STOREKEEPER RELATED1/G-Element Binding Protein (STKR1) Interacts with Protein Kinase SnRK1

Abstract

Sucrose nonfermenting related kinase1 (SnRK1) is a conserved energy sensor kinase that regulates cellular adaptation to energy deficit in plants. Activation of SnRK1 leads to the down-regulation of ATP-consuming biosynthetic processes and the stimulation of energy-generating catabolic reactions by transcriptional reprogramming and posttranslational modifications. Although considerable progress has been made during the last years in understanding the SnRK1 signaling pathway, many of its components remain unidentified. Here, we show that the catalytic a-subunits KIN10 and KIN11 of the Arabidopsis (Arabidopsis thaliana) SnRK1 complex interact with the STOREKEEPER RELATED1/G-Element Binding Protein (STKR1) inside the plant cell nucleus. Overexpression of STKR1 in transgenic Arabidopsis plants led to reduced growth, a delay in flowering, and strongly attenuated senescence. Metabolite profiling revealed that the transgenic lines exhausted their carbohydrates during the dark period to a greater extent than the wild type and accumulated a range of amino acids. At the global transcriptome level, genes affected by STKR1 overexpression were broadly associated with systemic acquired resistance, and transgenic plants showed enhanced resistance toward a virulent strain of the biotrophic oomycete pathogen Hyaloperonospora arabidopsidis Noco2. We discuss a possible connection of STKR1 function, SnRK1 signaling, and plant immunity.Plants are the prime example of photoautotrophic organisms, using photosynthesis to harness energy from sunlight for the conversion of CO 2 into energyrich carbohydrates. These photoassimilates are then directed to fuel plant growth and development. However, as sessile organisms, plants usually have to cope with strongly fluctuating environmental conditions, many of which negatively impact on energy availability, as they interfere with the production or distribution of photoassimilates. In order to maintain energy homeostasis and to promote survival, energy shortage triggers a massive cellular reprogramming characterized by nutrient remobilization, suppression of biosynthetic processes, and growth arrest (Baena-González, 2010). A central component of low-energy signaling in plants is the sucrose nonfermenting related kinase1 (SnRK1), which is orthologous to the AMP-dependent kinase (AMPK) and sucrose nonfermenting1 (SNF1) in mammals and yeast, respectively. Similar to its opisthokont counterparts, the SnRK1 holoenzyme is a heterotrimeric complex consisting of a catalytic a-subunit and noncatalytic b-and plant-specific bg-subunits (Ramon et al., 2013;Emanuelle et al., 2015). In Arabidopsis (Arabidopsis thaliana), the catalytic a-subunit is represented by two isoforms, SnRK1a1 (AKIN10; At3g01090) and SnRK1a2 (AKIN11; At3g29160), both of which appear to be expressed ubiquitously, although KIN10 accounts for the majority of SnRK1 activity (Jossier et al., 2009). Activation of SnRK1 involves the phosphorylation/ dephosphorylation of a T-loop Thr (Thr-172 of Arabidopsis SnRK1.1a) involving the upstream kinas...

Small RNAs from the plant pathogenic fungus Sclerotinia sclerotiorum highlight host candidate genes associated with quantitative disease resistance

“…In wheat, SnRK1 interacts with TaFROG, a protein mediating host resistance to Fusarium head blight and the mycotoxin deoxynivalenol (Perochon et al , ). In Arabidopsis , SnRK1 interacts with STOREKEEPER RELATED1/G‐Element Binding Protein (STKR1), which is associated with systemic acquired resistance and resistance to the oomycete Hyaloperonospora arabidopsidis (Nietzsche et al , ). Similarly, deficiencies in the control of SnRK1 activity may underlie the enhanced susceptibility of the snak2 mutant upon S. sclerotiorum inoculation.…”

Regulation of Gene Expression of Methionine Sulfoxide Reductases and Their New Putative Roles in Plants

“…In summary, 11 of the TFs (PDF2, SBF, WUSCHEL, TESMIN/TSO1-like CXC, KANADI1, GLK, DOF5.7, LHY, repressor AS1/AS2, GBF1, STK) that were predicted to bind the promoter regions of most of the analyzed Msrs act in plant growth and regulation. Studies have demonstrated that the above TFs are involved in shoot development [40], lateral root formation and development [41], embryo development [40], leaf development [42,43], stomata patterning [44], chloroplast development [45], the development of reproductive tissues [46], early embryogenesis [47], seedling development [48], senescence [49], the regulation of circadian rhythms [50], and cell-cycle-dependent transcription-enabling plant growth [47]. Interestingly, seven of the TFs that are listed in Table 2 (WUSCHEL, DIVARICITA, BELLRINGER, HB32 and HB34, RAP2.7, CRABS CLAW, ODO1) control the flowering process by regulating floral development [51,52], fragrance [53], and nectary development [54] and the initiation and repression of flowering [47,49,55,56].…”

SnRK1 and TOR: modulating growth–defense trade-offs in plant stress responses

“…Additional potential connections to plant immunity come from the interaction of SnRK1 catalytic subunits with STKR1, a protein whose overexpression affects genes related to systemic acquired resistance (SAR) and confers resistance towards the biotrophic oomycete Hyaloperonospora arabidopsidis (Hpa) (Nietzsche et al, 2016(Nietzsche et al, , 2018. In a different study, TOR silencing through RNAi increased resistance to Hpa in Arabidopsis, whereas overexpression of TOR rendered plants significantly more susceptible to this pathogen (Meteignier et al, 2017).…”