Plant target of rapamycin signaling network: Complexes, conservations, and specificities

Abstract

Target of rapamycin (TOR) is an evolutionarily conserved protein kinase that functions as a central signaling hub to integrate diverse internal and external cues to precisely orchestrate cellular and organismal physiology. During evolution, TOR both maintains the highly conserved TOR complex compositions, and cellular and molecular functions, but also evolves distinctive roles and strategies to modulate cell growth, proliferation, metabolism, survival, and stress responses in eukaryotes. Here, we review recent discoveries on the plant TOR signaling network. We present an overview of plant TOR complexes, analyze the signaling landscape of the plant TOR signaling network from the upstream signals that regulate plant TOR activation to the downstream effectors involved in various biological processes, and compare their conservation and specificities within different biological contexts. Finally, we summarize the impact of dysregulation of TOR signaling on every stage of plant growth and development, from embryogenesis and seedling growth, to flowering and senescence.

Target of rapamycin (TOR) regulates the response to low nitrogen stress via autophagy and hormone pathways inMalus hupehensis

“…Plants have evolved various mechanisms to ensure their growth and development under various environmental conditions, and the TOR signaling pathway is a conserved and central regulatory hub in these processes in all eukaryotes [ 33 ]. It senses various signals that affect plants, including nutrients, hormones, and stress signals [ 34 , 35 ]. Inorganic N and amino acids can activate the TOR signaling pathway to promote development [ 36 ].…”

The plant circadian clock regulates autophagy rhythm through transcription factor LUX ARRHYTHMO

“…In addition to the direct circadian regulation of autophagy in plants, there are indications of indirect evidence that associate circadian clock with autophagy. TOR is a central regulator of cell metabolism which integrates diverse endogenous and exogenous signals to plant growth and development (Liu and Xiong, 2021). Autophagy is negatively regulated by TOR in plants (Liu and Bassham, 2010; Pu et al, 2017).…”

Target of Rapamycin Regulates Photosynthesis and Cell Growth in Auxenochlorella pyrenoidosa

“…TOR protein and other proteins form TOR complex 1 (TORC1) and TORC2 in yeast and mammals [ 16 , 17 ]. However, there was only the conserved and functional TORC1 in plants, and TORC1 was composed of TOR, regulatory associate the protein target of rapamycin (RAPTOR) and lethal with sec-13 protein 8 (LST8) [ 18 , 19 ]. TORC2 core proteins RICTOR and SIN1 seem to be missing in photosynthetic eukaryotes, including plants and green algae [ 20 , 21 ].…”

“…Fortunately, TOR kinase inhibitors such as Torin1, AZD8055 and KU0063794 from mammals were developed and applied in plants, and have also been proved to specifically and efficiently inhibit TOR kinase activity in plants [ 15 , 27 , 28 ]. With the help of TOR inhibitors and various omics research methods, animal and plant conserved and plant-specific TOR signaling pathways have been revealed [ 18 , 29 ]. In plants, TOR regulates cell division and elongation, protein synthesis, nutrient and metabolism, and stress response by integrating multiple exogenous environmental signals and endogenous physiological signals [ 15 , 30 , 31 , 32 ].…”

“…In plants, TOR regulates cell division and elongation, protein synthesis, nutrient and metabolism, and stress response by integrating multiple exogenous environmental signals and endogenous physiological signals [ 15 , 30 , 31 , 32 ]. TOR affects plant growth and development from embryogenesis to photomorphogenesis, root and leaf development, flowering, and senescence in plants [ 13 , 18 , 33 ].…”