Data from: Duplication and sub/neofunctionalization of Malvolio, an insect homolog of Nramp, in the subsocial beetle Nicrophorus vespilloides

With growing numbers of sequenced genomes, increasing numbers of duplicate genes are uncovered. Here we examine Malvolio, a gene in the natural resistance-associated macrophage protein (Nramp) family, that has been duplicated in the subsocial beetle, Nicrophorus vespilloides, which exhibits advanced parental behavior. There is only one copy of Mvl in honey bees and Drosophila, whereas in vertebrates there are two copies that are subfunctionalized. We first compared amino acid sequences for Drosophila, beetles, mouse and humans. We found a high level of conservation between the different species, though there was greater variation in the C-terminal regions. A phylogenetic analysis across multiple insect orders suggests that Mvl has undergone several independent duplications. To examine the potential for different functions where it has been duplicated, we quantified expression levels of Mvl1 and Mvl2 in eight tissues in N. vespilloides. We found that while Mvl1 was expressed ubiquitously, albeit at varying levels, expression of Mvl2 was limited to brain and midgut. Because Mvl has been implicated in behavior, we examined expression during different behavioral states that reflected differences in opportunity for social interactions and expression of parental care behaviors. We found differing expression patterns for the two copies, with Mvl1 increasing in expression during resource preparation and feeding offspring, and Mvl2 decreasing in these same states. Given these patterns of expression, along with the protein analysis, we suggest that Mvl in N. vespilloides has experienced sub/neofunctionalization following its duplication, and may be evolving differing and tissue-specific roles in behavior and physiology.

随着测序完成的基因组数量持续增长，新发现的重复基因数目也日益增多。本研究聚焦于天然抗性相关巨噬细胞蛋白（natural resistance-associated macrophage protein, Nramp）家族中的Malvolio基因，该基因在展现出高级双亲抚育行为的亚社会性甲虫——埋葬虫（Nicrophorus vespilloides）中发生了基因复制事件。蜜蜂与果蝇体内仅存在单拷贝的Mvl基因，而脊椎动物中则存在两个发生了亚功能化的Mvl拷贝。我们首先比对了果蝇、甲虫、小鼠及人类的氨基酸序列，结果显示不同物种间的序列保守性较高，但C端区域的变异程度相对更大。针对多个昆虫纲的系统发育分析表明，Mvl基因经历了多次独立的基因复制事件。为探究基因复制后产生功能分化的潜在可能，我们对埋葬虫体内Mvl1与Mvl2在8种组织中的表达水平进行了定量检测。实验结果显示，Mvl1呈广谱表达（尽管表达水平存在差异），而Mvl2的表达仅局限于脑组织与中肠。鉴于Mvl基因已被证实与动物行为相关，我们进一步检测了其在不同行为状态下的表达情况，这些状态分别对应社会互动机会与双亲抚育行为的差异。我们观察到两个拷贝的表达模式存在显著差异：Mvl1在资源准备与饲喂幼虫阶段的表达量显著上升，而Mvl2在相同行为状态下的表达量则出现下降。结合上述表达模式与蛋白质序列分析结果，我们推测埋葬虫体内的Mvl基因在复制后经历了亚功能化/新功能化过程，并可能在行为与生理层面演化出了不同的组织特异性功能。