title: Characterization of multiple SPS knockout mutants reveals redundant functions of the four Arabidopsis sucrose phosphate synthase isoforms in plant viability, and strongly indicates that enhanced respiration and accelerated starch turnover can alleviate the blockage of sucrose biosynthesis.
abstract: We characterized multiple knock-out mutants of the four Arabidopsis sucrose phosphate synthase (SPSA1, SPSA2, SPSB and SPSC) isoforms. Despite their reduced SPS activity, spsa1/spsa2, spsa1/spsb, spsa2/spsb, spsa2/spsc, spsb/spsc, spsa1/spsa2/spsb and spsa2/spsb/spsc mutants displayed wild type (WT) vegetative and reproductive morphology, and showed WT photosynthetic capacity and respiration. In contrast, growth of rosettes, flowers and siliques of the spsa1/spsc and spsa1/spsa2/spsc mutants was reduced compared with WT plants. Furthermore, these plants displayed a high dark respiration phenotype. spsa1/spsb/spsc and spsa1/spsa2/spsb/spsc seeds poorly germinated and produced aberrant and sterile plants. Leaves of all viable sps mutants, except spsa1/spsc and spsa1/spsa2/spsc, accumulated WT levels of nonstructural carbohydrates. spsa1/spsc leaves possessed high levels of metabolic intermediates and activities of enzymes of the glycolytic and tricarboxylic acid cycle pathways, and accumulated high levels of metabolic intermediates of the nocturnal starch-to-sucrose conversion process, even under continuous light conditions. Results presented in this work show that SPS is essential for plant viability, reveal redundant functions of the four SPS isoforms in processes that are important for plant growth and nonstructural carbohydrate metabolism, and strongly indicate that accelerated starch turnover and enhanced respiration can alleviate the blockage of sucrose biosynthesis in spsa1/spsc leaves.
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain.
authors.forename: Abdellatif
authors.initials: A
authors.lastname: Bahaji
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain.
authors.forename: Edurne
authors.initials: E
authors.lastname: Baroja-Fernández
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain.
authors.forename: Adriana
authors.initials: A
authors.lastname: Ricarte-Bermejo
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain.
authors.forename: Ángela María
authors.initials: ÁM
authors.lastname: Sánchez-López
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain.
authors.forename: Francisco José
authors.initials: FJ
authors.lastname: Muñoz
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avenida Américo Vespucio 49, Isla de la Cartuja, 41092 Sevilla, Spain.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Romero
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avenida Américo Vespucio 49, Isla de la Cartuja, 41092 Sevilla, Spain.
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Ruiz
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain.
authors.forename: Marouane
authors.initials: M
authors.lastname: Baslam
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain.
authors.forename: Goizeder
authors.initials: G
authors.lastname: Almagro
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain.
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Sesma
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Iruñako etorbidea 123, 31192 Mutiloabeti, Nafarroa, Spain. Electronic address: javier.pozueta@unavarra.es.
authors.forename: Javier
authors.initials: J
authors.lastname: Pozueta-Romero
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D019069:Cell Respiration / Q000528:radiation effects; D002952:Citric Acid Cycle / Q000528:radiation effects; D005740:Gases / Q000378:metabolism; D055786:Gene Knockout Techniques; D005964:Glucosyltransferases / Q000235:genetics*; D006019:Glycolysis / Q000528:radiation effects; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008027:Light; D008320:Maltose / Q000378:metabolism; D055442:Metabolome / Q000528:radiation effects; D009154:Mutation / Q000235:genetics*; D010427:Pentose Phosphate Pathway / Q000528:radiation effects; D010641:Phenotype; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D013213:Starch / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*
chemical_list: D005740:Gases; D007527:Isoenzymes; D002245:Carbon Dioxide; D013395:Sucrose; D008320:Maltose; D013213:Starch; D005964:Glucosyltransferases; C022698:sucrose-phosphate synthase
keywords: Carbohydrate metabolism; Development; Functional interaction; Genetic redundancy; Growth; Sucrose