Molecular Genetics; Cellular Organization
Professor
PhD 1972 Stanford University
Postdoctoral work 1977 University of Wisconsin
Assistant Professor 1979 University at Buffalo
Associate Professor 1986 University at Buffalo
Professor 1997 University at Buffalo
Stephen J. Free
Department of Biological Sciences
370 Cooke Hall
State University of New York at Buffalo
Buffalo, NY 14260
(716) 645-2363 ext: 149
To send e-mail: free@acsu.buffalo.edu
Our major area of
interest is the molecular genetics and developmental biology of
filamentous fungi. Our current research is focused on the
phenomenon of anastomosis, the process of cell fusion between
vegetative hyphal cells. We are isolating and characterizing
mutants that are unable to undergo cell fusion events. The genes
involved in cell fusion are being identified by mapping cell
fusion mutations onto the sequenced Neurospora genome and using a
PCR-based gene amplification and sequencing strategy to identify
the altered gene in the mutant’s genomic DNA.
Several important characteristics of the cell fusion process have
come to light in our work. The cell wall plays an important role
in process. Alterations in the cell wall affecting the structure
of the oligosaccharides attached to cell glycoproteins give rise
to a fusion-defective phenotype. Similarly, mutants that are
unable to make the glycosylphosphotidylinositol structure used to
anchor a number of plasma membrane in the plasma membrane are
defective in the cell fusion process. Mutations affecting
individual plasma membrane and cytosolic proteins are being
identified and their roles in the cell fusion process studied.
Use of differential interference contrast microscopy to observe the flow of cytosolic organelles thru hyphal fusion bridges. Colonies of Neurospora hyphal cells were grown between two sheets of cellophane placed on top of a nutrient agar medium. Anastomizing hyphae, which engage in hyphal fusion events, are generated 1 to 2 mm behind the growing edge of the colony. A cellophane sandwich containing the anastomizing hyphae is cut from the agar plate, placed in an observation chamber, and viewed with the differential interference contrast microscope. The differential interference contrast microscope allows for the visualization of intracellular organelles. Using a time-lapse video recording system, we can readily see the flow of cytoplasmic organelles through fusion bridges that have been generated by the anastomizing hyphae. An example of a differential interference constrast time-lapse video showing the flow of cytoplasmic organelles through a short hyphal fusion bridge (arrow) is shown below. Mutants that are unable to participate in hyphal fusion events either fail to form hyphal fusion bridges or have no flow of cytoplasmic organelles through the hyphal fusion bridge-like structures that are formed.
Return to the directory
Return to the Main Page