β-cyclocitral as an apocarotenoid stress signal: biosynthesis, hormonal crosstalk, and emerging omics perspectives in plant abiotic stress tolerance
Abiotic stress, including drought, salinity, heavy metals, and extreme temperatures, severely limits plant growth, productivity, and survival. These stresses frequently occur simultaneously and disrupt cellular homeostasis, photosynthesis, and metabolic processes. To cope with such adverse conditions, plants activate complex physiological, biochemical, and molecular defense mechanisms. Among the emerging stress-related signaling compounds, β-cyclocitral, a β-carotene-derived apocarotenoid, has gained significant attention due to its crucial role in plant stress adaptation. β-Cyclocitral enhances photoprotection by scavenging free radicals and reducing singlet oxygen-mediated damage to photosynthetic machinery. It also modulates reactive oxygen species (ROS) homeostasis through the activation of antioxidant defense systems, thereby minimizing oxidative stress. In parallel, key phytohormones such as abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) regulate diverse stress-responsive pathways that improve plant tolerance and defense. Increasing evidence suggests that β-cyclocitral interacts closely with these hormonal signaling networks to coordinate stress responses and metabolic adjustments. This review highlights recent advances in the biosynthesis, physiological functions, and signaling roles of β-cyclocitral, with particular emphasis on its mechanistic crosstalk with ABA, JA, and SA pathways in enhancing abiotic stress tolerance in plants.