Abstract: Biological nitrification inhibitors (BNIs) are released from plant roots and inhibit the nitrification activity of microorganisms in soils, reducing NO₃^‒ leaching and N₂O emissions, and increasing nitrogen-use efficiency (NUE). Several recent studies have focused on the identification of new BNIs, while little is known about the genetic loci governing their biosynthesis and secretion. We applied a combined transcriptomic and metabolomic analysis to investigate possible biosynthetic pathways and transporters implicated in the biosynthesis and release of BNI 1,9-decanediol (1,9-D), previously identified in rice root exudates. Our results link four fatty acids, icosapentaenoic acid, linoleate, norlinolenic acid, and polyhydroxy-α,ω-divarboxylic acid, to 1,9-D biosynthesis, and three transporter families, namely the ATP-binding cassette protein family, the multidrug and toxic compound extrusion family, and the major facilitator superfamily, to 1,9-D release from roots into the soil medium. Our results provide candidates for further work on the genes implicated in the biosynthesis and secretion of 1,9-D and pinpoint genetic loci for crop breeding to improve NUE by enhancing 1,9-D secretion, with the promise of reducing NO₃^‒ leaching and N₂O emissions from agricultural soils.

Key words: biological nitrification inhibitor, nitrogen-use efficiency, 1,9-decanediol, transcriptomic analysis, metabolomic analysis