RUI: Characterization of the gene regulatory network promoting hormogonium development in the filamentous cyanobacterium Nostoc punctiforme

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The filamentous cyanobacteria are a group of photosynthetic microorganisms that first evolved about 2.5 billion years ago, making them one of the first multicellular organisms on earth. These relatively simple multicellular organisms provide an excellent, cost-effective model system for studying fundamental aspects of developmental biology. Additionally, because these bacteria are relatively easy to modify genetically, and are capable of both converting sunlight into energy and providing a source of nitrogen-based fertilizer to certain plants, they are of considerable interest for development in biofuel production and agriculture. This project is focused on characterizing the genetic mechanism controlling the development of specialized filaments that are capable of movement, using the model strain Nostoc punctiforme. As part of the broader impacts, this project will also provide training for both undergraduate and graduate students in state-of-the art genetic and molecular techniques, as well as an outreach program to local area schools which serve a diverse student body, many of whom are economically disadvantaged. Aspects of this project will be incorporated into teaching labs and several undergraduate and graduate students will participate in the research, including students recruited from the Community Involvement Program (C.I.P.) at University of the Pacific, which serves first generation college students from ethnically underrepresented and economically disadvantaged backgrounds. Students recruited from C.I.P. will be provided support for summer research assistantships and also participate in an outreach program for 5th-8th grade classrooms at local schools where they will disseminate a learning module using a portable fluorescence microscope to explore cell biology.Filamentous cyanobacteria are among the most developmentally complex prokaryotes and the study of these organisms has provided valuable insight into developmental biology. Many species develop an array of specialized cell types including motile filaments termed hormogonia that facilitate dispersal. Hormogonia are also essential for the formation of supracellular structures and the establishment of nitrogen-fixing plant- and fungal-cyanobacterial symbioses that contribute significantly to global nitrogen fixation. Currently, the underlying molecular interactions controlling hormogonium development and ecologically important hormogonium-dependent processes are largely undefined. Based on recent studies and preliminary data, the working hypothesis is that hormogonium development is governed by a conserved gene regulatory network that includes sigma factors, partner-switching regulatory systems, the hmp chemotaxis system, and several additional uncharacterized components. This project has two specific aims: 1) Identify and characterize components of the gene regulatory network promoting hormogonium development, and 2) Define the role of sigma factors and partner-switching regulatory systems in hormogonium development. The project uses forward and reverse genetic approaches combined with a range of phenotypic analyses of mutant strains including morphological analyses and immunological assays of hormogonium-specific protein and polysaccharide expression, as well as transcriptomic studies to define the gene regulatory network promoting hormogonium development in the model filamentous cyanobacterium Nostoc punctiforme. Completion of this project will lay the foundation for a model of the gene regulatory network promoting hormogonium development that can then be used to rationally design genetically modified strains of filamentous cyanobacteria for various applications including biofuel production and novel plant-cyanobacterial symbioses.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.