β-cyclocitral as a cross-species mediator of abiotic stress signaling: insights and future directions toward crop improvement.

Abiotic stresses such as drought, salinity, heavy-metal toxicity, and photooxidative damage severely constrain global crop productivity, a challenge intensified by ongoing climate change. The apocarotenoid β-cyclocitral (β-CC), produced via both carotenoid cleavage dioxygenase (CCD)-mediated and reactive oxygen species (ROS)-driven oxidation, has emerged as a conserved signaling molecule that enhances plant adaptation to environmental stress. β-CC mitigates oxidative damage, promotes root system remodeling, and activates detoxification pathways through ABA-independent mechanisms involving the transcriptional regulators MBS1 and SCL14. Its oxidized derivative, β-cyclocitric acid (β-CCA), extends this signaling framework by modulating the cyclin kinase inhibitor SMR5 and the cytochrome P450 gene CYP81D11, thereby strengthening photosynthetic capacity, ROS control, and developmental reprogramming under drought and high-light stress. Beyond vegetative responses, β-CC also enhances seed vigor and longevity through apocarotenoid-dependent regulation of antioxidant activity and aquaporin expression. Comparative studies across