The sperm proteome of the red abalone, Haliotis rufescens, and the discovery and characterization of an abundant, rapidly evolving acrosome protein

Abstract

Abalone, a broadcast spawning marine mollusk, is an important model for molecular interactions and positive selection in fertilization, but the focus has previously been on only two sperm proteins, lysin and sp18. We have used genomic and proteomic techniques to bring new insights to this model by characterizing the testis transcriptome and sperm proteome of the red abalone <italic>Haliotis rufescens</italic>. One pair of homologous testis-specific proteins contains a secretion signal and is small, abundant, and associated with the acrosome, here named sp6_4D and sp6_8D. Comparative analysis revealed that homologs are extremely divergent between species, and show strong evidence for positive selection. The acrosomal localization and rapid evolution of these proteins indicates that they play an important role in fertilization and could be involved in the species-specificity of sperm-egg interaction in abalone. Our genomic and proteomic characterization of abalone fertilization resulted in the identification of these interesting novel peptides that have eluded detection in this important model system for twenty years. Through additional work on these proteins, we have created a foundation for the future discovery of their interacting proteins and further investigations into their function.