Monosaccharide/proton symporter AtSTP1 plays a major role in uptake and response of Arabidopsis seeds and seedlings to sugars

Abstract

The aim of this study was to investigate the in vivo properties and function of the high-affinity monosaccharide/proton symporter AtSTP1 of Arabidopsis. We isolated an Atstp1 knock-out mutant and found that this plant grows and develops normally. The AtSTP1 gene is expressed in germinating seeds and seedlings, with AtSTP1 activity found mainly in the seedling root. The rate of uptake of [(14)C]-3-O-methylglucose and [(14)C]-D-glucose is 60% less in Atstp1 seedlings than in the wild type, showing that AtSTP1 is the major monosaccharide transporter in Arabidopsis seedlings. Transport of D-galactose and D-mannose is also up to 60% less in Atstp1 seedlings compared to wild type, but transport of D-fructose, L-arabinose and sucrose is not reduced. Germination of Atstp1 seed shows reduced sensitivity to D-mannose, demonstrating that AtSTP1 is active before germination. Atstp1 seedlings grow effectively on concentrations of D-galactose that inhibit wild-type growth, even at up to 100 mM D-galactose, indicating that active transport by AtSTP1 plays a major role at very high concentrations of exogenous sugar. These findings provide insight into the physiological function of AtSTP1 and clearly establish its importance in the uptake of extracellular sugars by the embryo and in seedlings.

Monosaccharide Absorption Activity of Arabidopsis Roots Depends on Expression Profiles of Transporter Genes under High Salinity Conditions

“…Our data showed that monosaccharide transport activity in Arabidopsis roots changed under conditions of high salinity as a result of changes in the expression level of transporter genes. It has been reported previously that STP1 is involved in the uptake of monosaccharides from the surrounding environment (11). In the present study we demonstrated that STP13 also plays an important role in the uptake of monosaccharides in Arabidopsis roots.…”

“…In addition, mannose strongly inhibits seed germination and postgermination growth (27). It has been previously reported that the stp1 mutant exhibits insensitivity to galactose and mannose (11). We also observed that the root lengths of the stp1 mutants were longer than those of wild type plants under high galactose conditions (Fig.…”

“…STP1, a monosaccharides/proton symporter, is involved in the absorption of monosaccharides in Arabidopsis (10). An stp1 knock-out mutant is insensitive to galactose and mannose, and the level of uptake of monosaccharides in stp1 mutant plants was shown to be lower than in wild type plants (11). However, the precise role of STP1 in the uptake of the monosaccharides in the roots was unclear because whole plants were used to measure the level of monosaccharide uptake.…”

Arabidopsis Peroxisomal Citrate Synthase Is Required for Fatty Acid Respiration and Seed Germination

“…Arabidopsis thaliana seeds were surface-sterilized, stratified, and germinated as described previously (Sherson et al, 2000). Seedlings were grown on half-strength MS medium (Sigma-Aldrich, Poole, Dorset, UK) with or without sucrose in continuous light (100 mmolÁm ÿ2 Ás ÿ1 ) at 228C unless otherwise stated.…”

Lipid Utilization, Gluconeogenesis, and Seedling Growth in Arabidopsis Mutants Lacking the Glyoxylate Cycle Enzyme Malate Synthase

“…The gene-specific primers MS50 (5Ј-ATG GAG CTC GAG ACC TCA GTT TAT C-3Ј), MS51 (5Ј-GCT GCT TTC GAG GAC GCT TTG TCT C-3Ј), MS30 (5Ј-GAG CCT TGA GAC ATT GAT AGG GTA G-3Ј), and MS31 (5Ј-ACA AGT ACG GAT GAG AAG ATC AGA G-3Ј) were used in combination with T-DNA left border primers (13,15,16). This screening identified an insertion in a plant in the Wassilewskija ecotype from the Versailles collection (15,16).…”