Direct targets of the transcription factors ABA-Insensitive(ABI)4 and ABI5 reveal synergistic action by ABI4 and several bZIP ABA response factors

Abstract

The plant hormone abscisic acid (ABA) is a key regulator of seed development. In addition to promoting seed maturation, ABA inhibits seed germination and seedling growth. Many components involved in ABA response have been identified, including the transcription factors ABA insensitive (ABI)4 and ABI5. The genes encoding these factors are expressed predominantly in developing and mature seeds, and are positive regulators of ABA mediated inhibition of seed germination and growth. The direct effects of ABI4 and ABI5 in ABA response remain largely undefined. To address this question, plants over-expressing ABI4 or ABI5 were used to allow identification of direct transcriptional targets. Ectopically expressed ABI4 and ABI5 conferred ABA-dependent induction of slightly over 100 genes in 11 day old plants. In addition to effector genes involved in seed maturation and reserve storage, several signaling proteins and transcription factors were identified as targets of ABI4 and/or ABI5. Although only 12% of the ABA- and ABI-dependent transcriptional targets were induced by both ABI factors in 11 day old plants, 40% of those normally expressed in seeds had reduced transcript levels in both abi4 and abi5 mutants. Surprisingly, many of the ABI4 transcriptional targets do not contain the previously characterized ABI4 binding motifs, the CE1 or S box, in their promoters, but some of these interact with ABI4 in electrophoretic mobility shift assays, suggesting that sequence recognition by ABI4 may be more flexible than known canonical sequences. Yeast one-hybrid assays demonstrated synergistic action of ABI4 with ABI5 or related bZIP factors in regulating these promoters, and mutant analyses showed that ABI4 and these bZIPs share some functions in plants.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-011-9733-9) contains supplementary material, which is available to authorized users.

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

“…Expression of ABI4, however, was reduced by ZFP3ox, suggesting that this AP2/Ethylene Responsive Factor (ERF)-type transcription factor can more directly be connected to developmental consequences of ZFP3 overexpression (Finkelstein et al, 1998;Wind et al, 2013). ABI4 regulates the expression of numerous ABAinduced genes, often in synergistic action with other transcription factors such as ABI5 (Reeves et al, 2011). Therefore, the germination of ZFP3-overexpressing seeds may be promoted by down-regulation of ABI4 and the modulation of expression of a set of genes controlled by this transcription factor (Wind et al, 2013).…”

MED18 interaction with distinct transcription factors regulates multiple plant functions

“…5e). The At5g24080 gene expression is completely dependent on ABI4 although its function is unknown 32 . To determine whether MED18 directly regulates the transcription of ABI5, we tested the recruitment of MED18 to the ABI5 promoter.…”

ABA-INSENSITIVE3, ABA-INSENSITIVE5, and DELLAs Interact to Activate the Expression ofSOMNUSand Other High-Temperature-Inducible Genes in Imbibed Seeds inArabidopsis

“…Thus, the increased ABA level observed at high temperature is likely to potentiate the activity of ABI3 as a transcriptional regulator. The activities of group A bZIPs have also been shown to be enhanced by ABA (Hobo et al, 1999;Finkelstein and Lynch, 2000;Gampala et al, 2002;Lopez-Molina et al, 2002;Finkelstein et al, 2005;Nakashima et al, 2006;Reeves et al, 2011;Wang et al, 2013) likely via the phosphorylation of group A bZIPs by the subclass III SUCROSE NONFERMENTING 1-RELATED PROTEIN KINASE2s, which are activated by the PYRABACTIN RESISTANCE/PYR1-LIKE/REGULATORY COMPONENTS OF ABA RECEPTOR-mediated inactivation of group A PROTEIN PHOS-PHATASE 2Cs in the presence of ABA (Furihata et al, 2006;Fujii et al, 2007Fujii et al, , 2009Piskurewicz et al, 2008;Nakashima et al, 2009;Umezawa et al, 2009;Dai et al, 2013;Wang et al, 2013). Thus, the high-temperature-induced increase in ABA levels is likely to enhance the activities of group A bZIPs as transcriptional regulators.…”