Genetic robustness control of auxin output in priming organ initiation

Abstract

Auxin signaling is essential for organ initiation in plants. How genetic robustness controls auxin output during organ initiation is largely unknown. Here, we identified <i>DORNROSCHEN-LIKE</i> (<i>DRNL</i>) as a target of MONOPTEROS (MP) that plays essential roles in organ initiation. We demonstrate that MP physically interacts with DRNL to inhibit cytokinin accumulation by directly activating <i>ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 6</i> and <i>CYTOKININ OXIDASE 6</i>. <i>DRN</i>, the paralogous gene of <i>DRNL</i>, acts redundantly with <i>DRNL</i> but is not coexpressed with <i>DRNL</i> in the organ founder cells in which <i>DRNL</i> is expressed. We demonstrate that DRNL directly inhibits <i>DRN</i> expression in the peripheral zone, whereas <i>DRN</i> transcripts are ectopically activated in <i>drnl</i> mutants and fully restore the functional deficiency of <i>drnl</i> in organ initiation. Our results provide a mechanistic framework for the robust control of auxin signaling in organ initiation through paralogous gene-triggered spatial gene compensation effects.