TOR in acTIon SIGNED

Project "TOR in acTIon" data sheet

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 Project objective

Translation is a critical step in the regulation of gene expression in eukaryotes. Most of the control occurs at the level of translation initiation, which is a rate-limiting step in protein synthesis. In mammals, cap-dependent translation initiation is under the regulation of the target of rapamycin (TOR) protein kinase, which suppresses the function of translation repressor proteins, the eIF4E-binding proteins (4E-BPs) that sequester the cap-binding factor eIF4E at the 5′-end of mRNA. The TOR signaling pathway integrates nutrient and energy sufficiency, hormones and growth factors to regulate protein synthesis in mammals and plants. How TOR signals environmental changes to regulate mRNA translation and ribosome production in plants is at present unknown. This project aims to define the role of the plant TOR kinase in translation regulation and to understand how plants have rewired the TOR signalling pathway for their specific translational programs. We have discovered putative plant translation repressor (TR) proteins that harbour eIF4E binding sites and TOR phosphorylation sites, and will study translation initiation mechanisms and their control by TOR in the shoot apical meristem—a specialized tissue containing a stem cell niche responsible for building the shoot. The main objective of proposed research is to uncover regulatory factors that function under the control of TOR in translation initiation and to identify their targets among meristematic mRNAs. A search for cellular mRNAs whose initiation is regulated by TOR and/or TR proteins will be performed using a global ribosomal profiling approach. The plant hormone auxin is an upstream effector of TOR and impacts stem cell niche activity. Thus, we shall study whether TOR mediates signaling from auxin to control TR activity and translation initiation. Finally, we will test whether TOR couples amino acid sensing to regulation of translation initiation.