GPT2: a glucose 6-phosphate/phosphate translocator with a novel role in the regulation of sugar signalling during seedling development.
OBJECTIVE
GPT2, a glucose 6-phosphate/phosphate translocator, plays an important role in environmental sensing in mature leaves of Arabidopsis thaliana. Its expression has also been detected in arabidopsis seeds and seedlings. In order to examine the role of this protein early in development, germination and seedling growth were studied.


METHODS
Germination, greening and establishment of seedlings were monitored in both wild-type Arabidopsis thaliana and in a gpt2 T-DNA insertion knockout line. Seeds were sown on agar plates in the presence or absence of glucose and abscisic acid. Relative expression of GPT2 in seedlings was measured using quantitative PCR.


RESULTS
Plants lacking GPT2 expression were delayed (25-40 %) in seedling establishment, specifically in the process of cotyledon greening (rather than germination). This phenotype could not be rescued by glucose in the growth medium, with greening being hypersensitive to glucose. Germination itself was, however, hyposensitive to glucose in the gpt2 mutant.


CONCLUSIONS
The expression of GPT2 modulates seedling development and plays a crucial role in determining the response of seedlings to exogenous sugars during their establishment. This allows us to conclude that endogenous sugar signals function in controlling germination and the transition from heterotrophic to autotrophic growth, and that the partitioning of glucose 6-phosphate, or related metabolites, between the cytosol and the plastid modulates these developmental responses.
Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
Beth C
BC
Dyson
Rachel E
RE
Webster
Giles N
GN
Johnson
D000040:Abscisic Acid / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics; D018548:Cotyledon / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D018525:Germination; D005947:Glucose / Q000378:metabolism; D019298:Glucose-6-Phosphate / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism; D016254:Mutagenesis, Insertional; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D015398:Signal Transduction
D029681:Arabidopsis Proteins; C000592795:GPT2 protein, Arabidopsis; D009004:Monosaccharide Transport Proteins; D010937:Plant Growth Regulators; D019298:Glucose-6-Phosphate; D000040:Abscisic Acid; D005947:Glucose
Arabidopsis thaliana; GPT2; Germination; glucose; greening; seedling development; sugar signalling