Overexpression of two different potato UDP-Glc 4-epimerases can increase the galactose content of potato tuber cell walls

Oomen, Roelof; Dao-Thi, Bang; Tzitzikas, Emmanouil N.; Bakx, Edwin J.; Schols, Henk A.; Visser, Richard G. F.; Vincken, Jean‐Paul

doi:10.1016/j.plantsci.2003.12.033

Cited by 21 publications

(21 citation statements)

References 30 publications

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“…Previous experiments with potato and Arabidopsis have indicated that UDP-Gal rather than b-1,4-galactan synthase might be limiting for b-1,4-galactan synthesis (Seifert et al, 2002;Oomen et al, 2004;Rösti et al, 2007). However, our results indicate that Arabidopsis leaves contain sufficient UDP-Gal to support a substantial increase in galactan synthesis.…”

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confidence: 66%

“…Plants overexpressing GALS1 already had a significantly increased C6/C5 sugar ratio in their cell walls and did not show any adverse phenotype. Given that UDP-Gal appeared to be limiting for galactan synthesis in some studies (Seifert et al, 2002;Oomen et al, 2004;Rösti et al, 2007), it is conceivable that an even higher level of galactan accumulation can be achieved by simultaneously overexpressing an appropriate isoform of UDP-Gal epimerase. Hence, the GALS genes may be important tools for developing bioenergy crops.…”

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Pectin Biosynthesis: GALS1 in Arabidopsis thaliana Is a β-1,4-Galactan β-1,4-Galactosyltransferase

et al. 2012

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b-1,4-Galactans are abundant polysaccharides in plant cell walls, which are generally found as side chains of rhamnogalacturonan I. Rhamnogalacturonan I is a major component of pectin with a backbone of alternating rhamnose and galacturonic acid residues and side chains that include a-1,5-arabinans, b-1,4-galactans, and arabinogalactans. Many enzymes are required to synthesize pectin, but few have been identified. Pectin is most abundant in primary walls of expanding cells, but b-1,4-galactan is relatively abundant in secondary walls, especially in tension wood that forms in response to mechanical stress. We investigated enzymes in glycosyltransferase family GT92, which has three members in Arabidopsis thaliana, which we designated GALACTAN SYNTHASE1, (GALS1), GALS2 and GALS3. Loss-of-function mutants in the corresponding genes had a decreased b-1,4-galactan content, and overexpression of GALS1 resulted in plants with 50% higher b-1,4-galactan content. The plants did not have an obvious growth phenotype. Heterologously expressed and affinity-purified GALS1 could transfer Gal residues from UDP-Gal onto b-1,4-galactopentaose. GALS1 specifically formed b-1,4-galactosyl linkages and could add successive b-1,4-galactosyl residues to the acceptor. These observations confirm the identity of the GT92 enzyme as b-1,4-galactan synthase. The identification of this enzyme could provide an important tool for engineering plants with improved bioenergy properties.

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confidence: 66%

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confidence: 99%

Pectin Biosynthesis: GALS1 in Arabidopsis thaliana Is a β-1,4-Galactan β-1,4-Galactosyltransferase

et al. 2012

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“…2 Recipient of a John Innes Centre MSc scholarship. 3 cates that UGE activity is rate-limiting for the biosynthesis of some cell wall polymers (14). Interestingly, overexpression of one potato UGE isoform increased galactose tolerance, whereas overexpression of the other isoform did not.…”

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confidence: 99%

Distinct Properties of the Five UDP-d-glucose/UDP-d-galactose 4-Epimerase Isoforms of Arabidopsis thaliana

Barber

Rösti

Rawat

et al. 2006

Journal of Biological Chemistry

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Plant genomes contain genetically encoded isoforms of most nucleotide sugar interconversion enzymes. Here we show that Arabidopsis thaliana has five genes encoding functional UDP-Dglucose/UDP-D-galactose 4-epimerase (named UGE1 to UGE5). All A. thaliana UDP-D-glucose 4-epimerase isoforms are dimeric in solution, maximally active in vitro at 30 -40°C, and show good activity between pH 7 and pH 9. In vitro, UGE1, -3, and -5 act independently of externally added NAD ؉ , whereas cofactor addition stimulates the activity of UGE2 and is particularly important for UGE4 activity. UGE1 and UGE3 are most efficiently inhibited by UDP. The five isoforms display k cat UDP-Gal values between 23 and 128 s ؊1 and K m UDP-Gal values between 0.1 and 0.3 mM. This results in enzymatic efficiencies ranging between 97 and 890 mM ؊1 s ؊1 for UGE4 ‫؍‬ UGE1 < UGE3 < UGE5 < UGE2.The K m UDP-Glc values, derived from the Haldane relationship, were 0.76 mM for UGE1, 0.56 mM for UGE4, and between 0.13 and 0.23 mM for UGE2, -3, and -5. The expression of UGE isoforms is ubiquitous and displays developmental and cell type-dependent variations. UGE1 and -3 expression patterns globally resemble enzymes involved in carbohydrate catabolism, and UGE2, -4, and -5 expression is more related to carbohydrate biosynthesis. UGE1, -2, and -4 are present in the cytoplasm, whereasUGE4 is additionally enriched close to Golgi stacks. All UGE genes tested complement the UGE4 rhd1 phenotype, confer increased galactose tolerance in planta, and complement the galactose metabolization deficiency in the Saccharomyces cerevisiae gal10 mutant. We suggest that plant UGE isoforms function in different metabolic situations and that enzymatic properties, gene expression pattern, and subcellular localization contribute to the differentiation of isoform function.The biosynthesis of plant carbohydrates requires specific glycosyltransferases that act on activated sugars, typically uridine diphosphate, adenosine diphosphate, and guanosine diphosphate hexoses and pentoses. In addition to acting as biosynthetic substrates, nucleotide sugars are modified at their glycosyl moieties by nucleotide sugar interconversion enzymes to generate different sugars and are intermediates in the uptake of the free sugars released from the breakdown of nutritional or storage carbohydrates and other sources. The biochemistry and reaction mechanism of many nucleotide sugar interconversion pathways have been reviewed previously (1). cDNAs coding for nucleotide sugar interconverting enzymes have been cloned and recombinant proteins purified, leading the way to x-ray crystallography (2-5). The complete sequencing of entire genomes revealed a surprising over-representation of genes encoding putative isoforms of nucleotide sugar interconversion enzymes in plant genomes (6, 7), but the functional significance of this apparent genetic redundancy remains to be established.One of the best characterized nucleotide sugar interconversion enzymes is UDP-glucose 4-epimerase (EC 5.1.3.2; UGE), 4 which interconve...

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“…However, no alterations were observed in the content of UDP-gal and UDPglu, albeit a maximal reduction in UGE activity of 10% compared to the wild type (Dörmann and Benning 1998). Several reports suggest that UDP-gal synthesized by UGE is utilized for the biosynthesis of cell wall polysaccharides (e.g., xyloglucan and rhamnogalacturonan) (Seifert et al 2002;Oomen et al 2004). UDP-gal and UDP-glu are also utilized as a sugar donor for anthocyanin and sucrose biosynthesis in apple skin, respectively.…”

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confidence: 97%

UDP-sugar biosynthetic pathway: contribution to cyanidin 3-galactoside biosynthesis in apple skin

Ban

Kondo

Ubi

et al. 2009

Planta

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UDP-galactose:flavonoid 3-O-galactosyltransferase (UFGalT) is responsible for cyanidin 3-galactoside (cy3-gal) synthesis from cyanidin (cy) and UDP-galactose (UDP-gal) which are, respectively, catalyzed by anthocyanidin synthase (ANS) and UDP-glucose 4-epimerase (UGE). To clarify the contribution of UDP-galactose pathway to cy3-gal accumulation in apple skin, we analyzed the contents of UDP-gal and UDP-glucose (UDP-glu), cy, and, cy3-gal contents along with UGE activity. We confirmed that transcript levels for apple ANS and UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) coincided with anthocyanin accumulation in three apple cultivars differing in their skin colors. During fruit development, changes in level of cy coincided with that of cy3-gal, whereas UDP-gal and UGE activity showed no similar trend with cy3-gal. Significant correlation was not observed between the changes in UGE activity and UDP-sugar contents. The effect of temperature and UV-B radiation (different environmental conditions) on the accumulation of UDP-sugars, cy and cy3-gal, and UGE activity were also investigated in a pale-red cultivar. High temperature tended to depress the accumulation of both UDP-sugars and cy concomitant with the decrease in cy3-gal content irrespective of UV-B radiation. Although there was no high inhibition of both cy and UDP-sugars at low-temperature without UV-B, cy3-gal accumulation was highly depressed. UGE activity was highest at low temperature with UV-B, but not much different under other conditions. Most of the parameters under different environmental conditions were significantly correlated with each other. Based on these results, contribution of UDP-sugar biosynthetic pathway to anthocyanin biosynthesis under different environmental conditions as well as during fruit development is discussed.

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Overexpression of two different potato UDP-Glc 4-epimerases can increase the galactose content of potato tuber cell walls

Cited by 21 publications

References 30 publications

Pectin Biosynthesis: GALS1 in Arabidopsis thaliana Is a β-1,4-Galactan β-1,4-Galactosyltransferase

Pectin Biosynthesis: GALS1 in Arabidopsis thaliana Is a β-1,4-Galactan β-1,4-Galactosyltransferase

Distinct Properties of the Five UDP-d-glucose/UDP-d-galactose 4-Epimerase Isoforms of Arabidopsis thaliana

UDP-sugar biosynthetic pathway: contribution to cyanidin 3-galactoside biosynthesis in apple skin

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