Reinhold, H. and Soyk, S. and Simkova, K. and Hostettler, C. and Marafino, J. and Mainiero, S. and Vaughan, Cara K. and Monroe, J.D. and Zeeman, S.C. (2011) beta-Amylase-like proteins function as transcription factors in Arabidopsis, controlling shoot growth and development. Plant Cell 23 (4), pp. 1391-1403. ISSN 1040-4651.Full text not available from this repository.
Plants contain beta-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 beta-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 b-amylases, do not influence their transcription factor function.
|School or Research Centre:||Birkbeck Schools and Research Centres > School of Science > Biological Sciences|
|Date Deposited:||20 Jun 2011 11:09|
|Last Modified:||17 Apr 2013 12:20|
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