MECHANISMS INVOLVED IN THE CELLULAR ENERGY HOMEOSTASIS IN PLANTS

JÁSIK, J.; BLANCO, N.E.; WHELAN, J.; LIEBSCH, D.E.; STRAND, Å

Parana

Congreso; 54th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2018

SAIB

The evolutionarily conserved AMPK/Snf1/SnRK1 kinase complex is a master regulator of cellular metabolism in eukaryotes, involved in adjusting the cell function to the energy status. In photosynthetic organisms, SnRK1 plays this role by maintaining the cellular energy homeostasis through a balance of energy yielding and energy requiring processes, in response to fluctuating environmental conditions. To fulfil this function, SnRK1 deploys a wide variety of molecular mechanisms, e.g. wide-ranging transcriptional reprogramming, translational regulation and/or metabolic reprogramming. Together with the Target of Rapamycin (TOR) kinase complex, SnRK1 has also been recently proposed to bea main regulator of developmental programs. While many mechanistic aspects of SNRK1 downstream functions related to energy management and developmental processes are relatively well characterized, how SnRK1 integrates cellular energy information to induce these processes is still unknown. This work is centered in revealing and understanding the factors that define SnRK1-mediated sensing of the cell energy status. Having as premise that SnRK1 might be receiving energy status information in a specific intracellular location, we conducted thoughtful localization study of this kinase. Our results identified and localized a non-nuclear fraction of SNRK1.1, the catalytically active subunit of SnRK1. Experiments of energy imbalance at the level of chloroplasts, the organelles of photosynthetic energy metabolism, revealed a link between cellular energy level and the intracellular distribution of SnRK1.1. These findings suggest that the non-nuclear SnRK1.1 fraction is responsive to cell energy fluctuations and hence might be directly gauging the cell energy status. The analysis of this dynamic behavior using photoconvertible probes of the DENDRA family, together with similar studies conducted on TOR provides novel evidence about the energy sensing mechanisms and the crosstalk between these two main regulatory pathways. Our work introduces a new model of the interaction of TOR and SnRK1 and the putative mechanisms connecting them with the energy production in photosynthetic organisms, with implications for eukaryotes in general.