Local auxin biosynthesis acts downstream of brassinosteroids to trigger root foraging for nitrogen

Abstract Lateral roots (LRs) dominate the overall root surface of adult plants and are crucial for soil exploration nutrient acquisition. When grown under mild nitrogen (N) deficiency, flowering develop longer LRs to enhance This response is partly mediated by brassinosteroids (BR) yet unknown mechanisms. Here, we show that local auxin biosynthesis modulates LR elongation while allelic coding variants YUCCA8 determine extent N deficiency. By up-regulating expression YUCCA8/3/5/7 Tryptophan Aminotransferase Arabidopsis 1 ( TAA1 ) deficiency accumulation increases in tips. We further demonstrate N-dependent acts epistatic downstream a canonical BR signaling cascade. The uncovered BR-auxin hormonal module its emphasize importance fine-tuning crosstalk boost adaptive responses availability offer path improve expanded systems plants.