Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA.
Animal Biomedical and Molecular Biology Laboratory, Faculty of Veterinary Medicine, Udayana University Bali, Denpasar, Bali, Indonesia.
Mol Biol Evol. 2018 May 1;35(5):1210-1224. doi: 10.1093/molbev/msy034.
To expand our capacity to discover venom sequences from the genomes of venomous organisms, we applied targeted sequencing techniques to selectively recover venom gene superfamilies and nontoxin loci from the genomes of 32 cone snail species (family, Conidae), a diverse group of marine gastropods that capture their prey using a cocktail of neurotoxic peptides (conotoxins). We were able to successfully recover conotoxin gene superfamilies across all species with high confidence (> 100× coverage) and used these data to provide new insights into conotoxin evolution. First, we found that conotoxin gene superfamilies are composed of one to six exons and are typically short in length (mean = ∼85 bp). Second, we expanded our understanding of the following genetic features of conotoxin evolution: 1) positive selection, where exons coding the mature toxin region were often three times more divergent than their adjacent noncoding regions, 2) expression regulation, with comparisons to transcriptome data showing that cone snails only express a fraction of the genes available in their genome (24-63%), and 3) extensive gene turnover, where Conidae species varied from 120 to 859 conotoxin gene copies. Finally, using comparative phylogenetic methods, we found that while diet specificity did not predict patterns of conotoxin evolution, dietary breadth was positively correlated with total conotoxin gene diversity. Overall, the targeted sequencing technique demonstrated here has the potential to radically increase the pace at which venom gene families are sequenced and studied, reshaping our ability to understand the impact of genetic changes on ecologically relevant phenotypes and subsequent diversification.
为了扩大从毒液生物基因组中发现毒液序列的能力,我们应用靶向测序技术,从 32 种圆锥蜗牛物种(科,Conidae)的基因组中选择性地回收毒液基因超家族和非毒素基因座,圆锥蜗牛是一种多样化的海洋腹足纲动物,它们使用神经毒性肽(conotoxin)鸡尾酒来捕获猎物。我们能够成功地以高置信度(>100×覆盖度)在所有物种中回收 conotoxin 基因超家族,并利用这些数据深入了解 conotoxin 进化。首先,我们发现 conotoxin 基因超家族由一个到六个外显子组成,通常长度较短(平均长度约为 85bp)。其次,我们扩展了对以下 conotoxin 进化遗传特征的理解:1)正选择,编码成熟毒素区域的外显子通常比其相邻的非编码区域有三倍的差异,2)表达调控,与转录组数据的比较表明,圆锥蜗牛只表达其基因组中可用基因的一部分(24-63%),3)广泛的基因更替,其中 Conidae 物种的 conotoxin 基因拷贝数从 120 到 859 不等。最后,使用比较系统发育方法,我们发现虽然饮食特异性不能预测 conotoxin 进化模式,但饮食广度与总 conotoxin 基因多样性呈正相关。总的来说,这里展示的靶向测序技术有可能极大地加快毒液基因家族测序和研究的速度,改变我们理解遗传变化对生态相关表型和随后多样化的影响的能力。