title: bHLH05 is an interaction partner of MYB51 and a novel regulator of glucosinolate biosynthesis in Arabidopsis.
abstract: By means of yeast (Saccharomyces cerevisiae) two-hybrid screening, we identified basic helix-loop-helix transcription factor05 (bHLH05) as an interacting partner of MYB51, the key regulator of indolic glucosinolates (GSLs) in Arabidopsis (Arabidopsis thaliana). Furthermore, we show that bHLH04, bHLH05, and bHLH06/MYC2 also interact with other R2R3-MYBs regulating GSL biosynthesis. Analysis of bhlh loss-of-function mutants revealed that the single bhlh mutants retained GSL levels that were similar to those in wild-type plants, whereas the triple bhlh04/05/06 mutant was depleted in the production of GSL. Unlike bhlh04/06 and bhlh05/06 mutants, the double bhlh04/05 mutant was strongly affected in the production of GSL, pointing to a special role of bHLH04 and bHLH05 in the control of GSL levels in the absence of jasmonic acid. The combination of two specific gain-of-function alleles of MYB and bHLH proteins had an additive effect on GSL levels, as demonstrated by the analysis of the double MYB34-1D bHLH05D94N mutant, which produces 20-fold more indolic GSLs than bHLH05D94N and ecotype Columbia-0 of Arabidopsis. The amino acid substitution D94N in bHLH05D94N negatively affects the interaction with JASMONATE-ZIM DOMAIN protein, thereby resulting in constitutive activation of bHLH05 and mimicking jasmonic acid treatment. Our study revealed the bHLH04, bHLH05, and bHLH06/MYC2 factors as novel regulators of GSL biosynthesis in Arabidopsis.
authors: Botanical Institute and Cluster of Excellence on Plant Sciences, University of Cologne, BioCenter, D-50674 Cologne, Germany (H.F., T.G.); the Plant Accelerator, Australian Plant Phenomics Facility, University of Adelaide, Urrbrae SA 5064, Australia (B.B.) t.gigolashvili@uni-koeln.de.
authors: Henning
authors: http://orcid.org/0000-0002-7067-2721
authors: H
authors: Frerigmann
authors: Botanical Institute and Cluster of Excellence on Plant Sciences, University of Cologne, BioCenter, D-50674 Cologne, Germany (H.F., T.G.); the Plant Accelerator, Australian Plant Phenomics Facility, University of Adelaide, Urrbrae SA 5064, Australia (B.B.) t.gigolashvili@uni-koeln.de.
authors: Bettina
authors: B
authors: Berger
authors: Botanical Institute and Cluster of Excellence on Plant Sciences, University of Cologne, BioCenter, D-50674 Cologne, Germany (H.F., T.G.); the Plant Accelerator, Australian Plant Phenomics Facility, University of Adelaide, Urrbrae SA 5064, Australia (B.B.) t.gigolashvili@uni-koeln.de.
authors: Tamara
authors: http://orcid.org/0000-0002-0416-4796
authors: T
authors: Gigolashvili
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D002460:Cell Line; D005961:Glucosinolates / Q000096:biosynthesis*; D006801:Humans; D054730:Protein Interaction Domains and Motifs; D012097:Repressor Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D005961:Glucosinolates; D012097:Repressor Proteins; D014157:Transcription Factors; C554741:JAZ1 protein, Arabidopsis; C000595372:MYB34 protein, Arabidopsis; C523452:MYB51 protein, Arabidopsis