Identification of a Xylogalacturonan Xylosyltransferase Involved in Pectin Biosynthesis in Arabidopsis Page: 1 of 16
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
Identification of a Xylogalacturonan Xylosyltransferase
Involved in Pectin Biosynthesis in Arabidopsis WOA
Jacob Kru" ger Jensen,a Susanne Oxenboll Sorensena Jesper Harholt,a Naomi Geshi,a Yumiko Sakuragi,a
Isabel Moller,b Joris Zandleven,c Adriana J. Bernal,b Niels Bjerg Jensen,a Charlotte Sorensen,a Markus
Pauly,d Gerrit Beldman,c William G.T. Willats,b and Henrik Vibe Schellera,e,l
a Laboratory of Molecular Plant Biology, Department of Plant Biology, Faculty of Life Sciences, University of Copenhagen, DK-1871
Frederiksberg C, Denmark
b Department of Molecular Biology, Faculty of Science, University of Copenhagen, DK-1353 Copenhagen, Denmark c
Laboratory of Food Chemistry, Department of Agrotechnology and Food Sciences, Wageningen University,
6700 EV Wageningen, The Netherlands
d Max Planck Institute for Molecular Plant Physiology, D-14476 Golm, Germany e
Feedstocks Division, Joint Bioenergy Institute, Emeryville, California 94608
Xylogalacturonan (XGA) is a class of pectic polysaccharide found in plant cell walls. The Arabidopsis thaliana locus At5g33290
encodes a predicted Type II membrane protein, and insertion mutants of the At5g33290 locus had decreased cell wall xylose.
Immunological studies, enzymatic extraction of polysaccharides, monosaccharide linkage analysis, and oligosaccharide mass
profiling were employed to identify the affected cell wall polymer. Pectic XGA was reduced to much lower levels in mutant than in
wild-type leaves, indicating a role of At5g33290 in XGA biosynthesis. The mutated gene was designated xylogalacturonan
deficient (xgdl). Transformation of the xgd1-1 mutant with the wild-type gene restored XGA to wild-type levels. XGD1 protein
heterologously expressed in Nicotiana benthamiana catalyzed the transfer of xylose from UDP-xylose onto oligogalacturonides and
endogenous acceptors. The products formed could be hydrolyzed with an XGA-specific hydrolase. These results confirm that the
XGD1 protein is a XGA xylosyltransferase. The protein was shown by expression of a fluorescent fusion protein in N. benthamiana
to be localized in the Golgi vesicles as expected for a glycosyltransferase involved in pectin biosynthesis.
INTRODUCTION
The plant cell wall provides support, defines cell and plant shape, and serves as a barrier against pathogens and the environment. Although
extracellular, cell walls are strong yet responsive, highly dynamic structures that allow cell expansion and division. Plant cell walls are
composed mostly of polysaccharides but also contain proteins, glycoproteins, and, in certain cells, lignin. Different classes of
polysaccharides are present in cell walls: microfibrils of cellulose are imbedded in a polymer matrix, the nature of which varies across plants
and cell types. The primary walls of growing cells typically contain approximately equal amounts of cellulose, pectin, and hemicelluloses;
xyloglucan is the most abundant hemicellulose in most plants. By contrast, grasses and other commelinoids have somewhat different walls,
with a lower content of pectin and an abundance of arabinoxylan rather than xyloglucan. Pectin is a complex group of polysaccharides that
are characterized by a high content of galacturonic acid and are relatively soluble. The major classes of pectic poly-saccharides are
homogalacturonan (HG), rhamnogalacturonan I (RGI), rhamnogalacturonan II (RGII), and xylogalacturonan (XGA) (Willats et al., 2001).
Some pectic domains are likely to be cova-lently linked in the wall (Ishii and Matsunaga, 2001; Nakamura et al., 2002). HG is composed of
a linear chain of a-1,4-linked GalA residues that are often methylesterified on C6 and can be acetylated on C2 and/or C3. RGI consists of a
backbone with the disaccharide [a-1,4-GalA-a-1,2-Rha] as the basic repeating unit. Rhamnose residues in RGI are often substituted with
side chains of galactan, arabinan, or arabinogalactan I, although RGI struc-tures are highly complex and variable (for a review, see Mohnen
1999). RGII is a polysaccharide with a complex structure that appears to be remarkably conserved in all vascular plants (Matsunaga et al.,
2004; O'Neill et al., 2004). RGII consists of a short stretch of HG substituted with four different side chains and is composed of 12 different
monosaccharides in >20 different linkages. XGA consists of a HG backbone that it is substituted with single b-1,3-Xyl residues or such
residues substituted with a few additional xylose residues (Zandleven et al., 2006). XGA has been reported especially in reproductive
tissues but is probably present in all tissues (Zandleven et al., 2007).
Pectin is synthesized by enzymes located in Golgi vesicles. Based on structural analysis, >50
different transferase activities are needed to synthesize pectin; most of these enzymes are glycosyltransferases, but methyl-
and acetyltransferases are also needed (Mohnen, 1999). Two transferase activities have been unambiguously assigned to specific proteins:
GAUT1 is a galacturonosyl transferase that can extend HG (Sterling et al., 2006), and RGXT1 and RGXT2 are isoforms of a xylosyltransfer-
ase that can transfer xylose onto the A-chain of RGII (Egelund et al., 2006). Putative pectin biosynthetic enzymes include ARAD1, which is
likely to be directly involved in synthesizing arabinan (Harholt et al., 2006), although the activity of the enzyme has not been demonstrated.
GUT1 is reported to be involved in transfer of glucuronic acid onto side chain A of RGII in Nicotiana peruvianum, but the specificity of the
enzyme is uncertain since the mutant lacking the enzyme has a more general deficiency in glucuronic acid (lwai et al., 2002, 2006). QUA1
has sequence similarity to GAUT1 and plays a role in pectin biosynthesis (Bouton et al., 2002), although the activity has not been
demonstrated and the mutant phenotype is pleiotropic (Orfila et al., 2005). For a recent review on pectin biosynthesis, see Scheller et al.
(2007).
Glycosyltransferases have been classified by Coutinho and Henrissat (1999) according to their domain structure into 91 different families, of
which 40 are represented in Arabidopsis thaliana. The members of the different glycosyltransferase fam-ilies can be conveniently accessed
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Pauly, Markus; Sorensen, Susanne Oxenboll; Harholt, Jesper; Geshi, Naomi; Sakuragi, Yumiko; Moller, Isabel et al. Identification of a Xylogalacturonan Xylosyltransferase Involved in Pectin Biosynthesis in Arabidopsis, article, August 19, 2009; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc1014698/m1/1/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.