The Arabidopsis Abscisic Acid Response Locus ABI4 Encodes an APETALA2 Domain Protein

Abstract

Arabidopsis abscisic acid (ABA)-insensitive abi4 mutants have pleiotropic defects in seed development, including decreased sensitivity to ABA inhibition of germination and altered seed-specific gene expression. This phenotype is consistent with a role for ABI4 in regulating seed responses to ABA and/or seed-specific signals. We isolated the ABI4 gene by positional cloning and confirmed its identity by complementation analysis. The predicted protein product shows homology to a plant-specific family of transcriptional regulators characterized by a conserved DNA binding domain, the APETALA 2 domain. The single mutant allele identified has a single base pair deletion, resulting in a frameshift that should disrupt the C-terminal half of the protein but leave the presumed DNA binding domain intact. Expression analyses showed that despite the seed-specific nature of the mutant phenotype, ABI4 expression is not seed specific.

ABI4 Activates DGAT1 Expression in Arabidopsis Seedlings during Nitrogen Deficiency

“…ABSCISIC ACID INSENSITIVE (ABI) transcription factors are essential for TAG metabolism. ABI4 encodes an Activator Protein-2/Ethylene-Responsive Factor transcription factor that binds the CE1-like element (CACCG) present in many ABA-and sugarresponsive promoters (Finkelstein et al, 1998;Niu et al, 2002;Acevedo-Hernández et al, 2005). ABI4 is a crucial determinant of ABA sensitivity during TAG breakdown in the embryo (Penfield et al, 2006).…”

Enhancement of Abscisic Acid Sensitivity and Reduction of Water Consumption in Arabidopsis by Combined Inactivation of the Protein Phosphatases Type 2C ABI1 and HAB1

“…As loss of function of the above-mentioned genes leads to enhanced ABA responsiveness, their corresponding gene products must represent negative regulators of ABA signaling. On the other hand, recessive mutations leading to reduced ABA sensitivity have been identified in the abi3 (Giraudat et al, 1992), abi4 (Finkelstein et al, 1998), abi5 (Finkelstein and Lynch, 2000), ost1 (Mustilli et al, 2002), rcn1 (Kwak et al, 2002), rpk1 (Osakabe et al, 2005), and the rbohD/F double mutants (Kwak et al, 2003). Therefore, these loci point out to positive regulators of ABA signal transduction.…”

“…Finally, many transcriptional factors (TFs) of ABA-inducible genes are known. The TFs comprise ABA-responsive element (ABRE)-binding proteins (ABA-INSENSITIVE5 [ABI5]/ABF/AREB/ AtbZIP family), ABI3/VP1/B3, ABI4/APETALA2, MYC, MYB, and HD-ZIP domain proteins (Giraudat et al, 1992;Suzuki et al, 1997;Finkelstein et al, 1998;Choi et al, 2000;Finkelstein and Lynch, 2000;Uno et al, 2000;Bensmihen et al, 2002;Himmelbach et al, 2002;Abe et al, 2003). Most of these TFs play a positive role in ABA signaling, but some of them function as repressors of ABA response (Himmelbach et al, 2002;Pandey et al, 2005;Song et al, 2005).…”

The Arabidopsis ZINC FINGER PROTEIN3 Interferes with Abscisic Acid and Light Signaling in Seed Germination and Plant Development

“…Three of the best characterized positive regulators of ABA signaling are transcription factors encoded by the ABI3, ABI4, and ABI5 genes, which were initially identified by screening for mutants exhibiting ABA-insensitive germination (Koornneef et al, 1984). ABI3, ABI4, and ABI5 belong to B3 DNA binding domain, APETALA2 (AP2), and basic leucine zipper (bZIP) domain protein families, respectively, that regulate overlapping subsets of seed-specific and ABAinducible genes and control seed maturation and germination (Finkelstein and Somerville, 1990;Giraudat et al, 1992;Parcy and Giraudat, 1997;Finkelstein et al, 1998;Finkelstein and Lynch, 2000;Carles et al, 2002;Lopez-Molina et al, 2002;Fujita et al, 2011;Mönke et al, 2012). AtPP2CA was identified in a library of complementary DNA (cDNA)-overexpressing lines, which were screened for the ability to germinate in the presence of inhibitory concentrations of ABA (Kuhn et al, 2006).…”