Mutation of Arabidopsis plastid phosphoglucose isomerase affects leaf starch synthesis and floral initiation.
We isolated pgi1-1, an Arabidopsis mutant with a decreased plastid phospho-glucose (Glc) isomerase activity. While pgi1-1 mutant has a deficiency in leaf starch synthesis, it accumulates starch in root cap cells. It has been shown that a plastid transporter for hexose phosphate transports cytosolic Glc-6-P into plastids and expresses restricted mainly to the heterotrophic tissues. The decreased starch content in leaves of the pgi1-1 mutant indicates that cytosolic Glc-6-P cannot be efficiently transported into chloroplasts to complement the mutant's deficiency in chloroplastic phospho-Glc isomerase activity for starch synthesis. We cloned the Arabidopsis PGI1 gene and showed that it encodes the plastid phospho-Glc isomerase. The pgi1-1 allele was found to have a single nucleotide substitution, causing a Ser to Phe transition. While the flowering times of the Arabidopsis starch-deficient mutants pgi1, pgm1, and adg1 were similar to that of the wild type under long-day conditions, it was significantly delayed under short-day conditions. The pleiotropic phenotype of late flowering conferred by these starch metabolic mutations suggests that carbohydrate metabolism plays an important role in floral initiation.
Yu
T S
TS
Graduate Institute of Life Science, National Defense Medical Center, Taipei 114, Taiwan, Republic of China.
Lue
W L
WL
Wang
S M
SM
Chen
J
J
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D003001:Cloning, Molecular; D005956:Glucose-6-Phosphate Isomerase / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D018515:Plant Leaves / Q000378:metabolism; D018087:Plastids / Q000201:enzymology* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013213:Starch / Q000096:biosynthesis*
D013213:Starch; D005956:Glucose-6-Phosphate Isomerase