Recent Publications
Sucrose Binding Protein Project
Overvoorde et al. (1995) A Soybean Sucrose
Binding Protein Independently Mediates Nonsaturable Sucrose Uptake in Yeast.
Plant Cell 8: 217-280.
Overvoorde and Grimes (1994) Topographical Analysis
of the Plasma Membrane-associated Sucrose Binding Protein. J. Biol.
Chem. 269:15154-15161.
Grimes et al. (1992) A 62 kD Sucrose Binding
Protein is Expressed and Localized in Tissues Actively Engaged in Sucrose
Transport Plant Cell 4:1561-1574.
Lipoxyenase/Nitrogen Storage Project
Bunker et al. (1995). Sink Limitation Induces
the Expression of Multiple Soybean Vegetative Lipoxygenase mRNAs while Endogenous
Jasmonic Acid Level Remains Low. Plant Cell 7:1319-1331.
Grimes et al. (1993). Expression and
Accumulation Patterns of Nitrogen-Responsive Lipoxygenase in Soybeans. Plant
Physiol. 103: 457-466.
Tranbarger et al. (1991). The Soybean
94-Kilodalton Storage Protein Is a Lipoxygenase That Is Localized in Paraveinal
Mesophyll Cell Vacuoles. Plant Cell 3: 973-987.
Franceschi and Grimes (1991). Induction of Soybean Vegetative Storage
Proteins and Anthocyanins by Low-level Atmospheric Methyl Jasmonate. Proc.
Natl. Acad. Sci. USA 88:6745-6749.
Abstracts
Overvoorde,Paul J., Frommer, Wolf
B. and Howard D. Grimes (1995)
A Soybean Sucrose Binding Protein Independently Mediates Nonsaturable
Sucrose Uptake in Yeast. Plant Cell 8: 217-280.
Heterologous expression of a cDNA encoding a 62-kD soybean sucrose binding
protein in yeast demonstrates that this protein, independent of other plant
proteins, mediates sucrose uptake across the plasma membrane. Sucrose binding
protein-mediated sucrose uptake is nonsaturable up to 30 mM sucrose, is
specific for sucrose, and is relatively insensitive to treatment with sulfhydryl-modifying
reagents. Alteration of the external pH or pretreatment of the yeast cells
with protonophores did not significantly affect the rate of 14C-sucrose
uptake. This demonstrates that sucrose binding protein-mediated sucrose
uptake is not dependent on H+ movement and delineates it from other plant
sucrose transporters. Physiological characterization of sucrose uptake into
higher plant cells has shown the presence of both saturable and nonsaturable
uptake components. The nonsaturable mechanism is relatively insensitive
to external pH, pre-treatment with protonophores, and treatment with sulfhydryl-modifying
reagents. Sucrose binding protein mediated sucrose uptake in yeast mimics
this physiologically described, but mechanistically undefined, nonsaturable
sucrose uptake mechanism in higher plants. Functional characterization of
the sucrose binding protein thus defines both a novel component of sucrose
uptake and provides important insight into this nonsaturable sucrose uptake
mechanism that has remained enigmatic since its physiological description.
Grimes, Howard D., and Paul J. Overvoorde (1995)
J. Expt. Botany X:xxx-xxx.
Overvoorde, Paul J., and Howard D.
Grimes (1994)
Topographical Analysis of the Plasma Membrane-associated Sucrose Binding
Protein. J. Biol. Chem. 269:15154-15161.
Plasma membranes of soybean cells actively engaged in sucrose transport
have a sucrose binding protein (SBP) that does not appear to be an integral
membrane protein. Experiments were undertaken to analyze the topographical
association of this protein with the membrane. Treatment of purified plasma
membrane vesicles with either 1 M KCl or KI released less than 35% of the
sucrose binding protein from the membrane whereas treatment with either
4 M urea of 0.1 M Na2CO3, pH11.5, disassociated between 50 and 50%, respectively,
of this protein from the membrane. SDS, at either 0.5x, 1x, or 10x of its
critical micelle concentration, effectively solubilized the sucrose binding
protein. The nonionic detergents Triton X-100 and CHAPS, at either 0.5x,
1x, or 10x of their critical micelle concentrations, solubilized between
65 and 75% of this protein. When either native plasma membrane-associated
or in vitro-transcribed and translated SBP were subjected to Triton
X-114 phase separation, 80% partitioned into the detergent-poor aqueous
phase. These results indicate that the SBP is a peripheral membrane protein
but also suggest that there is a population of this protein that is tethered
to the membrane.
Grimes, Howard D., Overvoorde, Paul J.,
Ripp, Kevin, Franceschi, Vincent R., and William D. Hitz (1992)
A 62 kD Sucrose Binding Protein is Expressed and Localized in Tissues
Actively Engaged in Sucrose Transport Plant Cell 4:1561-1574.
Sucrose transport from the apoplasm, across the plasma membrane,
and into the symplast is critical for growth and development in most plant
species. Phloem loading, the process of transporting sucrose against a concentration
gradient into the phloem, is an essential first-step in long distance transport
of sucrose and carbon partitioning. Here we report that a soybean 62 kD
sucrose binding protein is associated with the plasma membrane of several
cell types engaged in sucrose transport, including the mesophyll cells of
young sink leaves, the companion cells of mature phloem, and the cells of
the cotyledon. Furthermore, the temporal expression and accumulation patterns
of this gene and protein closely parallel the rate of sucrose uptake in
the cotyledon. Molecular cloning of a full-length cDNA for this 62 kD sucrose
binding protein indicates that the 62 kD sucrose binding protein is not
an invertase, contains a 29 amino acid leader peptide that is cleaved off
the mature protein, and is not an integral membrane protein. We conclude
that the 62 kD sucrose binding protein is involved in sucrose transport,
but is not performing this function independently.
Bunker, Thomas W., Koetje, David S., Stephenson,
Lowry C., Creelman, Robert A., Mullet, John E. and Howard D. Grimes (1995)
Sink Limitation Induces the Expression of Multiple Soybean Vegetative
Lipoxygenase mRNAs While The Endogenous Jasmonic Acid Level Remains Low.
Plant Cell 7:1319-1331.
The response of individual members of the lipoxygenase multigene family
in soybeans to sink deprivation was analyzed. RNase protection assays indicated
that a novel vegetative lipoxygenase gene, vlxC, and three other
vegetative lipoxygenase mRNAs accumulated in mature leaves in response to
a variety of sink limitations. These data suggest that several members of
the lipoxygenase multigene family are involved in assimilate partitioning.
The possible involvement of jasmonic acid as a signaling molecule regulating
assimilate partitioning into the vegetative storage proteins and lipoxygenases
was directly assessed by determining the endogenous level of jasmonic acid
in leaves from plants with their pods removed. There was no rise in the
level of endogenous jasmonic acid coincident with the strong increase in
both vlxC and vegetative storage protein VspB transcripts
in response to sink limitation. Thus, expression of the vegetative lipoxygenases
and vegetative storage proteins is not regulated by jasmonic acid in sink-limited
leaves.
Grimes, Howard D., Tranbarger, Timothy J.,
and Franceschi, Vincent R. (1993)
Expression and Accumulation Patterns of Nitrogen-Responsive Lipoxygenase
in Soybeans. Plant Physiol. 103: 457-466.
Tranbarger, Timothy J., Franchesci, Vincent R.,
Hildebrand, David F., and Howard D. Grimes (1991)
The Soybean 94-Kilodalton Storage Protein Is a Lipoxygenase That Is
Localized in Paraveinal Mesophyll Cell Vacuoles. Plant Cell 3: 973-987.
Franceschi, Vincent R. and Howard D. Grimes
(1991)
Induction of Soybean Vegetative Storage Proteins and Anthocyanins by
Low-level Atmospheric Methyl Jasmonate. Proc. Natl. Acad. Sci. USA
88:6745-6749.
