Autophagy (literally 'self-eating') has recently emerged as an important topic in biology, as it plays a key role in cellular development, aging, numerous human diseases and survival during nutrient limitation. Also called type II programmed cell death, autophagy involves recycling of cellular macromolecules and even whole organelles. Most of the molecular components involved have been identified and are highly conserved in species ranging from yeast to man. While autophagy has been studied in several model organisms, almost no information is available on autophagy in filamentous fungi. This is somewhat surprising, as the impact of filamentous fungi on human activity is enormous. While pathogenic fungi are responsible for numerous deaths and billions of dollars in crop damage each year, fungi used in the bioprocessing industry produce billions of dollars in beneficial products annually. Notably, in each of these cases, autophagy appears to play a prominent role. Not only is autophagy likely to be a fundamental response to nutrient limitation, it is hypothesized in this proposal that autophagy is also a normal, developmentally related phenomenon in filamentous fungi that occurs in nutrient rich conditions. Thus, autophagy is likely to have a significant impact on most of the fungal processes related to man.
The broad goal of this proposal is to develop a fundamental understanding of both molecular and cellular level phenomena associated with filamentous fungal autophagy. The function of specific genes, hypothesized to play a role in initiation and regulation of autophagy, will be studied. Because autophagy is likely to be an integral aspect of all fungal processes that affect humans, the fundamental understanding developed here is likely to have broad application. For example, novel components or effectors of the autophagy pathway may represent attractive candidates for the design of antifungal therapeutics. Furthermore, insight into mechanisms that suppress autophagy (either partially or completely) in bioprocesses may lead to increased productivity of secondary metabolites. In both cases, the financial impact would be enormous (billions$/yr). This research will also have broad impact on human capital. PhD level graduate students will conduct research in a cross-disciplinary environment and will be trained in cutting edge techniques. Undergraduates will also be involved in all aspects of the research. In addition, research described here will be incorporated in secondary level outreach modules, enhancing learning for both undergraduates and secondary level students.
The goal in this study was to understand how autophagy affects growth, branching and cell wall material properties in filamentous fungi. Autophagy is a cellular recycling pathway that’s active in species ranging from yeast to man. As a recycling pathway it is induced when cells are deprived of essential nutrients. Autophagy research has increased significantly in the last ten years, as autophagy has been connected with a number of important human diseases. Our findings show that autophagy also appears to play an important role in filamentous fungi, impacting growth, morphology and development. A better understanding of fungal autophagy will potentially provide information for combating fungal pathogens and also for improving bioprocesses that involve fungi producing valuable products. To determine the function of various genes thought to be involved with autophagy, our strategy was to delete these genes and then compare the behavior of these deletion strains with a strain which still contains the gene of interest. We found that one of these genes appears to play an important role in regulating the branching of fungal hyphae. We also determined that when autophagy is induced with the drug rapamycin, fungal cell walls appear to be thinner and stiffer. We used a technique called proteomic analysis and determined that when the autophagy pathway is induced, fungi show altered expression of genes related to (i) cell wall synthesis and (ii) chronological life span. Through this research, numerous students (7 undergraduate, 9 graduate, 1 postdoc) were trained in cross disciplinary research.
