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 pp

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

Accessed Oct

Accessed Oct

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, pp Crawshaw et al. Planta, pp Gomez, et al. Molecular Plant, pp

HG-Calcium complexes contribute to wall strength Grant, et al. FEBS Lett 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 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.

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

Genes Sterling et al. PNAS, 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, pp 1879–1900

structural motifs Pelloux et al. Trends in Plant Science pp

The pectin methylesterase (PME) catalyzed de-esterification of pectin Substrate binding to PME Markus et al. The EMBO Journal pp

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)

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.

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.