Positive selection in gamete interaction proteins in Carnivora

Area of Science:

• Molecular Evolution
• Reproductive Biology
• Genomics

Background:

• Interspecific reproductive isolation barriers are weak in Pantherinae, necessitating evolutionary studies of reproductive proteins.
• Zona pellucida (ZP) proteins and the IZUMO1-JUNO fusion pair are critical for gamete interaction.
• Previous research has not extensively explored the molecular evolution of these proteins across the Carnivora order.

Purpose of the Study:

• To investigate the molecular evolution of zona pellucida (ZP) proteins and the IZUMO1-JUNO gamete fusion pair in Carnivora.
• To compare evolutionary patterns between Feliformia and Caniformia suborders, with a focus on Pantherinae.
• To identify specific evolutionary forces, such as positive selection, acting on these reproductive proteins.

Main Methods:

• Utilized a chromosome-resolved jaguar genome assembly to obtain coding sequences for evolutionary analysis.
• Analyzed sequence variability and molecular evolution across over 30 Carnivora species.
• Applied phylogenetic methods to reconstruct evolutionary histories and detect signatures of positive selection.

Main Results:

• Feliformia displayed significantly lower sequence diversity compared to Caniformia.
• Positive selection was identified in ZP2 and ZP3 across Feliformia, Caniformia, and Pantherinae, but not linked to sperm binding.
• IZUMO1 showed strong positive selection in basal Carnivora lineages and Caniformia, while JUNO exhibited no positive selection. Eight Caniformia-specific positive selected sites in IZUMO1 were found within JUNO-interaction clusters.

Conclusions:

• The study provides novel insights into the evolutionary trajectories of ZP proteins and the IZUMO1-JUNO pair within Carnivora.
• Differential evolutionary pressures, including positive selection, have shaped these reproductive proteins.
• Findings contribute to understanding the molecular basis of reproductive isolation and speciation in carnivores.