Research Interests
The Chollet laboratory had a long-standing interest in plant metabolic enzymes and their post-translational regulation by reversible protein phosphorylation. Areas of most recent investigation focused on PEP carboxylase, pyruvate, Pi dikinase and sucrose synthase, three "target" enzymes previously discovered to undergo seryl- or threonyl-phosphorylation in intact, CO2-fixing leaves and/or N2-fixing legume root nodules. Their experimental approaches to these different regulatory phosphorylation systems, including the requisite protein Ser/Thr-kinases and -phosphatases, exploited the modern tools of molecular and cellular biology, enzymology, protein chemistry, and plant transformation. This general line of basic research in the Chollet laboratory was funded continuously by the U.S. National Science Foundation (NSF) between 1987 and 2007 (see above Webpage for 1978-2007 funding from NSF).
Recent Refereed Papers
- Chastain, C.J., W. Xu, K. Parsley, G. Sarath, J.M. Hibberd, and R. Chollet. 2008. The pyruvate,orthophosphate dikinase regulatory proteins of Arabidopsis possess a novel, unprecedented Ser/Thr protein kinase primary structure. The Plant Journal. 53: 854-863.
- Moellering, E.R., Y. Ouyang, T.G. Mamedov, and R. Chollet. 2007. The two divergent PEP-carboxylase catalytic subunits in the green microalga Chlamydomonas reinhardtii respond reversibly to inorganic-N supply and co-exist in the high- molecular-mass, hetero-oligomeric Class-2 PEPC complex. FEBS Lett. 581: 4871-4876.
- Xu,
W., S.J. Sato, T.E. Clemente, and R. Chollet. (2007) The PEP-carboxylase
kinase gene family in Glycine max (GmPpcK1-4): an in-depth molecular
analysis with nodulated, non-transgenic and transgenic plants. Plant J. 49: 910-923 .
- Xu,
W., S. Ahmed, H. Moriyama, and R. Chollet. (2006) The importance of the
strictly conserved, C-terminal glycine residue in phosphoenolpyruvate
carboxylase for overall catalysis. Mutagenesis and truncation of Gly-961
in the sorghum C4 leaf isoform. J. Biol. Chem. 281:17238-17245.
- Mamedov, T.G., E.R. Moellering,
and R. Chollet. (2005) Identification and expression analysis of two inorganic
C- and N-responsive genes encoding novel and distinct molecular forms of
eukaryotic phosphoenolpyruvate carboxylase in the green microalga
Chlamydomonas reinhardtii. Plant J. 42:832-843.
- Chastain, C.J., and R. Chollet.
(2003) Regulation of pyruvate,orthophosphate dikinase by ADP-/Pi-dependent
reversible phosphorylation in C3 and C4 plants. Plant
Physiol. Biochem. 41:523-532.
- Chollet, R., and R.J. Spreitzer,
Eds. (2003) The C-fixing enzymes in plants. Arch. Biochem. Biophys. 414:129-222.
- Ermolova, N.V., M.A. Cushman,
T. Taybi, S.A. Condon, J.C. Cushman, and R. Chollet. (2003) Expression,
purification, and initial characterization of a recombinant form of plant
PEP-carboxylase kinase from CAM-induced Mesembryanthemum crystallinum
with enhanced solubility in Escherichia coli. Protein Express. Purif.
29:123-131.
- Xu, W., Y. Zhou, and R. Chollet.
(2003) Identification and expression of a soybean nodule-enhanced PEP-carboxylase
kinase gene (NE-PpcK) that shows striking up-/down-regulation in
vivo. Plant J. 34:441-452.
- Chastain, C.J., J.P. Fries,
J.A. Vogel, C.L. Randklev, A.P. Vossen, S.K. Dittmer, E.E. Watkins, L.J.
Fiedler, S.A. Wacker, K.C. Meinhover, G. Sarath, and R. Chollet. (2002)
Pyruvate, orthophosphate dikinase in leaves and chloroplasts of C3
plants undergoes light-/dark-induced reversible phosphorylation. Plant Physiol.
128:1368-1378. [also featured in this issue's "On the Inside"
section on pages 1163-1164]
- Komina, O., Y. Zhou, G. Sarath,
and R. Chollet. (2002) In vivo and in vitro phosphorylation of membrane
and soluble forms of soybean nodule sucrose synthase. Plant Physiol. 129:1664-1673.
- Outlaw, W.H., Jr., Z. Du, F.X.
Meng, K. Aghoram, K.A. Riddle, and R. Chollet. (2002) Requirements for activation
of the signal-transduction network that leads to regulatory phosphorylation
of leaf guard-cell phosphoenolpyruvate carboxylase during fusicoccin-stimulated
stomatal opening. Arch. Biochem. Biophys. 407:63-71.
- Bakrim, N., J. Brulfert, J.
Vidal, and R. Chollet. (2001) Phosphoenolpyruvate carboxylase kinase
is controlled by a similar signaling cascade in CAM and C4 plants.
Biochem. Biophys. Res. Commun. 286:1158-1162.
- Dong, L., N.V. Ermolova, and
R. Chollet. (2001) Partial purification and biochemical characterization
of a heteromeric protein phosphatase 2A holoenzyme from maize (Zea mays
L.) leaves that dephosphorylates C4 phosphoenolpyruvate
carboxylase. Planta 213:379-389.
- Chastain, C.J., M. Botschner,
G.E. Harrington, B.J. Thompson, S.E. Mills, G. Sarath, and R. Chollet. (2000)
Further analysis of maize C4 pyruvate,orthophosphate dikinase
phosphorylation by its bifunctional regulatory protein using selective substitutions
of the regulatory Thr-456 and catalytic His-458 residues. Arch. Biochem.
Biophys. 375:165-170.
- Taybi, T., S. Patil, R. Chollet,
and J.C. Cushman. (2000) A minimal Ser/Thr protein kinase circadianly regulates
phosphoenolpyruvate carboxylase activity in Crassulacean acid metabolism-induced
leaves of the common ice plant. Plant Physiol. 123:1471-1481.
Recent Federal Funding
U.S. National Science Foundation/Metabolic Biochemistry and Integrative Plant
Biology Programs (May 1998 through April 2003): "Seryl-Phosphorylation/Dephosphorylation
of Plant Metabolic Enzymes in Leaves (PEPC) and Root Nodules (SuSy, PEPC)"
Abstract 9727236
U.S. National Science Foundation/Metabolic Biochemistry Program (May 2002 through
April 2007): "Molecular/Biochemical Investigations of PEPC (and its Novel
Ser/Thr-Kinase) and SuSy (Nodulin-100), Two Phosphorylated Metabolic Enzymes
in Plants" Abstract
0130057
Recent Professional Activities
Editorial Advisor to the textbook PLANT BIOCHEMISTRY (by F.K. Gleason, to be published during 2010 by Jones & Bartlett Publishers, Boston), 2008-2010
Co-Chair and Co-PI of the NSF-sponsored (MCB-0437115) workshop (December 2004, Washington, DC) on "Realizing the Vision: Leading Edge Technologies in Biological Sciences"
Co-Chair (August 2002, South Hadley, MA) and Co-Vice-Chair (September 1999, Oxford, UK) of the Gordon Research Conference on "CO2-Fixation and Metabolism in Green Plants"
Editorial Committees of the Annual Review of Plant Physiology & Plant Molecular Biology (1997-2001) and Archives of Biochemistry & Biophysics (1991-2008)
Guest Co-Editor of a "Highlight Issue" of Archives of Biochemistry & Biophysics (Vol. 414, No. 2, 15 June 2003) on "The C-Fixing Enzymes in Plants", 2002-2003
Appointed Advisory Committee member (grant-review panelist) for the U.S. National Science Foundation's Molecular & Cellular Biosciences (MCB) Division, 2000-2001 and 2002-2004
Appointed representative of the American Society of Plant Biologists (ASPB) to the American Association for the Advancement of Science [Biological Sciences, and Agriculture, Food & Renewable Resources Sections], 1996-2002
Appointed member of the Corresponding Membership Committee of ASPB, 1999-2002
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