TOR Mediates Stress Responses Through Global Regulation of Metabolome in Plants

Abstract

The target of rapamycin (TOR) kinase is an evolutionarily conserved atypical Ser/Thr protein kinase present in yeasts, plants, and mammals. In plants, TOR acts as a central signaling hub, playing a pivotal role in the precise orchestration of growth and development. Extensive studies have underscored its significant role in these processes. Recent research has further elucidated TOR's multifaceted roles in plant stress adaptation. Furthermore, mounting evidence indicates TOR's role in mediating the plant metabolome. In this review, we will discuss recent findings on the involvement of TOR signaling in plant adaptation to various abiotic and biotic stresses, with a specific focus on TOR-regulated metabolome reprogramming in response to different stresses.

Keywords: abiotic stress; biotic stress; metabolome; plant stress responses; target of rapamycin (TOR).

Figure 1

TOR regulates a large number of stress-responsive genes. (a) Structure and complex of TOR kinase in plants. (b) Overlapping genes between TOR-regulated and biotic stress-responsive genes. (c) Overlapping genes between TOR-regulated and abiotic stress-responsive genes. (d) KEGG analysis of overlapping genes in (b). (e) KEGG analysis of overlapping genes in (c).

Figure 2

TOR-mediated metabolic reprogramming enhances plant resilience against diverse abiotic and biotic stresses. Plants, as sessile organisms, are continuously exposed to a wide spectrum of environmental challenges. These challenges encompass both abiotic stresses, including salinity, drought, oxidative conditions, and extreme temperatures, and biotic stresses from various organisms such as microbes, pathogens, nematodes, herbivores, and parasites. Within the complex plant signaling network, TOR functions as a central regulatory hub that orchestrates metabolic reprogramming to enhance stress resilience. This master regulator integrates diverse upstream stress signals and modulates plant metabolism through multiple mechanisms. Specifically, TOR regulates transcriptional responses to enhance the production of stress-resistant metabolites, directly modifies the activity of key metabolic enzymes across various pathways, and employs additional regulatory mechanisms. Consequently, the accumulated stress-resistant compounds establish a protective biochemical “shield”, thereby significantly enhancing plant resilience against multiple environmental stressors. The sun symbolizes heat stress, while the snowflakes represent cold stress. Cracks in the ground signify drought stress, and the presence of Na⁺ reflects salt stress. ROS denotes oxidative stress, and microbes on the leaves or the roots indicate the invasion of plant pathogens.