RESUMEN
Our previous study documented expression of a male-transmitted cytochrome c oxidase subunit II protein (MCOX2), with a C-terminus extension (MCOX2e), in unionoidean bivalve testes and sperm mitochondria. Here, we present evidence demonstrating that MCOX2 is seasonally expressed in testis, with a peak shortly before fertilization that is independent of sperm density. MCOX2 is localized to the inner and outer sperm mitochondrial membranes and the MCOX2 antibody's epitope is conserved across >65 million years of evolution. We also demonstrate the presence of male-transmitted mtDNA and season-specific MCOX2 spatial variation in ovaries. We hypothesize that MCOX2 plays a role in reproduction through gamete maturation, fertilization and/or embryogenesis.
Asunto(s)
Complejo IV de Transporte de Electrones/genética , Complejo IV de Transporte de Electrones/fisiología , Óvulo/enzimología , Espermatozoides/enzimología , Unionidae/genética , Unionidae/fisiología , Animales , ADN Mitocondrial/genética , ADN Mitocondrial/metabolismo , Complejo IV de Transporte de Electrones/química , Evolución Molecular , Femenino , Masculino , Microscopía Electrónica , Reproducción/genética , Reproducción/fisiología , Estaciones del Año , Distribución TisularRESUMEN
Analyses of unionoidean bivalve male-transmitted (M) mtDNA genomes revealed an approximately 555 bp 3' coding extension to cox2. An antibody was generated against this predicted C-terminus extension to determine if the unique cox2 protein is expressed. Western blot and immunohistochemistry analyses demonstrated that the protein was predominantly expressed in testes. Weak expression was detected in other male tissues but the protein was not detected in female tissues. This is the first report documenting the expression of a cox2 protein with a long C-terminus in animals. Its universal presence in unionoidean bivalve testes suggests a functional significance for the protein.