title: Characterization of an activation-tagged mutant uncovers a role of GLABRA2 in anthocyanin biosynthesis in Arabidopsis.
abstract: In Arabidopsis, anthocyanin biosynthesis is controlled by a MYB-bHLH-WD40 (MBW) transcriptional activator complex. The MBW complex activates the transcription of late biosynthesis genes in the flavonoid pathway, leading to the production of anthocyanins. A similar MBW complex regulates epidermal cell fate by activating the transcription of GLABRA2 (GL2), a homeodomain transcription factor required for trichome formation in shoots and non-hair cell formation in roots. Here we provide experimental evidence to show that GL2 also plays a role in regulating anthocyanin biosynthesis in Arabidopsis. From an activation-tagged mutagenized population of Arabidopsis plants, we isolated a dominant, gain-of-function mutant with reduced anthocyanins. Molecular cloning revealed that this phenotype is caused by an elevated expression of GL2, thus the mutant was named gl2-1D. Consistent with the view that GL2 acts as a negative regulator of anthocyanin biosynthesis, gl2-1D seedlings accumulated less whereas gl2-3 seedlings accumulated more anthocyanins in response to sucrose. Gene expression analysis indicated that expression of late, but not early, biosynthesis genes in the flavonoid pathway was dramatically reduced in gl2-1D but elevated in gl2-3 mutants. Further analysis showed that expression of some MBW component genes involved in the regulation of late biosynthesis genes was reduced in gl2-1D but elevated in gl2-3 mutants, and chromatin immunoprecipitation results indicated that some MBW component genes are targets of GL2. We also showed that GL2 functions as a transcriptional repressor. Taken together, these results indicate that GL2 negatively regulates anthocyanin biosynthesis in Arabidopsis by directly repressing the expression of some MBW component genes.
authors.affiliation: Key Laboratory of Molecular Epigenetics of MOE & Institute of Genetics and Cytology, Northeast Normal University, Changchun, Jilin 130024, China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Laboratory of Molecular Epigenetics of MOE & Institute of Genetics and Cytology, Northeast Normal University, Changchun, Jilin 130024, China.
authors.forename: Xianling
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Laboratory of Molecular Epigenetics of MOE & Institute of Genetics and Cytology, Northeast Normal University, Changchun, Jilin 130024, China.
authors.forename: Qingnan
authors.initials: Q
authors.lastname: Hu
authors.affiliation: Key Laboratory of Molecular Epigenetics of MOE & Institute of Genetics and Cytology, Northeast Normal University, Changchun, Jilin 130024, China.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Dai
authors.affiliation: Key Laboratory of Molecular Epigenetics of MOE & Institute of Genetics and Cytology, Northeast Normal University, Changchun, Jilin 130024, China.
authors.forename: Hainan
authors.initials: H
authors.lastname: Tian
authors.affiliation: Key Laboratory of Molecular Epigenetics of MOE & Institute of Genetics and Cytology, Northeast Normal University, Changchun, Jilin 130024, China.
authors.forename: Kaijie
authors.initials: K
authors.lastname: Zheng
authors.affiliation: Key Laboratory of Molecular Epigenetics of MOE & Institute of Genetics and Cytology, Northeast Normal University, Changchun, Jilin 130024, China.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100094, China.
authors.forename: Tonglin
authors.initials: T
authors.lastname: Mao
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: Jin-Gui
authors.initials: JG
authors.lastname: Chen
authors.affiliation: Key Laboratory of Molecular Epigenetics of MOE & Institute of Genetics and Cytology, Northeast Normal University, Changchun, Jilin 130024, China.
authors.forename: Shucai
authors.initials: S
authors.lastname: Wang
mesh_terms: D000872:Anthocyanins / Q000096:biosynthesis*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D017343:Genes, Plant; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D009154:Mutation
chemical_list: D000872:Anthocyanins; D029681:Arabidopsis Proteins; C089991:GL2 protein, Arabidopsis; D018398:Homeodomain Proteins
keywords: Arabidopsis thaliana; GLABRA2; anthocyanin; flavonoid; transcription factor