Ectocarpus Ec32 HMG mutants

In many eukaryotes, genetic sex determination is not governed by XX/XY or ZW/ZZ systems but by a specialized region on the poorly studied U (female) or V (male) sex chromosomes. Previous studies have hinted at the existence of a dominant male-sex factor on the V chromosome in brown algae, a group of multicellular eukaryotes distantly related to animals and plants. The nature of this factor has remained elusive. Here, we demonstrate that an HMG-box gene acts as the male-determining factor in brown algae, mirroring the role HMG-box genes play in sex determination in animals. Over a billion-year evolutionary timeline, these lineages have independently co-opted the HMG box for male determination, representing a paradigm for evolution's ability to recurrently use the same genetic "toolkit" to accomplish similar tasks.

在诸多真核生物中，遗传性别决定并非由XX/XY或ZW/ZZ系统主导，而是由研究较少的U（雌性）或V（雄性）性染色体上的特化区域所调控。此前已有研究暗示，褐藻——一类与动物、植物亲缘关系较远的多细胞真核生物——的V染色体上存在显性雄性性别决定因子，但其本质长期以来始终不明。本研究证实，褐藻中的HMG框基因（HMG-box gene）正是雄性性别决定因子，其功能与动物中HMG框基因参与性别决定的角色如出一辙。在长达十亿年的演化历程中，这些演化支系独立招募了HMG框以实现雄性性别决定，这一案例为演化反复利用同一套遗传“工具箱”完成相似功能的能力提供了绝佳范式。