PROPOSAL: HUGHES SUMMER RESEARCH OPPORTUNITIES
HEATHER RISSLER, VISITING ASSISTANT PROFESSOR OF BIOLOGY
My primary research interest in photosynthesis is due to my appreciation for the variety of disciplines
this field of research encompasses, beginning at the atomic level and extending to whole ecosystems.
More specifically, I am interested in the balancing act that occurs between light harvesting and
photoprotection and the evolutionary history of these processes in photosynthetic eukaryotes. The
intricate balance between these two light-driven processes includes both immediate responses that are
independent of changes in gene expression, such as adjustments in light harvesting antennae
architecture and accumulation of photoprotective pigments, and longer-term responses that require
changes in gene expression and cross talk between the nucleus, plastid, and mitochondria.
My research goals encompass two lines of inquiry that investigate the balance between light harvesting
and photoprotection. By developing an active research program, I endeavour to advance research in
these areas and to provide a training platform for undergraduates who are interested in exploring
research-based laboratory work or who desire preparation in specific techniques for their graduate
studies. I am dedicated to providing a positive research experience for undergraduate students and I am
particularly interested in working with students that are underrepresented in the sciences. Throughout
my graduate and post-doctoral work, I worked consistently to promote science literacy through
community outreach and collaborations with science education reform groups. I am experientially
aware of the undergraduate research goals set forth by HHMI and support these goals in my research
program.
Several Carleton students (including Jessica Postlethwaite, Stephanie Contag, Jason Martin, and Joe
Osmundson) have worked with me on independent research projects during Fall and Winter term, and I
anticipate that two students will be doing independent research in my lab during Spring term. As a
Visiting Professor, I do not have external funding to support student research this summer. In order to
continue providing Carleton students with a stimulating research experience, I would like to request
that two students be funded for summer research in my lab through the HHMI grant. The students will
work on one of the following projects:
 Evolution of pigment binding capacity and plasticity in the LHC superfamily of proteins
Genomic and EST sequencing efforts have provided a wealth of opportunities for examining the
evolution of light harvesting antennae function. Elucidating the structure and function of diverse
antennae proteins completes a critical step towards the development and implementation of artificial
antennae for nanotechnology and biotechnology applications. Recombinant light-harvesting complex
proteins (LHCs) from diverse photosynthetic eukaryotes can be generated using publicly available
sequence data. My research blends traditional biochemical and biophysical approaches with molecular
homology modeling studies in order to probe the impact of changes in amino acid sequence on
pigment binding capacity and spectral tuning properties in LHCs from diverse photosynthetic
eukaryotes. To further address the evolution of LHC function we will examine rapid, stress-induced
changes in the macro-organization of light harvesting antennae from diverse photosynthetic organisms
using traditional biochemical and biophysical analyses, including non-denaturing gel electrophoresis
and confocal microscopy. Since antennae proteins serve as molecular markers for photosynthetic
microbes, an additional component of this project involves the development of techniques that can be
used in biomonitoring of ecosystem diversity. This project will provide an undergraduate research
experience that includes training in molecular biology, environmental microbiology, bioinformatics,
biochemistry, genomics, plant physiology, and biophysics.
 Interpreting intracellular signalling pathways in eukaryotes using Euglena gracilis as a model
organism
Progress is rapidly being made towards deciphering cross talk between organelle and nuclear genomes
in higher plants and yeast. However, given that the plastid of E. gracilis arose from a secondary
endosymbiotic event, I predict that such pathways may be quite different in this organism.
Furthermore, since E. gracilis possesses a fully competent tetrapyrrole biosynthetic pathway in both
the mitochondria and plastid, it provides an excellent system for teasing apart the potential role of
chlorophyll intermediates, heme, and bioenergetic pathways in mediating intracellular signal
transduction. Traditional studies using inhibitors that target potential signals for these pathways will be
continued in an effort to characterize the mechanism of organelle-nuclear genome signalling in
complex plastids. Specific genes have been identified in Arabidopsis that are important components of
the chloroplast-nuclear signal transduction cascade. The technique of RNA interference (RNAi) will be
used to reduce expression of homologues for these genes in E. gracilis in order to compare signalling
pathways in plastids that arose from a primary versus secondary endosymbiotic event. This project will
provide an undergraduate research experience that includes training in molecular genetics, cell
biology, and stress physiology.