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Arabidopsis transient expression analysis reveals that activation of GLABRA2 may require concurrent binding of GLABRA1 and GLABRA3 to the promoter of GLABRA2. Wang S, Chen JG. Plant Cell Physiol. 2008 Dec;49(12):1792-804. Epub 2008 Oct 22 ...... in Arabidopsis utilizes a lateral inhibition mechanism that relies on the interplay of transcription factors. GLABRA1 (GL1), an R2R3 MYB transcription factor, GLABRA3 (GL3), a basic helix-loop-helix (bHLH) transcription factor, and TRANSPARENT TESTA GLABRA1 (TTG1), a WD40 protein, are believed to form a transcriptional activator complex to control the transcription of GLABRA2 (GL2), which in turn induces trichome formation in shoots. However, the molecular mechanism of the regulation of GL2 ...... |
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Functional specialization of the TRANSPARENT TESTA GLABRA1 network allows differential hormonal control of laminal and marginal trichome initiation in Arabidopsis rosette leaves. Maes L, Inze D, Goossens A. Plant Physiol. 2008 Nov;148(3):1453-64. Epub 2008 Sep 10 ...... Trichome initiation in Arabidopsis (Arabidopsis thaliana) is controlled by the TRANSPARENT TESTA GLABRA1 (TTG1) network that consists of R2R3- and R1-type MYB-related transcription factors, basic helix-loop-helix (bHLH) proteins, and the WD40 protein TTG1. An experimental method was designed to investigate the molecular mechanisms by which ...... |
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...... a seemingly common effect on cell patterning by promoting trichome initiation but caused strikingly distinct effects on cell and trichome maturation. The phytohormonal control was mediated by transcriptional regulation of the established TTG1 complex and depended on the R2R3-MYB factor GLABRA1. However, unsuspected degrees of functional specialization of the bHLH factors and a resultant differential molecular regulation of trichome initiation on leaf lamina and leaf margins ...... |
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SAD2 in Arabidopsis functions in trichome initiation through mediating GL3 function and regulating GL1, TTG1 and GL2 expression. Gao Y, Gong X, Cao W, Zhao J, Fu L, Wang X, Schumaker KS, Guo Y. J Integr Plant Biol. 2008 Jul;50(7):906-17 ...... Most genes identified that control Arabidopsis trichome initiation and formation are transcription factors or regulatory components in transcriptional networks and include GLABROUS1 (GL1), GLABRA2 (GL2), GLABRA3 (GL3) and TRANSPARENT TESTA GLABRA1 (TTG1). Herein, we report that an importin beta-like protein, SENSITIVE TO ABA AND DROUGHT2 (SAD2), is required for trichome initiation. Mutations in SAD2 disrupted trichome initiation resulting in reduced trichome number, but had no ...... |
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...... mutant analysis of gl1 sad2 and gl3 sad2 indicated that SAD2 functions genetically, at least in part, in the same pathway with these two genes. Co-immunoprecipitation indicated that the sad2 mutation does not disrupt formation of the TTG1-GL3-GL1 complex. Analysis of GFP fusions of GL1, GL2, GL3 and TTG1 suggested that these proteins are most likely not direct cargo of SAD2. Our data suggest that SAD2 is involved in trichome initiation by regulating these nuclear genes. ...... |
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Two-dimensional patterning by a trapping/depletion mechanism: the role of TTG1 and GL3 in Arabidopsis trichome formation. Bouyer D, Geier F, Kragler F, Schnittger A, Pesch M, Wester K, Balkunde R, Timmer J, Fleck C, Hülskamp M. PLoS Biol. 2008 Jun 10;6(6):e141 ...... study the potential of the observed trapping/depletion mechanism, we formulated a mathematical model enabling us to evaluate the relevance of each parameter and to identify parameters explaining the paradoxical genetic finding that strong ttg1 alleles are glabrous, while weak alleles exhibit trichome clusters. ...... |
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...... cells. Current models explain this pattern by an activator-inhibitor feedback loop. Here, we report that also a newly discovered mechanism is involved by which patterning is governed by the removal of the trichome-promoting factor TRANSPARENT TESTA GLABRA1 (TTG1) from non-trichome cells. We demonstrate by clonal analysis and misexpression studies that Arabidopsis TTG1 can act non-cell-autonomously and by microinjection experiments that TTG1 protein moves between cells. While TTG1 is ...... |
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The TTG1-bHLH-MYB complex controls trichome cell fate and patterning through direct targeting of regulatory loci. Zhao M, Morohashi K, Hatlestad G, Grotewold E, Lloyd A. Development. 2008 Jun;135(11):1991-9. ...... A network of three classes of proteins consisting of bHLH and MYB transcription factors, and a WD40 repeat protein, TRANSPARENT TESTA GLABRA1 (TTG1), act in concert to activate trichome initiation and patterning. Using YFP-TTG1 translational fusions, we show that TTG1 is expressed ubiquitously in Arabidopsis leaves and is preferentially localized in the nuclei of trichomes at ...... |
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Two WD-repeat genes from cotton are functional homologues of the Arabidopsis thaliana TRANSPARENT TESTA GLABRA1 (TTG1) gene. Humphries JA, Walker AR, Timmis JN, Orford SJ. Plant Mol Biol. 2005 Jan;57(1):67-81. ...... and are developmentally similar to the trichomes of Arabidopsis thaliana. To identify genes involved in the molecular control of cotton fibre initiation, we isolated four putative homologues of the Arabidopsis trichome-associated gene TRANSPARENT TESTA GLABRA1 (TTG1). All four WD-repeat genes are derived from the ancestral D diploid genome of tetraploid cotton and are expressed in many tissues throughout the plant, including ovules and growing fibres. Two of the cotton genes were able to ...... |
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The YORE-YORE gene regulates multiple aspects of epidermal cell differentiation in Arabidopsis. Kurata T, Kawabata-Awai C, Sakuradani E, Shimizu S, Okada K, Wada T. Plant J. 2003 Oct;36(1):55-66. ...... of cer1 was normal, whereas that of the yre cer1 double mutant was heavily deformed, indicating that epicuticular wax is required for normal growth of trichomes. Double mutants of yre and trichome-morphology mutants, glabra2 (gl2) and transparent testa glabra1 (ttg1), showed that the phenotype of the trichome structure was additive, suggesting that the wax-requiring pathway is distinct from the trichome development pathway controlled by GL2 and TTG1. ...... |
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A network of redundant bHLH proteins functions in all TTG1-dependent pathways of Arabidopsis. Zhang F, Gonzalez A, Zhao M, Payne CT, Lloyd A. Development. 2003 Oct;130(20):4859-69. ...... GLABRA3 (GL3) encodes a bHLH protein that interacts with the WD repeat protein, TTG1. GL3 overexpression suppresses the trichome defect of the pleiotropic ttg1 mutations. However, single gl3 mutations only affect the trichome pathway with a modest trichome number reduction. A novel unlinked bHLH-encoding locus is ...... |
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TRANSPARENT TESTA GLABRA2, a trichome and seed coat development gene of Arabidopsis, encodes a WRKY transcription factor. Johnson CS, Kolevski B, Smyth DR. Plant Cell. 2002 Jun;14(6):1359-75. ...... development, in the endothelium of developing seeds (in which tannin is later generated) and subsequently in other layers of the seed coat, and in the atrichoblasts of developing roots. TTG2 acts downstream of the trichome initiation genes TTG1 and GLABROUS1, although trichome expression of TTG2 continues to occur if they are inactivated. Later, TTG2 shares functions with GLABRA2 in controlling trichome outgrowth. In the seed coat, TTG2 expression requires TTG1 function in the ...... |
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Ectopic expression of the Arabidopsis AtMYB23 gene induces differentiation of trichome cells. Kirik V, Schnittger A, Radchuk V, Adler K, Hulskamp M, Baumlein H. Dev Biol. 2001 Jul 15;235(2):366-77. ...... factor family, AtMYB23, that is involved in trichome development. Expression of the AtMYB23 gene under the control of the viral CaMV 35S promoter causes the development of ectopic trichomes. The formation of ectopic trichomes depends on TRANSPARENT TESTA GLABRA1 but not on GLABRA1. The absence of the negative regulator TRIPTYCHON leads to branching of the ectopic trichomes on cotyledons and the formation of ectopic trichomes in the leaf subepidermal cell layer. The CaMV 35S promoter-controlled ...... |
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GL3 encodes a bHLH protein that regulates trichome development in arabidopsis through interaction with GL1 and TTG1. Payne CT, Zhang F, Lloyd AM. Genetics. 2000 Nov;156(3):1349-62. ...... Arabidopsis trichome development and differentiation is a well-studied model for plant cell-fate determination and morphogenesis. Mutations in TRANSPARENT TESTA GLABRA1 (TTG1) result in several pleiotropic defects including an almost complete lack of trichomes. The complex phenotype caused by ttg1 mutations is suppressed by ectopic expression of the maize anthocyanin regulator R. Here it is demonstrated ...... |
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...... the Arabidopsis trichome development locus GLABRA3 (GL3) encodes an R homolog. GL3 and GLABRA1 (GL1) interact when overexpressed together in plants. Yeast two-hybrid assays indicate that GL3 participates in physical interactions with GL1, TTG1, and itself, but that GL1 and TTG1 do not interact. These data suggest a reiterated combinatorial model for the differential regulation of such diverse developmental pathways as trichome cell-fate determination, root hair spacing, and ...... |