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bioRxiv · 10.1101/2025.01.30.635362

Exploring the evolution of sex determination related genes through a cross-species genomics analysis

Nicolini, F.·Nuzhdin, S. V.·Luchetti, A.·Ghiselli, F.·Milani, L.
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Abstract

The molecular basis of sex determination (SD), while being extensively studied in model organisms, remains poorly understood in many animal groups. Bivalves, a diverse class of molluscs with a variety of reproductive modes, represent an ideal yet challenging clade for investigating SD and the evolution of sexual systems. However, the absence of a comprehensive framework has limited progress in this field, particularly regarding the study of sex-determination related genes (SRGs). In this study, we performed a genome-wide sequence evolutionary analysis of the Dmrt, Sox, and Fox gene families in more than 40 bivalve species. For the first time, we provide an extensive and phylogenetic-aware dataset of these SRGs, and we find support to the hypothesis that Dmrt-1L and Sox-H may act as primary sex-determining genes, by showing their high levels of sequence diversity within the bivalve genomic context. To validate our findings, we studied the same gene families in two well-characterized systems, mammals and Drosophila. In the former, we found that the male sex-determining gene Sry exhibits a pattern of amino acid sequence diversity similar to that of Dmrt-1L and Sox-H in bivalves, consistent with its role of master SD regulator. In contrast, no such pattern was observed among genes of the fruit fly SD cascade, which is controlled by a chromosomic mechanism. Overall, our findings highlight similarities in the sequence evolution of some mammal and bivalve SRGs, possibly driven by a comparable architecture of SD cascades. This work underscores once again the importance of employing a comparative approach when investigating understudied and non-model systems.

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Nicolini, F., Nuzhdin, S. V., Luchetti, A., Ghiselli, F., Milani, L.. 2025-01-31. Exploring the evolution of sex determination related genes through a cross-species genomics analysis. https://doi.org/10.1101/2025.01.30.635362

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