Laboratory of Molecular Biology, EMBRAPA Western Amazon, Brazil.
Comp Biochem Physiol B Biochem Mol Biol. 2010 Apr;155(4):419-26. doi: 10.1016/j.cbpb.2010.01.005. Epub 2010 Jan 21.
Two unique spidroins are present in the silk of the Amazon mygalomorph spider - Avicularia juruensis (Theraphosidae), and for the first time the presence and expression of a major ampullate spidroin 2-like in Mygalomorphae are demonstrated. Molecular analysis showed the presence of (GA)(n,) poly-A and GPGXX motifs in the amino acid sequence of Spidroin 2, the last being a motif described so far only in MaSp2 and Flag spidroins. Phylogenetic analysis confirmed the previously known orthologous silk gene clusters, and placed this gene firmly within the orbicularian MaSp2 clade. Gene tree-species tree reconciliations show a pattern of multiple gene duplication throughout spider silk evolution, and pinpoint the oldest speciation in which MaSps must have been present in spiders on the mygalomorph-araneomorph split, 240 MYA. Therefore, while not refuting orb weaver monophyly, MaSp2s, and major ampullate silks in general cannot be classified as orbicularian synapomorphies, but have to be considered plesiomorphic for Opisthothelae. The evidence presented here challenges the simplified notion that mygalomorphs spin only one kind of silk, and adds to the suite of information suggesting a pattern of early niche diversification between Araneomorphae and Mygalomorphae. Additionally, mygalomorph MaSp2-like might accommodate mechanical demands arising from the arboreal habitat preference of Avicularia.
两种独特的丝蛋白存在于亚马逊狼蛛科蜘蛛 - 阿维拉里亚·朱伦西斯（Theraphosidae）的丝中，这是首次证明 Mygalomorphae 中存在并表达一种主要的囊状丝蛋白 2 样蛋白。分子分析显示，丝蛋白 2 的氨基酸序列中存在（GA）（n，）多-A 和 GPGXX 基序，最后一个基序迄今为止仅在 MaSp2 和 Flag 丝蛋白中描述过。系统发育分析证实了先前已知的同源丝基因簇，并将该基因牢固地置于球形 MaSp2 分支内。基因树-种树调和表明，在蜘蛛丝进化过程中存在多次基因复制的模式，并确定了最早的物种形成，其中 MaSps 必须存在于蜘蛛的 Mygalomorph-Araneomorph 分裂中，距今约 2.4 亿年。因此，虽然 MaSp2s 并不否定 orb 织网者的单系性，但不能将其归类为球形的 synapomorphies，而必须被视为 Opisthothelae 的原始特征。这里提出的证据挑战了这样一种简化的观点，即 Mygalomorphae 只纺一种丝，并增加了一系列信息，表明 Araneomorphae 和 Mygalomorphae 之间存在早期生态位多样化的模式。此外，Mygalomorph MaSp2-like 可能适应了阿维拉里亚树栖栖息地偏好所产生的机械需求。
