背景:毒腺在几乎所有蜘蛛群的捕食和防御策略中起着关键作用。然而,蜘蛛家族Uloboridae缺乏毒腺,并且已经进化出一种适应性策略:它们直接用蜘蛛丝过度包裹猎物,而不是首先用毒素麻痹猎物。这种生存策略的转变非常迷人,但它背后的基因基础却知之甚少。
结果:跨越多个蜘蛛群,我们对中国八叶进行了多组学分析,并在基因组水平上描述了Uloboridae家族的适应性进化。我们观察到肌肉中肌球蛋白和twitchin的编码基因处于正选择状态,能量代谢功能增强,与气管发育和组织机械强度相关的基因家族扩大或出现,所有这些都与Uloboridae家族中蜘蛛的独特解剖结构和捕食行为有关。此外,我们还扫描了缺少或放松净化选择的元素,以及该家族2个物种基因组中的毒素基因同源物。结果表明,这些蜘蛛基因组中缺乏区域和放松选择的区域集中在与发育和神经系统相关的区域。对毒素同源物的搜索揭示了毒素和非毒素之间可能的基因功能转移,并证实该组基因组中没有可靠的毒素基因。
结论:这项研究证明了蜘蛛不同捕食策略之间的权衡,使用化学或物理策略,并提供了对这种权衡背后可能机制的见解。无毒蜘蛛需要动员与运动功能和肢体机械强度相关的多种发育和代谢途径,以弥补由于缺乏毒腺而导致的适应性下降。
BACKGROUND: Venom glands play a key role in the predation and defense strategies of almost all spider groups. However, the spider family Uloboridae lacks venom glands and has evolved an adaptive strategy: they excessively wrap their prey directly with spider silk instead of paralyzing it first with toxins. This shift in survival strategy is very fascinating, but the genetic underpinnings behind it are poorly understood.
RESULTS: Spanning multiple spider groups, we conducted multiomics analyses on Octonoba sinensis and described the adaptive evolution of the Uloboridae family at the genome level. We observed the coding genes of myosin and twitchin in muscles are under positive selection, energy metabolism functions are enhanced, and gene families related to tracheal development and tissue mechanical strength are expanded or emerged, all of which are related to the unique anatomical structure and predatory behavior of
spiders in the family Uloboridae. In addition, we also scanned the elements that are absent or under relaxed purifying selection, as well as toxin gene homologs in the genomes of 2 species in this family. The results show that the absence of regions and regions under relaxed selection in these
spiders\' genomes are concentrated in areas related to development and neurosystem. The search for toxin homologs reveals possible gene function shift between toxins and nontoxins and confirms that there are no reliable toxin genes in the genome of this group.
CONCLUSIONS: This study demonstrates the trade-off between different predation strategies in
spiders, using either chemical or physical strategy, and provides insights into the possible mechanism underlying this trade-off. Venomless
spiders need to mobilize multiple developmental and metabolic pathways related to motor function and limb mechanical strength to cover the decline in adaptability caused by the absence of venom glands.