title: Two cytosolic glutamine synthetase isoforms play specific roles for seed germination and seed yield structure in Arabidopsis.
abstract: Nitrogen (N) remobilization from reserves to sinks is essential for seedling establishment and seed production. Cytosolic glutamine synthetase (GS1) is up-regulated during both seed germination and seed filling in plants. However, the specific roles of the individual GS1 isogenes with respect to N remobilization, early seedling vigour, and final seed productivity are not known. In this study, impairment of seed germination and seedling establishment is demonstrated in the single knockout mutant gln1;2, and the double knockout mutant gln1;1:gln1;2. The negative effect of Gln1;2 deficiency was associated with reduced N remobilization from the cotyledons and could be fully alleviated by exogenous N supply. Following reproductive growth, both the single and double Gln1;2-knockout mutants showed decreased seed yield due to fewer siliques, less seeds per silique, and lower dry weight per seed. The gln1;1 single mutant had normal seed yield structure but primary root development during seed germination was reduced in the presence of external N. Gln1;2 promoter-green fluorescent protein constructs showed that Gln1;2 localizes to the vascular cells of roots, petals, and stamens. It is concluded that Gln1;2 plays an important role in N remobilization for both seedling establishment and seed production in Arabidopsis.
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Guan
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
authors.forename: I S
authors.initials: IS
authors.lastname: Møller
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark jks@plen.ku.dk.
authors.forename: J K
authors.initials: JK
authors.lastname: Schjoerring
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000235:genetics*; D005974:Glutamate-Ammonia Ligase / Q000235:genetics* / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D012639:Seeds / Q000201:enzymology*
chemical_list: D029681:Arabidopsis Proteins; D007527:Isoenzymes; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen
keywords: Arabidopsis; cytosolic glutamine synthetase; isoform; mutant; nitrogen; seed germination; seed productivity.