Could Oklahoma Crops Stimulate Witchweed Germination?
Mylissa Stover
10/31/2015
Fall Semester 2015
BIOC 6020: Mass Spec/Proteomics
Could Oklahoma Crops Stimulate Witchweed Germination? M. Stover Final Draft
Specific Aims
Africa loses $10 billion in crops annually to the parasitic plant Striga hermointhica or
witchweed. This plant has caused crop devastation in the Carolinas, so Oklahoma should be
prepared for possible infestation. Witchweed germinates in the presence of hormones called
strigolactones released into the soil by host plants. Oklahoma crops can release strigolactones
into the soil to attract mycorrhizae. Witchweed can detect up to 16 different strigolactones, and
also detect down to picomolar concentrations. After germinating it attaches to host plants’ roots
to drain nutrients. This occurs before witchweed breaks through topsoil. Each plant can produce
100,000 seeds that can lay dormant in soils for decades. Because we do not know if Oklahoma is
at risk of witchweed invasion, it is important to determine if Oklahoma crops produce the same
molecules that stimulate witchweed germination.
Our long-term goal is to determine if Oklahoma crops could germinate witchweed. Our
current objective is to identify the strigolactones produced by Oklahoma crops that stimulate
witchweed germination. Our mechanistic hypothesis is, Oklahoma crops produce hormones that
stimulate witchweed germination and could become potential host plants. Our hypothesis derives
from observations that host crops affected in the Carolinas are similar to Oklahoma crops in their
genus and specie. We are uniquely poised to address these questions because we have the best
triple quad MS in the country and access to the most extensive strigolactone library.
Specific Aim #1: Identify strigolactones produced by major Oklahoma crops.
The mechanistic hypothesis for this aim is that Oklahoma crops express strigolactones
that could stimulate witchweed germination. To test this hypothesis we will culture root tissues
of major Oklahoma crops and isolate the hormones expressed through HPLC. Mass spectrometry
will be used to identify the strigolactones present. We predict that Oklahoma crops will produce
known strigolactones. Results from this aim will reveal if Oklahoma crops have the potential to
stimulate witchweed germination and validate future studies.
Specific Aim #2: Compare Oklahoma crop strigolactones with a biorepository.
The mechanistic hypothesis for this aim is that strigolactones expressed in Oklahoma
crops have no significant difference to those found in the Hartson’s Institute of Little Green
Martians (HILGM) biorepository. To test this hypothesis we will compare the mass spectrometry
data from Oklahoma crops to that of the biorepository. We predict that strigolactones detected in
Oklahoma crops are no different than those in the biorepository. Results from this aim will
determine if Oklahoma crops produce strigolactones that are known.
Specific aim #3: Determine if Oklahoma crops are a potential host for witchweed.
The mechanistic hypothesis for this aim is that strigolactones expressed in Oklahoma
crops could be witchweed germination stimulators. To test this hypothesis we will compare the
abundance of strigolactones measured by mass spectrometry to known levels of strigolactones
that stimulate germination. We predict that the levels of strigolactones produced from tissue
culture are adequate for witchweed germination. Results from this aim will determine whether or
not further research and precautions should be made to protect crops from potential infestation.
Strigolactone production abundance and identity of African crops is known, but in
Oklahoma crops is unknown. Immediate payoffs would be the identification of strigolactones
produced by Oklahoma crops and whether or not they could germinate witchweed.
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Could Oklahoma Crops Stimulate Witchweed Germination? M. Stover Final Draft
Significance
It is crucial for the economy of Oklahoma to know if witchweed could be germinated by
their crops. Knowing could help prevent hunger and recession due to crop devastation.
According to Elizabeth Pennisi of Science journal, witchweed germination is activated by certain
strigolactones produced by potential host plants. Some of the crops most affected by witchweed
include corn, millet, rice, sorghum, and other cereals. Wheat, corn, sorghum, soybeans, and
cotton are the top producing crops in Oklahoma. Because these crops are similar to the ones
infested by witchweed in other places it is important to know if they are similar on the
strigolactone level.
Experimental Design
Our objective is to characterize strigolactone expression in Oklahoma crops and
determine if they could stimulate witchweed germination. Our mechanistic hypothesis is,
Oklahoma crops produce strigolactones that stimulate witchweed germination. Our approach will
be to grow major Oklahoma crops in a lab and measure abundance of strigolactones. Then we
will compare those strigolactones with a databank of known witchweed germination stimulators.
We anticipate that Oklahoma crops will produce strigolactones that stimulate witchweed
germination.
Technical Details
Tissues of corn, sorghum, cotton, and wheat acquired from Oklahoma State University
Extension will be cultured on appropriate media until roots differentiate and start producing
hormones. Hormones will be isolated and purified with HPLC using a 2mm C18 column and 30
minute methanol mobile phase. HPLC will be connected to a triple sector quadrupole to isolate
qualifying ions. We will measure concentrations of strigolactones using electrospray with MS
SIM, and confirm the metabolite identities using MS SRM. Ion Mz’s will then be compared to
fragment Mz’s and standard curves provided by the molecular libraries from HILGM
biorepository.
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Could Oklahoma Crops Stimulate Witchweed Germination? M. Stover Final Draft
Abstract/Summary
Knowing how susceptible Oklahoma is to crop devastation by witchweed could aid in
preventing nationwide [maybe even world] hunger and economic collapse. There are known
strigolactones that stimulate witchweed germination. The strigolactones expressed by Oklahoma
crops are currently unknown. We hypothesize that Oklahoma crops produce known
strigolactones. We will assay for strigolactones expressed by Oklahoma crops and measure their
abundance. We will then see whether Oklahoma crops could germinate witchweed. The payoff
of this research would provide reason to take precautions against possible witchweed infestation
and lead to further research on witchweed prevention.
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