Pectin Wen Dong 10152010 Structure Function Biosynthesis Pectin

Pectin Wen 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 Gal. UA

Structure Homogalacturonan (HG) Xylogalacturonan (XGA) Apiogalacturonan ( AGA) Rhamnogalacturonan I (RGI) Rhamnogalacturonan II (RGII)

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/rg 1. html Accessed Oct. 11 2010

RGII http: //glyconow. nrp. org. uk/page/plant Accessed 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 LM 6 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 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.

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 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

Detections HG can be detected by Monoclonal antibodies JIM 7 or JIM 5 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 GAUT 1 Fig. 4. SDS/PAGE of partially purified Arabidopsis solubilized membrane proteins.

two related proteins – JS 33 & JS 36 Fig. 5. Alignment of the amino acid sequences of JS 33 (GAUT 7) and JS 36 (GAUT 1).

Sites of genes’ transcription Fig. 6. RT-PCR expression analysis of JS 33 and JS 36 in Arabidopsis.

GAUT 1 vs Gal. AT activity. Fig. 1. GAUT 1 has Gal. AT activity

Immunoabsorption of Gal. AT Activity Fig. 7. Western blot analysis of media and cell lysates from transiently transfected HEK 293 cells.

Western analysis Fig. 8. Western blots of the GAUT 1 -depleted fractions

The ability of anti-GAUT 1 immunoprecipitates to elongate OGAs Fig. 2. Characterization of products made by anti-GAUT 1 immunoabsorbed protein.

Phylogenetic Analysis Fig. 3. Characterization of the Arabidopsis GAUT 1 - related gene superfamily.

Conclusions GAUT 1 is involved in HG synthesis as its antiserum immunoabsorbs HG: Gal. AT activity. GAUT 1 and other members of the GAUT 1 -related superfamily are highly conserved in vascular and nonvascular plants. Identified a family of 25 genes with high sequence similarity to GAUT 1 and homologous genes.