Plant Hormone-Mediated Regulation of Heat Tolerance in Response to Global Climate Change

Abstract

Agriculture is largely dependent on climate and is highly vulnerable to climate change. The global mean surface temperatures are increasing due to global climate change. Temperature beyond the physiological optimum for growth induces heat stress in plants causing detrimental and irreversible damage to plant development, growth, as well as productivity. Plants have evolved adaptive mechanisms in response to heat stress. The classical plant hormones, such as auxin, abscisic acid (ABA), brassinosteroids (BRs), cytokinin (CK), salicylic acid (SA), jasmonate (JA), and ethylene (ET), integrate environmental stimuli and endogenous signals to regulate plant defensive response to various abiotic stresses, including heat. Exogenous applications of those hormones prior or parallel to heat stress render plants more thermotolerant. In this review, we summarized the recent progress and current understanding of the roles of those phytohormones in defending plants against heat stress and the underlying signal transduction pathways. We also discussed the implication of the basic knowledge of hormone-regulated plant heat responsive mechanism to develop heat-resilient plants as an effective and efficient way to cope with global warming.

Keywords: heat response; heat stress; heat tolerance; phytohormone; signal transduction.

FIGURE 1

ABA enhances heat tolerance by mediating HSP and RBOH genes expression, and sucrose metabolism. Arrows indicate positive regulation. ABA, abscisic acid; H₂O₂, hydrogen peroxide; HSFs, heat shock transcription factors or heat shock factors; HSPs, heat shock proteins; RBOH, respiratory burst oxidase homologue.

FIGURE 2

Auxin regulates plant morphogenesis through transcription factor PIFs and is counteracted by phyB and CRY1. Arrows indicate positive regulation, blunt-ended lines indicate negative regulation. ARF, AUXIN RESPONSE FACTOR; Aux/IAA, AUXIN/INDOLE-3-ACETIC ACID; HDA9, HISTONE DEACETYLASE 9; HSPs, heat shock proteins; phyB, phytochrome B; PIFs, PHYTOCHROME INTERACTING FACTORs; CRY1, cryptochrome 1; TIR1, TRANSPORT INHIBITOR RESPONSE 1; YUC8, YUCCA8.

FIGURE 3

SA regulates heat response through induction of HSPs accumulation, ROS scavengers, and proline biosynthesis. Arrows indicate positive regulation. ROS, reactive oxygen species; SA, salicylic acid; HSPs, heat shock proteins.

FIGURE 4

High-temperatures induced jasmonate and ethylene antagonistically regulates plant heat response through unknown mechanisms.

FIGURE 5

Overview of phytohormones regulated heat stress tolerance described and discussed in this review. ABA, abscisic acid; ARF, AUXIN RESPONSE FACTOR; Aux/IAA, AUXIN/INDOLE-3-ACETIC ACID; CRY1, BRs, brassinosteroids; BZR1, BRASSINAZOLE-RESISTANT 1; cryptochrome 1; HDA9, HISTONE DEACETYLASE 9; H₂O₂, hydrogen peroxide; HSFs, heat shock transcription factors or heat shock factors; HSPs, heat shock proteins; phyB, phytochrome B; PIFs, PHYTOCHROME INTERACTING FACTORs; RBOHs, respiratory burst oxidase homologues; SA, salicylic acid; TIR1, TRANSPORT INHIBITOR RESPONSE 1; YUC8, YUCCA8.