RRC ID 12333
Author Reinhold H, Soyk S, Simková K, Hostettler C, Marafino J, Mainiero S, Vaughan CK, Monroe JD, Zeeman SC.
Title β-amylase-like proteins function as transcription factors in Arabidopsis, controlling shoot growth and development.
Journal Plant Cell
Abstract Plants contain β-amylase-like proteins (BAMs; enzymes usually associated with starch breakdown) present in the nucleus rather than targeted to the chloroplast. They possess BRASSINAZOLE RESISTANT1 (BZR1)-type DNA binding domains--also found in transcription factors mediating brassinosteroid (BR) responses. The two Arabidopsis thaliana BZR1-BAM proteins (BAM7 and BAM8) bind a cis-regulatory element that both contains a G box and resembles a BR-responsive element. In protoplast transactivation assays, these BZR1-BAMs activate gene expression. Structural modeling suggests that the BAM domain's glucan binding cleft is intact, but the recombinant proteins are at least 1000 times less active than chloroplastic β-amylases. Deregulation of BZR1-BAMs (the bam7bam8 double mutant and BAM8-overexpressing plants) causes altered leaf growth and development. Of the genes upregulated in plants overexpressing BAM8 and downregulated in bam7bam8 plants, many carry the cis-regulatory element in their promoters. Many genes that respond to BRs are inversely regulated by BZR1-BAMs. We propose a role for BZR1-BAMs in controlling plant growth and development through crosstalk with BR signaling. Furthermore, we speculate that BZR1-BAMs may transmit metabolic signals by binding a ligand in their BAM domain, although diurnal changes in the concentration of maltose, a candidate ligand produced by chloroplastic β-amylases, do not influence their transcription factor function.
Volume 23(4)
Pages 1391-403
Published 2011-4
DOI 10.1105/tpc.110.081950
PII tpc.110.081950
PMID 21487098
PMC PMC3101533
MeSH Arabidopsis / enzymology* Arabidopsis / genetics Arabidopsis / growth & development* Arabidopsis Proteins / chemistry Arabidopsis Proteins / metabolism* Base Sequence Gene Expression Regulation, Plant Genes, Plant / genetics Glucans / metabolism Hydrolysis Models, Biological Molecular Sequence Data Mutant Proteins / isolation & purification Mutant Proteins / metabolism Mutation / genetics Nuclear Proteins / metabolism Plant Leaves / genetics Plant Leaves / growth & development Plant Shoots / enzymology Plant Shoots / growth & development* Protein Binding Protein Structure, Tertiary Response Elements / genetics Trans-Activators / metabolism Transcription Factors / chemistry Transcription Factors / metabolism* beta-Amylase / chemistry beta-Amylase / metabolism*
IF 8.228
Times Cited 29
Arabidopsis / Cultured plant cells, genes pdx36441 pdx38715 pdx39980 pdz61236 pdz86189