Ph.D. Biological Sciences
1998, Dartmouth College
Research Focus Areas
Atmospheric nitrogen makes up over 70% of the air around us, but is unavailable to living organisms until it is reduced ("fixed") by certain bacteria. Legumes set up a symbiosis with some of these bacteria, supplying carbon to the bacteria while the bacteria fix nitrogen from the air for the plant inside special plant structures called nodules. Since legumes provide 33% of human nutrition in the world, a more detailed understanding of nodule development and the plant control of nodulation would benefit agricultural production, both in legumes and other plants. My lab focuses on molecular genetics in the legume model system Medicago truncatula to identify the plant genes involved in nodule number regulation and construct a signal transduction pathway for this process. Interestingly, many of the genes involved plant control of nodulation are genes involved in general plant growth and development, and especially in long distance signaling between the roots and shoots of plants.
We have identified several mutants that make too many nodules and are currently funded by the NSF to clone the genes and construct the pathway. For example, our sunn mutant, a mutation in a leucine-rich-repeat receptor kinase, makes 7-10-fold more nodules than wild type plants. Grafting experiments with sunn mutants have shown that the signal regulating nodule number occurs in the shoot and we are currently undertaking an immunoprecipitation approach to identifying SUNN interacting partners. A putative epigenetic silencer of SUNN, termed lss, is another mutant in the lab that has lead to experiments investigating genome organization, while a recently cloned root controlled nodule number mutant rdn encodes a conserved protein of unknown function; we are using cell biology and genetics to characterize this previously unknown gene family conserved in all green plants. We have other mutants that make too many nodules awaiting characterization, and several suppressors of the sunn mutation. We have begun to order the genes into a pathway regulating nodule development based on grafting experiments, auxin measurements, expression and epistasis analysis.
One of the components of our model is the plant hormone auxin: we are also interested in the role of auxin in nodulation. The sunn mutant has an increase in auxin flux between the shoot and root, which may account for the supernodulation phenotype.
I have a professional interest in research ethics, specifically the encouragement and transmission of ethical research practices (often called "best practices") to graduate students, and the definition of these practices. To that end, I interact frequently with Clemson's Rutland Institute for Ethics and Clemson’s Office of Research Integrity.
National Science Foundation
How Does the Plant Say No More?: A Molecular Genetic Approach to Nodule Number Regulation
2015 Alumni Distinguished Professor
2010 College of Engineering & Science Dean’s Mentorship Award
2008 Clemson Chapter of Sigma Xi, Young Investigator of the Year
2007 College of Agriculture, Forestry & Life Science Undergraduate Teacher of the Year
Fundamental of Genetics II
Fundamentals of Genetics II lab
Issues in Research
Kassaw, T., Schnabel, E., Bridges, W. and Frugoli, J. (2015) Multiple autoregulation of nodulation (AON) signals identified through split root analysis of M. truncatula sunn and rdn1 mutants, Plants 4:209-224.
Kassaw, T. and Frugoli, J. (2013) Journey to Nodule Formation: From Molecular Dialogue to Nitrogen Fixation, Symbiotic Endophytes, R. Aroca, ed, Springer Soil Biology series Vol 37 pp 3-24.
Kassaw, T. and Frugoli, J, (2012) Simple and efficient methods to generate split roots and grafted plants useful for long-distance signaling studies in Medicago truncatula and other small plants, Plant Methods, 8:38
Schnabel, E., Karve, A., Kassaw, T., Mukherjee, A., Zhou, X. , Hall, T., and Frugoli, J. (2012) The M. truncatula SUNN gene is expressed in vascular tissue, similarly to RDN1, consistent with the role of these nodulation regulation genes in long distance signaling, Plant Signaling and Behavior, 7:1-3.
Schnabel, E., Kassaw,T. Smith,L. Marsh, J., Oldroyd ,G., Long ,S. and Frugoli, J. (2011) ROOT DETERMINED NODULATION 1 regulates nodule number in M. truncatula and defines a highly conserved, uncharacterized plant gene family, Plant Physiology 157:328-340.
Schnabel, E., Smith, C., Long, S. and Frugoli, J. (2010) Transcript profiling in M. truncatula lss and sunn-1 mutants reveals different expression profiles despite disrupted SUNN gene function in both mutants, Plant Signaling and Behavior 5:1657-1659.
Schnabel, E., Mukherjee, A., Smith, L. Kassaw, T. Long, S. and Frugoli, J. (2010) The lss supernodulation mutant of Medicago truncatula reduces expression of the SUNN gene, Plant Physiology 154:1390-1402.
Frugoli, J., Etgen, A. M. and Kuhar, M. (2010) Developing and Communicating Responsible Data Management Policies to Trainees and Colleagues, Science & Engineering Ethics, 16:753-762.
Ané, J.M., Zhu, H., and Frugoli, J. (2008) Recent advances in Medicago truncatula genomics, International Journal of Plant Genomics, Vol 2008, Article ID 256597, doi:10.1155/2008/256597.
Frugoli, J. (2008) Medicago truncatula as a model plant in Plant Molecular Biology, in Handbook of New Technologies for Genetic Improvement of Legumes, P.B. Kirti, ed., the Haworth Press, New York pp 339-352.