Previously Featured Women In Science & Engineering

Dr. Celeste Sagui, Physics
Dr. Jean Ristaino, Plant Pathology
Dr. Julia A. Clarke, Marine, Earth & Atmospheric Sciences
Dr. Mary Schweitzer, Marine, Earth & Atmospheric Sciences

Physicist Sagui Earns NSF Career Award for Biomolecular Work

Media Contact:
Paul K. Mueller, News Services, 919/515-3470

Dr. Celeste Sagui

Dr. Celeste Sagui, assistant professor of physics at North Carolina State University, has received a National Science Foundation (NSF) Faculty Early Career Development (Career) Award.

The NSF Career Award is one of the highest honors granted by NSF to young university faculty in science and engineering, and is intended to advance the development of their research and careers.

The five-year, $400,000 grant was awarded to Sagui for her proposal entitled “Critical Issues for Biomolecular Simulations: Organic Solvents, Protein-Protein and Nucleotide-Protein Interactions.” The proposal outlines research in the field of computational biophysics designed to improve understanding of protein solvation and protein/nucleotide recognition.

This research builds on methodological advances made by Sagui and her colleagues aimed at improving the treatment of delicate long-range electrostatic interactions between biomolecules. This effort is part of a $3 million, NSF-funded grant to develop new multiscale methods for large-scale biomolecular simulations. Sagui leads the Triangle-area team conducting the research.

Sagui received her doctorate in physics in 1995 from the University of Toronto and performed postdoctoral work at McGill University and at the National Institutes of Environmental and Health Sciences. She joined the NC State faculty in 2000.


Dr. Jean Ristaino Identifies Pathogen Strain Responsible for Irish Potato Famine

Media Contact:
Mick Kulikowski, News Services, 919/515-3470

Dr. RistainoIn June 2001, North Carolina State University plant pathologist Jean Beagle Ristaino shocked the scientific world when she published a paper in the journal Nature that called into question the then-prevailing theories about the strain of pathogen – and its place of origin – that caused the Irish potato famine in the 1840s.

Using DNA fingerprinting analysis of 150-year-old leaves – evidence that had not previously been studied – Ristaino ruled out the longtime prime suspect behind the famine: the Ib haplotype, or strain, of the late-blight pathogen Phytophthora infestans, which was presumed to have originated in Mexico.

Now, in a new study, Ristaino and postdoctoral student Kim May point the finger at the Ia strain of P. infestans, and trace its probable roots to the Andes Mountains in South America.

The study will be published in the April 2004 edition of Mycological Research.

The researchers used DNA sequences from mitochondrial DNA to examine 186 specimens from six different regions of the world dating from as early as 1845 to as late as 1982. The specimens included ones from late-blight epidemics in Ireland, the United States and continental Europe, and came from collections housed in England, Ireland and the United States.

About 90 percent of the specimens were confirmed to be infected with P. infestans, the paper reports. About 86 percent of the specimens – including those involved in major epidemics in Ireland and other locations around the globe – were infected with the Ia haplotype of P. infestans. The Ib haplotype – the one previously presumed to be the culprit behind the Irish potato famine and other epidemics before Ristaino's groundbreaking 2001 study – was present only in more modern samples from Central and South America.

Moreover, the researchers found two strains – Ia and IIb – in potato specimens studied from 1950s Nicaragua. This finding further debunks the single-strain theory that prevailed before Ristaino's 2001 Nature paper.

Ristaino's lab is currently investigating the center of origin of P. infestans. She hypothesizes that the pathogen originated in South America and perhaps made its way to Europe and the United States via exports of potato seed on steamships. The data to support this hypothesis will be published by one of Ristaino's graduate students, Luis Gomez, in the next year.

There are four haplotypes of P. infestans – Ia, Ib, IIa and IIb – which is a fungus-like pathogen that causes severe lesions on leaves of potato and tomato plants.

The late-blight pathogen led to the Irish potato famine, which killed or displaced millions of Irish people, and other epidemics across the world. Late blight continues to wreak havoc as a major potato and tomato killer, which makes Ristaino's research all the more important.

“If we can understand the strains of P. infestans that are out there now and see how the pathogen has evolved over time – including how it mutates in response to fungicides or host resistance – we'll better be able to manage the disease,” Ristaino said.

The research is funded by the National Geographic Society, the USDA National Research Initiatives Cooperative Grants Program, the North Carolina State Agricultural Research Service and NC State's International Programs Office.

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An abstract of the paper follows:

“Identity of the Mitochondrial DNA Haplotype(s) of Phytophthora infestans in Historical Specimens from the Irish Potato Famine”
Authors : K.J. May and Jean Beagle Ristaino, North Carolina State University
Published : April 2004, in Mycological Research

Abstract : The mitochondrial DNA (mtDNA) haplotypes of the plant pathogen Phytophthora infestans present in dried potato and tomato leaves from herbarium specimens collected during the Irish potato famine and later in the 19th and early 20th century were identified. A 100bp fragment of ribosomal DNA (rDNA) specific for P. infestans was amplified from 90 percent of the specimens (n=186), confirming infection by P. infestans . Mitochondrial DNA primers were designed that distinguish the extant haplotypes. Eighty-six percent of the herbarium specimens from historic epidemics were infected with the Ia mtDNA haplotype. Two mid 20th century potato leaves from Ecuador (1967) and Bolivia (1944) were infected with the Ib mtDNA haplotype of the pathogen. Both the Ia and IIb haplotypes were found in specimens collected in Nicaragua in the 1950s. The data suggest that the Ia haplotype of P. infestans was responsible for the historic epidemics during the 19th century in the UK, Europe, and the U.S. The Ib mtDNA haplotype of the pathogen was dispersed later in the early 20th century from Bolivia and Ecuador. Multiple haplotypes were present outside Mexico in the 1950s indicating that pathogen diversity was greater than previously believed.

Marine Earth & Atmospheric Sciences Faculty Member Studies Bird Evolution

Dr. Julia A. Clarke, Assistant Professor in the Marine, Earth & Atmospheric Sciences Department and research curator of paleontology at the N.C. Museum of Natural Sciences, studies, among other things, bird evolution. An article in the Autumn 2004 edition of NC State magazine described some of Clarke's graduate work, in which she identified 40 million year-old penguin remains found at the southern tip of South America. Prior to the discovery of that particular fossil, "the oldest penguin fossil from South America was about 18 million years old," Clarke said.

For more information on Dr. Clarke and her current research, visit her web site.

NC State Paleontologist Discovers Soft Tissue in Dinosaur Bones

Media Contact:
Tracey Peake, News Services, 919/515-3470

Dr. Mary Schweitzer


Conventional wisdom among paleontologists states that when dinosaurs died and became fossilized, soft tissues didn't preserve – the bones were essentially transformed into “rocks” through a gradual replacement of all organic material by minerals. New research by a North Carolina State University paleontologist, however, could literally turn that theory inside out.

Dr. Mary Schweitzer, assistant professor of paleontology with a joint appointment at the N.C. Museum of Natural Sciences, has succeeded in isolating soft tissue from the femur of a 68-million-year-old dinosaur. Not only is the tissue largely intact, it's still transparent and pliable, and microscopic interior structures resembling blood vessels and even cells are still present.

In a paper published in the March 25 edition of the journal Science, Schweitzer describes the process by which she and her technician, Jennifer Wittmeyer, isolated soft organic tissue from the leg bone of a 68-million-year-old Tyrannosaurus rex .

Schweitzer was interested in studying the microstructure and organic components of a dinosaur's bone. All bone is made up of a combination of protein (and other organic molecules) and minerals. In modern bone, removing the minerals leaves supple, soft organic materials that are much easier to work with in a lab. In contrast, fossilized bone is believed to be completely mineralized, meaning no organics are present. Attempting to dissolve the minerals from a piece of fossilized bone, so the theory goes, would merely dissolve the entire fossil.

But the team was surprised by what actually happened when they removed the minerals from the T. rex femur fragment. The removal process left behind stretchy bone matrix material that, when examined microscopically, seemed to show blood vessels, osteocytes, or bone building cells, and other recognizable organic features.

Since current data indicates that living birds are more closely related to dinosaurs than any other group, Schweitzer compared the findings from the T. rex with structures found in modern-day ostriches. In both samples, transparent branching blood vessels were present, and many of the small microstructures present in the T. rex sample displayed the same appearance as the blood and bone cells from the ostrich sample.

Schweitzer then duplicated her findings with at least three other well-preserved dinosaur specimens, one 80-million-year-old hadrosaur and two 65-million-year-old tyrannosaurs. All of these specimens preserved vessels, cell-like structures, or flexible matrix that resembled bone collagen from modern specimens.

Current theories about fossil preservation hold that organic molecules should not preserve beyond 100,000 years. Schweitzer hopes that further research will reveal exactly what the soft structures isolated from these bones are made of. Do they consist of the original cells, and if so, do the cells still contain genetic information? Her early studies of the material suggest that at least some fragments of the dinosaurs' original molecular material may still be present.

“We may not really know as much about how fossils are preserved as we think,” says Schweitzer. “Our preliminary research shows that antibodies that recognize collagen react to chemical extracts of this fossil bone. If further studies confirm this, we may have the potential to learn more not only about the dinosaurs themselves, but also about how and why they were preserved in the first place.”

The research was funded by NC State, the N.C. Museum of Natural Sciences and the National Science Foundation.

- peake -

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