Culotta Jack A, Lindsey Amelia R I
Department of Entomology, University of Minnesota Twin Cities, 1980 Folwell Avenue, Saint Paul, MN 51108, USA.
G3 (Bethesda). 2025 Aug 6;15(8). doi: 10.1093/g3journal/jkaf129.
The tiny parasitoid wasp Trichogramma kaykai inhabits the Mojave Desert of the southwest United States. Populations of this tiny insect variably host up to 2 different sex-distorting genetic elements: (1) the endosymbiotic bacterium Wolbachia which induces the parthenogenetic reproduction of females, and (2) a B-chromosome, "Paternal Sex Ratio" (PSR), which converts would-be female offspring to PSR-transmitting males. We report here the genome of a Wolbachia-infected T. kaykai isofemale colony KSX58. Using Oxford Nanopore sequencing, we produced a final genome assembly of 205 Mbp with 34× coverage, consisting of 154 contigs with an N50 of 2.2 Mbp. The assembly is quite complete, with 92.67% complete Hymenoptera BUSCOs recovered: a very high score for Trichogrammatids that have been previously characterized for having high levels of core gene losses. We also report a complete mitochondrial genome for T. kaykai, and an assembly of the associated Wolbachia, strain wTkk. Finally, we identified copies of the parthenogenesis-inducing (PI) genes pifA and pifB in a remnant prophage region of the wTkk genome and compared their evolution to pifs from a suite of other PI Wolbachia. The T. kaykai assembly is one of the highest quality genome assemblies for the genus to date and will serve as a great resource for understanding the evolution of sex and selfish genetic elements.
微小的寄生蜂凯氏赤眼蜂栖息在美国西南部的莫哈韦沙漠。这种微小昆虫的种群中可变地存在多达2种不同的性别扭曲遗传元件：（1）内共生细菌沃尔巴克氏体，它诱导雌性孤雌生殖；（2）一条B染色体，即“父本性别比”（PSR），它将可能成为雌性的后代转化为传播PSR的雄性。我们在此报告感染沃尔巴克氏体的凯氏赤眼蜂同雌群体KSX58的基因组。使用牛津纳米孔测序技术，我们生成了一个最终基因组组装，大小为205兆碱基对，覆盖度为34倍，由154个重叠群组成，N50为2.2兆碱基对。该组装相当完整，恢复了92.67%的膜翅目昆虫单拷贝直系同源基因（BUSCOs）：对于此前已被表征为核心基因损失水平较高的赤眼蜂科昆虫来说，这是一个非常高的分数。我们还报告了凯氏赤眼蜂的完整线粒体基因组以及相关沃尔巴克氏体菌株wTkk的组装。最后，我们在wTkk基因组的一个残留前噬菌体区域中鉴定出了诱导孤雌生殖（PI）的基因pifA和pifB的拷贝，并将它们的进化与一系列其他PI沃尔巴克氏体的pif基因进行了比较。凯氏赤眼蜂的组装是该属迄今为止质量最高的基因组组装之一，将成为理解性别和自私遗传元件进化的重要资源。
