Novel Links in the Plant Target of Rapamycin Signaling Networks

doi:10.11983/CBB21183

Abstract

Abstract: Target of rapamycin (TOR) is a highly conserved serine/threonine-protein kinase among all eukaryotes. As a central regulator, TOR integrates nutrient, energy, growth factor and environmental signals to control cell proliferation, growth, and metabolism. With the establishment of TOR research systems in plants, tremendous progress has been made in, both conserved and unique functions of plant TOR have been uncovered in recent years. Here, we reviewed TOR complexes and the mechanisms of plant TOR integrating sugar, nitrogen, phosphate, sulfur, phytohormone and stress signals to orchestrate transcription, translation, metabolism, autophagy, and stress responses. We also highlight a few fundamental questions that will be of great interest to be resolved for fully revealing biofunctions of plant TOR.

Key words: TOR complexes, TOR signaling pathway, nutrient, phytohormone, stress

Yanyan Meng, Nan Zhang, Yan Xiong. Novel Links in the Plant Target of Rapamycin Signaling Networks[J]. Chinese Bulletin of Botany, 2022, 57(1): 1-11.

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URL: https://www.chinbullbotany.com/EN/10.11983/CBB21183

https://www.chinbullbotany.com/EN/Y2022/V57/I1/1

Figures/Tables 2

Figure 1 The domain structures and components of TOR complexes in plants and animals (A) TOR complex 1 (TORC1) in plants and animals. TORC1 mainly contains TOR, RAPTOR and LST8. TOR protein is highly conserved among plants and animals, composed of HEAT repeats, FAT, FRB, kinase and FATC domains. RAPTOR binds to the HEAT repeats, LST8 binds to the kinase domain, and FKBP12 mediates interact between the FRB domain and rapamycin. (B) TOR complex 2 (TORC2) in animals. TORC2 mainly contains TOR, RICTOR, SIN1 and LST8 in animal. RICTOR interacts with SIN1 and binds to HEAT repeats, and LST8 binds to the kinase domain. Either RICTOR or SIN1 has no homologous genes in plants, which indicates that TORC2 is not conserved.

Figure 2 The upstream regulators of TOR complex 1 (TORC1) in plants TORC1 in plants senses multiple upstream signals, and probably functions as a dimerization form. Glucose-energy, nitrogen/phosphate/sulfur, auxin-ROP2, and GA signals are positive upstream regulators of TOR; ABA-SnRK2 and cold stress are negative upstream regulators of TOR; viruses play both positive and negative roles on TOR activity. FKBP12- rapamycin and ATP competitive inhibitors Torin1/2, AZD8055, WYE132/354 and KU-63794 inhibit plant TOR kinase activity specifically and efficiently. The red arrows represent activation, the green T shape lines mean repression, and the black line represents both activation and repression exist.

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