September 21, 2009
WOOSTER, Ohio - A menacing microbe, the same one responsible for the Great Irish Potato
Famine, has been spreading throughout the northeastern United States since the
early 1990s, threatening both tomato and potato crops in the region - but its
days may be numbered. The genome of this disease-transmitting microscopic organism
(Phytophthora infestans or plant destroyer) has been sequenced by a large group of scientists, which includes William Morgan, professor of biology,
biochemistry and molecular biology at The College of Wooster, and Sophien
Kamoun, formerly of the Ohio Agricultural Research and Development Center
(OARDC). The two worked collaboratively with nearly 50 other scientists over a
10-year period. Their findings were published in the Sept. 13 issue of Nature.
The objective was to determine the entire genome sequence of the organism, which is unique from an evolutionary perspective, according to Morgan. "Several other related microbes, such as those that attacked soybean crops and oak trees, were sequenced previously," he said. "These three microbes have a common origin that is distinct from fungi. Consequently, chemical treatments
that control fungal pathogens often don't work on Phytophthora."
The significance of sequencing the complete genome, or genetic instructions, is that it opens the door for more detailed investigations into how the pathogen infects these plants. Ultimately, this information could be used to develop methods for controlling the pathogen, according to Morgan, who noted the value of the relationship between the College and the OARDC. "The arrangement
(between the two entities) allows faculty and students to take part in cutting-edge research on a wide range of projects," he said. "We are very fortunate to have a facility like (OARDC) so close to our campus."
Morgan's role in this project was to understand the genetic messages produced by the
organism. "The genome is sort of like a magazine," he explained. "There are a lot of images and advertisements that really don't mean much, but what's important is the text. The objective is to identify which portions of the text in the articles are copied into messages so that other researchers can find where they exist in the genome."
Morgan, who devoted his last research leave to supervising a co-worker on this study, took samples of the pathogen and dissolved them using standard biochemistry techniques. This process releases the chemical components of the organism and allows scientists to identify the RNA (Ribonucleic acid), which contains the genetic messages that are decoded to produce proteins, the molecular machines within a cell. "Our ultimate goal is to find the protein machinery that is
unique to this pathogen," said Morgan. "Then we can try to figure out which enzyme is capable of breaking down the wall of a plant, and find a way to block it from continuing that function."
Despite the excitement of figuring out the genome sequence of this fungus, Morgan and his associates acknowledge that the triumph may be short-lived. "Pathogens change quickly," he said. "Before long, a new strain may emerge that is resistant to the latest treatment, but our hope is that this additional information will allow the development of plants with 'durable resistance' that cannot be easily overcome by the pathogen."
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