John Doebley
University of Wisconsin
Current Research Activities: Research in my laboratory is focused on
the genetics of morphological evolution in plants (Doebley and Lukens
1998). In our research, we use maize and its relatives as a model system.
Our main interest is in understanding the genetic events responsible for
the domestication of maize from its ancestor, teosinte. Other projects
examine the genetic basis of morphological differences between natural
species of teosinte. We are examining the genetics of differences in tassel
morphology between Zea diploperennis and Zea mays ssp. parviglumis, and
differences in pigmentation (anthocyanin) and trichome density between
Zea mays ssp. mexicana and Zea mays ssp. parviglumis. Because the differences
between the taxa analyzed are quantitative and under the control of multiple
genes, we have used quantitative trait locus (QTL) mapping as the starting
point for each project (Doebley 1992). While most traits are controlled
by five to ten QTL, there have usually been one or two QTL of large effect
for any single trait. We have chosen these major QTL for more detailed
analyses. One of these is teosinte glume architecture (tga1), which controls
the formation of the cupulate fruitcase in teosinte (Dorweiler et al.
1995). During maize domestication, tga1 was altered so that the fruitcase
of maize no longer forms a hardened shell around each kernel (Dorweiler
and Doebley 1997). A second major QTL on which we have focused is teosinte
branched (tb1) (Doebley et al. 1995). tb1 is controls plant architecture:
maize with its short lateral branches vs. teosinte with its long lateral
branches. My lab cloned tb1 and found that it shares homology with cycloidea
(cyc) of snapdragon (Doebley et al. 1997). In collaboration with Enrico
Coen's group, we have established that tb1 and cyc belong to a family
of putative bHLH transcription factors that regulate plant organ growth
(Cubas et al. 1999).
My laboratory is also interested in understanding how selection, recombination
and polyploidy have shaped the maize genome. Brandon Gaut and I examined
the molecular evolution of duplicated genes in the maize genome and inferred
from the pattern of sequence divergence among them that maize arose as
a segmental allotetraploid (Gaut and Doebley 1997). More recently, my
colleagues at North Carolina State University, the University of California-Irvine,
Cornell University and I have formed a group to study the evolution of
the maize genome and to exploit this knowledge to better understand how
individual genes control agronomic traits. The primary role of my lab
in this project is to look at diversity in microsatellites. By this approach,
we will establish whether some regions of the maize genome have more diversity
than others and assess the impact of drift and selection during domestication.
Similarly, we will measure diversity for different geographic segments
of the maize germplasm pool and assess how drift, selection and migration
have influenced diversity.
Relationship to the Proposed Project: My laboratory has benefited enormously
over the past decade from collaborations with both developmental and population
geneticists. This proposal will help us maintain this type of interaction
but also allow us to expand our interactions to include systematists and
genomicists. I am particularly interested in interactions with labs taking
whole genome approaches for the analysis of gene expression, labs with
expertise in positional cloning and labs with a broad knowledge of plant
diversity. Through these interactions, we can begin to study how QTL alter
genome wide patterns of gene expression, improve our capabilities for
QTL cloning, and begin to study the role of maize genes (QTL) in controlling
phenotypes in other plant groups. The students and postdoctoral scientists
in my lab will particularly benefit from attending group meetings, visits
to other labs in the group, and participation in workshops.
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