Li Qing, Barghi Neda, Lu Aiping, Fedosov Alexander E, Bandyopadhyay Pradip K, Lluisma Arturo O, Concepcion Gisela P, Yandell Mark, Olivera Baldomero M, Safavi-Hemami Helena
Eccles Institute of Human Genetics, University of Utah.
Marine Science Institute, University of the Philippines-Diliman, Quezon City, Philippines.
Genome Biol Evol. 2017 Sep 1;9(9):2211-2225. doi: 10.1093/gbe/evx157.
The genus Conus comprises approximately 700 species of venomous marine cone snails that are highly efficient predators of worms, snails, and fish. In evolutionary terms, cone snails are relatively young with the earliest fossil records occurring in the Lower Eocene, 55 Ma. The rapid radiation of cone snail species has been accompanied by remarkably high rates of toxin diversification. To shed light on the molecular mechanisms that accompany speciation, we investigated the toxin repertoire of two sister species, Conus andremenezi and Conus praecellens, that were until recently considered a single variable species. A total of 196 and 250 toxin sequences were identified in the venom gland transcriptomes of C. andremenezi and C. praecellens belonging to 25 and 29 putative toxin gene superfamilies, respectively. Comparative analysis with closely (Conus tribblei and Conus lenavati) and more distantly related species (Conus geographus) suggests that speciation is associated with significant diversification of individual toxin genes (exogenes) whereas the expression pattern of toxin gene superfamilies within lineages remains largely conserved. Thus, changes within individual toxin sequences can serve as a sensitive indicator for recent speciation whereas changes in the expression pattern of gene superfamilies are likely to reflect more dramatic differences in a species' interaction with its prey, predators, and competitors.
芋螺属包含约700种有毒的海洋芋螺，它们是捕食蠕虫、蜗牛和鱼类的高效猎手。从进化角度来看，芋螺相对年轻，最早的化石记录出现在始新世早期，距今5500万年。芋螺物种的快速辐射伴随着毒素的高度多样化。为了阐明物种形成过程中的分子机制，我们研究了两个姐妹物种——安德烈内兹芋螺（Conus andremenezi）和卓越芋螺（Conus praecellens）的毒素库，这两个物种直到最近还被认为是一个单一的可变物种。在安德烈内兹芋螺和卓越芋螺的毒腺转录组中分别鉴定出了196个和250个毒素序列，它们分别属于25个和29个假定的毒素基因超家族。与亲缘关系较近的物种（特里布尔芋螺（Conus tribblei）和勒纳瓦蒂芋螺（Conus lenavati））以及亲缘关系较远的物种（地纹芋螺（Conus geographus））进行比较分析表明，物种形成与单个毒素基因（外基因）的显著多样化有关，而谱系中毒素基因超家族的表达模式在很大程度上保持保守。因此，单个毒素序列的变化可以作为近期物种形成的敏感指标，而基因超家族表达模式的变化可能反映出一个物种与其猎物、捕食者和竞争者相互作用中更显著的差异。
