|
Professor of Plant Biology
Department of Plant Biology Plant Biology Department |
 |
Research
What can we learn from early divergences on the eukaryotic tree of life using molecular phylogenetics and genomics?
My research focuses on some of the most ancient, distinctive, free-living eukaryotic protists, the Euglenophyta. Euglena was one of the first protists ever seen by Leeuwenhoek, but despite this early discovery, the vast majority of euglenoids are poorly known even among biologists who regularly encounter them in a multitude of environments. Euglenoids are critically positioned near the base of the eukaryotic evolutionary tree and are among the first eukaryotes to possess a mitochondrion. Research in my lab focuses on two aspects of euglenoid biology.
The first project is a modern monographic study of the Euglenophyta. We have surveyed the diversity of freshwater and marine euglenoids along the east coast of the U.S. and are now focusing on the wetlands of Michigan. Along with our field work we study the systematics and phylogeny of the euglenoids using a combined morphological, behavioral and molecular approach. We utilize light and electron microscopy to examine the organization of the flagellar apparatus, patterns of mitosis and cytokinesis, the structure of the cell surface and the construction of the feeding apparatus. From these studies we extract morphological characters which are used in phylogenetic studies. Behavioral characteristics such as response of the organisms to light and mode of swimming are recorded using video microscopy and are incorporated as phylogenetic characters. Another major effort of this research generates molecular data from ribosomal and protein coding genes. Because of its highly conserved nature, rDNA can be used effectively to infer phylogenetic relationships among organisms ranging from prokaryotes to man and we have concentrated on these genes. Data from the combined morphological, behavioral and molecular studies are used to deduce phylogenies which provide the basis for revising the systematics of the Euglenophyta.
The second project is designed to understand the origin and evolution of the euglenoid chloroplast. We are sequencing complete chloroplast genomes from three diverse photosynthetic euglenoids, and their most closely related colorless sister taxa which are believed to have independently lost their ability to photosynthesize. This will be followed up first with comparative genomics among the three pairs of euglenoid sister taxa (photosynthetic and non-photosynthetic), and second, by comparing euglenoid genomes with those of potential green algal chloroplast donor taxa. These data will address five primary questions:
1) What was the green algal lineage that provided the euglenoid chloroplast via endosymbiosis? 2) Was the acquisition of chloroplasts by euglenoids a single event or did it occur multiple times? 3) Are plastid genomes of photosynthetic euglenoids lineages collinear or do they have different gene rearrangements? 4) How has loss of photosynthesis occurred? What genes have been lost? Are the plastid genomes of colorless taxa collinear with their colored counterparts? With each other? and, 5) Do the plastid genomes show signs of gene transfer, reshuffling or reduction? Answering these questions will enable a better understanding of both the nature of endosymbiosis and chloroplast gene loss, when photosynthesis is lost independently multiple times within a single lineage. Moreover, within this single lineage we can track the transfer and reshuffling of plastid genes across three distinct genera of ancient eukaryotes. Consequently, we will be examining some of the basic mechanisms (genome acquisition and gene transfer) of endosymbiosis during the formation of early diverging eukaryotic organisms.
For additional information visit the Euglenoid Project Website at:
1. Triemer, R.E. and Farmer, M.A. (2007). A decade of euglenoid molecular phylogenetics.In:unravelling the algae: the past, present and future of algal systematics. (Brodie, J. & Lewis, J. eds). Systematics Association Series, CRC Press.
2. Triemer, R. E., Linton, E., Shin, W., Nudelman, A., Monfils, A., Bennett, M. and Brosnan, S. 2006. Phylogeny of the Euglenales based upon combined SSU and LSU rDNA sequence comparisons and description of Discoplastis gen. nov. (Euglenophyta) J. Phycol. 42:731-740.
3. Nudelman, M. A., Leonardi, P.I., Conforti, V. and Triemer, R. E. 2006. Fine Structure and Taxonomy of Monomorphina Aenigmatica comb. nov. (Euglenophyta). J. Phycol. 42:194-202.
4. Brosnan, S., Brown, P.J.P., Farmer, M.A. and Triemer, R. E. 2005. Morphological Separation of the Euglenoid Genera Trachelomonas and Strombomonas (Euglenophyta) Based on Lorica Development and Posterior Strip Reduction. J. Phycol. 41:590-605.
The Euglenoid Project II: Restructuring Phylogeny and Taxonomy. Systematic Biology Section, Special PEET competition (Partnership for Enhanced Expertise in Taxonomy)
The Euglenoid Project II: Restructuring Phylogeny and Taxonomy. Systematic Biology Section, Special PEET competition (Partnership for Enhanced Expertise in Taxonomy), National Science Foundation, Research Experiences for Undergraduates Supplement
Development of Teaching Modules Using Euglenoids as Model Systems. National Science Foundation Research Experience for Teachers Supplement.
Analyzing the Euglenoid Plastid Genome. NSF Microbial Genomics.
Current Lab Members
Matthew Bennett-Laboratory supervisor
Ionel Ciugulea-Postdoctoral fellow
Former Lab Members
Alejandra Nudelman -Postdoctoral fellow
Anna Monfils -Postdoctoral fellow
Eric Linton -Postdoctoral fellow
Lisa Weise - Visiting Teacher, Holt High School
