The impact of Arabidopsis thaliana SNF1‐related‐kinase 1 (SnRK1)‐activating kinase 1 (SnAK1) and SnAK2 on SnRK1 phosphorylation status: characterization of a SnAK double mutant

• Published in: The Plant journal : for cell and molecular biology 2017-03, Vol.89 (5), p.1031-1041
• Main Authors: Glab, Nathalie, Oury, Céline, Guérinier, Thomas, Domenichini, Séverine, Crozet, Pierre, Thomas, Martine, Vidal, Jean, Hodges, Michael
• Format: Article
• Language: English
• Subjects: Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Deoxyribonucleic acid; DNA; double mutant; Flowers; Gene Expression Regulation, Plant; Genetic crosses; Immunology; Kinases; Life Sciences; Mutants; Offspring; Open Reading Frames - genetics; Phenotypes; Phosphorylation; Phosphorylation - genetics; Phosphorylation - physiology; Plant growth; Plants, Genetically Modified - genetics; Plants, Genetically Modified - metabolism; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; Seeds; Signal Transduction - genetics; Signal Transduction - physiology; Signaling; signalling cascade; SNF1‐related protein kinase‐1; SnRK1‐activating kinase
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/tpj.13445

Summary Arabidopsis thaliana SNF1‐related‐kinase 1 (SnRK1)‐activating kinase 1 (AtSnAK1) and AtSnAK2 have been shown to phosphorylate in vitro and activate the energy signalling integrator, SnRK1. To clarify this signalling cascade in planta, a genetic‐ and molecular‐based approach was developed. Homozygous single AtSnAK1 and AtSnAK2 T‐DNA insertional mutants did not display an apparent phenotype. Crossing of the single mutants did not allow the isolation of double‐mutant plants, whereas self‐pollinating the S1−/− S2+/− sesquimutant specifically gave approximatively 22% individuals in their offspring that, when rescued on sugar‐supplemented media in vitro, were shown to be AtSnAK1 AtSnAK2 double mutants. Interestingly, this was not obtained in the case of the other sesquimutant, S1+/− S2−/−. Although reduced in size, the double mutant had the capacity to produce flowers, but not seeds. Immunological characterization established the T‐loop of the SnRK1 catalytic subunit to be non‐phosphorylated in the absence of both SnAKs. When the double mutant was complemented with a DNA construct containing an AtSnAK2 open reading frame driven by its own promoter, a normal phenotype was restored. Therefore, wild‐type plant growth and development is dependent on the presence of SnAK in vivo, and this is correlated with SnRK1 phosphorylation. These data show that both SnAKs are kinases phosphorylating SnRK1, and thereby they contribute to energy signalling in planta. Significance Statement The energy signalling integrator SNF1‐Related Kinase1 (SnRK1) can be phosphorylated and activated in vitro by two kinases, SnAK1 and SnAK2. Here we used a genetic approach to investigate in planta the impact of SnAK on SnRK1 phosphorylation‐status, and this showed that SnAK‐driven SnRK1 phosphorylation is required for normal plant growth and development.