Danaus plexippus Chromosome-scale assembly. Danaus plexippus plexippus

Unlike most female-heterogametic (WZ female / ZZ male) animals, moths and butterflies exhibit sex chromosome dosage compensation patterns typically seen only in male-heterogametic species. The monarch butterfly carries a newly-derived Z chromosome segment arising from an autosomal fusion with the ancestral Z. Using a chromosome-scale genome assembly, we show that Z chromosome gene expression is balanced between sexes, but the two segments exhibit distinct modes of compensation. This is the first known case of plurality of sex chromosome dosage compensation mechanisms along a single sex chromosome within a species.

与大多数雌性异配（雌性为WZ型、雄性为ZZ型）的动物不同，蛾类与蝶类所呈现的性染色体剂量补偿（sex chromosome dosage compensation）模式，通常仅见于雄性异配的物种中。帝王蝶拥有一段由常染色体与祖先Z染色体融合产生的新型Z染色体区段。本研究借助染色体级基因组组装（chromosome-scale genome assembly）技术，证实帝王蝶的Z染色体基因表达在两性间保持平衡，但该染色体的两个区段呈现出截然不同的剂量补偿模式。这是目前已知的首个在同一物种的单条性染色体上存在多种性染色体剂量补偿机制的案例。