Ethylene crosstalk with isoprenoid-derived signaling molecules in the context of salinity tolerance

Salinity is a significant environmental stressor that impacts plant growth and development, leading to severe loss of agricultural output across the world. One way to reduce salt-induced detrimental effects is with the use of hormones. Through synergistic or antagonistic crosstalk with other hormones, phytohormones regulate multiple signals required for growth and development under normal and environmental stress conditions. Ethylene is a well-known phytohormone involved in salt tolerance. Its signaling component EIN3/EIL has a positive regulatory effect in salinity tolerance that is mediated by the AP2/ERF transcription factor, through which ethylene maintains ionic and osmotic homeostasis, fine-tunes photosynthesis, and reduces salt-induced reactive oxygen species production in stressful environments. Furthermore, a negative regulator of ethylene signaling, CTR1, was found to have a positive role in stabilizing EIN3 and improving resistance to salinity. However, certain studies have demonstrated overproduction of ethylene and its signaling to have negative effects on plant growth and development, contradictory to its established positive role. Therefore, it can be considered that ethylene is involved in salinity tolerance and its interplay with other hormones enables it to finely regulate plant salinity response. This review focuses on a) a general introduction of salt stress, its impact on plants, and the responses of plants under salinity stress; b) the role of ethylene in salinity tolerance, along with its biosynthesis and signaling; c) an overview of isoprenoids and the synthesis of their derived phytohormones brassinosteroids, gibberellic acid, abscisic acid, cytokinins, and strigolactones; and d) crosstalk of ethylene with isoprenoid-derived phytohormones under salt stress.