School of Biological Sciences, University of Utah, Salt Lake City, Utah, United States of America.
Department of Human Genetics, University of Utah, Salt Lake City, Utah, United States of America.
PLoS Genet. 2020 May 20;16(5):e1008274. doi: 10.1371/journal.pgen.1008274. eCollection 2020 May.
Rock pigeons (Columba livia) display an extraordinary array of pigment pattern variation. One such pattern, Almond, is characterized by a variegated patchwork of plumage colors that are distributed in an apparently random manner. Almond is a sex-linked, semi-dominant trait controlled by the classical Stipper (St) locus. Heterozygous males (ZStZ+ sex chromosomes) and hemizygous Almond females (ZStW) are favored by breeders for their attractive plumage. In contrast, homozygous Almond males (ZStZSt) develop severe eye defects and often lack plumage pigmentation, suggesting that higher dosage of the mutant allele is deleterious. To determine the molecular basis of Almond, we compared the genomes of Almond pigeons to non-Almond pigeons and identified a candidate St locus on the Z chromosome. We found a copy number variant (CNV) within the differentiated region that captures complete or partial coding sequences of four genes, including the melanosome maturation gene Mlana. We did not find fixed coding changes in genes within the CNV, but all genes are misexpressed in regenerating feather bud collar cells of Almond birds. Notably, six other alleles at the St locus are associated with depigmentation phenotypes, and all exhibit expansion of the same CNV. Structural variation at St is linked to diversity in plumage pigmentation and gene expression, and thus provides a potential mode of rapid phenotypic evolution in pigeons.
岩鸽（Columba livia）表现出了令人瞩目的羽毛图案变异多样性。其中一种图案名为杏仁，其特点是羽毛颜色呈斑驳的拼布状，分布方式显然是随机的。杏仁是一种伴性、半显性特征，由经典的条纹（St）基因座控制。杂合雄性（ZStZ+性染色体）和半合子杏仁雌性（ZStW）因其吸引人的羽毛而受到饲养者的青睐。相比之下，纯合子杏仁雄性（ZStZSt）会出现严重的眼睛缺陷，并且常常缺乏羽毛色素沉着，这表明突变等位基因的高剂量是有害的。为了确定杏仁的分子基础，我们将杏仁鸽子的基因组与非杏仁鸽子进行了比较，并在 Z 染色体上确定了一个候选的 St 基因座。我们在分化区域内发现了一个拷贝数变异（CNV），该变异捕获了四个基因的完整或部分编码序列，包括黑素体成熟基因 Mlana。我们没有在 CNV 内的基因中发现固定的编码变化，但所有基因在杏仁鸟的再生羽芽领细胞中都表现出异常表达。值得注意的是，St 基因座的另外六个等位基因与脱色素表型有关，它们都表现出相同的 CNV 扩张。St 处的结构变异与羽毛色素沉着和基因表达的多样性有关，因此为鸽子的快速表型进化提供了一种潜在模式。
