Data from: The molecular evolution of spiggin nesting glue in sticklebacks

Gene duplication and subsequent divergence can lead to the evolution of new functions and lineage-specific traits. In sticklebacks, the successive duplication of a mucin gene (MUC19) into a tandemly arrayed, multigene family has enabled the production of copious amounts of ‘spiggin’, a secreted adhesive protein essential for nest construction. Here, we examine divergence between spiggin genes among three-spined sticklebacks (Gasterosteus aculeatus) from ancestral marine and derived freshwater populations, and propose underpinning gene duplication mechanisms. Sanger sequencing revealed substantial diversity among spiggin transcripts, including alternatively spliced variants and interchromosomal spiggin chimeric genes. Comparative analysis of the sequenced transcripts and all other spiggin genes in the public domain support the presence of three main spiggin lineages (spiggin A, spiggin B and spiggin C) with further subdivisions within spiggin B (B1, B2) and spiggin C (C1, C2). Spiggin A had diverged least from the ancestral MUC19, while the spiggin C duplicates had diversified most substantially. In silico translations of the spiggin gene open reading frames predicted that spiggins A and B are secreted as long mucin-like polymers, while spiggins C1 and C2 are secreted as short monomers, with putative antimicrobial properties. We propose that diversification of duplicated spiggin genes has facilitated local adaptation of spiggin to a range of aquatic habitats.

基因重复及其后续趋异演化可催生新功能与谱系特异性性状。在棘鱼中，粘蛋白基因MUC19经连续重复形成串联排列的多基因家族，得以合成大量spiggin——一种对巢穴构建至关重要的分泌型粘附蛋白。本研究针对三刺鱼（Gasterosteus aculeatus）体内spiggin基因的趋异情况展开分析，样本取自祖先海洋种群与衍生淡水种群，并提出该类基因重复的潜在基础机制。桑格测序结果显示，spiggin转录本存在丰富多样性，涵盖可变剪接变体与染色体间嵌合基因。对已测序转录本与公共数据库中收录的所有其他spiggin基因的比较分析表明，存在三个主要的spiggin进化支（spiggin A、spiggin B与spiggin C），其中spiggin B可进一步细分为B1、B2亚支，spiggin C可细分为C1、C2亚支。spiggin A与祖先MUC19的趋异程度最低，而spiggin C的重复基因分化程度最高。对spiggin基因开放阅读框的计算机模拟翻译预测显示，spiggin A与spiggin B以长粘蛋白样聚合物形式分泌，而spiggin C1与spiggin C2则以短单体形式分泌，且推测其具备抗菌活性。本研究认为，重复spiggin基因的分化促进了spiggin对多种水生栖息地的局部适应。