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Position: Professor
Education:
Ph.D.. Botany, University of California, Berkeley, 1979
PM.S. Botany, University of Illinois, Urbana, 1974
B.A. Biology, State University of New York, Oswego, 1972
Voice: (301) 405-1605
Email: wolniak@umbi.umd.edu
CBR Faculty Directory
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Research Overview
Cytoskeleton and Motility
All nucleated cells of plants and animals have internal structure----a sort of internal skeleton, consisting of specific proteins. These internal structures provide specific form, shape, and the ability to move around to the cell. Collectively, this internal skeleton is called the cytoskeleton. Cells are far more than bags of chemicals----they have elaborate structure, and this structure provides many functional capabilities, including the ability to move around and the ability to interact with neighboring cells. By studying the early stages of formation of the cytoskeleton, we learn about how these functions are carried out in normal cells in health, and also how things can go wrong in disease.
Reproductive Physiology
Elaborate communications and intercellular interactions take place between reproductive cells, and these processes are crucial to normal fertilization and reproduction. By studying the biology of these processes in a variety of model systems, we learn principles that provide insights into the normal biology of reproduction in general, and also have important potential applications in agriculture and medicine, including maximizing harvests and treating infertility.
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Research Description
Research Specialty: Formation of the Cytoskeleton and Motile Apparatus in Spermatids of Marsilea
Marsilea vestita is a water fern (Figure 1 ) that grows as a weed at the edges of vernal pools or in rice paddies. By all outward appearances, the plant resembles a large four-leafed clover (Figure 2 ), but in reality, it is only distantly related to the flowering plants. The meiotic products from the sporophyte, the microspores and megaspores, are found within hardened structures known as sporocarps (Figure 3 ). After being placed into water, the dry microspores develop into male gametophytes and the megaspores develop into female gametophytes. Fertilization in lower plants involves the fusion of a motile male gamete, the spermatozoid, with a non-motile female gamete that is encased in a flask-shaped array of vegetative cells known as an archegonium. Plant spermatozoids are structurally complex cells (Figure 1 ) that differentiate within an antheridium. The release of certain chemicals (i.e., pheromones) from female gametes stimulate changes in spermatozoid swimming behavior and direction; these cues effectively guide the spermatozoids toward the egg. This change in swimming behavior is known as chemotaxis, a word that was coined for the response of fern spermatozoids to chemicals present in egg exudates [Pfeffer, 1884]...
Almost 90 years ago, Lester Sharp [1912] described the rapid process of spermatozoid formation in the male gametophytes of M. vestita. He found that the placement of dry spores into water would result in sperm formation; the process reached completion in about eleven hours with the release of 32 of these spirally shaped spermatozoids. The development of the male gametophyte occurs entirely within the microspore wall. Sharp tracked the process microscopically and determined that during the first 5.5 hours, there were nine mitotic divisions, which occurred in precise division planes to produce a total of 39 cells (Figure 4 ) When the division cycles are complete, the gametophyte consists of one prothallial cell, six sterile jacket cells and 32 spermatids. Then, each of the 32 spermatid cells differentiates into a...
Complete Information...
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