Pectin
Wen Dong
10/15/2010
The plant cell wall is composed of polysaccharides and proteins.
The wall polysaccharides are often classified into cellulose, hemicelluloses and pectin
Pectin is by relatively high extractability using acid and a high content of GalUA
Homogalacturonan (HG)
Xylogalacturonan (XGA)
Apiogalacturonan ( AGA)
Rhamnogalacturonan I (RGI)
Rhamnogalacturonan II (RGII)
ONeill et al. Methods in Plant Biochemistry. 1990. pp 415-441.
ONeill, et al. Plant Review. 2003, pp 1–35.
ONeill, et al. Plant Review. 2003, pp 1–35.
http://www.ccrc.uga.edu/~mao/rg1/rg1.html
Accessed Oct.11 2010
http://glyconow.nrp.org.uk/page/plant
Accessed Oct.11 2010
Jesper Harholt, et al. Plant Physiology. 2010, pp 384–395.
Pectin as storage polymer
Galactan is highly abundant in the cotyledons of certain lupin (Lupinus)
species and is remobilized during seed germination.
Recently, it was shown that polymers containing LM6 epitopes, plausibly
arabinan, are remobilized during Arabidopsis seed germination and influence
germination negatively if removed before germination.
In Arabidopsis seeds, The Ara was shown by pulse-chase experiments to be
metabolized during germination. Hence, the arabinan in the seeds may have a
storage function, but it also has a more direct role in seed germination.
Hirst et al. Journal of the Chemical Society, 1947. pp 1225-1229.
Crawshaw et al. Planta, 1984. pp 449-454.
Gomez, et al. Molecular Plant, 2009. pp 966-976.
HG-Calcium complexes contribute to wall strength
Grant, et al. FEBS Lett. 1973. pp 195–198.
Liners, et al. Plant Physiology. 1989, pp 1419–1424.
RG-II borate complexes contribute to wall strength
ONeill, et al. Annual of Review of Plant Physiology. 2004, pp 109–139.
HG-Calcium complexes and RG-I arabinan affect stomatal function
HG-Calcium complexes and RG-I sidechains contribute to cell
adhesion
Pectic polysaccharides mediate defense, a barrier and signaling
mechanism
Orfila, et al. Plant Physiology. 2001, pp 210–221.
Franks, et al. Plant Physiology. 2001, pp 1577–1584.
Ferrari, et al. Plant Physiology. 2007, pp 669–681.
Location
Neumann, et al. Annal of Botany. 2003, pp 167–180.
Genes
Sterling et al. PNAS, 2006. pp 5236–5241
Enzyme
Pectin biosynthetic glycosyltransferase (GT)
Nucleotide-sugar interconverting enzymes
HG glycosyltransferases
Pectin methyltransferase
Pectin acetyltransferase
RG-I galactosyltransferases
RG-I glycosyltransferases
RG-I arabinosyltransferase
RG-II glycosyltransferase
Mohnen et al. Carbohydrate Research, 2009. pp 1879–1900
structural motifs
Pelloux et al. Trends in Plant Science. 2007. pp 267-278
The pectin methylesterase (PME) catalyzed de-esterification of pectin
Substrate binding to PME
Markus et al. The EMBO Journal . 2007. pp 3879 - 3887
Model of PME involvement in plant defences
HG can be detected by Monoclonal antibodies JIM 7 or JIM5
partially methyl esterified HGs
XGA and RG-II can be detected by anti-XG, and anti-RGII rabbit polyclonal antibodies
Testillano et al. Journal of Experimental Botany, 2010, pp 1159–1175
Functional identification of an Arabidopsis
pectin biosynthetic homogalacturonan
galacturonosyltransferase
Sterling et al. PNAS, March 28, 2006(vol.103; no.13:5236–5241)
Identification of GAUT1
Fig. 4. SDS/PAGE of partially purified Arabidopsis solubilized membrane proteins.
two related proteins – JS33 & JS36
Fig. 5. Alignment of the amino acid sequences of JS33 (GAUT 7) and JS36 (GAUT 1).
Sites of genes’ transcription
Fig. 6. RT-PCR expression analysis of JS33 and JS36 in Arabidopsis.
GAUT1 vs GalAT activity.
Fig. 1. GAUT1 has GalAT activity
Immunoabsorption of GalAT Activity
Fig. 7. Western blot analysis of media and cell lysates from transiently transfected HEK293 cells.
Western analysis
Fig. 8. Western blots of the GAUT1-depleted fractions
The ability of anti-GAUT1 immunoprecipitates to elongate OGAs
Fig. 2. Characterization of products made by anti-GAUT1 immunoabsorbed protein.
Phylogenetic Analysis
Fig. 3. Characterization of the Arabidopsis GAUT1- related gene superfamily.
GAUT1 is involved in HG synthesis as its antiserum immunoabsorbs HG:GalAT
activity.
GAUT1 and other members of the GAUT1-related superfamily are highly
conserved in vascular and nonvascular plants.
Identified a family of 25 genes with high sequence similarity to GAUT1 and
homologous genes.