Regulation of Translation by TOR, eIF4E and eIF2α in Plants: Current Knowledge, Challenges and Future Perspectives

Abstract

An important step in eukaryotic gene expression is the synthesis of proteins from mRNA, a process classically divided into three stages, initiation, elongation, and termination. Translation is a precisely regulated and conserved process in eukaryotes. The presence of plant-specific translation initiation factors and the lack of well-known translational regulatory pathways in this kingdom nonetheless indicate how a globally conserved process can diversify among organisms. The control of protein translation is a central aspect of plant development and adaptation to environmental stress, but the mechanisms are still poorly understood. Here we discuss current knowledge of the principal mechanisms that regulate translation initiation in plants, with special attention to the singularities of this eukaryotic kingdom. In addition, we highlight the major recent breakthroughs in the field and the main challenges to address in the coming years.

Keywords: TOR; eIF2α; eIF4E; plant development; stress; translation initiation.

FIGURE 1

Regulation of translation initiation by the (TOR) pathway, eIF4E activity and eIF2α phosphorylation in response to developmental and environmental cues in plants. Different treatments activate plants’ TOR and GCN2 that promote downstream phosphorylation of S6K and eIF2α, respectively. In addition, eIF4E and eIFiso4E activity could be also regulated in these organisms, although the possible mechanisms involved in this regulation has not been elucidated yet. Despite that these events could lead to regulation of translation initiation (based on the information in other eukaryotes), in some cases the precise role of these pathways in translational control remains unclear in plants. Solid lines highlight experimentally demonstrated associations among processes; in contrast, dashed lines represent possible links that are missing or unresolved in plants.