Effects of Gene Duplication, Positive Selection, and Shifts in Gene Expression on the Evolution of the Venom Gland Transcriptome in Widow Spiders.
Effects of Gene Duplication, Positive Selection, and Shifts in Gene Expression on the Evolution of the Venom Gland Transcriptome in Widow Spiders.
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DOI：
10.1093/gbe/evv253
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发表时间：
2016-01-05
影响因子：
3.3
通讯作者：
Garb JE
中科院分区：
文献类型：
--
作者：
Haney RA;Clarke TH;Gadgil R;Fitzpatrick R;Hayashi CY;Ayoub NA;Garb JE
基因复制和正选择可能是毒液进化的重要决定因素，毒液是一种富含蛋白质的分泌物，用于捕获和防御猎物。在典型的毒液进化模型中，基因复制在正选择的作用下切换到毒腺表达并改变功能，与进一步的复制一起产生编码不同毒素的大基因家族。虽然这些过程已经在单个毒素家族中得到了证明，但对密切相关的有毒物种进行高通量多组织测序可以在整个毒腺转录组的规模上提供对进化动态的洞察。通过组装和分析西方黑寡妇蜘蛛和两个具有不同毒力表型的密切相关物种的多组织转录本，我们没有发现与广泛表达的家族相比，毒腺偏向表达的基因家族的基因复制和重复保留更大。正向选择作用于一些毒液毒素家族，但对于有毒腺偏向表达的家族来说，似乎并不过度。此外，我们还发现了309个具有单一转录本的不同基因家族的毒腺偏向表达，这表明在许多不相关的基因家族中，基因向毒腺表达的切换已经成为进化的主导模式。我们还发现毒腺特异转录物的蛋白质序列、特定血统的家族大小以及物种间的同源表达存在着很大的差异。这种变异可能是这些物种毒力变化的原因之一。
Gene duplication and positive selection can be important determinants of the evolution of venom, a protein-rich secretion used in prey capture and defense. In a typical model of venom evolution, gene duplicates switch to venom gland expression and change function under the action of positive selection, which together with further duplication produces large gene families encoding diverse toxins. Although these processes have been demonstrated for individual toxin families, high-throughput multitissue sequencing of closely related venomous species can provide insights into evolutionary dynamics at the scale of the entire venom gland transcriptome. By assembling and analyzing multitissue transcriptomes from the Western black widow spider and two closely related species with distinct venom toxicity phenotypes, we do not find that gene duplication and duplicate retention is greater in gene families with venom gland biased expression in comparison with broadly expressed families. Positive selection has acted on some venom toxin families, but does not appear to be in excess for families with venom gland biased expression. Moreover, we find 309 distinct gene families that have single transcripts with venom gland biased expression, suggesting that the switching of genes to venom gland expression in numerous unrelated gene families has been a dominant mode of evolution. We also find ample variation in protein sequences of venom gland–specific transcripts, lineage-specific family sizes, and ortholog expression among species. This variation might contribute to the variable venom toxicity of these species.