title: Heterologous expression of yeast Hxt2 in Arabidopsis thaliana alters sugar uptake, carbon metabolism and gene expression leading to glucose tolerance of germinating seedlings.
abstract: The hexose transporter 2 gene (Hxt2) from Saccharomyces cerevisiae was expressed in Arabidopsis thaliana under control of the 35S promoter. Several independent transgenic lines were selected after confirming single gene insertion by southern blot analysis in the T4 generation. Northern blots revealed the presence of heterologous transcript. Radiolabeling experiments revealed an increased rate of incorporation of the non-metabolizable analog 3-O-methyl-[U-14C]-glucose. This confirmed that the yeast Hxt2 transporter was functional in Arabidopsis. No phenotypic changes at the vegetative and reproductive stages could be detected in the transgenic lines when compared to wild type plants. Shortly after germination some differences in development and glucose signaling were observed. Transgenic seedlings cultivated in liquid medium or on solid agar plates were able to grow with 3% glucose (producing bigger plants and longer roots), while development of wild type plants was delayed under those conditions. Metabolite analysis revealed that the Hxt2 transgenic lines had higher rates of sugar utilization. Transcriptional profiling showed that particular genes were significantly up- or down-regulated. Some transcription factors like At1g27000 were repressed, while others, such as At3g58780, were induced. The mRNA from classical sugar signaling genes such as STP1, Hxk1, and ApL3 behaved similarly in transgenic lines and wild type lines. Results suggest that the Hxt2 transgene altered some developmental processes related to the perception of high carbon availability after the germination stage. We conclude that the developmental arrest of wild type plants at 3% glucose not only depends on Hxk1 as the only sugar sensor but might also be influenced by the route of hexose transport across the plasma membrane.
authors.affiliation: Facultad de Química, Departamento de Bioquímica, Universidad Nacional Autónoma de México, 04510, México D.F., México.
authors.forename: Daniel
authors.initials: D
authors.lastname: Padilla-Chacón
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Cordoba
authors.forename: Teresa
authors.initials: T
authors.lastname: Olivera
authors.forename: Sobeida
authors.initials: S
authors.lastname: Sánchez
authors.forename: Patricia
authors.initials: P
authors.lastname: Coello
authors.forename: Patricia
authors.initials: P
authors.lastname: León
authors.forename: Axel
authors.initials: A
authors.lastname: Tiessen
authors.forename: Eleazar
authors.initials: E
authors.lastname: Martínez-Barajas
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D001692:Biological Transport; D002244:Carbon / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D018525:Germination; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics*; D006601:Hexoses / Q000378:metabolism; D010641:Phenotype; D030821:Plants, Genetically Modified / Q000254:growth & development / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D015398:Signal Transduction
chemical_list: D051246:Glucose Transport Proteins, Facilitative; C084498:HXT2 protein, S cerevisiae; D006601:Hexoses; D029701:Saccharomyces cerevisiae Proteins; D002244:Carbon; D005947:Glucose