The brown egg 4 (b-4) is a recessive mutant in the silkworm (Bombyx mori), whose egg and adult compound eyes exhibit a reddish-brown color instead of normal purple and black, respectively. By double digest restriction-site associated DNA sequencing (ddRAD-seq) analysis, we narrowed down a region linked to the b-4 phenotype to approximately 1.1 Mb that contains 69 predicted gene models. RNA-seq analysis in a b-4 strain indicated that one of the candidate genes had a different transcription start site, which generates a short open reading frame. We also found that exon skipping was induced in the same gene due to an insertion of a transposable element in other two b-4 mutant strains. This gene encoded a putative amino acid transporter that belongs to the β-group of solute carrier (SLC) family and is orthologous to Drosophila eye color mutant gene, mahogany (mah). Accordingly, we named this gene Bmmah. We performed CRISPR/Cas9-mediated gene knockout targeting Bmmah. Several adult moths in generation 0 (G₀) had totally or partially reddish-brown compound eyes. We also established three Bmmah knockout strains, all of which exhibit reddish-brown eggs and adult compound eyes. Furthermore, eggs from complementation crosses between the b-4 mutants and the Bmmah knockout mutants also exhibited reddish-brown color, which was similar to the b-4 mutant eggs, indicating that Bmmah is responsible for the b-4 phenotypes.

的褐色鸡蛋4（B-4 ）是在家蚕隐性突变体（家蚕），其卵和成人复眼表现出红棕色的，而不是正常的紫色和黑色，分别。通过双酶切限制位点相关 DNA 测序 (ddRAD-seq) 分析，我们将与b-4表型相关的区域缩小到大约 1.1 Mb，其中包含 69 个预测基因模型。b-4菌株中的 RNA-seq 分析表明，其中一个候选基因具有不同的转录起始位点，从而产生一个短的开放阅读框。我们还发现，由于在其他两个基因中插入了转座因子，在同一基因中诱导了外显子跳跃。b-4突变株。该基因编码一种假定的氨基酸转运蛋白，属于溶质载体 (SLC) 家族的 β 组，与果蝇眼睛颜色突变基因桃花心木( mah )直系同源。因此，我们将该基因命名为Bmmah 。我们进行了针对Bmmah 的CRISPR/Cas9 介导的基因敲除。几只第 0 代 (G ₀ ) 的成虫具有完全或部分红棕色复眼。我们还建立了三个Bmmah敲除品系，所有品系都表现出红褐色的卵和成虫复眼。此外，来自互补的卵在b-4突变体和Bmmah敲除突变体也表现出红棕色，这与b-4突变体卵相似，表明Bmmah是b-4表型的原因。