The wheat cytosolic glutamine synthetase GS1.1 modulates N assimilation and spike development by characterizing CRISPR-edited mutants

Glutamine synthetase (GS) mediates the first step in the assimilation of inorganic nitrogen (N) into amino acids, however the function of GS encoding genes is not well understood in wheat ( Triticum aestivum ). We found that the cytosolic TaGS1.1 was the major transcripted GS1 gene and was up-regulated by low-N availability. CRISPR/Cas9 mediated genome editing was employed to develop two gs1.1 mutants with mutated TaGS1.1-6A, −6B , and -6D . Both mutants had lower grains per spike and grain yield per plant than the wild type under both low-N and high-N conditions in field experiments. In a hydroponic culture treated with different N resources, the two mutants was more sensitive to low-N stress than the wild type, but showed similar sensitivity to high ammonium stress with the wild type. The growth deficiency and impaired spike development were associated with the imbalance of N metabolites in the mutant plants. During grain filling, TaGS1.1 mutation reduced N translocation efficiency and delayed leaf N loss and grain N filling. Our results suggested that TaGS1.1 is important for N assimilation and remobilization, and required for wheat adaptation to N-limited conditions and spike development. Highlight The wheat cytosolic glutamine synthetase TaGS1.1 is important for N assimilation and remobilization, and is required for wheat adaptation to low-N stress and spike development.