The Pivotal Role of Ethylene in Plant Growth

Being continuously exposed to variable environmental conditions, plants produce phytohormones to react quickly and specifically to these changes. The phytohormone ethylene is produced in response to multiple stresses. While the role of ethylene in defense responses to pathogens is widely recognized, recent studies in arabidopsis and crop species highlight an emerging key role for ethylene in the regulation of organ growth and yield under abiotic stress. Molecular connections between ethylene and growth-regulatory pathways have been uncovered, and altering the expression of ethylene response factors (ERFs) provides a new strategy for targeted ethylene-response engineering. Crops with optimized ethylene responses show improved growth in the field, opening new windows for future crop improvement. This review focuses on how ethylene regulates shoot growth, with an emphasis on leaves. An increasing number of transcriptome studies in plants exposed to biotic or abiotic stress highlight a role for ethylene under a broad range of stresses. The role of ethylene under stress is dual: it regulates a defense response, mostly in full-grown leaves, and a growth response in young leaves. In young leaves, ethylene and the downstream ERFs emerge as central regulators of leaf growth inhibition, orchestrating both cell division and cell expansion. The knowledge of ethylene-mediated growth inhibition can be successfully implemented in crops to improve plant growth and stress tolerance.