pectin wen dong 10/15/2010. the plant cell wall is composed of polysaccharides and proteins. the...
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Pectin
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)
Structure
RGI
http://www.ccrc.uga.edu/~mao/rg1/rg1.htmlAccessed Oct.11 2010
RGII
http://glyconow.nrp.org.uk/page/plantAccessed Oct.11 2010
Function
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.
Function
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.
Function
RG-II borate complexes contribute to wall strength
ONeill, et al. Annual of Review of Plant Physiology. 2004, pp 109–139.
Function
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
Franks, et al. Plant Physiology. 2001, pp 1577–1584.
Orfila, et al. Plant Physiology. 2001, pp 210–221.
Ferrari, et al. Plant Physiology. 2007, pp 669–681.
Biosynthesis
Enzyme
Pectin biosynthetic glycosyltransferase (GT)Nucleotide-sugar interconverting enzymesHG glycosyltransferasesPectin methyltransferasePectin acetyltransferaseRG-I galactosyltransferasesRG-I glycosyltransferasesRG-I arabinosyltransferaseRG-II glycosyltransferase
Mohnen et al. Carbohydrate Research, 2009. pp 1879–1900
The pectin methylesterase (PME) catalyzed de-esterification of pectin
Substrate binding to PME
Markus et al. The EMBO Journal . 2007. pp 3879 - 3887
Detections
HG can be detected by Monoclonal antibodies JIM 7 or JIM5partially 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)
Fig. 4. SDS/PAGE of partially purified Arabidopsis solubilized membrane proteins.
Identification of GAUT1
two related proteins – JS33 & JS36
Fig. 5. Alignment of the amino acid sequences of JS33 (GAUT 7) and JS36 (GAUT 1).
Immunoabsorption of GalAT Activity
Fig. 7. Western blot analysis of media and cell lysates from transiently transfected HEK293 cells.
The ability of anti-GAUT1 immunoprecipitates to elongate OGAs
Fig. 2. Characterization of products made by anti-GAUT1 immunoabsorbed protein.
Conclusions
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.