During meiotic prophase I, tightly regulated processes take place, from pairing and synapsis of homologous chromosomes to recombination, which are essential for the generation of genetically variable haploid gametes. These processes have canonical meiotic features conserved across different phylogenetic groups. However, the dynamics of meiotic prophase I in non-mammalian vertebrates are poorly known. Here, we compare four species from Sauropsida to understand the regulation of meiotic prophase I in reptiles: the Australian central bearded dragon (Pogona vitticeps), two geckos (Paroedura picta and Coleonyx variegatus) and the painted turtle (Chrysemys picta). We first performed a histological characterization of the spermatogenesis process in both the bearded dragon and the painted turtle. We then analyzed prophase I dynamics, including chromosome pairing, synapsis and the formation of double strand breaks (DSBs). We show that meiosis progression is highly conserved in reptiles with telomeres clustering forming the bouquet, which we propose promotes homologous pairing and synapsis, along with facilitating the early pairing of micro-chromosomes during prophase I (i.e., early zygotene). Moreover, we detected low levels of meiotic DSB formation in all taxa. Our results provide new insights into reptile meiosis.

Departament de Biologia Cel·lular Fisiologia i Immunologia Universitat Autònoma de Barcelona Cerdanyola del Vallès Spain

Department of Ecology Evolution and Organismal Biology Iowa State University Ames IA United States

Department of Ecology Faculty of Science Charles University Prague Czech Republic

Genome Integrity and Instability Group Institut de Biotecnologia i Biomedicina Universitat Autònoma de Barcelona Cerdanyola del Vallès Spain

Institute for Applied Ecology University of Canberra Canberra ACT Australia

School of Biotechnology and Biomolecular Sciences Faculty of Science UNSW Sydney NSW Australia

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