes in Auchenorrhyncha (the clade containing treehoppers, leafhoppers, spittlebugs, cicadas, and planthoppers), revealing X conservation across more than 300 million years. These findings shed light on chromosomal evolution dynamics in treehoppers and the role of chromosomal rearrangements in sex chromosome evolution.
与基因组的其他部分相比，性染色体遵循着截然不同的进化轨迹。在许多情况下，性染色体（X和Y或Z和W）彼此之间会显著分化，从而形成异形性染色体系统。这种异形系统被认为是一种进化陷阱，会阻止性染色体系统随后的更替。对于古老、退化的性染色体系统而言，与常染色体的染色体融合可能是性染色体“更新”其序列内容的一种方式。我们利用角蝉（沫蝉科半翅目昆虫）对此类动态进行了研究，角蝉在进化史上具有XX/X0性染色体。我们为粗角恩氏角蝉组装了迄今为止最为完整的角蝉参考基因组，并对另外12种角蝉进行了比较基因组分析，以分析不同进化时间尺度上的X染色体变异。我们发现，X染色体在很大程度上是保守的，唯一的例外是阴暗角蝉的X-常染色体融合。我们还将角蝉的祖先X染色体与蝉亚目（包含角蝉、叶蝉、沫蝉、蝉和蜡蝉的进化枝）中的其他X染色体进行了比较，揭示了超过3亿年的X染色体保守性。这些发现揭示了角蝉的染色体进化动态以及染色体重排在性染色体进化中的作用。
