Pectic Polysaccharides Research Articles

Resolving the nanostructure of sodium carbonate extracted pectins (DASP) from apple cell walls with atomic force microscopy and molecular dynamics

The diluted alkali-soluble fraction of the cell wall pectic matrix extracted with sodium carbonate (DASP) from apple fruit (M. domestica cv. Golden Delicious) was subjected to extensive analysis aimed at refining the current view concerning its molecular structure. Pectins were examined by means of atomic force microscopy (AFM) and HPLC chemical analysis. In addition to this, computational chemistry was employed to characterize the structural features of the basic plant cell wall polysaccharides and their possible assemblies. The AFM imaging revealed that DASP molecules deposited on mica structurally resembled rod-like objects, consisting of relatively long linear sections separated by bend points or branches. Locally molecules also formed aggregates, which were visible as an amorphous phase, concentrated around linear sections. Based on chemical analysis combined with molecular dynamics (MD) the linear chains were identified as sections of unbranched homogalacturonan, while the second most abundant polysaccharide present in DASP – arabinose – was considered to constitute the amorphous aggregates. The study showed that despite being present in small amounts, rhamnose is an important factor affecting the formation of the characteristic shape of DASP molecules on mica. The structural characterization of the bend points showed that linear molecules oriented at specific angles are most likely to be formed by two sections of homogalacturonan separated by a single rhamnose unit. AFM images confirmed that this is a common feature of the molecular structure of the DASP fraction, suggesting a possible role in the networking of pectic polysaccharides. Rhamnose interspersions within the homogalacturonan chains lead to the formation of spatial structures, which resemble kinked rods with segments having the ability to change their relative positions. The higher mobility of the linear sections as well as the higher number of segments increases the number of possible interactions with surrounding molecules and thus increases its ability to form gels. Therefore, it is expected that the number of rhamnose units and the length of the linear homogalacturonan sections will be one of the factors that influence the gelling abilities of pectin. Furthermore, it was proposed that branch points are created, similar to bend points, by single interspersions of rhamnose, which connect three homogalacturonan chains or short sections (two or three dimers) of rhamnogalacturonan-I with a homogalacturonan side branch. The third proposed alternative was a complex of two adjacent homogalacturonan chains, one of them having a single rhamnose insertion causing a bend in the structure.

Identification of iron-chelating phenolics contributing to seed coat coloration in soybeans (Glycine max (L.) Merr.) expressing aryloxyalkanoate dioxygenase-12

Soybeans (Glycine max (L.) Merr.) genetically modified to express aryloxyalkanoate dioxygenase-12 (AAD-12), an enzyme that confers resistance to the herbicide 2,4-D, can sometimes exhibit a darker seed coat coloration than equivalent unmodified soybeans. The biochemical basis for this coloration was investigated in a non-commercial transgenic event, DAS-411Ø4-7 that exhibited more pronounced AAD-12-associated seed coat coloration than the commercial event, DAS-444Ø6-6. Analysis of color-enriched seed coat fractions from DAS-411Ø4-7 showed that the color was due to localized accumulation of iron-chelating phenolics, particularly the isoflavone genistin, that are associated with seed coat pectic polysaccharide and produce a brown chromophore. The association between genistin, iron, and pectic polysaccharide was characterized using a variety of analytical methods. Darker seeds from commercial soybean event DAS-444Ø6-6 also show higher genistin content localized to the darker colored portions of the seed coat (with no increase in whole seed genistin levels).

Molecular binding between anthocyanins and pectic polysaccharides – Unveiling the role of pectic polysaccharides structure

The interaction between cyanidin-3-O-glucoside and four citrus pectic fractions was investigated using a combined molecular approach, including isothermal titration calorimetry (ITC), magnetic nuclear resonance (NMR) and UV–Visible spectrophotometry. These pectic fractions differed on their type and degree of esterification (amidated (AHG 30%), low (HG 30%) and high methyl esterified fractions (HG 70%)) and on the pattern of esterification (blockwise (HG-B 70%) vrs random (HG-R 70%)). The binding constant (Ka) and the associated thermodynamic parameters determined showed weak noncovalent interactions, particularly due to electrostatic interactions, hydrogen bonding and hydrophobic effect. The degree and the type of esterification of each pectic fractions had a significant effect on the binding constants determined by ITC and NMR experiments. The binding constants ranged from 102 to 104 M−1, with the highest Ka value observed for the interaction between cy3glc and low methylesterified fraction, followed by the amidated fraction. Pectic fractions with a higher degree of methyl esterification, resulted on lower binding affinities, with these interactions being mostly driven by hydrophobic effect compared to enthalpy. The different binding affinities could be correlated with anthocyanins colour impact, as a higher red colour intensity could be observed for a cy3glc model solution fortified with a low methylated fraction. However, this colour improvement was not observed for amidated fraction, presumably due to charge repulsive forces, lowering the stability of the flavylium cation.

Polysaccharide composition of an anticoagulant fraction from the aqueous extract of Marsypianthes chamaedrys (Lamiaceae)

Marsypianthes chamaedrys (Lamiaceae) is a medicinal plant popularly used against envenomation by snakebite. Pharmacological studies have shown that extracts of M. chamaedrys have antiophidic, anti-inflammatory and anticoagulant properties, supporting the ethnopharmacological use. In this study, an aqueous extract of aerial parts of M. chamaedrys showed anticoagulant activity in the activated partial thromboplastin time assay (0.54 IU/mg). The bioassay-guided fractionation using ethanol precipitation and gel filtration chromatography on Sephadex G-50 and Sephadex G-25 resulted in a water-soluble fraction with increased anticoagulant activity (Fraction F2−A; 2.94 IU/mg). A positive correlation was found between the amount of uronic acids and the anticoagulant potential of the active samples. Chemical and spectroscopic analyses indicated that F2−A contained homogalacturonan, type I rhamnogalacturonan, type II arabinogalactan and α-glucan. UV and FT–IR spectra indicated the possible presence of ferulic acid. Pectic polysaccharides and type II arabinogalactans may be contributing to the anticoagulant activity of the aqueous extract of M. chamaedrys in the APTT assay.

Extraction of low methoxylated pectin from pea hulls via RSM

Nowadays, low methoxylated pectin (LMP) is generated in a multi-step process from high methoxylated pectin using fruit by-products as a raw material. In this study, we prove that LMP may be directly extracted from pea hulls. Extraction was conducted according to a central composite design (CCD) and evaluated via response surface methodology (RSM). The influence of different parameters (pH, temperature, time) on yield and composition of the extracted pectic polysaccharides (PPS) was investigated using nitric acid and citric acid as extraction media. Citric acid yielded higher amounts of PPS (3.5–9.8%) compared to nitric acid (1.4–8.0%). However, there is a conflict of aims between a high yield and the purity of the extracted PPS. Composition analysis suggests that under ‘mild’ extraction conditions (pH 2, 70 °C) PPS consist of homogalacturonan, xylogalacturonan and rhamnogalacturonan with arabinose and galactose side chains (RG-I). With increasing temperature (90°), yield is maximised due to an increased solubilisation of cell wall polysaccharides. Under “harsh” conditions (pH 1, 90 °C) the purity of PPS increases in terms of a relatively higher content of uronic acids, but yield decreases. This is attributed to a cleavage of non-GalA components and an ongoing depolymerisation of the pectic galacturonan. PPS extracted under these conditions is characterised by a low degree of acetylation (4%) and a relatively high protein content (7%).

Extraction and characterization of pectic polysaccharides from Chaenomeles sinensis fruit by hot compressed water

The effects of extraction conditions on the yield of polysaccharides from the fruit of Chaenomeles sinensis (FCS) using a hot compressed water method were investigated. The results showed that an appropriately high temperature (150 °C) and a moderate extraction time (45 min) at a material to water ratio of 1 to 10 g/mL led to a high yield of alcohol precipitation polysaccharide (PA). The purified polysaccharides (CSP-1, CSP-2, and CSP-3) were successfully obtained using a DEAE-52 chromatographic column. Chemical analysis showed that CSP-2 and CSP-3 were homogenous and exhibited characteristics of esterified pectins, whereas CSP-2 mainly consisted of galacturonic acid (GalA), galactose (Gal), arabinose (Ara), rhamnose (Rha), and mannose (Man) with an average molecular weight of 59.1 kDa. Furthermore, CSP-1 possessed stronger antioxidant ability according to DPPH scavenging and reducing power compared with CSP-2 and CSP-3. However, it was weaker with respect to OH scavenging. The technical data presented in this study could help the industry make use of polysaccharides from FCS as a source of pectin for a range of pharmaceutical, culinary, and cosmetic products.

Pectin extracted from persimmon peel: A physicochemical characterization and emulsifying properties evaluation

In this study, pectin was extracted from persimmon peel by hot-acid extracting method. GalA content and Mw of the obtained persimmon peel pectin (PPP) were 71.39 ± 0.32% and 227 ± 4.20 kg/mol, respectively. Structural characterization, including FTIR, XRD, NMR, demonstrated that PPP was a low-methoxy acetylated pectin. Moreover, PPP exhibited significantly better emulsification performance than commercial citrus pectin (CCP). When the concentration of PPP was increased to 1.5% (wt%), a stable emulsion containing 50% or 65% (v/v) oil fraction can be obtained. In addition, PPP has more than the biological activity of a typical pectic polysaccharide, which can afford additional oxidation stability of lipids to the emulsion. Taken together, our results indicated that persimmon peel can serves as a new source of emulsifier with antioxidant activity, providing a promising alternative for natural emulsifiers that can be used in the food industry.

Pectic polysaccharides extracted from pot marigold (Calendula officinalis) industrial waste

Residues from the essential oil and the natural pigment industry are cheap, abundant and insufficiently investigated wastes with a great valorization potential. Such underexplored biomass is derived from the pot marigold (Calendula officinalis) used industrially for lutein extraction and obtaining of essential oil. The aim of the present work was to investigate the potential of two pot marigold wastes as a source of polysaccharides: the first obtained after 1,1,1,2-tetrafluoroethane (freon R134a) extraction of marigold (F-waste), and second obtained after hydrodistillation (HD-waste). The potential of wastes as a source of polysaccharides was estimated by dilute hydrochloric acid extraction whereupon the F and HD yielded 9.81 ± 0.58% and 3.12 ± 0.24% of polysaccharides, respectively. The chemical composition, physicochemical properties and infrared spectroscopy data suggested that they were acidic pectic type polysaccharides with galacturonic acid content 632.86 ± 2.30 μg mg−1 and 617.99 ± 3.15 μg mg−1 polysaccharide, degree of methoxylation 63.7 ± 1.5% and 48.9 ± 2.5%, and degree of acetylation 3.5 ± 0.1% and 3.3 ± 0.1% for F and HD polysaccharides, respectively. The rheological properties of acid-extractable polysaccharides were investigated and it was found that F-polysaccharide yielded strong gel. The polysaccharides were investigated by differential thermal analysis and the analyses revealed that they start decomposing significantly after 230–240 °C. Consecutive fractional extraction with four extractants was performed for the first time, and information about the polysaccharide content and the different polysaccharide fractions present in the wastes was obtained. The overall polysaccharide yield of 14.35 ± 1.01% and 20.01 ± 0.56% from HD and F marigold waste respectively, suggested that marigold waste could be an alternative source of pectic polysaccharides.

Interactions of arabinan-rich pectic polysaccharides with polyphenols

Given the high prevalence of arabinan side chains in pectic polysaccharides, this work aims to unveil the impact of their structural diversity on pectic polysaccharides-polyphenol interactions. To assess the effect of arabinan branching degree, sugar beet arabinans (branched and debranched) were used and compared to the well-known structure of apple arabinan and other pectic polysaccharides. Furthermore, arabinans contribution to pectic polysaccharides/polyphenol interactions was assessed. The interactions were evaluated using chlorogenic acid, phloridzin and procyanidins (degree of polymerization of 9). Linear arabinans had 8-fold and 2-fold higher retention for chlorogenic acid and phloridzin, respectively, than branched arabinans. This trend was also observed for the interaction of arabinans with procyanidins. However, arabinans with covalently linked polyphenols showed lower interactions. The interactions involved between arabinans and polyphenols explained 1–28 % of the interactions of pectic polysaccharides, allowing us to conclude that the whole polysaccharide structure is more relevant for polyphenol interactions than each part.

Structural characterization of a galacturonic acid-rich polysaccharide from Ziziphus Jujuba cv. Muzao

Jujube (Zizyphus jujuba Mill.) have been widely used as a health food and medicinal herb in oriental medicine. In the present study, a novel galacturonic acid-rich polysaccharide (PZMP3-2) was isolated from Zizyphus Jujuba cv. Muzao through hot water extraction, ethanol precipitation, and purification with DEAE-Sepharose Fast Flow and Sephacryl S-300 column chromatography. The chemical structures of PZMP3-2 were elucidated by methylation analysis, along with HPGPC, FT-IR spectroscopy, GC-MS, 1D NMR spectroscopy, and 2D NMR spectroscopy. Its morphological properties were further characterized by SEM, AFM, and XRD. Monosaccharide compositional analysis of PZMP3-2 revealed the presence of rhamnose, arabinose, galactose, and galacturonic acid at a molar ratio of 1.74:2.00: 1.00:18.69, and the HPGPC data demonstrated an average molecular weight of 58.21 kDa. Structural and linkage analysis by GC-MS and NMR spectroscopy suggested that PZMP3-2 was a homogalacturonan (HG)-like pectic polysaccharide branched at C-2 with some Araf and Rhap residues. Such unique structure of PZMP3-2 may indicate distinct bioactivities and further application in food and even clinic.

Fractionation and antioxidant activities of the water-soluble polysaccharides from Lonicera japonica Thunb

L. japonica has been used as food and healthy beverage due to the good nutrition. Although the chemical compounds have been extensively studied, polysaccharide compositions remain unclear. In this study, water-soluble polysaccharides of L. japonica were fractionated into one neutral fraction (LJP-N) and four acidic fractions (LJP-A-1 ~ LJP-A-4) by a combination of ion-exchange and gel permeation chromatographies. The structures and antioxidant activities of these factions were determined by HPLC, FT-IR and the radical scavenging activities, anti-hemolysis inhibitory ability, protective effect against DNA damage. Results showed that LJP-N was a starch-like glucan with some arabinogalactan; acidic fractions were all pectic polysaccharide, with the average molecular weights approximately ranging from 19.0 to 383.8 kDa. LJP-A-2 ~ LJP-A-4 were similar to each other, mainly composed of GalA (>50%) with some Gal and Ara residues, while LJP-A-1 mainly composed of Gal and Ara (>70%). LJP-A-3 was defined as HG-type pectic polysacchride, with a trace of RG-I domain by NMR experiment. The antioxidant activity of LJP fractions showed different activities, and LJP-A-3 and LJP-A-4 exhibited noticeable antioxidant activities by six kinds of evaluated methods comparable with others. The results indicated that LJP-A-3 and LJP-A-4 could be used as a potential natural source of antioxidant.

Preliminary Structural Characteristic of Polysaccharides Extracted From the Callus Tissue of Sosnowskyi’s Hogweed (Heracleum Sosnowskyi Manden) Stem by Aqueous Ammonium Oxalate

Pectic polysaccharides have been isolated from callus tissue of the stem of Sosnowskyi’s hogweed (Heracleum sosnowskyi Manden) by extraction with a 0.7% aqueous solution of ammonium oxalate and characterized. It was shown that they differ from pectic polysaccharides of a native plant by a lower content of D‑galacturonic acid residues and a higher content of arabinose and galactose residues. The results obtained by a combination of ion exchange chromatography, enzymatic hydrolysis, periodate oxidation, methylation and NMR spectroscopy indicated the presence of low-methyl esterified 1,4-α-D-galacturonan, rhamogalacturonan-I, arabinan and galactan or arabinogalactan. The terminal 1,2- and 1,5-linked arabinofuranose residues, terminal, 1,3-, 1,6-linked and 3,6-substituted galactopyranose residues and 1,4-linked hexopyranose (galactopyranose or glucopyranose) residues were identified in the composition of neutral carbohydrate chains. The presence in the NMR spectra of trans-glycosyl correlation peaks of the methyl groups of 2,4-di-O-substituted rhamnose residues indirectly confirm the attachment arabinan, galactan or arabinogalactan carbohydrate chains to rhamnopyranose residues of the backbone at C-4 position.

Emulsifying properties of pectic polysaccharides obtained by sequential extraction from black tomato pomace

The polysaccharides in black tomato pomace (BTP) were extracted by water, cyclohexane-trans-1,2-diamine tetraacetic acid, Na2CO3 and KOH to obtain hemicellulose fraction (HF) and pectic fractions including water-soluble pectin (WEP), chelator-extractable pectin (CEP), sodium carbonate extractable pectin (NEP). Structural characterization indicated that WEP, CEP and NEP were high-methylated (68.02%, 61.58% and 59.70%, respectively). Percentage content of the major domain, linear homogalacturonan (HG), in WEP, CEP and NEP were 70.44%, 84.07% and 60.08%, respectively, while the percentage content of branched rhamnogalacturonan (RG-I) were 10.97%, 5.32% and 29.08%, respectively. The results were also confirmed by atomic force microscope (AFM) images. DSC results showed that the Tm of CEP and NEP was higher than WEP. Evaluation of emulsifying property suggested that the pectic fractions could stabilize emulsion containing 50% oil phase at a concentration as high as 1.5% (w/v) and pH 4.0–8.0. Pectin's ability to lower surface tension and increase viscosity, along with the repulsion in pectin molecules, facilitated emulsion formation. Protein residue (WEP) and structure difference (CEP and NEP) might be responsible to the distinction of emulsifying capacity.

Chemical characterization and bioactivities of polysaccharides from Apocynum venetum leaves extracted by different solvents

Apocynum venetum has a long history as a Chinese traditional tea. As one of the major components, polysaccharides from Apocynum venetum leaves were extracted with acid (HCl), distilled water and alkaline (NaOH) to study the effect of the extraction solvents on their chemical composition and biological activities in this work. Monosaccharide composition revealed that polysaccharides from acidic and distilled water extraction were pectic polysaccharides, while those from alkaline extraction consisted of pectin and hemicellulose. Chemical analysis and FT-IR spectra indicated the co-extraction of protein and polyphenol contents in alkaline extracted polysaccharides, which exhibited strongest antioxidant and digestive enzyme inhibition activities. The antioxidant capacities were 185.26–286.30 mg TE/g for DPPH radical scavenging, 409.06–502.00 mg TE/g for ABTS radical scavenging, and 152.12–260.70 mg TE/g sample for reducing power assay, respectively. The lowest IC50 for α-glucosidase and lipase inhibition activities were 16.75 μg/mL and 820 μg/mL, respectively. Further purification of alkaline extracts was carried out and characterized. The results showed that acid hydrolysis could successfully reduce polyphenol and protein contents, and purified polysaccharides showed even higher antioxidant activities and α-glucosidase inhibition activity. These results provide a scientific support for functional application and extraction of polysaccharides from Apocynum venetum leaves.

Structural Characterization and Immunomodulatory Activities of Modified Pectic Polysaccharide from Decalepis hamiltonii (Swallow root)

Structural Characterization and Immunomodulatory Activities of Modified Pectic Polysaccharide from Decalepis hamiltonii (Swallow root)

In-Vitro Prebiotic Analysis of Microbiota Accessible Pectic Polysaccharides.

Pectin is a diverse polysaccharide comprising of polygalacturonic acid, rhamnogalactouronan, and neutral polysaccharides (arabinan and arabinogalactan) as side chains or branches. They are resistant to salivary amylase and gastric juice. In the present study the prebiotic potentials of different pectic derived substrates were performed by using intestinal cultures and measuring the growth, change in pH and short chain fatty acid, (SCFA) production. Arabinan, arabinogalactan, and rhamnogalacturonan were fermented by probiotic bacteria such as Bifidobacterium breve, Bi. longum, Bi. bifidum, and Bacteroides thetaiotaomicron (commensal bacteria). While, polygalacturonic acid was fermented by Ba. fragilis, Ba. thetaiotaomicron, and Ba. uniformis. All the screened bacteria significantly decreased the pH from 7 to 5 (pH difference of ≈ 2), which clearly indicated that the above bacteria produced the enzymes necessary for the digestion of the pectic derived polysaccharides. The SCFA profiles of the above screened bacteria clearly demonstrated the production of lactate, acetate and propionate which are the key metabolites involved in maintaining gut health and prevention of several intestinal diseases. Thus, pectic polysaccharides hold potential application in food industry as prebiotic ingredients or dietary fibers.

Pectic polysaccharides from purple passion fruit peel: A comprehensive study in macromolecular and conformational characterizations

A polysaccharide (PFPP) from purple passion fruit peel was optimally extracted, with the highest yield (10.05%, w/w) obtained under 35 °C extraction temperature, 240 W ultrasonic power, 65:1 mL/g liquid-to-solid ratio, 0.6% (w/v) ammonium oxalate, 30 min extraction time and pH 2.0. According to composition analyses, pectic PFPP and its fractions (PFPP-10, -15 and -20) were revealed as linear homogalacturonans interrupted by rhamnogalacturonan I in different lengths and extensities, where low esterification degrees (35.35–39.66%) were indicated via FT-IR. Furthermore, based on macromolecular models, comprehensive analyses on macromolecular and conformational characterizations of PFPP fractions were conducted quantitatively through, e.g., shape factor (1.42–1.79), Mark-Houwink-Sakurada exponent (0.55–0.74), conformational power-law exponent (0.52–0.58), fractal dimension (1.72–1.94) and persistence length (6.73–13.47 nm). Therefore, different semi-flexible coil conformations were proposed schematically, where lower molecular-weight PFPP fractions were less flexible. This could provide a molecular basis for precise re-utilizations of PFPP in food and pharmaceutical industries.

MICROBIAL PECTINASES: A REVIEW ON MOLECULAR AND BIOTECHNOLOGICAL PERSPECTIVES

Pectinases are upcoming enzymes in the biotechnological sector. This large group of enzymes involves in break down of pectic polysaccharides, the major component of middle lamella in plant cell wall. The pectin degrading enzymes are categorized according to their mode of action and release of degradative products. Various filamentous fungi, yeast, and bacteria are the common sources of microbial pectinases. Solid state fermentation is more preferable for extracellular microbial pectinases production over the submerged fermentation. A group of genes regulates the expression of pectinolytic enzymes. Mostly, all the enzymes share a common parallel  helix topology which consists of a single domain of parallel -strands folded into a large right-handed cylinder. These enzymes are eco-friendly tools for industrial applications and being used in various sectors like wine, food, paper industry, waste paper recycling, fruit juice preparation, processing of tea–coffee, animal feed preparation.

Polyphenols associated to pectic polysaccharides account for most of the antiproliferative and antioxidant activities in olive extracts

• Olive extracts rich in polysaccharides associated with polyphenols were obtained. • The extracts showed strong antioxidant and antiproliferative activities. • These activities were reduced when the phenols were removed by sodium chlorite. • Bleached extracts had a similar antiproliferative activity as citrus modified pectin. Extracts rich in pectic polysaccharides associated to polyphenols were obtained from alperujo, the by-product of olive oil extraction, by different thermal treatments and subsequent chemical treatments. The resulting “Pectoliv” extracts exhibited strong antioxidant activities and a high antiproliferative capacities in vitro against colon carcinoma Caco-2 and leukemia monocytic THP-1 cell lines. Bleaching of the extracts with sodium chlorite removed the phenolic compounds and significantly reduced antiproliferative and antioxidant activities, confirming that these were due mainly to the associated polyphenols present in Pectoliv. However, even after bleaching, these activities remained very similar to that of a commercial citrus modified pectin obtained by chemical treatment from citrus pectin, which has been implicated in cancer treatment and prevention. Thus Pectolivs have a high potential as antiproliferative or antioxidant agents.

New steps in mucilage biosynthesis revealed by analysis of the transcriptome of the UDP-rhamnose/UDP-galactose transporter 2 mutant.

Upon imbibition, epidermal cells of Arabidopsis thaliana seeds release a mucilage formed mostly by pectic polysaccharides. The Arabidopsis mucilage is composed mainly of unbranched rhamnogalacturonan-I (RG-I), with low amounts of cellulose, homogalacturonan, and traces of xylan, xyloglucan, galactoglucomannan, and galactan. The pectin-rich composition of the mucilage and their simple extractability makes this structure a good candidate to study the biosynthesis of pectic polysaccharides and their modification. Here, we characterize the mucilage phenotype of a mutant in the UDP-rhamnose/galactose transporter 2 (URGT2), which exhibits a reduction in RG-I and also shows pleiotropic changes, suggesting the existence of compensation mechanisms triggered by the lack of URGT2. To gain an insight into the possible compensation mechanisms activated in the mutant, we performed a transcriptome analysis of developing seeds using RNA sequencing (RNA-seq). The results showed a significant misregulation of 3149 genes, 37 of them (out of the 75 genes described to date) encoding genes proposed to be involved in mucilage biosynthesis and/or its modification. The changes observed in urgt2 included the up-regulation of UAFT2, a UDP-arabinofuranose transporter, and UUAT3, a paralog of the UDP-uronic acid transporter UUAT1, suggesting that they play a role in mucilage biosynthesis. Mutants in both genes showed changes in mucilage composition and structure, confirming their participation in mucilage biosynthesis. Our results suggest that plants lacking a UDP-rhamnose/galactose transporter undergo important changes in gene expression, probably to compensate modifications in the plant cell wall due to the lack of a gene involved in its biosynthesis.