de la Herrán Roberto, Hermida Miguel, Rubiolo Juan Andres, Gómez-Garrido Jèssica, Cruz Fernando, Robles Francisca, Navajas-Pérez Rafael, Blanco Andres, Villamayor Paula Rodriguez, Torres Dorinda, Sánchez-Quinteiro Pablo, Ramirez Daniel, Rodríguez Maria Esther, Arias-Pérez Alberto, Cross Ismael, Duncan Neil, Martínez-Peña Teresa, Riaza Ana, Millán Adrian, De Rosa M Cristina, Pirolli Davide, Gut Marta, Bouza Carmen, Robledo Diego, Rebordinos Laureana, Alioto Tyler, Ruíz-Rejón Carmelo, Martínez Paulino
Departamento de Genética, Facultad de Ciencias, Universidad de Granada, Granada, Spain.
Departamento de Zoología, Genética y Antropología Física; Facultad de Veterinaria, Universidade de Santiago de Compostela, Lugo, Spain.
Mol Ecol Resour. 2023 May;23(4):886-904. doi: 10.1111/1755-0998.13750. Epub 2023 Jan 15.
Sex determination (SD) shows huge variation among fish and a high evolutionary rate, as illustrated by the Pleuronectiformes (flatfishes). This order is characterized by its adaptation to demersal life, compact genomes and diversity of SD mechanisms. Here, we assembled the Solea senegalensis genome, a flatfish of great commercial value, into 82 contigs (614 Mb) combining long- and short-read sequencing, which were next scaffolded using a highly dense genetic map (28,838 markers, 21 linkage groups), representing 98.9% of the assembly. Further, we established the correspondence between the assembly and the 21 chromosomes by using BAC-FISH. Whole genome resequencing of six males and six females enabled the identification of 41 single nucleotide polymorphism variants in the follicle stimulating hormone receptor (fshr) consistent with an XX/XY SD system. The observed sex association was validated in a broader independent sample, providing a novel molecular sexing tool. The fshr gene displayed differential expression between male and female gonads from 86 days post-fertilization, when the gonad is still an undifferentiated primordium, concomitant with the activation of amh and cyp19a1a, testis and ovary marker genes, respectively, in males and females. The Y-linked fshr allele, which included 24 nonsynonymous variants and showed a highly divergent 3D protein structure, was overexpressed in males compared to the X-linked allele at all stages of gonadal differentiation. We hypothesize a mechanism hampering the action of the follicle stimulating hormone driving the undifferentiated gonad toward testis.
性别决定（SD）在鱼类中表现出巨大差异且进化速率很高，鲽形目（比目鱼）就是例证。该目鱼类的特点是适应底栖生活、基因组紧凑且性别决定机制多样。在此，我们将具有重大商业价值的比目鱼——塞内加尔鳎的基因组组装成了82个重叠群（614 Mb），结合了长读长和短读长测序，随后使用高密度遗传图谱（28,838个标记，21个连锁群）进行支架搭建，该图谱覆盖了组装序列的98.9%。此外，我们通过BAC-FISH确定了组装序列与21条染色体之间的对应关系。对6只雄性和6只雌性进行全基因组重测序，在促卵泡激素受体（fshr）中鉴定出41个单核苷酸多态性变异，与XX/XY性别决定系统一致。在更广泛的独立样本中验证了观察到的性别关联，提供了一种新的分子性别鉴定工具。fshr基因在受精后86天雄性和雌性性腺之间表现出差异表达，此时性腺仍是未分化的原基，同时雄性和雌性中分别激活了抗缪勒管激素（amh）和细胞色素P450 19A1A（cyp19a1a），这两个基因分别是睾丸和卵巢的标记基因。Y连锁的fshr等位基因包含24个非同义变异，且显示出高度不同的三维蛋白质结构，在性腺分化的所有阶段，与X连锁等位基因相比，在雄性中过度表达。我们推测存在一种机制，阻碍促卵泡激素的作用，从而促使未分化的性腺发育为睾丸。
