Conserved immunophilins: A unifying link across three phytomyxid pathogens

Immunophilins are a conserved family of proteins present in all organisms, including bacteria, fungi, plants, and animals. Immunophilins are sub-classified into three subfamilies: cyclophilins, FK-506 binding proteins, and parvulins, and are involved in essential cellular functions, especially protein folding. Despite their broad biological relevance, little is known about immunophilins in Phytomyxea, a group of obligate biotrophic pathogens of oomycetes, diatoms, brown algae, and plants. In this study, we analysed the immunophilins in Maullinia ectocarpii that infects brown algae, and compared them to the immunophilins of the plant pathogens Plasmodiophora brassicae and Spongospora subterranea. Through protein domain, structural, and phylogenetic analyses, we identified and characterized immunophilins. Also, the expression of selected immunophilins in M. ectocarpii was validated throughout the full life cycle. Our results reveal a conserved nature of immunophilins across phytomyxid lineages infecting evolutionarily distinct hosts. We found a strong conservation of functional domains and protein structure in selected immunophilins in both plant- and algae-associated pathogens. This conservation suggests that immunophilins play fundamental roles in the biology of phytomyxids, but also a potentially conserved role of these proteins in host adaptation nd infection strategies, offering insights into pathogen-host interactions.