Department of Biology, Washington and Lee University, Lexington, VA 24450, USA.
BMC Genomics. 2014 May 23;15(1):365. doi: 10.1186/1471-2164-15-365.
Spiders (Order Araneae) are essential predators in every terrestrial ecosystem largely because they have evolved potent arsenals of silk and venom. Spider silks are high performance materials made almost entirely of proteins, and thus represent an ideal system for investigating genome level evolution of novel protein functions. However, genomic level resources remain limited for spiders.
We de novo assembled a transcriptome for the Western black widow (Latrodectus hesperus) from deeply sequenced cDNAs of three tissue types. Our multi-tissue assembly contained ~100,000 unique transcripts, of which > 27,000 were annotated by homology. Comparing transcript abundance among the different tissues, we identified 647 silk gland-specific transcripts, including the few known silk fiber components (e.g. six spider fibroins, spidroins). Silk gland specific transcripts are enriched compared to the entire transcriptome in several functions, including protein degradation, inhibition of protein degradation, and oxidation-reduction. Phylogenetic analyses of 37 gene families containing silk gland specific transcripts demonstrated novel gene expansions within silk glands, and multiple co-options of silk specific expression from paralogs expressed in other tissues.
We propose a transcriptional program for the silk glands that involves regulating gland specific synthesis of silk fiber and glue components followed by protecting and processing these components into functional fibers and glues. Our black widow silk gland gene repertoire provides extensive expansion of resources for biomimetic applications of silk in industry and medicine. Furthermore, our multi-tissue transcriptome facilitates evolutionary analysis of arachnid genomes and adaptive protein systems.
蜘蛛（蛛形纲）是每个陆地生态系统中必不可少的捕食者，主要是因为它们进化出了强大的丝腺和毒液。蜘蛛丝是由几乎完全由蛋白质组成的高性能材料，因此是研究新型蛋白质功能的基因组进化的理想系统。然而，蜘蛛的基因组资源仍然有限。
我们从三种组织类型的深度测序 cDNA 中从头组装了西部黑寡妇（Latrodectus hesperus）的转录组。我们的多组织组装包含约 100,000 个独特的转录本，其中 >27,000 个通过同源性进行了注释。比较不同组织中转录本的丰度，我们鉴定出了 647 个丝腺特异性转录本，包括少数已知的丝纤维成分（例如，六种蜘蛛丝纤维蛋白、丝蛋白）。与整个转录组相比，丝腺特异性转录本在几个功能中富集，包括蛋白质降解、抑制蛋白质降解和氧化还原。包含丝腺特异性转录本的 37 个基因家族的系统发育分析表明，丝腺中存在新的基因扩张，并且来自其他组织中表达的同源基因的多个丝特异性表达被共同选择。
我们提出了一个丝腺的转录程序，该程序涉及调节丝腺特异性合成丝纤维和胶成分，然后保护和将这些成分加工成功能性纤维和胶。我们的黑寡妇丝腺基因库为工业和医学中仿生丝的应用提供了广泛的资源扩展。此外，我们的多组织转录组促进了蛛形纲基因组和适应性蛋白质系统的进化分析。
