A-to-Z Index

Jonathan Monroe

Jonathan Monroe

Professor of Biology

B.S. - University of Michigan
Ph.D. - Cornell University


E-mail - monroejd@jmu.edu
Phone - 540-568-6649
Fax - 540-568-3333
Office - Bioscience 3028B

Office Hours

Courses:   Cell and Molecular Biology (214), Plant Biology (BIO 360), Plant Physiology (455/555)

Research Interests:  Plant Biochemistry and Molecular Biology.

 

We study several of the nine b-amylase (BAM) genes in the model plant Arabidopsis thaliana. These
enzymes hydrolyze starch 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. Starch-degrading enzymes must therefore be catalytically active and located in these organelles
to function as starch hydrolases. We’ re curious about several BAM proteins that are either catalytically
inactive or are not located in chloroplasts, or both. The primary question is what are they doing? By
fusing BAM coding sequences to GFP and transforming Arabidopsis plants with these gene constructs,
we discovered that two of the BAMs are targeted to the nucleus where they act as transcription factors
regulating the expression of other genes. How and why they do this is currently under investigation. A
different BAM protein is in the chloroplasts but isn’ t active. We use two, complementary approaches to
investigate these proteins; mutant plants that are missing one or more BAM proteins, and purified BAM
proteins expressed in bacteria. Besides learning more about how plants work, 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.
We study several of the nine beta-amylase (BAM) genes in the model plant Arabidopsis thaliana. These enzymes hydrolyze starch 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. Starch-degrading enzymes must therefore be catalytically active and located in these organelles to function as starch hydrolases. We are curious about several BAM proteins that are either catalytically inactive or are not located in chloroplasts, or both. The primary question is what are they doing? By fusing BAM coding sequences to GFP and transforming Arabidopsis plants with these gene constructs, we discovered that two of the BAMs are targeted to the nucleus where they act as transcription factors regulating the expression of other genes. How and why they do this is currently under investigation. A different BAM protein is in the chloroplasts but is not active. We use two, complementary approaches to investigate these proteins; mutant plants that are missing one or more BAM proteins, and purified BAM proteins expressed in bacteria. Besides learning more about how plants work, 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.


Selected Publications:   *undergraduate co-author

 

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.