Projects Available for PhD and Honours
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Current position
Research Officer
Research interests
Application of organic analytical chemistry, with an emphasis
on mass spectrometry (Fisons MD800 GC/MS, Thermo Finnigan PolarisQ
GC/MS, Thermo Finnigan LCQ DECA XP Plus ProteomeX LC/MS, Bruker
Omniflex MALDI-TOF MS), to solve biological problems. This work
has entailed developing separation/purification protocols for
samples and the use of appropriate derivatives, as required for
structural elucidation and quantification by mass spectrometry.
Current work includes identification and quantification of cell
wall derived polysaccharides in Arabidopsis thaliana mutants which
are defective in cellulose synthesis, and identification of chemical
signals regulating the interaction of rice and Rhizobium isolates
from the Nile Delta.
Other work includes the analysis of phytohormones (cytokinin
and auxin) and of chemical residues retained in archaeological
artifacts (fatty acids, kava and betel). An informal analytical
service and advice for other researchers is also provided with
respect to amino acid and carbohydrate analysis, proteomics and
metabolomics.
Student Research Projects
Compositional changes in plant cell wall polysaccharides in
cellulose deficient Arabidopsis thaliana mutants
Cellulose is a key structural component of plant cell walls and
we have access to a unique collection of temperature-dependent
mutants of Arabidopsis thaliana which are deficient in synthesising
cellulose. These plants have proven crucial in starting to unravel
the complex mechanism of cellulose biosynthesis and to date we
have identified three genes which are involved in this process.
We have some preliminary evidence from the accumulation, in the
mutants, of short chains of cellulose linked to a lipid, that
the process involves the transfer of glucose or glucose chains
to a lipid linker.
Several possibilities for further research have arisen:
1. completing the structural determination of the lipid linked
glucan and developing methods for its quantification;
2. examining the length of the cellulose chains present in the
mutants, using a laser light scattering technique to determine
the molecular weight distribution of the dissolved cellulose,
and comparing this with the distribution in the wild type plant;
and
3. determining any compensating changes in the level or quality
of the pectins and hemicelluloses present in the cell walls of
these mutants.
This work will involve the development of new HPLC methods to
quantify uronic acids, the use of matrix assisted laser desorption
ionisation time of flight mass spectrometry (MALDI-TOF MS) to
examine intact polysaccharides and the glucan, and GC/MS to identify
monosaccharides and their linkages.
Selected Publications
R.E. Williamson, J. Burn, R. Birch, T. Baskin, T. Arioli, A.
Betzner and A. Cork. Morphogenesis in rsw1, a cellulose-deficient
mutant of Arabidopsis thaliana. Protoplasma (2001) 215, 116-127.
K. Sugimoto, R.E. Williamson and G.O. Wasteneys. Wall architecture
in the cellulose-deficient rsw1 mutant of arabidopsis: microfibrils
but not microtubules lose their transverse alignment before microfibrils
become unrecognisable in the mitotic and elongation zones of roots.
Protoplasma (2001) 215, 172-183
L. Peng, C.H. Hocart, J.W. Redmond and R.E. Williamson. Fractionation
of carbohydrates in Arabidopsis root cell walls shows that three
radial swelling loci are specifically involved in cellulose production.
Planta (2000) 211, 406-414.
D.R. Lane, A. Wiedemeier, L. Peng, H. Höfte, S. Vernhettes,
T. Desprez, C.H. Hocart, R.J. Birch, T.I. Baskin, J.E. Burn, T.Arioli,
A.S. Betzner, and R.E. Williamson. Temperature-sensitive alleles
of RSW2 link the KORRIGAN endo-1,4--glucanase to cellulose synthesis
and cytokinesis in Arabidopsis. Plant Physiology (2001) 126, 278-288.
R.E. Williamson, J.E. Burn and C.H. Hocart. Cellulose synthesis:
mutational analysis and genomic perspectives using Arabidopsis
thaliana. Cellular and Molecular Life Sciences (2001) 58, 1475-1490.
J.E. Burn, C.H. Hocart, R.J. Birch, A.C. Cork and R.E. Williamson.
Functional analysis of the cellulose synthase genes CesA1, CesA2,
and CesA3 in Arabidopsis. Plant Physiology (2002) 129, 797-807.
J.E. Burn, C.H. Hocart, R.J. Birch, A.C. Cork and R.E. Williamson.
Functional analysis of the cellulose synthase genes CesA1, CesA2,
and CesA3 in Arabidopsis. Plant Physiology (2002) 129,797-807.
J.W.H Yong, S.C. Wong, D.S. Letham, C.H. Hocart and G.D. Farquhar.
Effects of elevated [CO2] on cytokinins in the xylem sap and leaves
of cotton. Plant Physiology (2000) 124, 767-779.
C.H. Hocart and B. Fankhauser. Identification of Betel nut alkaloids
in ornamentally stained teeth. Experientia (1996) 52, 281 - 285.
C.H. Hocart, B. Fankhauser and D. Buckle. Chemical archaeology
of kava - a potent brew. Rapid Communications in Mass Spectrometry
(1993) 7, 219-224.
Metabolomic
studies of model legume Medicago truncatula (PDF file)
Prof
Richard Williamson
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