Nitrogen form dependent root foraging is regulated by auxin and brassinosteroid signaling (Plant Physiol.)

Root growth is highly sensitive to nitrogen (N), and affected by both the form and distribution of N. The hormone auxin is a major player in root growth response to N heterogeneity. Devi et al. report on the intricate interplay of auxin and brassinosteroid (BR) signaling in determining the root growth response to low N, to ammonium, and to nitrate. Analysis of auxin and BR signaling mutants revealed transcriptome changes in support of the observed root phenotypes.   Under low N, the augmented auxin transport and signaling facilitated by BR favors root elongation. By contrast, high ammonium suppresses BR signaling, which down regulates auxin transport and signaling leading to an arrest of root elongation. Nitrate-dependent root elongation also showed a close dependence on BRI1-mediated BR signaling. Thus, N-dependent root growth is coordinately regulated by auxin and BR signaling, which ensures optimum root foraging phenotype. (Summary by Lekshmy Sathee @lekshmysnair) Plant Physiol.  10.1093/plphys/kiac157