Sustaining rice productivity with reduced fertilization using zaxinone mimics

• The biostimulants MiZax3 and MiZax5 boost paddy rice yield >65% under half-strength fertilization. • Neither MiZax3 nor MiZax5 was detected in harvested grains. • Exogenous application of MiZax3 and MiZax5 improved root architecture, stimulated nutrient transporter expression, and elevated essential metabolites. • These compounds significantly lessen dependence on chemical fertilizers while sustaining high productivity in both paddy and upland systems. Food insecurity urgently demands innovative strategies to enhance rice productivity. While chemical fertilizers have historically increased yields, their excessive use poses serious environmental risks and threatens the long-term sustainability of crop production. The apocarotenoid zaxinone plays a vital role in rice development and nutrient acquisition. In this study, we assessed the agronomic potential of two zaxinone mimics, MiZax3 and MiZax5, in both paddy rice (Tainung 67, TNG67) and upland rice (Nakabo) through two consecutive years of field trials conducted in Taichung, Taiwan (2023-2024). Remarkably, exogenous application of these compounds increased paddy rice fresh grain yield per plant by over 65% under half-strength fertilization, reaching levels comparable to those achieved with full fertilization. In upland rice, yield improvements were associated with a significant reduction in the empty seed numbers by approximately 30% per plant. These effects are likely mediated by improved root architecture, upregulation of nutrient transporters, and increased accumulation of primary metabolites and essential nutrients. Notably, RNA-seq analysis revealed that several nutrient transporters, including nitrate and phosphate transporters, were significantly upregulated (approximately 1.5-fold) following MiZax3 and MiZax5 treatments, particularly upon shoot application. Importantly, grain analysis confirmed that neither MiZax3 nor MiZax5 was present in the harvested grains. Our findings highlight MiZax3 and MiZax5 as promising biostimulants for sustainably improving rice productivity while reducing dependence on chemical fertilizers.