Roles of ethylene in plant growth, development, and stress responses

Ethylene, a pivotal gaseous phytohormone, regulates diverse processes in plant growth, development, and stress adaptation. In Arabidopsis, ethylene perception by endoplasmic reticulum (ER)-localized receptors initiates a canonical signaling cascade involving CONSTITUTIVE TRIPLE RESPONSE 1 (AtCTR1) and ETHYLENE INSENSITIVE 2 (AtEIN2). This pathway culminates in nuclear translocation of AtEIN2-CEND and activation of the transcription factor AtEIN3/EIN3-LIKE1 (AtEIL1). Rice employs conserved (OsEIN2, OsCTR2, OsEIL1/2) and unique (Mao Huzi 3 [MHZ3], MHZ11, MHZ1) components for ethylene signaling, reflecting adaptations to semi-aquatic environments. Ethylene regulates developmental processes including seed germination, apical hook formation, root architecture, flowering, and senescence, often via intricate crosstalk with auxin, abscisic acid (ABA), jasmonic acid (JA), gibberellins (GA), and brassinosteroids (BR). Ethylene signaling also influences rice yield-related traits such as grain filling, grain size, and starch biosynthesis. Moreover, ethylene modulates responses to abiotic stresses (such as submergence, hypoxia, salinity, drought, and temperature fluctuations) and nutrient imbalances. This review synthesizes current understanding of ethylene signaling and its functions, focusing on the model dicot Arabidopsis thaliana and the monocot rice (Oryza sativa). It highlights conserved and diverged mechanisms, underscoring ethylene's potential as a target for enhancing crop resilience and productivity in changing environments.