title: Phosphoenolpyruvate Carboxylase in Arabidopsis Leaves Plays a Crucial Role in Carbon and Nitrogen Metabolism.
abstract: Phosphoenolpyruvate carboxylase (PEPC) is a crucial enzyme that catalyzes an irreversible primary metabolic reaction in plants.Previous studies have used transgenic plants expressing ectopic PEPC forms with diminished feedback inhibition to examine the role of PEPC in carbon and nitrogen metabolism. To date, the in vivo role of PEPC in carbon and nitrogen metabolism has not been analyzed in plants. In this study, we examined the role of PEPC in plants, demonstrating that PPC1 and PPC2 were highly expressed genes encoding PEPC in Arabidopsis (Arabidopsis thaliana) leaves and that PPC1 and PPC2 accounted for approximately 93% of total PEPC activity in the leaves. A double mutant, ppc1/ppc2, was constructed that exhibited a severe growth-arrest phenotype. The ppc1/ppc2 mutant accumulated more starch and sucrose than wild-type plants when seedlings were grown under normal conditions. Physiological and metabolic analysis revealed that decreased PEPC activity in the ppc1/ppc2 mutant greatly reduced the synthesis of malate and citrate and severely suppressed ammonium assimilation. Furthermore, nitrate levels in the ppc1/ppc2 mutant were significantly lower than those in wild-type plants due to the suppression of ammonium assimilation. Interestingly, starch and sucrose accumulation could be prevented and nitrate levels could be maintained by supplying the ppc1/ppc2 mutant with exogenous malate and glutamate, suggesting that low nitrogen status resulted in the alteration of carbon metabolism and prompted the accumulation of starch and sucrose in the ppc1/ppc2 mutant. Our results demonstrate that PEPC in leaves plays a crucial role in modulating the balance of carbon and nitrogen metabolism in Arabidopsis.
authors.forename: Jianghua
authors.initials: J
authors.lastname: Shi
authors.forename: Keke
authors.initials: K
authors.lastname: Yi
authors.forename: Yu
authors.initials: Y
authors.lastname: Liu
authors.forename: Li
authors.initials: L
authors.lastname: Xie
authors.forename: Zhongjing
authors.initials: Z
authors.lastname: Zhou
authors.forename: Yue
authors.initials: Y
authors.lastname: Chen
authors.forename: Zhanghua
authors.initials: Z
authors.lastname: Hu
authors.forename: Tao
authors.initials: T
authors.lastname: Zheng
authors.forename: Renhu
authors.initials: R
authors.lastname: Liu
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Chen
authors.forename: Jinqing
authors.initials: J
authors.lastname: Chen
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D055786:Gene Knockout Techniques; D017343:Genes, Plant; D018698:Glutamic Acid / Q000494:pharmacology; D008293:Malates / Q000494:pharmacology; D055432:Metabolomics; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009928:Organ Specificity / Q000187:drug effects / Q000235:genetics; D010641:Phenotype; D010730:Phosphoenolpyruvate Carboxylase / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology*
chemical_list: D064751:Ammonium Compounds; D029681:Arabidopsis Proteins; D008293:Malates; D009566:Nitrates; D018698:Glutamic Acid; D002244:Carbon; C030298:malic acid; C000604186:PPC1 protein, Arabidopsis; C000604187:PPC2 protein, Arabidopsis; D010730:Phosphoenolpyruvate Carboxylase; D009584:Nitrogen