Cell Fate in the Arabidopsis Root Epidermis Is Determined by Competition between WEREWOLF and CAPRICE    

Abstract

The root hair and nonhair cells in the Arabidopsis (Arabidopsis thaliana) root epidermis are specified by a suite of transcriptional regulators. Two of these are WEREWOLF (WER) and CAPRICE (CPC), which encode MYB transcription factors that are required for promoting the nonhair cell fate and the hair cell fate, respectively. However, the precise function and relationship between these transcriptional regulators have not been fully defined experimentally. Here, we examine these issues by misexpressing the WER gene using the GAL4-upstream activation sequence transactivation system. We find that WER overexpression in the Arabidopsis root tip is sufficient to cause epidermal cells to adopt the nonhair cell fate through direct induction of GLABRA2 (GL2) gene expression. We also show that GLABRA3 (GL3) and ENHANCER OF GLABRA3 (EGL3), two closely related bHLH proteins, are required for the action of the overexpressed WER and that WER interacts with these bHLHs in plant cells. Furthermore, we find that CPC suppresses the WER overexpression phenotype quantitatively. These results show that WER acts together with GL3/EGL3 to induce GL2 expression and that WER and CPC compete with one another to define cell fates in the Arabidopsis root epidermis.

Root Hairs

“…A possible explanation for CPC's negative action is provided by the nature of its gene product; CPC encodes a small protein with a single R3 Myb repeat with the bHLH-and DNA-binding domains but without a typical transcriptional activation domain (Wada et al, 1997). Consistent with this structure, CPC appears to inhibit the function of the WER-GL3/EGL3-TTG complex by interfering with WER binding to GL3/EGL3 in a competitive manner Tominaga et al, 2007;Song et al, 2011;Kang et al, 2013). Interestingly, CPC is capable of moving from cell-to-cell in the developing root, enabling it to act as a signaling molecule to repress non-hair cell fate specification in neighboring H cells (Kurata et al, 2005;Kang et al, 2013).…”

“…Although the protein sequence does not provide a clear mechanistic understanding of its role, TTG is able to physically interact with the basic helix-loop-helix (bHLH) transcriptional activators GL3 and EGL3, which act in a partially functionally redundant manner (Bernhardt et al 2003). GL3 and EGL3 also physically interact with WER (Bernhardt et al, 2003;Song et al, 2011), which implies that a tripartite transcription factor complex is responsible for directing the non-hair cell fate.…”

“…During root hair tip growth, newly-synthesized cell wall components are packaged into secretory vesicles that emerge from plant trans-Golgi network (TGN) membranes, and are subsequently targeted and delivered to the apical plasma membrane region of growing root hairs. In Arabidopsis, formation and delivery of at least one subpopulation of these secretory vesicles is regulated by the specific recruitment of members of the RabA family of plant Rab GTPases to these membrane compartments (Preuss et al, 2004;Ovecka et al, 2010;Kang et al, 2011). In their active, GTP-bound conformation, Rab GTPases function through the recruitment of cytosolic "effector proteins" to their target membranes.…”

Tissue-Specific Profiling Reveals Transcriptome Alterations inArabidopsisMutants Lacking Morphological Phenotypes

“…The WER/ MYB23 and EGL3/GL3 proteins appear to participate in a multimeric transcriptional regulatory complex with the TTG WD-repeat protein to induce non-hair cell differentiation, as well as expression of the TRY/CPC one-repeat Mybs (Lee and Schiefelbein, 1999;Ryu et al, 2005;Wang et al, 2008). The family of one-repeat Mybs engages in a lateral inhibition mechanism by moving from cell to cell and hindering formation of the MYB23/WER-EGL3/GL3-TTG complex, which permits expression of hair cell differentiation genes (Wada et al, 1997;Schellmann et al, 2002;Kurata et al, 2005;Tominaga et al, 2007;Wang et al, 2007Wang et al, , 2008Song et al, 2011). The relative abundance of the MYB23/WER-EGL3/GL3-TTG transcriptional complex in the presumptive hair cells and non-hair cells of the developing root epidermis appears to be controlled by cell position-dependent SCRAMBLED receptor kinase signaling (Kwak et al, 2005;Kwak and Schiefelbein, 2008;Savage et al, 2008).…”

Identification and characterization of mRNAs of receptor-like kinases MhyGSO1 and MhyGSO2 in flowering parasitic plant Monotropa hypopitys

“…Идентичность ПЦ и окружающих его инициалей, а также радиальное структурирование корня зависят от транскрипционных факторов SHORTROOT (SHR) и SCARECROW (SCR), взаимодействующих с белками JACKDAW (JKD) и MAGPIE (MGP) (Wildwater et al, 2005;Ogasawara et al, 2011). Спецификация судьбы эпидермаль-ных корневых клеток связана с транскрипционными фак-торами WEREWOLF (WER), GLABRA2 (GL2), GLABRA3 (GL3), ENHANCER OF GLABRA3 (EGL3) и CAPRICE (CPC) (Song et al, 2011) и межклеточным сообщением, опосредованным двумя рецепторными киназами (ACR4 и CLV1) и сигнальным пептидом CLAVATA3 (CLV3) (Stahl et al, 2013). Рецепторная киназа SCRAMBLED (SCM) обра батывает позиционные сигналы дифференцировки эпидермальных клеток в корне (Kwak, Schiefelbein, 2007.…”