Gene duplication and gene expression changes play a role in the evolution of candidate pollen feeding genes in Heliconius butterflies

Heliconius possess a unique ability among butterflies to feed on pollen. Pollen feeding significantly extends their lifespan, and is thought to have been important to the diversification of the genus. We used RNA sequencing to examine feeding-related gene expression in the mouthparts of four species of Heliconius and one non-pollen feeding species, Eueides isabella. We hypothesized that genes involved in morphology and protein metabolism might be upregulated in Heliconius because they have longer proboscides than Eueides, and because pollen contains more protein than nectar. Using de novo transcriptome assemblies, we tested these hypotheses by comparing gene expression in mouthparts against antennae and legs. We first looked for genes upregulated in mouthparts across all five species and discovered several hundred genes, many of which had functional annotations involving metabolism of proteins (cocoonase), lipids and carbohydrates. We then looked specifically within Heliconius where we ...在蝴蝶类群中，袖蝶属（Heliconius）拥有独一无二的花粉取食能力。花粉取食可显著延长其寿命，且被认为对该属的物种分化具有关键意义。我们通过RNA测序（RNA sequencing），对4种袖蝶以及1种非花粉取食物种——伊莎贝拉粉蝶（Eueides isabella）的口器中与取食相关的基因表达水平进行了检测。我们提出如下假说：鉴于袖蝶拥有比伊莎贝拉粉蝶更长的喙，且花粉相较于花蜜含有更为丰富的蛋白质，因此袖蝶体内与形态发育及蛋白质代谢相关的基因可能呈现上调表达。我们借助从头转录组组装（de novo transcriptome assembly）技术，通过对比口器与触角、足中的基因表达情况，验证了上述假说。我们首先筛选了5个物种在口器中均上调表达的基因，共发现数百个相关基因，其中多数的功能注释涉及蛋白质（如茧酶（cocoonase））、脂质及碳水化合物的代谢。随后我们专门针对袖蝶属展开分析，在该属中我们……