3 years ago

Phosphoglycerate kinases are co-regulated to adjust metabolism and to optimize growth.

Anoman, Toujani, Rosa-Téllez, Muñoz-Bertomeu, Fernie, Ros, Nebauer, Segura, Alseekh, Flores-Tornero
In plants, phosphoglycerate kinase (PGK) converts 1,3-bisphosphoglycerate into 3-phosphoglycerate (3-PGA) in glycolysis, but also participates in the reverse reaction in gluconeogenesis and the Calvin-Benson cycle. In the databases we found three genes that encode putative PGKs. PGK1 was localized exclusively in the chloroplasts of photosynthetic tissues, while PGK2 was expressed in the chloroplast/plastid of photosynthetic and non-photosynthetic cells. PGK3 was ubiquitously expressed in the cytosol of all studied cell types. Measurements of carbohydrate content and photosynthetic activities in PGK mutants and silenced lines corroborated that PGK1 was the photosynthetic isoform, while PGK2 and PGK3 were the plastidial and cytosolic glycolytic isoforms, respectively. The pgk1.1 knock-down mutant displayed reduced growth, lower photosynthetic capacity and starch content. The pgk3.2 knock-out mutant was characterized by a reduced growth, but a higher starch levels than the wild-type. The pgk1.1 pgk3.2 double mutant was bigger than pgk3.2, and displayed an intermediate phenotype between the two single mutants in all measured biochemical and physiological parameters. Expression studies in PGK mutants showed that PGK1 and PGK3 were down-regulated in pgk3.2 and pgk1.1, respectively. These results indicate that the down-regulation of photosynthetic activity could be a plant strategy when glycolysis is impaired to achieve metabolic adjustment and optimize growth. The double mutants of PGK3 and the triose-phosphate transporter (pgk3.2 tpt3) displayed a drastic growth phenotype, but were viable. This implies that other enzymes or non-specific chloroplast transporters could provide 3-PGA to the cytosol. Our results highlight both the complexity and the plasticity of the plant primary metabolic network.

Publisher URL: http://doi.org/10.1104/pp.17.01227

DOI: 10.1104/pp.17.01227

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