TheMYB23Gene Provides a Positive Feedback Loop for Cell Fate Specification in theArabidopsisRoot Epidermis  

Abstract

The specification of cell fates during development requires precise regulatory mechanisms to ensure robust cell type patterns. Theoretical models of pattern formation suggest that a combination of negative and positive feedback mechanisms are necessary for efficient specification of distinct fates in a field of differentiating cells. Here, we examine the role of the R2R3-MYB transcription factor gene, AtMYB23 (MYB23), in the establishment of the root epidermal cell type pattern in Arabidopsis thaliana. MYB23 is closely related to, and is positively regulated by, the WEREWOLF (WER) MYB gene during root epidermis development. Furthermore, MYB23 is able to substitute for the function of WER and to induce its own expression when controlled by WER regulatory sequences. We also show that the MYB23 protein binds to its own promoter, suggesting a MYB23 positive feedback loop. The localization of MYB23 transcripts and MYB23-green fluorescent protein (GFP) fusion protein, as well as the effect of a chimeric MYB23-SRDX repressor construct, links MYB23 function to the developing non-hair cell type. Using mutational analyses, we find that MYB23 is necessary for precise establishment of the root epidermal pattern, particularly under conditions that compromise the cell specification process. These results suggest that MYB23 participates in a positive feedback loop to reinforce cell fate decisions and ensure robust establishment of the cell type pattern in the Arabidopsis root epidermis.

Tissue-Specific Profiling Reveals Transcriptome Alterations inArabidopsisMutants Lacking Morphological Phenotypes

“…Asterisks indicate significant deviation from the wild type (P < 0.05). development using standard analysis methods, mutations in the other members (cpc, gl3, or wer) cause significant cell specification defects, and the double mutant combinations (try cpc, egl3 gl3, or myb23 wer) have extreme phenotypes, essentially lacking one of the two cell types (Figures 1B and 1C; see Supplemental Table 1 online), consistent with previously published data (Lee and Schiefelbein, 1999;Schellmann et al, 2002;Bernhardt et al, 2003Bernhardt et al, , 2005Simon et al, 2007;Kang et al, 2009;TominagaWada et al, 2012).…”

Mathematical Modelling Plant Signalling Networks

“…Such switches in steady states enable cells to make irreversible decisions during developmental processes. An example of a positive feedback loop which may reinforce cell fate decisions and cell type patterning has been identified in the epidermis of the root of Arabidopsis [50]. The transcription factor gene MYB23 is part of a positive feedback loop: MYB23 gene transcription is promoted by a complex that includes the MYB23 protein.…”

MYB transcription factor genes as regulators for plant responses: an overview

“…The functions of MYB proteins have been investigated in numerous plant species such as Arabidopsis, maize, cotton, rice (Oryza sativa), petunia (Petunia hybrida), snapdragon (Antirrhinum majus), grapevine (Vitis vinifera L.), poplar (Populus tremuloides) and apple (Malus domestica), using both genetic and molecular analyses. In the past decade, the R2R3-MYB genes have been extensively studied and members of the MYB family have been found to be involved in a variety of biological functions like phenylpropanoid metabolism (Grotewold et al 1994;Hichri et al 2011), biotic and abiotic stress (Segarra et al 2009;Lippold et al 2009), cell shape such as Am MIXTA (Noda et al 1994), differentiation (Oppenheimer et al 1991;Kang et al 2009;Xie et al 2010), hormone responses i.e. AtMYB2 (Urao et al 1993), GAMYB and CpMYB (Gubler et al 1995 ;Iturriaga et al 1996), formation of B-type cyclin (Ito et al 2001) or during plant defense reactions i.e.…”