In Arabidopsis thaliana, Lateral Root Initiation (LRI) is hallmarked by coordinated asymmetric divisions in adjacent xylem pole pericycle cells. Similar to many developmental processes, it is strongly regulated by the plant hormone auxin.
Introduction
 Lateral root priming occurs in the basal meristem. Schematic overview of the different root tissues (a) and the auxin signaling maximum present (b) as reported by the DR5::GUS marker line (De Smet et al., 2007). The regularly spaced auxin accumulation sites in the protoxylem primes the adjacent pericycle cells to become pericycle founder cells (Péret et al., 2009). |
 Schematic representation of the auxin signaling modules acting successively during lateral root founder cell specification in the basal meristem (module 1) and nuclear migration and lateral root initiation processes (modules 2 and 3). As a consequence of module 1, GATA23 is hypothesized to be involved in the determination of founder cell identity in the xylem pole pericycle cells (De Rybel et al., 2010). |
 Early events during lateral root initiation. Local auxin accumulation in primed xylem pole pericycle cells activates the auxin signaling cascade. Auxin causes the degradation of IAA14, thereby de-repressing ARF7 and 19 and activating downstream gene expression. The receptor-like kinase ACR4 promotes formative divisions in the primordium and represses cell divisions in surrounding pericycle cells (De Smet et al., 2008). Abbreviation: LOB, LATERAL ORGAN BOUNDARIES (Péret et al., 2009). |
 GATA23 expression analysis. Section through a stage I lateral root primordium showing pGATA23::GUS expression at one side of the xylem pole pericycle (XPP). Asterisks and arrowheads indicate phloem pole and XPP cells, respectively (De Rybel et al., 2010). |
De Rybel B, Vassileva V, Parizot B, Demeulenaere M, Grunewald W, Audenaert D, Van Campenhout J, Overvoorde P, Jansen L, Vanneste S, Moller B, Wilson M, Holman T, Van Isterdael G, Brunoud G, Vuylsteke M, Vernoux T, De Veylder L, Inzé D, Weijers D, Bennett MJ, Beeckman T
A Novel aux/IAA28 Signaling Cascade Activates GATA23-dependent Specification of Lateral Root Founder Cell Identity
CURR BIOL 2010 20, 1697–1706. [full text]
De Smet I, Vassileva V, De Rybel B, Levesque MP, Grunewald W, Van Damme D, Van Noorden G, Naudts M, Van Isterdael G, De Clercq R, Wang JY, Meuli N, Vanneste S, Friml J, Hilson P, Jürgens G, Ingram GC, Inzé D, Benfey PN, Beeckman T
Receptor-like kinase ACR4 restricts formative cell divisions in the Arabidopsis root.
SCIENCE. 2008 322, 594-597. [full text]
De Smet I, Tetsumura T, De Rybel B, Frei Dit Frey N, Laplaze L, Casimiro I, Swarup R, Naudts M, Vanneste S, Audenaert D, Inze D, Bennett MJ, Beeckman T
Auxin-dependent regulation of lateral root positioning in the basal meristem of Arabidopsis
DEVELOPMENT. 2007 134, 681-690. [full text]
Himanen K, Vuylsteke M, Vanneste S, Vercruysse S, Boucheron E, Alard P, Chriqui D, Van Montagu M, Inzé D, Beeckman T
Transcript profiling of early lateral root initiation
PROC NATL ACAD SCI USA 2004 101, 5146-5151. [full text]
Himanen K, Boucheron E, Vanneste S, de Almeida Engler J, Inzé D and Beeckman T
Auxin?mediated cell cycle activation during early lateral root initiation
PLANT CELL 2002 14, 2339?2351. [free full text]
Péret B, De Rybel B, Benkova E, Swarup R, Casimiro I, Beeckman T, Laplaze L and Bennett M
Arabidopsis lateral root development: an emerging story
TRENDS PLANT SCI 2009 14, 399-408. [full text]
Vanneste S, De Rybel B, Beemster GT, Ljung K, De Smet I, Van Isterdael G, Naudts M, Iida R, Gruissem W, Tasaka M, Inzé D, Fukaki H, Beeckman T
Cell Cycle Progression in the Pericycle Is Not Sufficient for SOLITARY ROOT/IAA14-Mediated Lateral Root Initiation in Arabidopsis thaliana
PLANT CELL 2005 17, 3035-3050. [free full text]