Biology
students interested in summer research at Williams--
To learn
about honors research opportunities, use the following resources:
á
Information
session with faculty Tuesday February 12 at 7:00 PM in TBL 112
á
Department
website: http://www.williams.edu/Biology/Research/Summer/summer.shtml
Application deadline is February 18th
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Faculty
accepting summer students for Summer 2008
Art, Banta, Edwards, Hutson, Lynch, Morales, and Ting
[descriptions of their
research are below; print copies of this info will be available at the Tuesday info session and outside the Biology Department Office TBL 219]
Hank Art
TBL 302 (Laboratory), TBL 203 (Office), x2461, hart@williams.edu
Vernal Pool Ecology
Adjacent to the Hopkins Memorial Forest are
two vernal pools (predator-free
shallow pools that are prone to drying-out during the summer) known to provide
breeding habitat for spotted salamanders, spring peepers, wood frogs, and the
rare JeffersonÕs salamander. Other
species of amphibians and reptiles use these pools as well. This project involves the monitoring of
drift fences and pitfall traps to determine the phenology, directions of
migrations, sex distributions, population structures, etc. of amphibians
utilizing these pools during their breeding seasons (starts in mid-March to
early April and continues for various species through the summer). The data for 2007 will be
compared with that collected in 2006 to determine the degree of fidelity in
migration patterns for spotted salamanders. Digital videos of the peak of the
salamander and wood frog mating season can be seen at: http://www.williams.edu/CES/hopkins/landscape/video.htm
Birch
Strips & Woodlots: The Impacts of Land Use on Forest Recovery
In
the Hopkins Forest there are two on-going observational experiments that
investigate the recovery of biotic communities following massive
disturbances. One of these sites
is the ÒFarm Forestry Unit,Ó a tract that was a 18th Century woodlot
that appears to have been clear-cut around the mid-19th Century and 
now
supports a magnificent red oak stand.
This tract has been periodically censused since 1947, the last time in
2001. The other site is the ÒBirch
Strips,Ó a field experiment initiated by the U.S. Forest Service in 1954 and
periodically inventoried, most recently in 1996. The Birch Strips were clear cut and soils treated
differentially in an attempt to regenerate paper birch. The reinventory and interpretation of
these two sites will give insights into how human disturbances of primary and
secondary woodlots influence community composition, biomass accumulation, and
carbon processing in Northeastern forests. The changes in these manipulated stands will be compared to
the changes evident in the old aged Beinecke Stand, which will also be
reinventoried.
Lois Banta
TBL301
(Laboratory), TBL213 (Office), x4330, lbanta@williams.edu
In the Banta lab, we study the
interactions between the soil bacterium Agrobacterium tumefaciens and its host plants. In particular, we are interested in the
transport of a large fragment of DNA across the membrane system surrounding the
bacterium, and in the plant defense responses elicited by the bacterium. Infection of susceptible plants by A.
tumefaciens results in
crown gall tumor formation. The
disease mechanism involves the transfer and integration into the plant genome
of a specific DNA molecule (T-DNA) from a bacterial tumor-inducing (Ti)
plasmid). Sequences on the T-DNA
encode enzymes responsible for the biosynthesis of plant growth hormones;
expression of these genes in the host plant leads to uncontrolled hormone
production and hence unregulated plant cell division ("plant
cancerÓ). This naturally occurring
process of DNA transfer to plants is widely used to introduce new genes into
plants, but its utility is limited by the fact that some plants, including the
agriculturally important grains rice, wheat, corn and barley, are poor
hosts. Thus, advances in our
understanding of the mechanism of DNA delivery, and in particular the
contributions made by bacterial proteins that are required for infection of
some but not all hosts, may further the work of those scientists engaged in
efforts to increase global food productivity.
T-DNA processing and transfer are
mediated by a number of Ti plasmid-encoded virulence (Vir) proteins. Movement of the T-DNA requires the
eleven products of the virB
operon, as well as the VirD4 protein.
The goal of our research is to probe the interactions between the
VirB/VirD4 pore and the transported substrates, which include not only the
T-DNA, but also at least five proteins. The substantial sequence homologies between
VirB proteins and the proteins required for pertussis toxin export (causing
whooping cough), as well as for pathogenicity in Helicobacter pylori (which causes stomach ulcers and can
lead to stomach cancer) and several other bacteria, indicate that our findings
regarding assembly of the VirB pore may have important implications for the
assembly and functioning of multi-protein transporters responsible for the
delivery of a variety of pathogenic substrates to mammalian host cells.
A major goal of my current research is to elucidate the functions of two virulence proteins, VirC1 and VirC2, which appear to enhance the efficiency of T-DNA delivery to the host plant. We postulate that VirC1 and VirC2 work together to tether the Ti plasmid, through VirC1Õs reported affinity for a sequence adjacent to the T-DNA, to the bacterial cell membrane. Such intimate association between the VirB/D4 transport apparatus and the Ti plasmid would ensure that, in the presence of an attached plant cell, the T-DNA could transit directly into the recipient cell. Maggie Lowenstein Õ07 and Oliver BurtonÕ06, together with lab technician Gape Machao Ô06 have been using biochemical and molecular approaches to confirm the key tenets of this hypothesis. The observation that the virC operon is required for virulence on some, but not all, host species has led us to hypothesize further that efficient delivery of T-DNA may be essential in overcoming the host defenses normally mounted by plants in response to Agrobacterium infection. Merritt Edlind Õ07 is currently exploring the defense responses in the model plant Arabidopsis and their role in determining the efficiency of the infection process. The ability of VirC1 and VirC2 to modulate host cell responses will be a possible subject of research for next yearÕs students. Finally, Ian Buchanan Õ07 has been using fluorescence and scanning electron microscopy to study the attachment of Agrobacteria to the host plant. The extracellular polysaccharides (EPS) that surround the bacteria appear to play a key role in attachment to the plant, and may also influence whether the bacterium is perceived by the plant as a threat. We have initiated a genomics project to investigate the assembly of this EPS and its contribution to host range, and future students will be able to pursue this topic.
Joan Edwards
TBL012 (Laboratory); TBL217 (Office);
x2472; jedwards@williams.edu
My
research covers three broad areas: the mechanisms and adaptive behavior of
ultra-rapid movements in plants, the adaptive significance of transparency in
the larvae of and insects and
long-term plant population dynamics.
Studies
of the adaptive behavior of ultra-rapid movements in plants focus on how plants
carry out rapid movements and why they behave this way. Much of this work is
done collaboratively with Prof. Dwight Whitaker in the Physics Department. Examples of study plants include a.)
bunchberry (Cornus canadensis), which we have discovered has the fastest blooming flower (opens
in <0.05ms!), b.) sphagnum moss (Sphagnum spp.) which has a
spore-filled capsule that explodes open propelling the spores over 15cm into
the air, c) fruit explosion in touch-me-not (Impatiens spp.), which use a
slingshot-lime mechanism to propel seeds away from the parent plant, d.)
catapulting pollen in gaywings (Polygala paucifolia), and stinging nettle (Urtica spp.). These studies involved using high-speed
cameras (filming at up to 30,000fps), microscopy (including SEM and EM), and
work in the field that focuses on understanding the plants in situ.
The
studies of the behavior of the sawfly, Empria obscurata, focus on determining their
life history characteristics and the adaptive significance of having larvae
that are transparent. These
remarkable larvae turn the color of whatever they eat so that they can remain
cryptically colored even when eating very different colored foods. So far, our
studies have shown that larvae that eat both flowers (yellow) and leaves
(green) have higher survivorship, achieve a larger adult size and develop more
quickly that larve fed on either flowers or leaves alone. The sawfly work will continue with life
history studies but also explore potential for speciation in Empria by host-shift.
The
long-term plant population studies currently focus on two species: a.) the
population growth and impact of the invasive plant, Alliaria petiolata (Garlic mustard) and the
growth, survivorship and reproduction of arctic plants which are growing at the
southern edge of their range on Isle Royale National Park, Lake Superior. For the Garlic Mustard study we just
completed the 8th year of observation of three sub-populations in early, mid-
and late successional sites. We
also are maintaining removal plots where we are measuring the impact of garlic
mustard on native plant populations.
For the arctic plant study we have permanently marked individuals of
arctic and non-arctic plants which we have followed since 1998. The artic plants are at the
southernmost edge of their ranges and are sub-populations that are most likely
to be impacted by global warming. We are measuring the changes in these
populations in response to changes in climate.
A summary of the projects include
working on:
- long-term studies of the invasive
garlic mustard populations in three different aged forest stands in
Hopkins Forest.
- long-term studies of arctic alpine
disjuncts at Isle Royale National Park.
- sawfly feeding behavior, host-shift
and evolution.
- ultra-high speed plant movements
(with special focus on Impatiens exploding fruit capsules and catapulting pollen/spores
in Polygala,
Urtica, and Sphagnum).
Lara Hutson
BSC 032 (Laboratory); TBL201 (Office);
x4508, lhutson@williams.edu
Our laboratory is interested how members
of the small heat shock protein family regulate embryonic development in the
zebrafish (Danio rerio).
Our primary focus is on how HSP27 regulates the migration of neuronal growth
cones, and thus overall wiring of the nervous system, by virtue of its ability
to regulate actin cytoskeletal dynamics. In addition, we are currently
beginning to test development of skeletal and smooth muscle development.
Ultimately, we plan to identify all sHSPs in the zebrafish (there are predicted
to be at least ten) and systematically analyze the function of each during
normal development and in protection from environmental stressors. The primary
techniques we use to explore these questions include molecular cloning (to
identify sHSP cDNAs), in situ hybridization (to examine mRNA expression
patterns), dye labeling (to fluorescently label growth cones in fixed and
living zebrafish embryos), immunohistochemistry (to analyze the consequences of
gene disruption), generation and analysis of transgenic zebrafish (to
misexpress sHSP gene variants in our tissue of choice), and confocal microscopy
(to image growth cones in intact embryos). For more information, and links to
timelapse movies of growth cones, please visit
https://www.williams.edu/Biology/Faculty_Staff/lhutson/lhutson.shtml.
Daniel Lynch
BSC
261 (Laboratory), BSC262 (Office), x2330, dlynch@williams.edu
Sphingolipids
have been demonstrated to play important roles as both membrane components and
as signaling molecules involved in regulating cellular processes in animals and
fungi. While sphingolipids are
quantitatively important components of specific plant membranes and recent
evidence points to sphingolipids serving as signaling molecules in plants,
surprisingly little is known about plant sphingolipid function. Research in the Lynch lab, funded by the
NSF 2010 program (to characterize all 26,000 genes in Arabidopsis thaliana) is focusing on the network
of genes predicted to be involved in plant sphingolipid metabolism. These genes will be identified and the
functions of the respective protein products of the genes (e.g., the specific
reaction catalyzed by the gene product, its substrate specificity, subcellular
location, expression and activity in tissues) will be determined. As
opportunities arise, the specific roles of different sphingolipids in plants
will be investigated by characterizing the properties and behavior of mutant
plants defective in specific sphingolipid metabolic genes and so incapable of
synthesizing a given sphingolipid.
These various projects will involve aspects of molecular biology and
biochemistry (including lipid analysis and assays of enzyme activities) in
addition to others.
Manuel
Morales
TBL 011 (Laboratory); TBL215
(Office); x2983, mmorales@williams.edu
Research in my lab focuses on
understanding the population dynamics of insect-plant interactions, especially
mutualism. Summer research projects and theses are typically field based.
Currently, my research explores aspects of the mutualism between ants and
treehoppers, an insect that feed on goldenrod plants. In this interaction, ants
collect the sugar-rich excretions ("honeydew") of treehoppers in
return for protecting treehoppers from predators and pathogens.
The main research projects
this summer will be a study exploring the role of mutualism with treehoppers on
the spread of an invasive ant recently discovered in Williamstown, and the
analysis of vibrational communication between ants and treehoppers. This
research will take place at Hopkins Memorial Forest as well as field sites
bordering the Hoosic River throughout NY, VT, and MA.
More detailed information on
my research (including study system) can be
accessed from my web site (http://mutualism.williams.edu)
Claire Ting
TBL 023 (Laboratory); TBL 214 (Office), x4053, cting@williams.edu
Photosynthesis is a fundamental biological process upon which the majority of Earth's life depends. Research in my laboratory focuses on photosynthetic processes and proteins and on the response of photosynthetic organisms to environmental stress. Projects are interdisciplinary in nature and integrate tools and concepts from fields including biochemistry, cell biology, genomics, ecology, and evolution.
One area we are addressing is how differences
at the genome level between closely related photosynthetic organisms translate
into selective physiological advantages in photosynthetic capacity and in
tolerance to abiotic stress. For this project, we are focusing on the
environmentally important marine cyanobacteria, Prochlorococcus and Synechococcus. These cyanobacteria are the most abundant
photosynthetic prokaryotes in the world's oceans, and in certain regions, more
than 10,000 cells can be found in a single drop of sea water. In
particular, Prochlorococcus plays a
key role in marine primary production and in global energy cycles, and because
it evolves oxygen and possesses a chlorophyll a/b light-harvesting antenna complex, it is an excellent
model for plant photosynthesis. In recognition of their ecological
significance, the complete genomes of several Prochlorococcus and Synechococcus strains have been sequenced recently. We have used
our comparative genomic analyses and genome-based predictions as the foundation
for our laboratory experiments examining photosynthesis and stress response
mechanisms. Although Prochlorococcus
is closely related to marine Synechococcus, it has evolved striking differences in its photosynthetic apparatus
and biological responses to major environmental factors, including temperature
and light.