Horizontal gene transfer (HGT) has been documented in many herbivorous insects, conferring the ability to digest plant material and promoting their remarkable ecological diversification. Previous reports suggest HGT of antibacterial enzymes may have contributed to the insect immune response and limit bacterial growth. Carnivorous insects also display many evolutionary successful lineages, but in contrast to the plant feeders, the potential role of HGTs has been less well-studied. Using genomic and transcriptomic data from 38 species of ladybird beetles, we identified a set of bacterial cell wall hydrolase (cwh) genes acquired by this group of beetles. Infection with Bacillus subtilis led to upregulated expression of these ladybird cwh genes, and their recombinantly produced proteins limited bacterial proliferation. Moreover, RNAi-mediated cwh knockdown led to downregulation of other antibacterial genes, indicating a role in antibacterial immune defense. cwh genes are rare in eukaryotes, but have been maintained in all tested Coccinellinae species, suggesting that this putative immune-related HGT event played a role in the evolution of this speciose subfamily of predominant predatory ladybirds. Our work demonstrates that, in a manner analogous to HGT-facilitated plant feeding, enhanced immunity through HGT might have played a key role in the prey adaptation and niche expansion that promoted the diversification of carnivorous beetle lineages. We believe that this represents the first example of immune-related HGT in carnivorous insects with an association with a subsequent successful species radiation.

中文翻译：

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与瓢虫适应性辐射相关的水平获得的抗菌基因


水平基因转移（HGT）已在许多草食性昆虫中得到记录，赋予其消化植物材料的能力并促进其显着的生态多样化。先前的报告表明，抗菌酶的 HGT 可能有助于昆虫免疫反应并限制细菌生长。肉食性昆虫也表现出许多进化成功的谱系，但与植物饲养者相比，HGT 的潜在作用尚未得到充分研究。利用 38 种瓢虫的基因组和转录组数据，我们鉴定了这组甲虫获得的一组细菌细胞壁水解酶 (cwh) 基因。枯草芽孢杆菌感染导致这些瓢虫 cwh 基因的表达上调，并且它们重组产生的蛋白质限制了细菌增殖。此外，RNAi介导的cwh敲低导致其他抗菌基因下调，表明其在抗菌免疫防御中发挥作用。 cwh 基因在真核生物中很少见，但在所有测试的瓢虫亚科物种中都得到了保留，这表明这种假定的免疫相关 HGT 事件在主要捕食性瓢虫的这一特殊亚科的进化中发挥了作用。我们的工作表明，以类似于 HGT 促进植物取食的方式，通过 HGT 增强的免疫力可能在猎物适应和生态位扩展中发挥了关键作用，从而促进了食肉甲虫谱系的多样化。我们相信，这是食肉昆虫中免疫相关 HGT 的第一个例子，并与随后成功的物种辐射有关。