Boosting Drought Resilience in Rice: The Priming Effects of Zaxinone and Its Mimics

Climate change increasingly threatens global agriculture, with drought emerging as a major constraint on crop productivity. Plants activate complex adaptive responses, involving genetic, physiological, and hormonal networks, to cope with water deficit. Among these, carotenoid-derived phytohormones, abscisic acid, and strigolactones regulate drought responses through modulation of stomatal conductance, antioxidant defenses, and hormonal crosstalk. Zaxinone, an apocarotenoid metabolite, and its synthetic analogs Mimic of Zaxinone 3 (MiZax3) and MiZax5 have recently emerged as plant growth regulators and SL biosynthesis inhibitors in Oryza sativa. This study investigates the effects of zaxinone and its mimics on rice drought encompassing morphometric, ecophysiological, biochemical, and molecular analysis. Exogenous treatment prior to the water deficit revealed compound-specific effects, in an organ-specific manner, on stomatal conductance, transpiration rate, and stem water potential. We also observed differential ABA and zaxinone content and transcriptional regulation of stress-related genes across water regimes. Notably, MiZax5 treatment maintained higher Ψ_stem and modulated stress-responsive gene expression at the end of drought, suggesting improved osmotic adjustments and enhanced stress resilience. Our results highlight the potential of zaxinone-based compounds as promising biostimulants capable of priming rice for improved drought resilience, offering a sustainable approach to boost crop performance under abiotic stress.