Project description:The aims of this study were to investigate the proteome of koala (Phascolarctos cinereus) spermatozoa and that of the prostatic bodies with which they form intimate contact at the moment of ejaculation. For this purpose, spermatozoa and prostatic bodies were obtained from four adult male koala by electroejaculation and analysed by high performance liquid chromatography coupled to a mass spectrometer. This strategy successfully identified and 744 koala sperm and 1,297 prostatic body proteins, which were subsequently attributed to 482 and 776 unique gene products, respectively. Gene ontology curation of the koala sperm proteome revealed an abundance of proteins mapping to the canonical sirtuin and 14-3-3 signalling pathways. By contrast, protein ubiquitination and unfolding protein response pathways dominated the equivalent analysis of proteins uniquely identified in koala prostatic bodies. In terms of functional annotation, koala sperm proteins commonly mapped to the categories of cellular compromise/inflammatory response, whilst those of the prostatic body revealed an over-representation of molecular chaperone and stress-related proteins associated with cell survival. Cross-species comparisons demonstrated that the koala sperm proteome displays greater conservation with that of eutherians (human; 93%) as opposed to reptile (crocodile; 39%) and avian (rooster; 27%) spermatozoa. Similarly, koala prostatic body proteins also presented a relatively high degree of overlap (70%) with those identified in sub-populations of large human seminal plasma extracellular vesicles. Together, this work contributes our overall understanding of the core sperm proteome and has identified candidate markers that may contribute to the exceptional longevity of koala spermatozoa during ex vivo storage.
