Roles of jasmonates and brassinosteroids in rice responses to high temperature stress – A review

High temperature (HT) stress has become one of the most detrimental stresses in crop production among constantly changing environmental factors. Exploiting approaches to enhance crop thermotolerance would have great significance in assuaging adverse effects of HT stress on crop growth and development. As jasmonates (JAs) and brassinosteroids (BRs) are novel phytohormones and play important roles in responses to biotic and abiotic stresses and in a wide range of plant developmental processes, this paper reviewed the roles and mechanisms of JAs and BRs in mitigating HT stress, with focus on rice (Oryza sativa L.) subjected to HT stress during anthesis. It is demonstrated that JAs alleviate spikelet-opening impairment and BRs ameliorate pistil fertilization ability under HT stress during anthesis of rice, although there are controversial observations. Activating the defense system, enhancing osmotic regulation, protecting photosynthesis, and interacting with other phytohormones, especially with ethylene and abscisic acid, are main physiological mechanisms by which JAs or BRs attenuate HT stress to plants. Elevating levels of JAs or BRs in plants could be considered as an important approach to enhance crop thermotolerance through breeding new varieties. Using JAs or BRs as chemical regulators and adopting proper water and nitrogen management practices could reduce the harm of HT stress to rice. Further research is needed to elucidate the roles of JAs and BRs in different plant tissues in responses to HT stress under different genetic backgrounds and environments, reveal the molecular mechanism underlying JAs and BRs mediating HT stress, understand the cross-talk between phytohormones in modulating HT stress, and establish integrated crop management to minimize the hazard of HT stress in rice production.