Welcome to the Lab
of Dr. John M. Burke
Department of Plant Biology
– University of Georgia
– Athens, GA
Our main focus is plant evolutionary genetics and genomics.
More specifically, we're studying the genetic basis of
evolutionary divergence within the sunflower family (i.e.,
the Compositae or the Asteraceae). We also maintain an
interest in the ecological and evolutionary impact of
transgene escape from genetically modified crops into their
wild relatives. What follows is a brief overview of our
work...
Evolution
Under Domestication:
The domestication of crop plants typically involves rapid and
dramatic phenotypic evolution in response to strong
selection. Research in our lab is aimed at understanding the
genetic basis of such evolutionary transitions using
sunflower (
Helianthus annuus) as a model system. We
are taking a genetic map-based approach in order to localize
regions of the genome that harbor genes controlling
domestication-related traits, and are also hunting for genes
that bear the population genetic 'signature of selection,' as
such genes are especially likely to be of evolutionary and
agronomic interest. We are also developing the resources
necessary for similar studies in safflower (
Carthamus
tinctorius).
Reducing the
Risks of Transgene Escape:
The commercial introduction of genetically modified crop
plants makes possible the evolution of increasingly weedy or
invasive wild plants (so-called "superweeds") following
transgene escape via hybridization. A number of methods of
mitigating the risks associated with transgene escape have
been proposed. We are investigating the utility of one such
strategy: the placement of transgenes in close proximity to
genes at which the cultivar alleles are negatively selected
in the wild. Assuming that such genes are sufficiently
negatively selected, they should offset the advantages
provided by a given transgene, thus slowing (or stopping) its
spread.
The Genetics
of Speciation:
The genus
Stephanomeria contains three especially
interesting cases of speciation. The first is the derivation
of
S. malheurensis from
S. exigua. This
speciation event seemingly occurred in sympatry, running
counter to the classical view of how species form. The second
involves the origin of
S. diegensis, which is a
diploid hybrid species formed following hybridization between
S. exigua and
S. virgata. We are currently
developing the molecular tools necessary to map the genomes
of these species as part of our ongoing efforts to: (1)
investigate patterns of chromosomal evolution across the
genus, and (2) genetically map the reproductive barriers
distinguishing these species. Finally, we are investigating
the origin and evolution of the allopolyploid
S.
elata which, like
S. diegensis, arose following
hybridization between
S. exigua and
S.
virgata.