InterPro domain: IPR044759

This is the bZIP domain found in plant transcription factors with similarity to Oryza sativa RF2a and RF2b, which are important for plant development. RF2a and b interact, as homodimers or heterodimers, with each other, and activate transcription from the RTBV (rice tungro bacilliform virus) promoter, which is regulated by sequence-specific DNA-binding proteins that bind to the essential cis element BoxII. They show differences in binding affinities to BoxII, expression patterns in different rice organs, and subcellular localisation. Transgenic rice with increased RF2a and RF2b display increased resistance to rice tungro disease (RTD) with no impact on plant development [ 1 , 2 ].

bZIP domains from Arabidopsis have been classified into 11 groups (groups A–I and S), the ones included in this entry belong to group I such as VIP1 or PosF21 (also known as bZIP transcription factor 59) [ 3 , 4 , 5 , 6 ].

bZIP factors act in networks of homo and heterodimers in the regulation of a diverse set of cellular processes. The bZIP structural motif contains a basic region and a leucine zipper, composed of alpha helices with leucine residues 7 amino acids apart, which stabilize dimerization with a parallel leucine zipper domain. Dimerization of leucine zippers creates a pair of the adjacent basic regions that bind DNA and undergo conformational change. Dimerization occurs in a specific and predictable manner resulting in hundreds of dimers having unique effects on transcription [ 7 ].

1. Functional analysis of the activation domain of RF2a, a rice transcription factor. Plant Biotechnol J 8, 835-44
2. RF2b, a rice bZIP transcription activator, interacts with RF2a and is involved in symptom development of rice tungro disease. Proc Natl Acad Sci U S A 101, 687-92
3. bZIP transcription factors in Arabidopsis. Trends Plant Sci. 7, 106-11
4. Calcium signalling regulates the functions of the bZIP protein VIP1 in touch responses in Arabidopsis thaliana. Ann Bot 122, 1219-1229
5. The bZIP Protein VIP1 Is Involved in Touch Responses in Arabidopsis Roots. Plant Physiol 171, 1355-65
6. Analysis of functions of VIP1 and its close homologs in osmosensory responses of Arabidopsis thaliana. PLoS One 9, e103930
7. Structural basis for the diversity of DNA recognition by bZIP transcription factors. Nat. Struct. Biol. 7, 889-93