Dual DNA Binding Property of ABA insensitive 3 Like Factors Targeted to Promoters Responsive to ABA and Auxin

Abstract

The ABA responsive ABI3 and the auxin responsive ARF family of transcription factors bind the CATGCATG (Sph) and TGTCTC core motifs in ABA and auxin response elements (ABRE and AuxRE), respectively. Several evidences indicate ABI3s to act downstream to auxin too. Because DNA binding domain of ABI3s shows significant overlap with ARFs we enquired whether auxin responsiveness through ABI3s could be mediated by their binding to canonical AuxREs. Investigations were undertaken through in vitro gel mobility shift assays (GMSA) using the DNA binding domain B3 of PvAlf (Phaseolus vulgaris ABI3 like factor) and upstream regions of auxin responsive gene GH3 (-267 to -141) and ABA responsive gene Em (-316 to -146) harboring AuxRE and ABRE, respectively. We demonstrate that B3 domain of PvAlf could bind AuxRE only when B3 was associated with its flanking domain B2 (B2B3). Such strict requirement of B2 domain was not observed with ABRE, where B3 could bind with or without being associated with B2. This dual specificity in DNA binding of ABI3s was also demonstrated with nuclear extracts of cultured cells of Arachis hypogea. Supershift analysis of ABRE and AuxRE bound nuclear proteins with antibodies raised against B2B3 domains of PvAlf revealed that ABI3 associated complexes were detectable in association with both cis elements. Competition GMSA confirmed the same complexes to bind ABRE and AuxRE. This dual specificity of ABI3 like factors in DNA binding targeted to natural promoters responsive to ABA and auxin suggests them to have a potential role in conferring crosstalk between these two phytohormones.

Deciphering gene regulatory networks that control seed development and maturation in Arabidopsis

“…Interestingly, some key proteins in auxin signaling (i.e. ARFs) also belong to the B3 family, and an ABI3 homolog of bean (Phaseolus vulgaris) is able to bind the auxin-responsive element (Nag et al, 2005). Consistent with the latter result, ABI3 appears to be involved in auxin signaling as well as lateral root development (Brady et al, 2003).…”

Over-represented promoter motifs in abiotic stress-induced DREB genes of rice and sorghum and their probable role in regulation of gene expression

“…In Phaseolus vulgaris, an ABA responsive transcription factor ABI3 was shown to bind to both ABA and auxin response elements. 19 Hence cross-talk between ABA and auxin signaling may be involved in regulating the expression of DREB genes.…”

The Conserved Splicing Factor SUA Controls Alternative Splicing of the Developmental Regulator ABI3 in Arabidopsis

“…The A1 domain is an acidic transcriptional activator (McCarty et al, 1991), and B1 can interact with the seed-specific transcription factor ABI5 (Nakamura et al, 2001). B2 and B3 are two basic DNA binding domains responsible for the ABA-dependent activation of seed maturation genes (Suzuki et al, 1997;Ezcurra et al, 2000;Nag et al, 2005).…”