Scanlan Jack L, Battlay Paul, Robin Charles
School of BioSciences, The University of Melbourne, Parkville Campus, Melbourne, Victoria, 3010, Australia.
Curr Res Insect Sci. 2022 Jan 16;2:100030. doi: 10.1016/j.cris.2022.100030. eCollection 2022.
A unique aspect of metabolic detoxification in insects compared to other animals is the presence of xenobiotic phosphorylation, about which little is currently understood. Our previous work raised the hypothesis that members of the taxonomically restricted ecdysteroid kinase-like (EcKL) gene family encode the enzymes responsible for xenobiotic phosphorylation in the model insect (Diptera: Ephydroidea)-however, candidate detoxification genes identified in the EcKL family have yet to be functionally validated. Here, we test the hypothesis that EcKL genes in the rapidly evolving Dro5 clade are involved in the detoxification of plant and fungal toxins in . The mining and reanalysis of existing data indicated multiple Dro5 genes are transcriptionally induced by the plant alkaloid caffeine and that adult caffeine susceptibility is associated with a novel naturally occurring indel in (Dro5-8) in the Drosophila Genetic Reference Panel (DGRP). CRISPR-Cas9 mutagenesis of five Dro5 EcKLs substantially decreased developmental tolerance of caffeine, while individual overexpression of two of these genes- (Dro5-1) and (Dro5-7)-in detoxification-related tissues increased developmental tolerance. In addition, we found Dro5 loss-of-function animals also have decreased developmental tolerance of the fungal secondary metabolite kojic acid. Taken together, this work provides the first compelling functional evidence that EcKLs encode detoxification enzymes and suggests that EcKLs in the Dro5 clade are involved in the metabolism of multiple ecologically relevant toxins in . We also propose a biochemical hypothesis for EcKL involvement in caffeine detoxification and highlight the many unknown aspects of caffeine metabolism in and other insects.
与其他动物相比，昆虫代谢解毒的一个独特方面是存在外源性物质磷酸化，目前对此了解甚少。我们之前的工作提出了一个假设，即在分类学上受限的蜕皮甾类激酶样（EcKL）基因家族的成员编码了模型昆虫（双翅目：水蝇总科）中负责外源性物质磷酸化的酶——然而，在EcKL家族中鉴定出的候选解毒基因尚未得到功能验证。在这里，我们测试了一个假设，即快速进化的Dro5分支中的EcKL基因参与了果蝇对植物和真菌毒素的解毒过程。对现有数据的挖掘和重新分析表明，多个Dro5基因在转录水平上受到植物生物碱咖啡因的诱导，并且在果蝇遗传参考面板（DGRP）中，成年果蝇对咖啡因的敏感性与Dro5-8中一个新的自然发生的插入缺失有关。对五个Dro5 EcKL基因进行CRISPR-Cas9诱变显著降低了果蝇对咖啡因的发育耐受性，而在解毒相关组织中单独过表达其中两个基因——Dro5-1和Dro5-7——则提高了发育耐受性。此外，我们发现Dro5功能丧失的动物对真菌次生代谢产物曲酸的发育耐受性也降低了。综上所述，这项工作提供了首个令人信服的功能证据，证明EcKLs编码解毒酶，并表明Dro5分支中的EcKLs参与了果蝇对多种生态相关毒素的代谢。我们还提出了一个关于EcKL参与咖啡因解毒的生化假设，并强调了果蝇和其他昆虫中咖啡因代谢的许多未知方面。
