PectinWen Dong

10/15/2010

Structure

Function

Biosynthesis

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

HG

ONeill et al. Methods in Plant Biochemistry. 1990. pp 415-441.

XGA

ONeill, et al. Plant Review. 2003, pp 1–35.

AGA

ONeill, et al. Plant Review. 2003, pp 1–35.

RGI

http://www.ccrc.uga.edu/~mao/rg1/rg1.htmlAccessed Oct.11 2010

RGII

http://glyconow.nrp.org.uk/page/plantAccessed Oct.11 2010

Structure

Jesper Harholt, et al. Plant Physiology. 2010, pp 384–395.

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

Location

Neumann, et al. Annal of Botany. 2003, pp 167–180.

Biosynthesis

Genes

Sterling et al. PNAS, 2006. pp 5236–5241

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

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

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).

Fig. 6. RT-PCR expression analysis of JS33 and JS36 in Arabidopsis.

Sites of genes’ transcription

Fig. 1. GAUT1 has GalAT activity

GAUT1 vs 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.

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.