Mutation of Arabidopsis Plastid Phosphoglucose Isomerase Affects Leaf Starch Synthesis and Floral Initiation

• Published in: Plant physiology (Bethesda) 2000-05, Vol.123 (1), p.319-325
• Main Authors: Yu, Tien-Shin, Lue, Wei-Ling, Wang, Shue-Mei, Chen, Jychian
• Format: Article
• Language: English
• Subjects: ADG1 gene; Amino Acid Sequence; Arabidopsis - enzymology; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis thaliana; Biological and medical sciences; Biology and morphogenesis of the reproductive apparatus. Photoperiodism, vernalisation; Carbohydrate metabolism; Chloroplasts; Cloning, Molecular; Enzymes; Flowering; Fundamental and applied biological sciences. Psychology; Genetics, Genomics, and Molecular Evolution; Glucose-6-Phosphate Isomerase - chemistry; Glucose-6-Phosphate Isomerase - genetics; Leaves; Molecular Sequence Data; Mutation; PGI1 gene; PGM1 gene; Phosphoglucose isomerase; Plant cells; Plant Leaves - metabolism; Plant physiology and development; Plants; Plastids; Plastids - enzymology; Plastids - metabolism; Root cap; Sequence Homology, Amino Acid; Starch; Starch - biosynthesis; Starches; Vegetative and sexual reproduction, floral biology, fructification
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.123.1.319

We isolated pg1-1, 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.