ABI3-VP1 Transcription Factor Family
Suzuki et al. (1997) showed that when expressed and purified as a separate peptide, the B3 domain has a highly cooperative
DNA binding activity that is specific for the Sph sequence. They found that the properties of this activity are in
compelling agreement with the functional analyses of VP1 and regulatory sequences in the C7 promoter. These results identify
a new class of DNA binding proteins, which thus far are known only in the plant kingdom, that have critical functions in
development .
ABI3/VP1 proteins are members of a large group of transcription factors which act as intermediaries in regulating abscisic
acid (ABA)-responsive genes during seed development. Lesions in the genes affect the later stages of seed development and
have adverse effects on many important processes such as reserve deposition, dormancy imposition and the acquisition of a
tolerance of seed tissues to desiccation. ABI3 does not act in isolation to control gene expression central to seed
maturation programmes, but rather acts in concert with various other transcription factors such as LEC1, LEC2 and FUS3;
these interactions prevent the precocious activation of genes associated with germination and growth . Maize (Zea mays)
Viviparous1 (VP1) and Arabidopsis ABI3 are orthologous transcription factors.
ABI3/VP1 is a multidomain transcription factor that functions as both an activator and a repressor depending on the promoter
context . Three basic protein domains, B1, B2, and B3, are highly conserved among ABI3/VP1 factors from various plant
species. The C-terminal B3 domain of VP1 binds specifically to the Sph DNA element in the maize C1 promoter, whereas the
N-terminal B1 and B2 domains are implicated in nuclear localization and interactions with other proteins. The N-terminal
co-activation repression domain is necessary and sufficient for ABA-dependent co-activation functions and repressor
activities of VP1/ABI3, whereas the C-terminal B3 is required for a discrete subset of gene activation functions. Recent
genetic analysis of abi3 alleles has revealed further complexity of the role of ABI3 in ABA signaling, suggesting that
multiple ABA-signaling pathways are perceived through ABI3. Moreover, modification of chromatin structure by PvALF, the
Phaseolus sp. ABI3 ortholog, has been shown, suggesting that VP1/ABI3 has a potential to recruit additional DNA-binding
proteins to promoters
(taken from TOBFAC).
80 putative ABI3-VP1 TF peptide,
CDS, cDNA sequences;
blast HSP, and gene level multiple sequence alignment in Legume TFKB. Some are full length proteins and CDS.
68 B3 domain peptide sequences with alignmnet,
and phylogeny tree.
29 ABI3-VP1 Protein
and DNA
sequences with
annotations for soybean in EST-based PlantTFDB. Most are partial sequences.
Last updated by Dr. Jeff Chen on
June 6, 2009.
