Two cytosolic glutamine synthetase isoforms play specific roles for seed germination and seed yield structure in Arabidopsis

J Exp Bot. 2015 Jan;66(1):203-12. doi: 10.1093/jxb/eru411. Epub 2014 Oct 14.

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.

Keywords: Arabidopsis; cytosolic glutamine synthetase; isoform; mutant; nitrogen; seed germination; seed productivity..

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis Proteins* / genetics
  • Arabidopsis Proteins* / metabolism
  • Gene Expression Regulation, Plant*
  • Germination / genetics*
  • Glutamate-Ammonia Ligase / genetics*
  • Glutamate-Ammonia Ligase / metabolism*
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Nitrogen / metabolism*
  • Seeds / enzymology*

Substances

  • Arabidopsis Proteins
  • Isoenzymes
  • Glutamate-Ammonia Ligase
  • Nitrogen