The GA octodinucleotide repeat binding factor BBR participates in the transcriptional regulation of the homeobox gene Bkn3

Abstract

Summary In the dominant mutant Hooded (K), the barley gene BKn3 is overexpressed as a result of a duplication of 305 bp in intron IV. When fused to a cauliflower mosaic virus 35S minimal promoter, the 305 bp element activates gene expression in tobacco, as does a 655 bp BKn3 promoter sequence. Both DNA fragments contain a (GA)8 repeat (GA/TC)8. A one‐hybrid screen using the 305 bp element as the DNA target led to the cloning of the barley b recombinant (BBR) protein, which binds specifically to the (GA/TC)8 repeat. BBR is nuclear targeted and is a characterized nuclear localization signal (NLS) sequence, a DNA‐binding domain extended up to 90 aa at the C‐terminus and a putative N‐terminal activation domain. The corresponding gene has no introns and is ubiquitously expressed in barley tissues. In co‐transfection experiments, BBR activates (GA/TC)8‐containing promoters, and its overexpression in tobacco leads to a pronounced leaf shape modification. BBR has properties of a GAGA‐binding factor, but the corresponding gene has no sequence homology to Trl and Psq of Drosophila, which encode functionally analogous proteins. In Arabidopsis, (GA/TC)8 repeats occur particularly within 1500 bp upstream of gene start codons included in some homeodomain genes of different classes. The data presented suggest that expression of the barley BKn3 is regulated, at least in part, by the binding of the transcription factor BBR to GA/TC repeats.

BASIC PENTACYSTEINE Proteins Mediate MADS Domain Complex Binding to the DNA for Tissue-Specific Expression of Target Genes in Arabidopsis

“…In fact, this GAGA binding protein was first described in soybean (Glycine max) (GAGA Binding Protein [GBP]; Sangwan and O'Brian, 2002) and subsequently also in barley (Hordeum vulgare) (B Recombinant barley [BBR]; Santi et al, 2003) and rice (Oryza sativa) (Meister et al, 2004). Conservation of their function in different plant species is further suggested by the observation that in the promoter of the STK ortholog in rice, MADS13 (Dreni et al, 2007), C-box sequences are also present.…”

Genetics of Barley Hooded Suppression

“…existence of similar dominant insertional mutants in F 2 data, nevertheless, supported the concept, already the corresponding intron of the maize ortholog Knotted1 evident from the consideration of F 1 results, that the (reviewed in Santi et al 2003). To shed light on the short-awn phenotype of all suK mutants is a character molecular network involving Bkn3, a number of experiunder control of the K allele and not of the suK recessive mental strategies have been adopted.…”

“…In this region, the mutant differs from the III in maize). The importance of this noncoding region as the putative regulatory region was recently put forwild type (WT) in the size of the cells of the adaxial epidermis and in the direction of cell division (Stebbins ward (Inada et al 2003;Santi et al 2003). This noncoding region makes it possible to screen for second-site and Yagil 1966).…”

“…This is mediated by a (GA/ a bait in a yeast one-hybrid screen. This approach led to the isolation of four barley cDNA clones encoding TC) 8 sequence binding site of the nuclear-targeted BBR protein (Santi et al 2003). The BBR gene is one of four for putative binding proteins, one of which one is extensively characterized (Santi et al 2003).…”

Common mechanisms regulating expression of rice aleurone genes that contribute to the primary response for gibberellin

“…A novel family of DNA binding proteins, BASIC PENTACYSTEINE (BPC), has been proposed to be a plant substitute of GAFs [57]. BPC bind to GA-repeat sequences and influence expression of genes in different plant species and processes [57,58]. Arabidopsis BPC1 functions as an active repressor of the homeotic gene SEEDSTICK (STK) [59].…”