Dual and Dynamic Intracellular localisation of SnRK1.1

BLANCO, NICOLÁS E

Bischoffsheim

Workshop; Target of rapamycin (TOR) signaling in photosynthetic organisms; 2018

EMBO

The evolutionary conservedTOR and SnRK1 kinase complexes are key regulators in adjusting plant cellularmetabolism in response to cellular energy status. During starvation, growthpromoting conditions or situations of excess of energy, the function of thesecomplexes is to reach a metabolic homeostasis by establishing anabolic orcatabolic regimes. Both complexes deploy a wide variety of molecular mechanismsto fulfil this function (e.g. wide-ranging transcriptional reprogramming,translational regulation and/or metabolic reprogramming). Moreover, theantagonistic functioning of TOR/SnRK1.1 has been recently proposed to regulatemain developmental programs (Baena-González and Hanson, 2017). Both functions,in general metabolic control as well as in a more profound effect on thedevelopmental program, require that TOR and SnRK1 complexes receive andintegrate exact information of the cell energy status. Sugar content isconsidered one of the candidates to be the energy level signal, though how thisinformation is perceived by TOR and SnRK1 is still unknown (Robaglia et al.,2012; Lunn et al., 2014; Dobrenel et al., 2016; Emanuelle et al., 2016). Havingas premise that SnRK1 might be receiving this information in a specificintracellular location, we conducted thoughtful localisation studies of thiskinase. Our results confirm the existence of a SnRK1.1 non-nuclear fractionable to act as energy sensor and hence to gauge the cell energy status.Experiments of energy imbalance at chloroplast level revealed a link betweenthis cellular energy level and the intracellular distribution of SnRK1.1. Theanalysis of this dynamic behaviour, together with similar studies conducted onTOR, provides novel evidence about the energy sensing mechanisms and thecrosstalk between these two main regulatory pathways. To sum up, our work introducesa new model of the interaction of TOR and SnRK1 and the putative mechanismsthat relate them with the energy production in photosynthetic organisms.