A Recently Evolved Isoform of the Transcription Factor BES1 Promotes Brassinosteroid Signaling and Development in Arabidopsis thaliana

• Published in: The Plant cell 2015-02, Vol.27 (2), p.361-374
• Main Authors: Jiang, Jianjun, Zhang, Chi, Wang, Xuelu
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Arabidopsis; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Base Sequence; Brassicaceae; Brassinosteroids; Brassinosteroids - metabolism; Cell Nucleus - metabolism; Darkness; DNA-Binding Proteins; Evolution; Evolution, Molecular; Gene expression regulation; Gene Expression Regulation, Plant; Genes; Green Fluorescent Proteins - metabolism; Hypocotyl - growth & development; Hypocotyl - metabolism; Molecular Sequence Data; Nicotiana - genetics; Nuclear Proteins - chemistry; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Phenotype; Phenotypes; Plant cells; Plant Development; Plants; Plants, Genetically Modified; Protein isoforms; Protein Isoforms - chemistry; Protein Isoforms - genetics; Protein Isoforms - metabolism; Protein Transport; Proteins; Seedlings; Signal Transduction - genetics; Subcellular Fractions - metabolism; Transcription Factors - chemistry; Transcription Factors - genetics; Transcription Factors - metabolism; Transcription, Genetic
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.114.133678

Brassinosteroids (BRs) are essential steroid hormones that regulate plant growth and development. The transcription factor BRI1-EMS-SUPPRESSOR1 (BES1) regulates the expression of thousands of target genes in response to BRs. Here, we report an Arabidopsis thaliana-specific long isoform of BES1, BES1-L, which has stronger activity in promoting BR signaling than the canonical and widely used short BES1-S. The BES1-L isoform contains an additional N-terminal bipartite nuclear localization signal, which strongly promotes its nuclear localization. BES1-L also promotes the nuclear localization of BES1-S and BRASSINAZOLE-RESISTANT1 via dimerization. The transcription of BES1-L and BES1-S is differentially regulated by BRs due to the presence of G-box element in the BES1-S promoter. Moreover, BES1-L uniquely exists in the majority of A. thaliana ecotypes, but not in other species, even its Brassicaceae relatives, including Arabidopsis lyrata. The phenotypes of the BES1-L overexpression lines and plants with truncated BES1-L indicate that BES1-L is a more important isoform of BES1 in Arabidopsis and may have contributed to the evolution and expansion of A. thaliana.