Abstract
Australia's most iconic animal, the koala (Phascolarctos cinereus), faces significant population decline and while conservation has focused on assisted breeding technology and reproductive pathologies, koala reproductive biology remains poorly understood. In particular, the koala (P. cinereus) prostate has a vital role in the production of seminal plasma and facilitating successful reproduction. Furthermore, prostatitis regularly occurs as a consequence of chlamydiosis, a substantial factor in the ongoing decline of koala populations. Despite this, little is known about the koala prostate's molecular physiology. This study presents the first proteomic profile of the koala prostate, offering insights into its histological segmentation and broader functional significance. Prostatic tissue was collected from six mature male koalas, with samples taken from the anterior and posterior segments. Proteins were digested using filter-aided sample preparation and analysed via liquid chromatography-tandem mass spectrometry with Zeno-SWATH acquisition. Peptide spectra were processed using DIA-NN and evaluated in RStudio to identify differentially expressed proteins and compare the koala prostate proteome with those of other species. Functional annotation and pathway analysis revealed that whole prostate activity was primarily centered on protein translation and muscle function. Segment-specific proteomic profiles demonstrated slight proteomic differentiation, with secretory proteins contributing to segment-specific functions. Cross-species comparisons showed strong homology between the koala and human prostate proteomes. This proteome provides a foundation for future investigations into prostate-related pathologies in koalas. Furthermore, understanding the koala prostate at a molecular level helps advance wildlife conservation through a better comprehension of its role in male fertility and offers broader evolutionary insight into marsupial reproduction.