The Haustorium of Phytopathogenic Fungi: A Short Overview of a Specialized Cell of Obligate Biotrophic Plant Parasites

Among all biotic stresses to which plants are subjected, the biotrophic fungal pathogens of rust and powdery mildew are the most economically relevant. They are characterized by their ability to develop specialized infective structures called haustoria. The fungal haustorium has been recognized as a fungal structure with a key role in disease establishment and has been implicated in essential processes, such as nutrient uptake and effector delivery. However, despite the early description of this fungal structure, many details of its composition, development or effector functions remain unsolved. In this work, we provide an overview of the current knowledge of the fungal haustorium, including the most recent isolation techniques and expression studies. We can conclude that the fungal haustorium is a complex structure, with a high level of expression of genes associated with nutrient uptake and pathogenesis and with a high level of protein synthesis, which seems to be related to the release of secreted proteins. Although recent molecular studies have significantly advanced the knowledge of this structure, many questions remain unsolved. We hope that the development of novel techniques of genetic manipulation based on the capability of the fungal haustorium to uptake dsRNA, siRNA or T-DNA will allow us to answer these questions in the near future.