Transcript Pectin
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.