Auxin Transport Promotes Arabidopsis Lateral Root Initiation

Abstract

Lateral root development in Arabidopsis provides a model for the study of hormonal signals that regulate postembryonic organogenesis in higher plants. Lateral roots originate from pairs of pericycle cells, in several cell files positioned opposite the xylem pole, that initiate a series of asymmetric, transverse divisions. The auxin transport inhibitor N -1-naphthylphthalamic acid (NPA) arrests lateral root development by blocking the first transverse division(s). We investigated the basis of NPA action by using a cell-specific reporter to demonstrate that xylem pole pericycle cells retain their identity in the presence of the auxin transport inhibitor. However, NPA causes indoleacetic acid (IAA) to accumulate in the root apex while reducing levels in basal tissues critical for lateral root initiation. This pattern of IAA redistribution is consistent with NPA blocking basipetal IAA movement from the root tip. Characterization of lateral root development in the shoot meristemless1 mutant demonstrates that root basipetal and leaf acropetal auxin transport activities are required during the initiation and emergence phases, respectively, of lateral root development.

Strigolactones fine-tune the root system

“…Adventitious roots forming from Arabidopsis hypocotyls initiate from a cell layer proximate to the central cylinder and in this regard show similarity to the lateral roots that emerge from pericycle founder cells (Casimiro et al 2001). In many important crop species (including rice, maize and wheat), adventitious roots are formed via vascular cambial cell divisions whereby phloem initials start to divide to produce a primordium (Naija et al 2009) callus in which tracheids differentiate, elongate and eventually form the center of a complete root primordium (Bollmark et al 1988;Lorbiecke and Sauter 1999;Rasmussen and Hunt 2010).…”

“…This is evidenced in auxin receptor mutants (tir1afb2afb3) that show a drastic reduction in lateral root formation (Dharmasiri et al 2005;Pérez-Torres et al 2008) and in several mutants perturbed in AUX/IAAand ARF-mediated signaling that display severe defects in lateral root organogenesis, or block it completely [in the case of stabilized SOLITARY ROOT(SLR)/IAA14 or loss of ARF7 and ARF19 (Vanneste et al 2005)]. Local accumulation of auxin in root pericycle cells is ensured by PINdependent auxin recirculation inside the root tip (Casimiro et al 2001), a process that is very well described elsewhere and falls beyond the scope of this review. Following lateral root initiation, organogenesis of lateral root primordia is achieved by highly coordinated cell division and differentiation patterns (Benková and Bielach 2010).…”

The Arabidopsis Auxin-Inducible Gene ARGOS Controls Lateral Organ Size

“…Recent genetic and biochemical analyses have suggested that ubiquitin-related proteolysis is central to several aspects of auxin response (Gray et al, 1999(Gray et al, , 2001Dharmasiri and Estelle, 2002;Kepinski and Leyser, 2002;Leyser, 2002). As a model system, some advances in how auxin promotes lateral root formation have been reported recently (Xie et al, 2000;Casimiro et al, 2001;Xie et al, 2002). However, little is known about how auxin regulates the development of the aerial parts of plants.…”

Multiscale modelling of auxin transport in the plant-root elongation zone

“…1). In the root, auxin regulates the gravitropic response (Marchant et al 1999;Ottenschlager et al 2003), maintains the root apical meristem (Jiang and Feldman 2005) and promotes the initiation of lateral roots (Benková et al 2003;Casimiro et al 2003Casimiro et al , 2001De Smet et al 2007). Therefore, understanding the distribution and transport of auxin within root tissue could help explain key processes in root development.…”