expression in natural populations of Andropogon
bluestem (Andropogon gerardii) is one of the most abundant and ecologically
important plant species in tallgrass prairie.
Predicted changes in precipitation patterns in the Great Plains will
affect big bluestem directly and indirectly through its effects on the
pathogens of big bluestem, their vectors, and competing plant species.
Rust fungi can substantially reduce plant productivity and commonly
infect big bluestem in tallgrass prairie; rust fungi benefit from higher
humidity and lengthier periods of leaf surface wetness.
Barley yellow dwarf virus (BYDV) can also cause important losses in
plant productivity and we have found it more common in big bluestem at Konza
Prairie Biological Station in areas with higher levels of drought stress.
Both positive and negative interactions between rust fungi and plant
viruses have been reported.
first step, we compared gene expression between big bluestem plants exposed
to two experimental treatments in a field setting: ambient water
availability and delayed water availability associated with climate change
predictions for the Great Plains. Using a microarray chip with over 12,000
individual genes developed for corn, we were able to assess the up and
down-regulation of big bluestem genes in response to delayed water
availability. Analysis of a total of thirteen pairs of plants from the two
treatments resulted in the hybridization of over 2000 cDNAs from bluestem of
sufficient intensity that it was possible to assess the response of
expression to treatment. Differential gene expression ranged enormously
across up and down regulation. Assessment of the functional groups of genes
that were most consistently up-regulating indicated that many genes related
to the photosynthesis process (e.g. chlorophylly binding proteins) and
chloroplast functioning were turned on in response to delayed water
availability. This is in contrast to earlier physiological measurements
which indicate that production and photosynthetic activity is lower for
plants in the delayed treatments. As such, our results may indicate a
disconnect between the expression of the genes and the final products of
photosynthesis. Our results also indicate a handful of enzymes unrelated to
photosynthesis that may be interesting loci for future studies of selection
and adaptation to changing environments.
have also begun an experiment to determine the effects of burning frequency
and topography on the population genetic structure of big bluestem.
We have identified amplified fragment length polymorphism markers for
use in characterizing the populations of big bluestem for comparison.
Garrett, K.A., L.V. Madden, G. Hughes, and W.F. Pfender (2004). New applications of statistical tools in plant pathology. Phytopathology 94:999-1003.
Monosi, B., Wisser R. J., Pennill, L. and S.H. Hulbert (2004). Full-Genome analysis of resistance gene homologs in rice. Theor. Appl. Genet. 109:1434-1447.