A network of redundant bHLH proteins functions in all TTG1-dependent pathways of Arabidopsis.
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 described here, ENHANCER OF GLABRA3 (EGL3). When mutated, egl3 gives totally glabrous plants only in the gl3 mutant background. The double bHLH mutant, gl3 egl3, has a pleiotropic phenotype like ttg1 having defective anthocyanin production, seed coat mucilage production, and position-dependent root hair spacing. Furthermore, the triple bHLH mutant, gl3 egl3 tt8, phenocopies the ttg1 mutation. Yeast two-hybrid and plant overexpression studies show that EGL3, like GL3, interacts with TTG1, the myb proteins GL1, PAP1 and 2, CPC and TRY, and it will form heterodimers with GL3. These results suggest a combinatorial model for TTG1-dependent pathway regulation by this trio of partially functionally redundant bHLH proteins.
Zhang
Fan
F
Molecular Cell and Developmental Biology, and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA.
Gonzalez
Antonio
A
Zhao
Mingzhe
M
Payne
C Thomas
CT
Lloyd
Alan
A
D017360:Arabidopsis / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D018257:Helix-Loop-Helix Motifs / Q000502:physiology*; D009154:Mutation; D000073718:Pancreatitis-Associated Proteins; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D002352:Carrier Proteins; D000073718:Pancreatitis-Associated Proteins; D014157:Transcription Factors; C417284:GL3 protein, Arabidopsis; C000612141:REG3A protein, human; C417767:TT8 protein, Arabidopsis; C121067:TTG1 protein, Arabidopsis