Dr. Anne Desjardins
From the Special Topic of
According to our Special Topics analysis on mycotoxin
research over the past decade, the scientist whose work
ranks at #5 by total citations is Dr. Anne Desjardins, with
27 papers cited a total of 545 times. She is also ranked at
#18 by total papers and #2 by cites per paper.
Science IndicatorsSMfromClarivate, her record
includes 50 papers, the majority of which are classified
in the field of Plant & Animal Science, cited 955
times between January 1, 1997 and December 31, 2007. She
is also the author of Fusarium Mycotoxins:
Chemistry, Genetics, and Biology (American
Phytopathological Society Press, 2006).
Dr. Desjardins is currently a Research Chemist in the Mycotoxin
Research Unit of the United States Department of Agriculture's Agricultural
Research Service in Peoria, Illinois. She is also on the Editorial Board
of The Journal of Applied and Environmental Microbiology, as well
as a Fellow of the American Phytopathological Society and of AAAS.
In the interview below, she talks with
ScienceWatch.com correspondent Gary Taubes about her
highly cited research.
How did you first begin studying mycotoxins
and what was the USDA’s interest at the time?
Let me first tell you about the USDA interest. Back in the late 1970s/early
‘80s, Alexander Haig was at the U.N. talking about the Russians and
how they were using bio-warfare agents in Southeast Asia—yellow rain.
That’s how it all started, because trichothecenes were implicated in
yellow rain. That’s why the USDA started a program on these toxins.
I started working on them in 1984, specifically on these trichothecenes
implicated in bio-warfare. How were they bio-synthesized? How could they be
controlled? Within four or five years it became very clear that the natural
occurrence of these toxins was a much more serious, real problem than any
intentional distribution of them. That’s when the project took off
and why it stayed funded for 25 years.
How are mycotoxins a problem
History again: in 1993, there were floods in the Midwest, which really
started the consistent year-to-year problems with trichothecene
contamination in grain, mainly wheat. The other related issue was what we
call conservation tillage, or low-tillage agriculture, which was introduced
in the ‘70s and ‘80s. Most US farmers don’t plow under
crop residues anymore. The reason is to conserve the soil; prevent soil
erosion. The debris is left on the fields through the whole winter, and
that helps keep the rain and wind from blowing off the topsoil. The
downside is that certain fungi, the trichothecene-producing fungi among
them, survive the winter in this crop residue.
"We went from being, in 1984,
perhaps the only lab in the US doing genetics and
biochemistry on these fungi, to probably one of 50 or
60 and now hundreds worldwide."
So there is the whole constellation of factors, including public awareness
of mycotoxins, that kept us interested and the USDA interested. Climate
change comes in here too, speculatively, and the very dominant growth of
corn in this country. All of these factors led to the particular fungi that
make trichothecenes, mainly Fusarium graminearum, becoming very,
very well established. It’s always been around; it’s always
caused problems, but now it’s exceedingly well established. The
toxins are now regulated: if certain levels of trichothecenes appear in
grain, it cannot be used for human food. Above certain levels it cannot be
used for animal feed.
This all feeds into the continuing interest in controlling these
mycotoxins. In 1988, we began working on new Fusarium species and a new
Fusarium toxin, known as fumonisins, and they actually are carcinogenic,
although much less so than aflatoxins. They also cause a variety of animal
health problems. They’ve been tied to neural tube defects in
populations that eat high levels of maize. Since 1984, we’ve worked
as a multidisciplinary group, with chemists, geneticists, and biologists,
studying these two kinds of toxins.
What prompted your highly cited 1999 paper on the
polyketide synthase gene required for biosynthesis of fumonisins
(Proctor RH, et al., "A polyketide synthase gene required for
biosynthesis of fumonisin mycotoxins in Gibberella fujikoroi slating
population A," Fungal Genet. Biol. 27: 100-12, June
Our job is to characterize these toxins. Where do they occur? What fungal
species make them? The second thing we do is identify the genes required
for the synthesis of toxins, the biosynthetic pathways. These are complex
pathways with many enzymes, many steps, and many genes. Our program has
done the complete pathway for both these toxins. It’s been a very
long-term effort, with lots of people involved.
Once the pathways are known and the genes are available, then we do gene
function analysis. That 1999 paper was looking at the fumonisin gene, the
first gene required for the biosynthesis of fumonisin. That was the first
time anyone discovered a gene required for these toxins. It’s pretty
straightforward and that’s why it’s so highly cited. Robert
Proctor, Ronald Plattner, and I were the three main people on the fumonisin
What do you find to be the most challenging aspect
of your mycotoxin research?
To be perfectly honest, it’s making this long-term collaboration
between biologists, geneticists, and chemists work, year after year after
year. That was the hardest part of the project. It wasn’t the
scientific problems. We had all the tools and the technologies and
equipment we needed. The people here are very well trained. The hardest
thing is to coordinate it all.
Take a project like this. You’re doing very difficult chemistry in
complex agricultural matrices. You need very, very good chemists.
You’re also doing cutting-edge molecular biology, so you need very,
very good molecular biologists, and they’re constantly trolling for
new techniques, new methods. And then everybody is working together, year
after year, toxin after toxin. Then we add to this research the
gene-function analysis, using gene knockouts. People do this in mice and
you can do it in fungi. We were the first lab in the US to take these
genetically modified, knockout fungi into the field and we saw how the
actual agricultural interrelationship changes when we eliminate this gene.
This was really groundbreaking work in determining why these fungi make
these very complex metabolites. But it involved, again, a whole pyramid of
chemists, geneticists, and biologists, all working together over a very
long period of time. I think maintaining that network was the hardest thing
to do. Everyone had to feel that they were treated fairly; that they got
You seem obviously pleased with how it worked
I think we did that very successfully, yes. I think our group is very
unique in that we maintained this coordinated approach on all fronts. If
you can picture the whole thing: you’ve got chemists working with
mass spectrometers; you’ve got cloners typing data into GenBank, then
making knockout mutants, characterizing them in the lab and taking them
into the field.
The field work with these mutants was done under stringent regulations from
the USDA animal plant health inspection service out of Washington. They
regulate any movement of genetically modified fungi. All this research had
to be cleared with them. That was the whole process we did for 20 years and
we did it pretty well.
What turns out to be the function of these complex
metabolites that are mycotoxins?
For trichothecenes, it turns out that they are virulence factors. If you
knock out the toxin you get less disease in the plants. So the toxins are
actually acting to inhibit protein synthesis in the plant, which makes it
more susceptible to the disease. This was very clear in the trichothecenes
"...if certain levels of
trichothecenes appear in grain, it cannot be used for
In fumonisins, it actually didn’t turn out to be the case. With this
other class of toxin, all our field work indicated that those toxins were
what you would call dispensable. It still remains a mystery what is
selecting for maintaining toxin production in that population.
There’s a reason these fungi make the fumonisins, but we don’t
know what it is at this point. Knockout mutants are completely pathogenic.
They make no toxins but cause the same level of disease in the host plants.
How has the field and mycotoxin research evolved
in the years since you published the 1999 FGB paper?
The field is just enormous now. The USDA has a Fusarium head blight
initiative for wheat and barley. It’s funded by a special grant from
Congress, several million dollars a year to support research on this
problem. It’s huge now, or at least huge for agricultural
research—we’re not the NIH.
When the USDA-NSF fungal gene-sequencing initiative started around 2001, I
think Fusarium graminearum was the third fungal genome that was
sequenced. That was finished in 2003. The Fusarium that makes fumonisin
toxins was sequenced about two years later. These were very high priority
in these genome-sequencing projects. Once the genomes were sequenced, a lot
of people got interested. We went from being, in 1984, perhaps the only lab
in the US doing genetics and biochemistry on these fungi, to probably one
of 50 or 60 and now hundreds worldwide. It really has become huge.
How hard is it to keep up with 50 or 60 local
competitors when you used to have the field to yourself?
I try to work on unique aspects of the problem. In the last few years,
I’ve tried to work more in maize and Arabidopsis. It does
become more difficult when the field becomes so heavily populated. You
really need to be smart and you need to pick projects that are unique and
that other people aren’t working on.
What message would you like to give to the general
public about your research?
I’d have to say that it’s always important for us to stay
connected with the real world and particularly with the real world of
agriculture. As laboratory researchers, we have to remember who we
ultimately work for. And that’s sort of a mantra for the whole USDA.
We work for the public. We work for the agricultural industry. We wear two
hats and we have to keep that in mind. And we need to do this better than
we have. We can’t stay isolated in the research areas, where
we’re not interacting with the real needs of both the public and the
Anne E. Desjardins
Peoria, IL, USA
Desjardins's most-cited paper
with 91 cites to date:
Proctor RH, et al., "A polyketide synthase gene
required for biosynthesis of fumonisin mycotoxins in
Gibberella fujikori slating population A," Fungal
Genet. Biol. 27(1): 100-12, June 1999. Source:
Essential Science Indicators