Studies on potentiation mechanism of auxin response via secreted peptide signalling in lateral root development

Abstract

The phytohormone auxin is a key developmental signal in plants. Until now, only auxin perception has been described to trigger the release of transcription factors termed AUXIN RESPONSE FACTORs (ARFs) from their AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) repressor proteins and transcription of auxin-responsive gene expressions. Here, I show that phosphorylation of ARF7 and ARF19 via BRASSINOSTEROID-INSENSITIVE2 (BIN2) can also potentiates auxin signalling output during lateral root organogenesis. BIN2-mediated phosphorylation of ARF7 and ARF19 suppresses their interaction with AUX/IAAs, facilitates degradation of AUX/IAA, and subsequently enhances the transcriptional activity to their target genes LATERAL ORGAN BOUNDARIES-DOMAIN16 (LBD16) and LBD29. In this context, BIN2 is under the control of the TRACHEARY ELEMENT DIFFERENTIATION INHIBITORY FACTOR (TDIF) – TDIF RECEPTOR (TDR) module. TDIF-initiated TDR signalling directly acts on BIN2-mediated ARF phosphorylation, leading to the regulation of auxin signalling during lateral root development. In summary, this study delineates a TDIF-TDR-BIN2 signalling cascade controlling auxin perception-independent regulation of ARF and AUX/IAA interaction during lateral root development and provides important node for connecting diverse signaling networks in auxin-driven plant growth and development