Daniels Emily V, Murad Rabi, Mortazavi Ali, Reed Robert D
Department of Ecology and Evolutionary Biology, University of California Irvine, 321 Steinhaus Hall, Irvine, CA, 92697-2525, USA.
Mol Ecol. 2014 Dec;23(24):6123-34. doi: 10.1111/mec.12988. Epub 2014 Dec 4.
In the eastern United States, the buckeye butterfly, Junonia coenia, shows seasonal wing colour plasticity where adults emerging in the spring are tan, while those emerging in the autumn are dark red. This variation can be artificially induced in laboratory colonies, thus making J. coenia a useful model system to examine the mechanistic basis of plasticity. To better understand the developmental basis of seasonal plasticity, we used RNA-seq to quantify transcription profiles associated with development of alternative seasonal wing morphs. Depending on the developmental stage, between 547 and 1420 transfrags were significantly differentially expressed between morphs. These extensive differences in gene expression stand in contrast to the much smaller numbers of differentially expressed transcripts identified in previous studies of genetic wing pattern variation in other species and suggest that environmentally induced phenotypic shifts arise from very broad systemic processes. Analyses of candidate endocrine and pigmentation transcripts revealed notable genes upregulated in the red morph, including several ecdysone-associated genes, and cinnabar, an ommochrome pigmentation gene implicated in colour pattern variation in other butterflies. We also found multiple melanin-related transcripts strongly upregulated in the red morph, including tan and yellow-family genes, leading us to speculate that dark red pigmentation in autumn J. coenia may involve nonommochrome pigments. While we identified several endocrine and pigmentation genes as obvious candidates for seasonal colour morph differentiation, we speculate that the majority of observed expression differences were due to thermal stress response. The buckeye transcriptome provides a basis for further developmental studies of phenotypic plasticity.
在美国东部，七叶树蝴蝶（苎麻珍蝶）表现出季节性的翅膀颜色可塑性，春季羽化的成虫翅膀呈棕褐色，而秋季羽化的成虫翅膀为深红色。这种差异可以在实验室种群中人工诱导产生，因此苎麻珍蝶成为研究可塑性机制基础的有用模型系统。为了更好地理解季节性可塑性的发育基础，我们使用RNA测序来量化与交替季节性翅膀形态发育相关的转录谱。根据发育阶段的不同，两种形态之间有547至1420个转录片段存在显著差异表达。这些基因表达上的广泛差异与之前在其他物种中对翅膀遗传图案变异的研究中鉴定出的数量少得多的差异表达转录本形成对比，这表明环境诱导的表型转变源自非常广泛的系统性过程。对候选内分泌和色素沉着转录本的分析揭示了在红色形态中上调的显著基因，包括几个与蜕皮激素相关的基因，以及朱砂基因，这是一种与其他蝴蝶颜色图案变异有关的眼色素沉着基因。我们还发现多个与黑色素相关的转录本在红色形态中强烈上调，包括棕褐色和黄色家族基因，这使我们推测秋季苎麻珍蝶的深红色色素沉着可能涉及非眼色素。虽然我们确定了几个内分泌和色素沉着基因是季节性颜色形态分化的明显候选基因，但我们推测观察到的大多数表达差异是由于热应激反应。七叶树蝴蝶的转录组为进一步研究表型可塑性的发育提供了基础。
