Lateral root emergence: a difficult birth.

Lateral root initiation takes place deep within the parental root, requiring new primordia to break through the overlying tissues before they emerge into the soil. Lateral root emergence has been well described at the cellular level but, until recently, the molecular mechanisms involved were unclear. Scientists in the 19th and 20th centuries hypothesized that the cell wall of the overlying tissues was modified by enzymes released by cells within the primordium. Recent studies in the model plant Arabidopsis thaliana revealed the existence of a complex transcellular signalling network regulated by auxin that controls cell wall remodelling in cells overlying lateral root primordia. In the first part of this review, early observations on the cell biology of lateral root formation and emergence are summarized, and in the following two sections recent observations in Arabidopsis that led to the identification of the molecular mechanism regulating lateral root emergence are described.

[1]  Tom Beeckman,et al.  Arabidopsis lateral root development: an emerging story. , 2009, Trends in plant science.

[2]  Steffen Vanneste,et al.  Auxin: A Trigger for Change in Plant Development , 2009, Cell.

[3]  P. Gantet,et al.  Molecular Genetics of Rice Root Development , 2009, Rice.

[4]  S. Swain,et al.  ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE1 (ADPG1), ADPG2, and QUARTET2 Are Polygalacturonases Required for Cell Separation during Reproductive Development in Arabidopsis[W] , 2009, The Plant Cell Online.

[5]  L. Herrera-Estrella,et al.  Phosphate Availability Alters Lateral Root Development in Arabidopsis by Modulating Auxin Sensitivity via a Mechanism Involving the TIR1 Auxin Receptor[C][W][OA] , 2008, The Plant Cell Online.

[6]  Christophe Godin,et al.  An Auxin Transport-Based Model of Root Branching in Arabidopsis thaliana , 2008, PloS one.

[7]  Corey Nislow,et al.  Combination chemical genetics. , 2008, Nature chemical biology.

[8]  Tom Beeckman,et al.  The auxin influx carrier LAX3 promotes lateral root emergence , 2008, Nature Cell Biology.

[9]  D. Gibbs,et al.  Branching out in new directions: the control of root architecture by lateral root formation. , 2008, The New phytologist.

[10]  Frank Hochholdinger,et al.  Conserved and diverse mechanisms in root development. , 2008, Current opinion in plant biology.

[11]  J. Verbelen,et al.  Xyloglucan endotransglucosylase activity loosens a plant cell wall. , 2007, Annals of botany.

[12]  J. Roberts,et al.  Expression of polygalacturonases and evidence to support their role during cell separation processes in Arabidopsis thaliana. , 2007, Journal of experimental botany.

[13]  J. Kirkegaard,et al.  Pathways of infection of Brassica napus roots by Leptosphaeria maculans. , 2007, The New phytologist.

[14]  D. Pilbeam,et al.  Signalling mechanisms underlying the morphological responses of the root system to nitrogen in Arabidopsis thaliana. , 2007, Journal of experimental botany.

[15]  Karen S. Osmont,et al.  Hidden branches: developments in root system architecture. , 2007, Annual review of plant biology.

[16]  Tom Beeckman,et al.  Auxin-dependent regulation of lateral root positioning in the basal meristem of Arabidopsis , 2007, Development.

[17]  Wen-Hsiung Li,et al.  Patterns of expansion and expression divergence in the plant polygalacturonase gene family , 2006, Genome Biology.

[18]  Malcolm J Bennett,et al.  Auxin transport: a field in flux. , 2006, Trends in plant science.

[19]  Reeta Prusty,et al.  Expression profiling of auxin-treated Arabidopsis roots: toward a molecular analysis of lateral root emergence. , 2006, Plant & cell physiology.

[20]  Peter J. Gregory,et al.  Rhizosphere geometry and heterogeneity arising from root-mediated physical and chemical processes. , 2005, The New phytologist.

[21]  A. Theologis,et al.  Tissue-specific expression of stabilized SOLITARY-ROOT/IAA14 alters lateral root development in Arabidopsis. , 2005, The Plant journal : for cell and molecular biology.

[22]  W. Armstrong,et al.  Rice: sulfide-induced barriers to root radial oxygen loss, Fe2+ and water uptake, and lateral root emergence. , 2005, Annals of botany.

[23]  David R Spring,et al.  Chemical genetics to chemical genomics: small molecules offer big insights. , 2005, Chemical Society reviews.

[24]  Masashi Yamada,et al.  Sites and Regulation of Auxin Biosynthesis in Arabidopsis Roots , 2005, The Plant Cell Online.

[25]  W. Park,et al.  Release of the benzoxazinoids defense molecules during lateral- and crown root emergence in Zea mays. , 2004, Journal of plant physiology.

[26]  G. Jürgens,et al.  Local, Efflux-Dependent Auxin Gradients as a Common Module for Plant Organ Formation , 2003, Cell.

[27]  L. Herrera-Estrella,et al.  The role of nutrient availability in regulating root architecture. , 2003, Current opinion in plant biology.

[28]  G. Seymour,et al.  Pectate lyases, cell wall degradation and fruit softening. , 2002, Journal of experimental botany.

[29]  P. Casero,et al.  Lateral Root Initiation , 2002 .

[30]  G. Sandberg,et al.  AUX1 Promotes Lateral Root Formation by Facilitating Indole-3-Acetic Acid Distribution between Sink and Source Tissues in the Arabidopsis Seedling , 2002, The Plant Cell Online.

[31]  K. Ljung,et al.  Shoot-derived auxin is essential for early lateral root emergence in Arabidopsis seedlings. , 2002, The Plant journal : for cell and molecular biology.

[32]  P. Doerner,et al.  Early primordium morphogenesis during lateral root initiation in Arabidopsis thaliana , 2001, Planta.

[33]  D. Inzé,et al.  Auxin Transport Promotes Arabidopsis Lateral Root Initiation , 2001, Plant Cell.

[34]  P. Doerner,et al.  Pericycle cell proliferation and lateral root initiation in Arabidopsis. , 2000, Plant physiology.

[35]  B. Stockwell.  Chemical genetics: ligand-based discovery of gene function , 2000, Nature Reviews Genetics.

[36]  J. Verbelen,et al.  In Vivo Colocalization of Xyloglucan Endotransglycosylase Activity and Its Donor Substrate in the Elongation Zone of Arabidopsis Roots , 2000, Plant Cell.

[37]  P. Casero,et al.  Pericycle proliferation pattern during the lateral root initiation in adventitious roots ofAllium cepa , 1996, Protoplasma.

[38]  D. Inzé,et al.  Superroot, a recessive mutation in Arabidopsis, confers auxin overproduction. , 1995, The Plant cell.

[39]  B. Scheres,et al.  Cellular organisation of the Arabidopsis thaliana root. , 1993, Development.

[40]  D. Clarkson,et al.  The development and function of roots. , 1977 .

[41]  T. Pesacreta,et al.  DEVELOPMENT AND STRUCTURE OF THE VASCULAR CONNECTION BETWEEN THE PRIMARY AND SECONDARY ROOT OF GLYCINE MAX (L.) MERR. , 1977 .

[42]  E. M. Gifford,et al.  SEQUENCE AND PATTERN OF LATERAL ROOT FORMATION IN FIVE SELECTED SPECIES , 1970 .

[43]  Corresponding authors. , 2008 .

[44]  H. Fukaki,et al.  Auxin-mediated lateral root formation in higher plants. , 2007, International review of cytology.

[45]  A. Hodge,et al.  Plastic plants and patchy soils. , 2006, Journal of experimental botany.

[46]  Woong June Park,et al.  From weeds to crops: genetic analysis of root development in cereals. , 2004, Trends in plant science.

[47]  H. Fukaki,et al.  Lateral root formation is blocked by a gain-of-function mutation in the SOLITARY-ROOT/IAA14 gene of Arabidopsis. , 2002, The Plant journal : for cell and molecular biology.

[48]  B. J. van der Zaal,et al.  A novel subtilisin-like protease gene from Arabidopsis thaliana is expressed at sites of lateral root emergence. , 1999, DNA research : an international journal for rapid publication of reports on genes and genomes.

[49]  A. Eshel,et al.  Plant roots : the hidden half , 1991 .

[50]  C. Peterson,et al.  Ontogeny and anatomy of lateral roots , 1986 .

[51]  M. Jackson.  New Root Formation in Plants and Cuttings , 1986, Developments in Plant and Soil Sciences.

[52]  W. L. Stern,et al.  The Development and Function of Roots , 1977 .

[53]  H. Guttenberg.  Der primäre Bau der Angiospermenwurzel , 1940 .