Identification and characterization of sperm motility‐initiating substance‐2 gene in internally fertilizing Cynops species. (9th March 2023)

• Record Type: Journal Article
• Authors: Furukawa, Haruka; Mito, Shinya; Nishio, Jun; Sato, Nozomi; Ando, Yoshihiro; Tominaga, Atsushi; Toyama, Fubito; Nakauchi, Yuni; Takayama‐Watanabe, Eriko; Watanabe, Akihiko
• Is Part Of: Development growth and differentiation. Volume 65:Number 3(2023)
• Page Start: 144
• Page End: 152
• Publication Date: 2023-03-09
• Subjects: gene evolution -- internal fertilization -- neofunctionalization -- sperm motility -- urodela; Embryology -- Periodicals; Developmental biology -- Periodicals; Growth -- Periodicals; 574.3
• DOI: 10.1111/dgd.12846
• Languages: English
• ISSNs: 0012-1592

Abstract

Abstract: Sperm motility‐initiating substance (SMIS) is an oviductal protein critical for internal fertilization in urodeles. It contributes to the establishment of various reproductive modes in amphibians and is thus a unique research model for the gene evolution of gamete‐recognizing ligands that have diversified among animal species. In this study, a paralogous SMIS gene, smis2, was identified via the RNA sequencing of the oviduct of the newt, Cynops pyrrhogaster . The base sequence of the smis2 gene was homologous (˃90%) to that of the original smis gene ( smis1 ), and deduced amino acid sequences of both genes conserved six cysteine residues essential for the cysteine knot motif. Furthermore, smis2 complementary DNA was identified in the oviduct of Cynops ensicauda, and the base substitution patterns also suggested that the smis gene was duplicated in the Salamandridae. Nonsynonymous/synonymous substitution ratios of smis1 and smis2 genes were 0.79 and 2.6, respectively, suggesting that smis2 gene evolution was independently driven by positive selection. Amino acid substitutions were concentrated in the cysteine knot motif of SMIS2. The smis2 gene was expressed in some organs in addition to the oviduct; in contrast, SMIS1 was only expressed in the oviduct. The SMIS2 protein was suggested to be produced and secreted at least in the oviduct and redundantly act in sperm. These results suggest that smis1 plays the original role in the oviduct, whereas smis2 may undergo neofunctionalization, which rarely occurs in gene evolution. Abstract : A gene of sperm motility‐initiating substance was predicted to be duplicated in Salamandridae. The original role of that gene is to regulate sperm motility, while one of the duplicates may have evolved independently under the influence of nonreproductive organs, leading to the neofunctionalization.