Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT 84602, USA.
Data Science Lab, Smithsonian Institution, Washington, DC 20002, USA.
Philos Trans R Soc Lond B Biol Sci. 2019 Oct 28;374(1784):20190206. doi: 10.1098/rstb.2019.0206. Epub 2019 Sep 9.
Caddisfly (Trichoptera) larvae assemble a variety of underwater structures using bioadhesive silk. The order is divided into two primary sub-orders distinguished by how the larvae deploy their silk. Foraging Integripalpia larvae construct portable tube cases. Annulipalpia larvae construct stationary retreats, some with suspended nets to capture food. To identify silk molecular adaptations that may have contributed to caddisfly diversification, we report initial characterization of silk from a net-spinner genus, Parapsyche, for comparison with the silk of a tube case-maker genus, Hesperophylax. Overall, general features of silk structure and processing are conserved across the sub-orders despite approximately 200 Ma of divergence: the H-fibroin proteins comprise repeating phosphoserine-rich motifs, naturally spun silk fibres contain approximately 1 : 1 molar ratios of divalent metal ions to phosphate, silk fibre precursors are stored as complex fluids of at least two types of complexes, and silk gland proteins contain only traces of divalent metal ions, suggesting metal ions that solidify the fibres are absorbed from the aqueous environment after silk extrusion. However, the number and arrangement of the repeating phosphoserine blocks differ between genera, suggesting molecular adaptation of H-fibroin through duplication and shuffling of conserved structural modules may correspond with the radiation of caddisflies into diverse environments. This article is part of the theme issue 'Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.
水虿（蜉蝣目）幼虫使用生物黏合丝来组装各种水下结构。该目分为两个主要亚目，区别在于幼虫如何部署它们的丝。觅食的内翅目幼虫构建便携式管状外壳。环翅目幼虫构建固定的避难所，有些带有悬挂的网来捕获食物。为了确定可能有助于水虿多样化的丝分子适应，我们报告了网纺科（Parapsyche）的丝的初步特征，以便与管状外壳制造者科（Hesperophylax）的丝进行比较。尽管在大约 2 亿年的分化过程中，丝结构和加工的总体特征在亚目中是保守的：H-丝素蛋白由重复的磷酸丝氨酸丰富的基序组成，天然纺丝纤维含有大约 1:1 摩尔比的二价金属离子与磷酸盐，丝纤维前体以至少两种类型的复合物的复杂流体形式储存，丝腺蛋白只含有痕量的二价金属离子，这表明在丝挤出后，凝固纤维的金属离子是从水相环境中吸收的。然而，重复的磷酸丝氨酸块的数量和排列在属之间存在差异，这表明 H-丝素蛋白通过重复和保守结构模块的重排的分子适应可能与水虿辐射到不同环境相对应。本文是主题为“生物系统中粘附和粘合剂的跨学科方法”的特刊的一部分。
