The SCARECROW Gene Regulates an Asymmetric Cell Division That Is Essential for Generating the Radial Organization of the Arabidopsis Root

Abstract

In the Arabidopsis root meristem, initial cells undergo asymmetric divisions to generate the cell lineages of the root. The scarecrow mutation results in roots that are missing one cell layer owing to the disruption of an asymmetric division that normally generates cortex and endodermis. Tissue-specific markers indicate that a heterogeneous cell type is formed in the mutant. The deduced amino acid sequence of SCARECROW (SCR) suggests that it is a member of a novel family of putative transcription factors. SCR is expressed in the cortex/endodermal initial cells and in the endodermal cell lineage. Tissue-specific expression is regulated at the transcriptional level. These results indicate a key role for SCR in regulating the radial organization of the root.

Large-scale analysis of the GRAS gene family in Arabidopsis thaliana

“…1a). Of 33 GRAS genes, only a third was genetically analyzed: GAI, RGA, RGL1, RGL2, RGL3, SCR, SHR, PAT1, SCL13, and SCL18/ LAS (Di Laurenzio et al 1996;Peng et al 1997;Silverstone et al 1998;Bolle et al 2000;Helariutta et al 2000;Dill and Sun 2001;Lee et al 2002;Wen and Chang 2002;Greb et al 2003;Tyler et al 2004;Torres-Galea et al 2006). Typically, GRAS proteins share signature motifs of VHIID flanked by two leucine heptad repeats (LHRI and LHRII), PFYRE and SAW (designated after the profound amino acid residues in the conserved regions) with rather variable N-terminal regions (Pysh et al 1999;Bolle 2004).…”

“…GRAS proteins belong to a plant specific transcription factor family, named after the three founding members, GIBBERELLIC ACID INSENSITIVE (G AI), REPRESSOR OF GA1 (R G A), and SCARECROW (S CR) (Di Laurenzio et al 1996;Peng et al 1997;Silverstone et al 1998;Pysh et al 1999;Bolle 2004). Typically, GRAS proteins consist of variable N-terminal region, VHIID flanked by two leucine heptad repeats (LHRI and LHRII), PFYRE, and SAW motifs (Pysh et al 1999;Bolle 2004).…”

“…According to the current genome annotation (version 7.0), a total of 33 GRAS genes are predicted in Arabidopsis thaliana (TAIR, http://www.arabidopsis.org). Of them, only 10 GRAS genes were analyzed in detail thus far: GAI, RGA, RGL1, RGL2, RGL3, SCR, SHR, PAT1, SCL13, and SCL18/LAS (Di Laurenzio et al 1996;Peng et al 1997;Silverstone et al 1998;Bolle et al 2000;Helariutta et al 2000;Dill and Sun 2001;Lee et al 2002;Wen and Chang 2002;Greb et al 2003;Tyler et al 2004;Torres-Galea et al 2006). These genes play a crucial role in diverse plant growth and development, ranging from GA signaling, root radial pattering, light signal transduction, and axillary shoot meristem formation.…”

An R2R3-type transcription factor gene AtMYB59 regulates root growth and cell cycle progression in Arabidopsis

“…Mutations of SHR and SCR result in shorter roots. SHR may specify endodermal cell fate, whereas SCR mediates the division of the cortex/endodermal initial daughter cell [33,34]. Another MYB coiled-coil transcription factor gene, APL, may be necessary for phloem cell formation [35].…”

Externally imposed electric field enhances plant root tip regeneration

“…The transcription factor SCARECROW (SCR) is a key regulator for radial pattern formation in Arabidopsis root, as well as in the establishment of the stem cell niche (Di Laurenzio et al. 1996; Sabatini et al. 2003).…”