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Review
. 2021 May;46(5):417-428.
doi: 10.1016/j.tibs.2020.11.004. Epub 2020 Dec 9.

A Tour of TOR Complex Signaling in Plants

Graham M Burkart  1 , Federica Brandizzi  2
Affiliations
Review

A Tour of TOR Complex Signaling in Plants

Graham M Burkart et al. Trends Biochem Sci. 2021 May.

Abstract

To identify the appropriate times for growth and development, organisms must sense and process information about the availability of nutrients, energy status, and environmental cues. For sessile eukaryotes such as plants, integrating such information can be critical in life or death decisions. For nearly 30 years, the conserved phosphatidylinositol 3-kinase-related protein kinases (PIKKs) target of rapamycin (TOR) has been established as a central hub for integrating external and internal metabolic cues. Despite the functional conservation across eukaryotes, the TOR complex has evolved specific functional and mechanistic features in plants. Here, we present recent findings on the plant TOR complex that highlight the conserved and unique nature of this critical growth regulator and its role in multiple aspects of plant life.

Keywords: autophagy; cellular nutrition and homeostasis; circadian cycle; energy sensing; photosynthesis; phytohormones; symbiotic relationships.

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Figures

Figure 1.
Figure 1.
Overview of mammalian TOR complex signaling. A) Upstream activators/repressors and downstream effectors of mTORC1 regulate numerous metabolic and catabolic processes. Activators, effectors, and processes in green are conserved TOR–regulated processes in plants. B) Signaling through mTORC2 modulates diverse cellular functions.
Figure 2.
Figure 2.
Summary of plant TOR signaling in A. thaliana and C. reinhardtii. A) Inputs and mechanisms for the activation/inhibition of TOR signaling and the downstream processes regulated by TOR in A. thaliana. Activators/inhibitors, effectors, and cellular processes in red are conserved with mammalian TOR signaling. Those in green are plant specific. B) Inputs and mechanisms for the activation/inhibition of TOR signaling and the downstream processes regulated by TOR in C. reinhardtii. Activators/inhibitors, effectors, and cellular processes in green are conserved with the Arabidopsis TOR signaling. N-assimiliation in C. reinhardtii is highlighted in red as TOR seems to have the opposite regulation on this process compared to Arabidopsis.
Figure 3.
Figure 3.
Overview of interaction between TOR-signaling and phytohormones in A. thaliana. Proteins in red are conserved regulators or effectors of TOR signaling in the mammalian system.
See this image and copyright information in PMC

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