Transcript profiling of early lateral root initiation

Abstract

At the onset of lateral root initiation in Arabidopsis thaliana, the phytohormone auxin activates xylem pole pericycle cells for asymmetric cell division. However, the molecular events leading from auxin to lateral root initiation are poorly understood, in part because the few responsive cells in the process are embedded in the root and are thus difficult to access. A lateral root induction system, in which most xylem pole pericycle cells were synchronously activated by auxin transport inhibition followed by auxin application, was used for microarray transcript profiling. Of 4,600 genes analyzed, 906 significantly differentially regulated genes were identified that could be grouped into six major clusters. Basically, three major patterns were discerned representing induced, repressed, and transiently expressed genes. Analysis of the coregulated genes, which were specific for each time point, provided new insight into the molecular regulation and signal transduction preceding lateral root initiation in Arabidopsis. The reproducible expression profiles during a time course allowed us to define four stages that precede the cell division in the pericycle. These early stages were characterized by G 1 cell cycle block, auxin perception, and signal transduction, followed by progression over G 1͞S transition and G2͞M transition. All these processes took place within 6 h after transfer from N-1-naphthylphthalamic acid to 1-naphthalene acetic acid. These results indicate that this lateral root induction system represents a unique synchronized system that allows the systematic study of the developmental program upstream of the cell cycle activation during lateral root initiation.auxin ͉ cell cycle ͉ microarray

MDR‐like ABC transporter AtPGP4 is involved in auxin‐mediated lateral root and root hair development

“…Based on microarray transcript profiling, AtPGP4 has been suggested to be involved in early lateral root initiation [18]. Additionally, Digital Northern analysis (www.genevestigator.ethz.ch, [26]) supported a predominant expression of AtPGP4 in the root while expression in aerial parts of the plant is significantly lower (Suppl.…”

“…While an interpretation for root hair development is complicated by interaction among hormone response pathways [21], a shoot-derived auxin pulse has been suggested to promote the emergence of LR primordia [17]. Lately, in a microarray-based approach to profile early lateral root initiation, a homologue of AtPGP1, AtPGP4, was shown to be induced 2 h after external lateral root induction [18]. Here we Abbreviations: PAT, polar auxin transport; IAA, indole-3-acetic acid; NPA, 1-N-naphtylphtalamic acid; LR, lateral root; RH, root hair; ACC, aminocyclopropane carboxylic acid; AVG, ethylene biosynthesis inhibitor aminovinylglycine; GC-MS, gas chromatography-coupled mass spectrometry; MS, Murashige and Skoog basal medium; SE, standard error; ORF, open reading frame show that loss-of-function mutant alleles of AtPGP4 reveal more lateral roots and longer root hairs at early stages.…”

A Transcriptome-Based Characterization of Habituation in Plant Tissue Culture

“…the transcriptome) within whole plants (Rashotte et al, 2003;Bergmann et al, 2004), specific plant tissues (Che et al, 2002;Himanen et al, 2004), and even particular cells within a tissue type (Birnbaum et al, 2003). It is the changes in protein expression rather than the changes in mRNA expression, however, that truly The fold-change for the expression of each gene in habituated calli maintained in the absence of cytokinin is presented relative to the expression of the gene in nonhabituated calli maintained in the presence of cytokinin.…”

The Emerging Role of Reactive Oxygen Species Signaling during Lateral Root Development

“…As very few pericycle cells located deep inside the primary root contribute to LR formation (Kurup et al, 2005), an LR-inducible system was developed previously that allows synchronized LRP formation along the entire pericycle (Himanen et al, 2002(Himanen et al, , 2004. More recently, cell sorting of GFP-labeled root cells (e.g.…”