(475a) Understanding the Role of Autophagy in Filamentous Fungi

The impact of filamentous fungi on human activity cannot be understated. Pathogenic fungi detrimentally impact both people and plants and are responsible for thousands of deaths and billions of dollars in crop losses annually. In contrast, beneficial species are used to produce billions of dollars of chemicals, foodstuffs, and pharmaceuticals annually. In all these situations, fungi are likely to experience some degree of starvation, where survival requires recycling internal components in a process called "autophagy." Autophagy has been extensively studied in a few model organisms, is ubiquitous in eukaryotic cells, and its components are strongly conserved from yeast to man. However, in spite of it's likely involvement in most fungal processes, relatively little information is available on autophagy, or its related effects, in filamentous fungi.

We have systematically deleted a number of putative autophagy genes from the model fungus Aspergillus nidulans, and are using a sophisticated set of experimental tools to assess subsequent phenotypes providing insight regarding gene function. Proteomic analysis shows that gene deletions at different points in the autophagy induction pathway affect a wide range of cellular processes. Atomic force and electron microscopy show autophagy leads to fungal cell walls which are stiffer, thinner and weaker, implying autophagic fungi may be more susceptible to fragmentation during large scale fermentation. Fungi lacking a particular autophagy gene (Anatg13) show a significant reduction in both growth and branching rates in complete minimal medium, implying autophagy may be active even in the absence of starvation. In addition, the Anatg13 deletion appears to impact morphology as these mutants show no significant change in branching rate in any of the various growth environments employed. This implies autophagy, or the AnAtg13 protein, plays a role in regulation of fungal branching.