How do plants feel the heat?

In plants, the heat stress response (HSR) is highly conserved and involves multiple pathways, regulatory networks and cellular compartments. At least four putative sensors have recently been proposed to trigger the HSR. They include a plasma membrane channel that initiates an inward calcium flux, a histone sensor in the nucleus, and two unfolded protein sensors in the endoplasmic reticulum and the cytosol. Each of these putative sensors is thought to activate a similar set of HSR genes leading to enhanced thermotolerance, but the relationship between the different pathways and their hierarchical order is unclear. In this review, we explore the possible involvement of different thermosensors in the plant response to warming and heat stress. In plants, the heat stress response (HSR) is highly conserved and involves multiple pathways, regulatory networks and cellular compartments. At least four putative sensors have recently been proposed to trigger the HSR. They include a plasma membrane channel that initiates an inward calcium flux, a histone sensor in the nucleus, and two unfolded protein sensors in the endoplasmic reticulum and the cytosol. Each of these putative sensors is thought to activate a similar set of HSR genes leading to enhanced thermotolerance, but the relationship between the different pathways and their hierarchical order is unclear. In this review, we explore the possible involvement of different thermosensors in the plant response to warming and heat stress. a group of plant steroid hormones that regulate growth, development and responses to different environmental stresses. a family of TFs that contain a basic leucine zipper (bZIP) domain and regulate many central developmental and physiological processes in plants, such as photomorphogenesis, energy homeostasis, and abiotic and biotic stress responses. a calcium-binding protein family that can bind to and regulate several different protein targets in plants. dehydration-responsive element-binding TF is a key regulator of drought and HSRs in plants. a transmembrane serine/threonine-protein kinase/endoribonuclease that transmits the UPR signal across the ER or nuclear membranes. a transcriptional regulator required for basal thermotolerance that regulates ethylene, salicylic acid and trehalose responses during heat stress. an enzyme that hydrolyzes phospholipids into fatty acids and other lipophilic substances and is involved in lipid and calcium signaling in plants. an ATP-dependent multisubunit protein complex involved in chromatin remodeling, histone replacement and gene expression regulation in eukaryotic organisms. a TF containing the WRKY domain (defined by the conserved amino acid sequence WRKYGQK at its N-terminal end). WRKY39 is involved in the response of plants to heat and other environmental stresses.