Chemistry Defending Plants
Photo courtesy of the Canola Council of Canada
According
to Dr. Soledade C. Pedras, her greatest success and pride is in being able
to apply her passion for and knowledge of chemistry in the field of plant
biology (known as bio-organic chemistry). It is, in fact, an unusual
combination, but the spin-offs can be extremely beneficial for the field
of agriculture and in helping to solve the problem of famine in some parts
of the world.
After
obtaining a doctorate from the University of Alberta, Dr. Pedras pursued a
career at the NRC’s Plant Biotechnology Institute of Saskatoon. In 1994,
she was offered a position as Assistant Professor of
Chemistry at the University of Saskatchewan where she directs a
research team of approximately 10 graduate students, research associates,
and technician assistants. Dr. Pedras and her team are studying the
molecular and enzymatic defence reactions of plants to attacks by
pathogens. Her goal is to discover the chemical and biological strategies
that plants use to resist various toxins (often transmitted by microbes,
insects or other creatures) found in their natural environment. Once they
are well known and analysed, these particular defence strategies can be
transmitted to other plant species through traditional plant breeding or
modern genetic engineering.
The
following is a very concrete example of what is keeping Dr. Pedras busy at
present. Western Canada is known for the numerous agricultural species
under cultivation, including canola and mustard plants. Unfortunately,
these plants are subject to attacks from disease-causing micro-organisms
that release phytotoxins. Destruxin B is a phytotoxin produced in plants
attacked by the Alternaria blackspot microbe. However, a certain type of
white mustard, also attacked by micro-organisms, will not develop
Alternaria blackspot because it has developed a very effective defence
mechanism. And what Dr. Pedras has succeeded in discovering is this very
special defence mechanism.
To
discover the mechanism, she had to use modern chemical techniques. First,
HPLC (high-performance liquid chromatography) was used to analyse the
disappearance of destruxin B concentrations in white mustard plants. Dr.
Pedras then isolated the transformed destruxin B product, by separation
methods such as FCC (flash column chromatography). The crucial phase was
to determine the chemical structure and composition of the extracted
product, which was done through the application of NMR and HRMS techniques
(nuclear magnetic resonance and high-resolution mass spectroscopy). This
was how Dr. Pedras discovered that enzymatic protein was transforming the
destruxin B into an inoffensive HO-destruxin-B molecule. Using the same
chemical techniques, Dr. Pedras’ team succeeded in isolating and
characterising this enzyme.
In
the not too distant future, it will be possible to sequence this protein
and determine the gene that contains the code responsible for synthesizing
the enzyme. Through Dr. Pedras’ work and the collaboration with
molecular biologists, this coding gene can be used and introduced into the
gene pool of other species of plants (such as canola) to make them
resistant to Alternaria blackspot. Thus, through her research and
relentless work, Dr. Pedras will soon find the key to defending plants
through, environmentally friendly solution (eliminating insecticides and
fungicides) while increasing farmers’ harvest yields.
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