title: Monosaccharide absorption activity of Arabidopsis roots depends on expression profiles of transporter genes under high salinity conditions.
abstract: Plant roots are able to absorb sugars from the rhizosphere but also release sugars and other metabolites that are critical for growth and environmental signaling. Reabsorption of released sugar molecules could help reduce the loss of photosynthetically fixed carbon through the roots. Although biochemical analyses have revealed monosaccharide uptake mechanisms in roots, the transporters that are involved in this process have not yet been fully characterized. In the present study we demonstrate that Arabidopsis STP1 and STP13 play important roles in roots during the absorption of monosaccharides from the rhizosphere. Among 14 STP transporter genes, we found that STP1 had the highest transcript level and that STP1 was a major contributor for monosaccharide uptake under normal conditions. In contrast, STP13 was found to be induced by abiotic stress, with low expression under normal conditions. We analyzed the role of STP13 in roots under high salinity conditions where membranes of the epidermal cells were damaged, and we detected an increase in the amount of STP13-dependent glucose uptake. Furthermore, the amount of glucose efflux from stp13 mutants was higher than that from wild type plants under high salinity conditions. These results indicate that STP13 can reabsorb the monosaccharides that are released by damaged cells under high salinity conditions. Overall, our data indicate that sugar uptake capacity in Arabidopsis roots changes in response to environmental stresses and that this activity is dependent on the expression pattern of sugar transporters.
authors: Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
authors: Kohji
authors: K
authors: Yamada
authors: Motoki
authors: M
authors: Kanai
authors: Yuriko
authors: Y
authors: Osakabe
authors: Haruka
authors: H
authors: Ohiraki
authors: Kazuo
authors: K
authors: Shinozaki
authors: Kazuko
authors: K
authors: Yamaguchi-Shinozaki
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D005690:Galactose / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000235:genetics; D008358:Mannose / Q000378:metabolism; D009005:Monosaccharides / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054712:Salinity; D012965:Sodium Chloride / Q000494:pharmacology; D027981:Symporters / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D009005:Monosaccharides; C510622:STP13 protein, Arabidopsis; D027981:Symporters; D012965:Sodium Chloride; D008358:Mannose; D005690:Galactose