Department of Zoology, University of Cambridge, Downing Street, Cambridge CB23EJ, UK.
BMC Genomics. 2011 Jan 26;12:62. doi: 10.1186/1471-2164-12-62.
Heliconius butterflies are an excellent system for studies of adaptive convergent and divergent phenotypic traits. Wing colour patterns are used as signals to both predators and potential mates and are inherited in a Mendelian manner. The underlying genetic mechanisms of pattern formation have been studied for many years and shed light on broad issues, such as the repeatability of evolution. In Heliconius melpomene, the yellow hindwing bar is controlled by the HmYb locus. MicroRNAs (miRNAs) are important post-transcriptional regulators of gene expression that have key roles in many biological processes, including development. miRNAs could act as regulators of genes involved in wing development, patterning and pigmentation. For this reason we characterised miRNAs in developing butterfly wings and examined differences in their expression between colour pattern races.
We sequenced small RNA libraries from two colour pattern races and detected 142 Heliconius miRNAs with homology to others found in miRBase. Several highly abundant miRNAs were differentially represented in the libraries between colour pattern races. These candidates were tested further using Northern blots, showing that differences in expression were primarily due to developmental stage rather than colour pattern. Assembly of sequenced reads to the HmYb region identified hme-miR-193 and hme-miR-2788; located 2380 bp apart in an intergenic region. These two miRNAs are expressed in wings and show an upregulation between 24 and 72 hours post-pupation, indicating a potential role in butterfly wing development. A search for miRNAs in all available H. melpomene BAC sequences (~2.5 Mb) did not reveal any other miRNAs and no novel miRNAs were predicted.
Here we describe the first butterfly miRNAs and characterise their expression in developing wings. Some show differences in expression across developing pupal stages and may have important functions in butterfly wing development. Two miRNAs were located in the HmYb region and were expressed in developing pupal wings. Future work will examine the expression of these miRNAs in different colour pattern races and identify miRNA targets among wing patterning genes.
凤蝶是研究适应性趋同和发散表型特征的绝佳系统。翅膀颜色图案被用作向捕食者和潜在配偶发出的信号，并以孟德尔方式遗传。多年来，人们一直在研究图案形成的潜在遗传机制，这些研究揭示了广泛的问题，例如进化的可重复性。在凤蝶属 melpomene 中，黄色后翅条纹由 HmYb 基因座控制。MicroRNAs（miRNAs）是基因表达的重要转录后调控因子，在许多生物学过程中发挥关键作用，包括发育。miRNAs 可以作为参与翅膀发育、图案形成和色素沉着的基因的调节剂。出于这个原因，我们在发育中的蝴蝶翅膀中对 miRNAs 进行了特征描述，并检查了它们在不同颜色图案品种之间的表达差异。
我们从小蝶翅两种颜色图案品种的小 RNA 文库中测序，并检测到 142 种与 miRBase 中发现的其他凤蝶属 miRNAs 同源的 miRNAs。在颜色图案品种之间的文库中，几个高度丰富的 miRNAs 差异表达。进一步使用 Northern blot 对这些候选物进行了测试，结果表明表达差异主要是由于发育阶段而不是颜色图案。测序reads 组装到 HmYb 区域鉴定出 hme-miR-193 和 hme-miR-2788；在一个基因间区域相距 2380 个碱基对。这两个 miRNAs 在翅膀中表达，并在蛹后 24 至 72 小时之间上调，表明它们在蝴蝶翅膀发育中具有潜在作用。在所有可用的 H. melpomene BAC 序列（约 2.5 Mb）中搜索 miRNAs 并没有发现其他 miRNAs，也没有预测到新的 miRNAs。
在这里，我们描述了第一个蝴蝶 miRNAs，并对它们在发育中的翅膀中的表达进行了特征描述。一些在不同的发育蛹阶段表达差异，可能在蝴蝶翅膀发育中具有重要功能。两个 miRNAs 位于 HmYb 区域，并在发育中的蛹翅中表达。未来的工作将检查这些 miRNAs 在不同颜色图案品种中的表达，并鉴定翅膀图案形成基因中的 miRNA 靶标。
