title: Sedoheptulose accumulation under CO₂ enrichment in leaves of Kalanchoë pinnata: a novel mechanism to enhance C and P homeostasis?
abstract: In contrast to the well-documented roles of its mono- and bisphosphate esters, the occurrence of free sedoheptulose in plant tissues remains a matter of conjecture. The present work sought to determine the origin of sedoheptulose formation in planta, as well as its physiological importance. Elevated CO2 and sucrose induction experiments were used to study sedoheptulose metabolism in the Crassulacean acid metabolism (CAM) plants Kalanchoë pinnata and Sedum spectabile. Experimental evidence suggested that sedoheptulose is produced from the oxidative pentose phosphate pathway intermediate sedoheptulose-7-phosphate, by a sedoheptulose-7-phosphate phosphatase. Carbon flux through this pathway was stimulated by increased triose-phosphate levels (elevated CO2, compromised sink availability, and sucrose incubation of source leaves) and attenuated by ADP and inorganic phosphate (Pi). The accumulation of free sedoheptulose is proposed to act as a mechanism contributing to both C and P homeostasis by serving as an alternative carbon store under elevated CO2 or a compromised sink capacity to avoid sucrose accumulation, depletion of inorganic phosphate, and suppression of photosynthesis. It remains to be established whether this acclimation-avoiding mechanism is confined to CAM plants, which might be especially vulnerable to Pi imbalances, or whether some C3 and C4 plants also dispose of the genetic capacity to induce and accelerate sedoheptulose synthesis upon CO2 elevation.
authors: Faculty of Bioscience Engineering, Department of Biosystems, Division of Crop Biotechnics, KU Leuven, Willem De Croylaan 42, B-3001 Heverlee, Belgium.
authors: Johan
authors: J
authors: Ceusters
authors: Christof
authors: C
authors: Godts
authors: Darin
authors: D
authors: Peshev
authors: Rudy
authors: R
authors: Vergauwen
authors: Natalia
authors: N
authors: Dyubankova
authors: Eveline
authors: E
authors: Lescrinier
authors: Maurice P
authors: MP
authors: De Proft
authors: Wim
authors: W
authors: Van den Ende
mesh_terms: D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism* / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D006539:Heptoses / Q000378:metabolism*; D031962:Kalanchoe / Q000187:drug effects / Q000378:metabolism*; D010427:Pentose Phosphate Pathway; D052585:Phloem / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism*; D011755:Pyrophosphatases / Q000378:metabolism; D031963:Sedum / Q000187:drug effects / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism / Q000494:pharmacology; D013403:Sugar Phosphates / Q000378:metabolism
chemical_list: D006539:Heptoses; D010710:Phosphates; D013403:Sugar Phosphates; D002245:Carbon Dioxide; C020495:sedoheptulose 7-phosphate; C003011:sedoheptulose; D013395:Sucrose; D002244:Carbon; D011755:Pyrophosphatases
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