Early evolution of the venom system in lizards and snakes
Early evolution of the venom system in lizards and snakes
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DOI：
10.1038/nature04328
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发表时间：
2006-02-02
期刊：
影响因子：
64.8
通讯作者：
Kochva, E
中科院分区：
文献类型：
--
作者：
Fry, BG;Vidal, N;Kochva, E
在现存的爬行动物中，已知只有两种谱系进化出了毒液传递系统，即高级蛇和helodermatid蜥蜴（吉拉怪物和串珠蜥蜴）(1)。毒液系统的进化被认为是高级蛇（3000种蛇中的2500种）令人印象深刻的辐射的基础（2-5）。相比之下，蜥蜴毒液系统被认为仅限于两个物种，并且是独立于蛇毒系统进化而来的(1)。在这里，我们报告了另外两个蜥蜴谱系（巨蜥和鬣蜥）中存在的毒液毒素，并表明所有拥有分泌毒素的口腔腺的谱系形成了一个分支，证明了蜥蜴和蛇的毒液系统有一个单一的早期起源。腺体互补dna文库的构建和转录本的系统发育分析表明，蜥蜴和蛇共有9种毒素。对蕾丝监视器Varanus varius毒液成分的毒物学分析显示，它对血压和凝血能力有强大的影响，与猎物迅速失去意识和大量出血有关的生物活性。鬣蜥Pogona barbata保留了祖先毒液系统的特征，即上下颌骨上的连续小叶非复合毒液分泌腺，而高级蛇和anguimmorph蜥蜴（包括巨蜥，吉拉怪物和串珠蜥蜴）则有更多的衍生毒液系统，其特征是下颌（下）或上颌（上）腺的丧失。蛇、鬣蜥和鳗形兽形成一个分支的证明，为蜥蜴和蛇的毒液系统的单一、早期起源提供了压倒性的支持。这些结果为了解鳞状爬行动物毒液系统的进化提供了新的见解，并为利用迄今未开发的毒液蛋白进行生物医学研究和药物设计开辟了新的途径。
Among extant reptiles only two lineages are known to have evolved venom delivery systems, the advanced snakes and helodermatid lizards ( Gila Monster and Beaded Lizard)(1). Evolution of the venom system is thought to underlie the impressive radiation of the advanced snakes ( 2,500 of 3,000 snake species)(2-5). In contrast, the lizard venom system is thought to be restricted to just two species and to have evolved independently from the snake venom system(1). Here we report the presence of venom toxins in two additional lizard lineages ( Monitor Lizards and Iguania) and show that all lineages possessing toxin-secreting oral glands form a clade, demonstrating a single early origin of the venom system in lizards and snakes. Construction of gland complementary-DNA libraries and phylogenetic analysis of transcripts revealed that nine toxin types are shared between lizards and snakes. Toxinological analyses of venom components from the Lace Monitor Varanus varius showed potent effects on blood pressure and clotting ability, bioactivities associated with a rapid loss of consciousness and extensive bleeding in prey. The iguanian lizard Pogona barbata retains characteristics of the ancestral venom system, namely serial, lobular non-compound venom-secreting glands on both the upper and lower jaws, whereas the advanced snakes and anguimorph lizards ( including Monitor Lizards, Gila Monster and Beaded Lizard) have more derived venom systems characterized by the loss of the mandibular ( lower) or maxillary ( upper) glands. Demonstration that the snakes, iguanians and anguimorphs form a single clade provides overwhelming support for a single, early origin of the venom system in lizards and snakes. These results provide new insights into the evolution of the venom system in squamate reptiles and open new avenues for biomedical research and drug design using hitherto unexplored venom proteins.