Professor of Biology
Mechanisms of Plant Cell Growth / Expansins / Cell Walls
Telephone: (814) 863-3892
|B.S., University of Massachusetts, 1974|
|Ph.D., Stanford University, 1980|
Cell expansion plays a crucial role in shaping the form and size of plants. My research
focuses on the cellular and molecular mechanisms of cell expansion. By use of biophysical,
biochemical and molecular techniques, in combination with whole-plant measurements, we are
trying to determine (a) which processes limits growth under normal and stressed conditions
and (b) how plants regulate their growth rates. Current projects include the following:
Mechanisms of Cell Enlargement - Wall Loosening Proteins
We have identified a highly conserved family of proteins - named expansins - that
catalyze wall extension. For this work we devised a novel reconstitution assay to measure
the ability of extracted proteins to induce extension of isolated walls, and then purified
the active fractions using HPLC, electrophoresis and related techniques. We have found
that expansins do not act by the conventional theory of wall loosening by polysaccharide
hydrolysis; rather, they disrupt hydrogen bonding between wall polysaccharide in a unique
way that might have commercial applications.
Current work is focused on the molecular genetics and biochemistry of expansins, for
a deeper understanding of the function and evolution of these proteins. By use of
transgenic plants with alterations in the expression of expansins, we plan to decipher the
role of these proteins in cell enlargement, plant morphogenesis, and wall structure.
Identification of genetic mutants in which T-DNA or transposon insertions interrupt
expansin genes is also underway. In our studies to date, we have found that expansins are
phylogenetically widespread and may serve a common function in regulating wall yielding
and cell expansion in vascular plants.
Grass pollen allergens as b-expansins
Group I allergens are the major allergens of grass pollen and cause seasonal asthma and
related immune response in many people. We showed these group-I allergens to be
structurally related to expansins. Extracts of maize pollen possess potent expansin-like
activity, as measured in wall extension and wall stress relaxation assays. This activity
is selective for grass cell walls and is, at least partly, due to the action of maize
group I allergens. It is likely that group I allergens facilitate invasion of the pollen
tube into the maternal tissues by loosening the cell walls of the grass stigma and
style. Additionally, the presence of related mRNAs in vegetative tissues of rice,
Arabidopsis and soybean implies that allergen homologs may function to loosen walls in
growing vegetative tissues as well. Future work will examine the development roles and
biochemical functions of this subfamily of expansins.
Growth Adaptations to Water Stress
Growing maize roots respond to mild water deficits by increasing the extensibility
of cell walls in the apical growth zone, thereby permitting the roots to continue to
grow. We are exploring the molecular basis of this change in wall properties. Part of this
adaptive response appears to be mediated by a build up of expansins in the cell walls.
Other possible changes in wall structure are also being explored.
Mechanisms of Gravitropism and Phototropism
Plants sense gravity and light, and modulate their growth so that they bend towards
or away from the stimulus. Our studies show that growth is altered by dramatic changes in
the wall extensibility of the growing tissues. However, the biochemical means by which
this is accomplished is largely unknown. We are pursuing the idea that transient changes
in the wall environment, such as redox potential or pH, affect the activity of wall
loosening and stiffening enzymes to modulate wall expansion. Expression of expansins and
other wall-loosening factors may also play a role in these growth phenomena.
Selected Recent Publications
- Sampedro J. and D.J. Cosgrove. 2008. Genomic History and Gene Family
Evolution in Angiosperms: Challenges and Opportunities. Genome Dynamics 4:
- Valdivia E.R., Sampedro J., Lamb C., Chopra S., and Cosgrove, D.J. 2007.
Recent Proliferation and Translocation of Pollen Group 1 Allergen Genes in
the Maize Genome. Plant Physiology 143: 1269-81
- Valdivia E.R., Wu Y., Li L.-C., Cosgrove D.J. and A.G. Stephenson. 2007.
A group-1 grass pollen allergen influences the outcome of pollen competition
in maize. PloS One E154 (7 p)
- Yennawar N, L.-C. Li, D.M. Dudzinski, A. Tabuchi, and D.J. Cosgrove.
2006. Crystal structure and activities of EXPB1 (Zea m 1), a beta-expansin
and group-1 pollen allergen from maize. Proc. Natl. Acad. Sci. 103:
- Sampedro, J., Carey, R. E. and D. J. Cosgrove. 2006. Genome histories
clarify evolution of the expansin superfamily: new insights from the poplar
genome and pine ESTs. J. Plant Res. 119: 11-21
- Cosgrove, D. J. Growth of the plant cell wall. 2005. Nature Review
Molecular & Cell Biology, 6: 850-861.
- Marga, F.; Grandbois, M.; Cosgrove, D. J. and T. I. Baskin. 2005. Cell
wall extension results in the coordinate separation of parallel microfibrils:
Evidence from scanning electron microscopy and atomic force microscopy.
Plant J. 43:181-90.
- Sampedro J., Cosgrove, D. J. 2005.
Protein Family Review: Expansins. Genome Biology, 6: 242-250.
- Li, L.-C.; Bedinger, P.A.; Folk, C.; Jones, A.D.; Cosgrove,D.J. 2003
Purification and characterization of four β-expansins (Zea m 1 isoforms)
from maize (Zea mays L.) pollen. Plant Physiology 132:2073-85
- Cosgrove, D.J., Li, L.-C., Cho, H.T., Hoffmann-Benning, S. Moore, R.C.,
Blecker, D. 2002. The growing world of expansins. Plant & Cell Physiology
- Cho, H. T. and D. J. Cosgrove. 2002.
The regulation of Arabidopsis root hair initiation and expansin gene
expression by development, hormone, and environment factors. Plant Cell 14:
- Li L. C. and D. J. Cosgrove. 2001.
Grass group I pollen allergens (beta-expansins) lack proteinase
activity and do not cause wall loosening via proteolysis. Eur.J.Biochem.
- Yuan, S., Y. Wu, and D. J. Cosgrove. 2001.
A fungal endoglucanase with plant cell wall extension activity. Plant
- Wu, Y., R. B. Meeley, and D. J. Cosgrove.
2001. Analysis and Expression of the
alpha-Expansin and beta-Expansin Gene Families in Maize. Plant Physiol
- Wu, Y., E. T. Thorne, R. E. Sharp, and D.
J. Cosgrove. 2001. Modification of expansin
transcript levels in the maize primary root at low water potentials. Plant
- Cho, H. T. and D. J. Cosgrove. 2000.
Altered expression of expansin modulates leaf growth and pedicel
abscission in Arabidopsis thaliana. Proc.Natl.Acad.Sci.USA 97:9783-9788.
- Cosgrove, D.J. 2000. Loosening of plant cell walls by expansins.
- Im, K. H., D. J. Cosgrove, and A. M. Jones.
2000. Subcellular localization of expansin mRNA in xylem cells. Plant
- Cosgrove, D.J. 2000. New genes and new biological roles for expansins.
Current Opinion in Plant Biology 3:73-78
- Cosgrove, D.J. 2000. Expansive growth of plant cell walls. Plant
Physiology and Biochemistry 38:1-16
- Cosgrove, D.J. 1999. Enzymes and other agents that enhance cell wall
extensibility. Annu. Rev. Plant Physiol. Plant Mol. Biol. 50: 391-417
- Fenwick, K.M., Apperley, D. C., Cosgrove D. J., and Jarvis, M. C. 1999.
Polymer mobility in cell walls of cucumber hypocotyls. Phytochem. 51:17-22
- Cosgrove, D.J., Bedinger, P.A., and Durachko, D.M. 1997. Group I allergens of grass
pollen as cell wall loosening agents. Proc. Natl. Acad. Sci. USA, 94: 6559-6564
- Link, B. M. and Cosgrove D. J. 1998. Acid-growth response and
a-expansins in suspension cultures of bright yellow 2 tobacco. Plant Physiol.
- Veytsman, B. A. and Cosgrove D. J. 1998. A model of cell wall expansion
based on thermodynamics of polymer networks. Biophys.J. 75:2240-2250
- Cosgrove, D.J. 1997. Relaxation in a high-stress environment: The molecular basis of
extensible walls and cell enlargement. Plant Cell, 1031-1041
- Shcherban,T., J. Shi, D.M. Durachko, M.J. Guiltinan, S.J. McQueen-Mason, Cosgrove, D.J.
1995. Molecular cloning and sequence analysis of expansins - a highly conserved, multigene
family of proteins that catalyze cell wall extension in plants. Proc. Nat. Acad.
Sci. USA 92:9245-9249
Medline for articles by DJ Cosgrove.
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