Genome-wide analysis of the UDP-glucose dehydrogenase gene family in Arabidopsis, a key enzyme for matrix polysaccharides in cell walls

Abstract

Arabidopsis cell walls contain large amounts of pectins and hemicelluloses, which are predominantly synthesized via the common precursor UDP-glucuronic acid. The major enzyme for the formation of this nucleotide-sugar is UDP-glucose dehydrogenase, catalysing the irreversible oxidation of UDP-glucose into UDP-glucuronic acid. Four functional gene family members and one pseudogene are present in the Arabidopsis genome, and they show distinct tissue-specific expression patterns during plant development. The analyses of reporter gene lines indicate gene expression of UDP-glucose dehydrogenases in growing tissues. The biochemical characterization of the different isoforms shows equal affinities for the cofactor NAD(+) ( approximately 40 microM) but variable affinities for the substrate UDP-glucose (120-335 microM) and different catalytic constants, suggesting a regulatory role for the different isoforms in carbon partitioning between cell wall formation and sucrose synthesis as the second major UDP-glucose-consuming pathway. UDP-glucose dehydrogenase is feedback inhibited by UDP-xylose. The relatively (compared with a soybean UDP-glucose dehydrogenase) low affinity of the enzymes for the substrate UDP-glucose is paralleled by the weak inhibition of the enzymes by UDP-xylose. The four Arabidopsis UDP-glucose dehydrogenase isoforms oxidize only UDP-glucose as a substrate. Nucleotide-sugars, which are converted by similar enzymes in bacteria, are not accepted as substrates for the Arabidopsis enzymes.

Characterization of GDP-mannose Dehydrogenase from the Brown Alga Ectocarpus siliculosus Providing the Precursor for the Alginate Polymer

“…The alkaline pH optimum for EsGMD1 is approximately pH 8.5-and thus near to the pK a -value of the Cys residue. Similar pH optima were observed for UGDs from plants (17,18). For the Pseudomonas GMD Roychoudhury et al (9) report a significantly lower and very sharp pH optimum of pH 7.7 which seems to be an exception for this group of enzymes.…”

Up-regulation of biosynthetic processes associated with growth by trehalose 6-phosphate

“…PIF4 may also be involved in auxin signaling as shown by the lack of induction of the auxin-inducible IAA29 UDP-glucuronic acid, from which it is estimated that in Arabidopsis 50% of cell wall biomass is derived. 10 We found that four UDPG dehydrogenases (UDPG-DH) genes which form UDP-glucuronic acid from UDPG were upregulated by T6P ( Table 1, Fig. 2).…”

“…These enzymes are tightly correlated with cell division and growth. 10 In trees they are used as a marker enzyme for cambial meristem. Three UDP-glucuronic acid decarboxylases which form xylose from UDP-glucuronic acid and a UDP-xylose epimerase which forms xylose from arabinose were also upregulated, together with two glucuronic acid epimerases which catalyze formation of UDP-galacturonic acid and a rhamnose synthase.…”

“…The cell wall of Arabidopsis consists of large amounts of hemicelluloses which contain xylose and galacturonic acid in particular, and pectin which consists of α-1,4-linked galacturonic acid units. 10 These are predominantly synthesized from inhibiting the starvation response mediated by SnRK1 and in the upregulation of genes involved in biosynthetic processes. Particularly significant for the regulation of growth in Arabidopsis seedlings are effects on genes encoding enzymes of cell wall synthesis, which accounts for a major portion of carbon utilization.…”

Gibberellins Regulate Lateral Root Formation inPopulusthrough Interactions with Auxin and Other Hormones

“…Likewise, two UDP-glucose dehydrogenase (UGD) genes that encode important enzymes in the synthesis of pectins and hemicelluloses were also activated in the transgenic plants. Expression of UGD genes is typically restricted to growing cells (Johansson et al, 2002;Klinghammer and Tenhaken, 2007).…”