Dataset Information

Sucrose and light regulation of a cold-inducible UDP-glucose pyrophosphorylase gene via a hexokinase-independent and abscisic acid-insensitive pathway in Arabidopsis.

ABSTRACT: UDP-glucose pyrophosphorylase (UGPase) is a key enzyme producing UDP-glucose, which is involved in an array of metabolic pathways concerned with, among other functions, the synthesis of sucrose and cellulose. An Arabidopsis thaliana UGPase-encoding gene, Ugp, was profoundly up-regulated by feeding sucrose to the excised leaves and by an exposure of plants to low temperature (5 degrees C). The UGPase activity and its protein content also increased under conditions of sucrose feeding and exposure to cold. The sucrose effect on Ugp was apparently specific and was mimicked by exposure of dark-adapted leaves to light. Drought and O2 deficiency had some down-regulating effects on expression of Ugp. The sugar-signalling pathway for Ugp regulation was independent of hexokinase, as was found by using transgenic plants with increased and decreased expression of the corresponding gene. Subjecting mutants deficient in abscisic acid (ABA) to cold stress conditions had no effect on Ugp expression profiles. Okadaic acid was a powerful inhibitor of Ugp expression, whereas it up-regulated the gene encoding sucrose synthase (Sus1), indicating distinct transduction pathways in transmitting the sugar signal for the two genes in A. thaliana. We suggest that Ugp gene expression is mediated via a hexokinase-independent and ABA-insensitive pathway that involves an okadaic acid-responsive protein phosphatase. The data point towards Ugp as a possible regulatory entity that is closely involved in the homoeostatic readjustment of plant responses to environmental signals.

SUBMITTER: Ciereszko I

PROVIDER: S-EPMC1221629 | biostudies-other | 2001 Feb

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:Leishmaniases are a set of tropical and sub-tropical diseases caused by protozoan parasites of the genus Leishmania whose severity ranges from self-healing cutaneous lesions to fatal visceral infections. Leishmania parasites synthesise a wide array of cell surface and secreted glycoconjugates that play important roles in infection. These glycoconjugates are particularly abundant in the promastigote form and known to be essential for establishment of infection in the insect midgut and effective transmission to the mammalian host. Since they are rich in galactose, their biosynthesis requires an ample supply of UDP-galactose. This nucleotide-sugar arises from epimerisation of UDP-glucose but also from an uncharacterised galactose salvage pathway. In this study, we evaluated the role of the newly characterised UDP-sugar pyrophosphorylase (USP) of Leishmania major in UDP-galactose biosynthesis. Upon deletion of the USP encoding gene, L. major lost the ability to synthesise UDP-galactose from galactose-1-phosphate but its ability to convert glucose-1-phosphate into UDP-glucose was fully maintained. Thus USP plays a role in UDP-galactose activation but does not significantly contribute to the de novo synthesis of UDP-glucose. Accordingly, USP was shown to be dispensable for growth and glycoconjugate biosynthesis under standard growth conditions. However, in a mutant seriously impaired in the de novo synthesis of UDP-galactose (due to deficiency of the UDP-glucose pyrophosphorylase) addition of extracellular galactose increased biosynthesis of the cell surface lipophosphoglycan. Thus under restrictive conditions, such as those encountered by Leishmania in its natural habitat, galactose salvage by USP may play a substantial role in biosynthesis of the UDP-galactose pool. We hypothesise that USP recycles galactose from the blood meal within the midgut of the insect for synthesis of the promastigote glycocalyx and thereby contributes to successful vector infection.

Dataset Information

Sucrose and light regulation of a cold-inducible UDP-glucose pyrophosphorylase gene via a hexokinase-independent and abscisic acid-insensitive pathway in Arabidopsis.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets