Abstract: Karrikins (KARs) are a class of butenolide compounds produced by the combustion of plant-derived materials. Early studies demonstrated that KARs can significantly promote seed germination in a wide range of plant species. Molecular biological evidence has revealed that the signaling pathway through which plants perceive KARs is a highly conserved molecular mechanism, with core components including the receptor protein KARRIKIN INSENSITIVE 2 (KAI2), the F-box protein MORE AXILLARY BRANCHES 2 (MAX2), and the downstream transcriptional repressors SUPPRESSOR OF MAX2 1 (SMAX1)/SMAX1-LIKE 2 (SMXL2). The KAR signaling pathway not only regulates key processes of plant growth and development (e.g., promoting seed germination, inhibiting hypocotyl elongation, and modulating root system development) but also enhances plant resistance to various abiotic stresses (such as drought, high salinity, extreme high temperature, and extreme low temperature) and biotic stresses. Based on the current research progress, this review systematically summarizes the composition, signal transduction mechanism, and biological functions of the KAR signaling pathway. It aims to provide a reference for in-depth elucidation of the regulatory mechanisms underling KAR signal-mediated plant growth and development as well as stress adaptation, and to offer insights for future research directions.

Key words: Growth and development, Karrikins, Stress adaptation