Jonathan Monroe: Professor
B.S. - University of Michigan
Ph.D. - Cornell University
Phone - 540-568-6649
Fax - 540-568-3333
Office - Bioscience 3028B
Courses: Protein Structure and Function (BIO 426), Plant Physiology (455/555)
Research Interests: Plant Biochemistry and Molecular Biology.
We use the tools of molecular biology, genetics, and biochemistry to try to understand the physiological functions of some of the nine beta-amylase (BAM) genes in the model plant Arabidopsis thaliana. Beta-amylases are enzymes that hydrolyze starch in chloroplasts forming the disaccharide maltose. Starch, the primary storage form of sugar in plants, accumulates in chloroplasts each day and is degraded at night to fuel metabolism when there is no sunlight. We use two complementary approaches to investigate these proteins: mutant plants that are missing one or more of the BAM genes, and purified BAM proteins that we express in bacteria.
Only four of the nine BAM proteins are catalytically active and targeted to chloroplasts. We are characterizing the properties and expression patterns of these four proteins to understand their specific roles. Of the remaining five, one is active but being cytosolic its function is still a mystery. Two of the inactive BAMs that are located in chloroplasts probably play regulatory roles but little is known about how and what they do. We discovered that the remaining pair of BAMs are targeted to the nucleus where they act as transcription factors regulating the expression of other genes. In addition to wet-lab experiments we also use sequence alignments to identify uniquely conserved amino acids, and map them on 3D models of the proteins to predict unique features of each protein.
Besides learning more about how plants function, what we learn may also benefit humanity because starch is a fundamental component of our diet, a potential biofuel, and a raw material for many industrial applications.
*undergraduate co-author
Storm A, Kohler M*, Berndsen C, Monroe J. (2018) Glutathionylation Inhibits the Catalytic Activity of Arabidopsis β‑Amylase3 but Not That of Paralog β‑Amylase1. Biochemistry. http://dx.doi.org/10.1021/acs.
Monroe, J.D., J.S. Breault*, L.E. Pope*, C.E. Torres*, T.B. Gebrejesus*, C.E. Berndsen, and A.R. Storm (2017) Arabidopsis β-amylase2 is a K+-requiring, catalytic tetramer with sigmoidal kinetics. Plant Physiology, DOI: https://doi.org/10.1104/pp.17.
Seung D, Boudet J, Monroe J, Schreier TB, David L, Abt M, Lu K-J, Zanella M, Zeeman SC (2017) Homologs of PROTEIN TARGETING TO STARCH control starch granule initiation in Arabidopsis leaves. The Plant Cell 29: 1657–1677.
Monroe, J.D., A.R. Storm, E.M. Badley*, M.D. Lehman*, S.M. Platt*, L.K. Saunders*, J.M. Schmitz*, and C.E. Torres* (2014) β-Amylase1 and β-amylase3 are plastidic starch hydrolases in Arabidopsis that appear to be adapted for different thermal, pH, and stress conditions. Plant Physiology, 166: 1748–1763.
Reinhold, H., S. Soyk, K. Simkova, C. Hostettler, J. Marafino*, S. Mainiero*, C.K. Vaughan, J.D. Monroe and S.C. Zeeman (2011) Beta-amylase-like proteins function as transcription factors in Arabidopsis, controlling shoot growth and development. The Plant Cell, 23: 1391-403.
Temple, L., Cresawn, S., and Monroe. J. (2010) Genomics and Bioinformatics in undergraduate curricula: Contexts for hybrid lab/lecture courses for entering and advanced science students. Biochemistry and Molecular Biology Education. 38: 23-28.
Doyle, E.A., A.M. Lane*, J.M. Sides*. M.B. Mudgett, and J.D. Monroe. (2007) An α-amylase (At4g25000) in Arabidopsis leaves is secreted and induced by biotic and abiotic stress. Plant Cell and Environment 30: 388–398.
Monroe, J.D., M.L. Garcia-Cazarin, K.A. Poliquin*, and S.K. Aivano* (2003) Antisense Arabidopsis plants indicate that apoplastic α−glucosidase has α−xylosidase activity. Plant Physiology and Biochemistry 41: 877-885.
Monroe, J.D., C.M. Gough, L.E. Chandler*, C.M. Loch*, J.E. Ferrante*, and P.W. Wright* (1999) Structure, properties, and tissue localization of apoplastic α-glucosidase in crucifers. Plant Physiology, 119: 385-397.
