Fungi are integral to the productivity of all terrestrial ecosystems as they play critical roles in nutrient cycling, soil structure and as parasites and symbionts. The estimates for the number of fungal species on the planet range from 1.5 to over 5 million and it is thought that likely over 90% of fungi remain to be identified. To date, a relatively small percentage of the identified fungi are associated with marine environments. However, fungi have been found from the surface of the ocean to depths of many kilometers in ocean sediment, and these organisms have potential key roles in carbon cycling and degradation of anthropogenic materials. Fungi that survive in the marine environment have remarkable abilities to respond to the myriad of stresses, including UV exposure, limited nutrients and high salinity that are features of the ocean. This work examines how marine fungi cope with environmental stresses by changing cell shapes and controlling how the cells divide. Fundamental understanding of growth, division and stress response is a missing link to understanding how marine fungi can contribute to the function of oceans. The work will involve the training of undergraduate and graduate student researchers along with several community outreach efforts.
Cell function is intimately tied to cell morphogenesis across the biosphere. This is especially clear in fungi where combinations of spherical, ovoid and hyphal-shaped cells build diverse structures across many scales. From micrometer-sized spores, centimeter-sized mushrooms and kilometer-spanning hyphae, a conserved family of cytoskeletal proteins called septins is integral to creating this morphological diversity. Despite their ubiquity, the basic biophysical properties and regulation of septin polymers are only beginning to be understood. This project links biophysical properties of septin polymers at the nanometer scale to their function in cell morphology at the micron scale. Septin form and function will be analyzed across highly morphologically diverse fungal systems called “black yeasts†that were isolated from the ocean. Fungi in this group are considered to be amongst the most stress tolerant eukaryotes. Comparative analysis of protein sequence variation, biophysics and cell biology of septins in these diverse black yeast species will reveal how plasticity in the septin cytoskeleton supports diversity in cell shape, function and stress tolerance. The research will analyze this problem from three scales: 1. Polymer properties: How do biophysical properties of septin filaments control higher-order structures? 2. Dynamics: How are septin dynamics used to sculpt assemblies and enable stress responses? 3. Morphogenesis: How do different septin assemblies promote distinct cell morphologies. These questions will be addressed using interdisciplinary approaches including biochemical reconstitution, advanced live cell imaging, molecular genetics and quantitative modeling. Integral to this research plan is the training of undergraduate and graduate student scientists, along with several community outreach activities.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
