Auxin minimum defines a developmental window for lateral root initiation

Abstract

Root system architecture depends on lateral root (LR) initiation that takes place in a relatively narrow developmental window (DW). Here, we analyzed the role of auxin gradients established along the parent root in defining this DW for LR initiation. Correlations between auxin distribution and response, and spatiotemporal control of LR initiation were analyzed in Arabidopsis thaliana and tomato (Solanum lycopersicum). In both Arabidopsis and tomato roots, a well defined zone, where auxin content and response are minimal, demarcates the position of a DW for founder cell specification and LR initiation. We show that in the zone of auxin minimum pericycle cells have highest probability to become founder cells and that auxin perception via the TIR1/AFB pathway, and polar auxin transport, are essential for the establishment of this zone. Altogether, this study reveals that the same morphogen-like molecule, auxin, can act simultaneously as a morphogenetic trigger of LR founder cell identity and as a gradient-dependent signal defining positioning of the founder cell specification. This auxin minimum zone might represent an important control mechanism ensuring the LR initiation steadiness and the acropetal LR initiation pattern

The Autoregulation Gene SUNN Mediates Changes in Root Organ Formation in Response to Nitrogen through Alteration of Shoot-to-Root Auxin Transport

“…Our finding that auxin transport was strongly negatively correlated with lateral root density suggests that auxin concentration in the root might be superoptimal for lateral root initiation or early emergence in M. truncatula. This seems counterintuitive, as external auxin application usually increases lateral root number (Wightman et al, 1980), but it agrees with detailed measurements of auxin gradients in the root, which show that lateral root founder cells are established at sites of auxin minima (Dubrovsky et al, 2011).…”

The anthocyanin reduced Tomato Mutant Demonstrates the Role of Flavonols in Tomato Lateral Root and Root Hair Development

“…Similarly, both mechanical and chemical treatments that block auxin movement from the shoot into the root reduce lateral root development (Reed et al, 1998). In tomato, although the positive role of auxin and auxin transport in lateral root development was reported decades ago (Muday and Haworth, 1994;Muday et al, 1995), limited numbers of studies have explored the mechanisms for this regulation (Ivanchenko et al, 2006;de Jong et al, 2009;Negi et al, 2010;Dubrovsky et al, 2011;Bassa et al, 2012;Gupta et al, 2013). One consistent finding in both Arabidopsis and tomato is that treatments or mutations (such as those resulting in elevated levels of ethylene) that enhanced long-distance IAA transport at the expense of local accumulation of auxin can impair lateral root initiation (Negi et al, 2008(Negi et al, , 2010.…”

Ecological relevance of strigolactones in nutrient uptake and other abiotic stresses, and in plant-microbe interactions below-ground

“…Therefore, SLs may regulate RSA by affecting auxin sensitivity. Lateral root development and primary root growth depend on auxin influx from the polar auxin transport stream, which is mainly fed by auxin produced in the apex and young leaves (Aloni 2013; Dubrovsky et al 2011). In Arabidopsis, GR24 application reduced the auxin level in young developing rosette leaves, resulting in a decreased leaf area .…”