# AP2/ERF transcription factor family

The AP2/ERF transcription factor family is a large group of plant-specific transcription factors defined by at least one AP2/ERF DNA-binding domain, a conserved motif of roughly 60 to 70 amino acid residues, and it regulates plant growth, development, hormone signaling, and responses to biotic and abiotic stress.<sup>[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC12112388/)</sup><sup> • </sup><sup>[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10815832/)</sup> The name combines APETALA2, the [Arabidopsis](https://www.edgepedia.org/arabidopsis) gene in which the domain was first described, and ERF, the ethylene-responsive element binding factor.<sup>[3](https://www.sciencedirect.com/science/article/pii/S0098847224001217)</sup>

| Key fact | Detail |
|---|---|
| Defining feature | At least one AP2 domain, a DNA-binding motif of approximately 60 to 70 amino acids containing a single α-helix and three β-sheets<sup>[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC12112388/)</sup> |
| Subfamilies | Five groups classified by Sakuma et al. from domain number and structure: AP2, ERF, DREB, RAV, and Soloist<sup>[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC12112388/)</sup> |
| Domain composition | AP2 proteins carry two AP2 domains; ERF and DREB carry one; RAV carries an AP2 domain plus a B3 domain; Soloist carries an AP2-like domain<sup>[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10815832/)</sup> |
| DNA binding | DREBs recognize the DRE/CRT element with an A/GCCGAC core; ERFs bind the GCC box (AGCCGCC); many members bind both elements<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup> |
| Family size | Genome-wide counts include 145 members in Arabidopsis, 170 in rice, 178 in sorghum, 200 in poplar, 291 in Chinese cabbage, 171 in foxtail millet, and 116 in moso bamboo<sup>[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC4943945/)</sup> |
| Stress roles | Regulate tolerance to cold, heat, drought, high salinity, flooding, and pathogen attack by controlling downstream stress-responsive genes<sup>[3](https://www.sciencedirect.com/science/article/pii/S0098847224001217)</sup><sup> • </sup><sup>[6](https://journalajaar.com/index.php/AJAAR/article/view/573)</sup> |
| Breeding relevance | Constitutive DREB overexpression improves stress tolerance but causes growth penalties such as dwarfism; stress-inducible promoters such as rd29A are used to separate the two effects<sup>[7](https://doi.org/10.1007/s10343-026-01401-2)</sup> |

## Structure and classification

The AP2/ERF domain binds DNA through a structure containing a single α-helix and three β-sheets, and the family is divided into five subfamilies based on the number of AP2 domains and additional structural features.<sup>[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC12112388/)</sup> The AP2 subfamily, the earliest identified, contains two AP2 domains. The ERF and DREB subfamilies each contain a single AP2 domain, but the amino acid residues at positions 14 and 19 of the domain differ between them, and this difference underlies their distinct DNA-binding preferences.<sup>[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC12112388/)</sup> The RAV subfamily, first reported by Kagaya and colleagues in 1999, combines an AP2 domain with a B3-like domain, and the Soloist group contains AP2-like domains that fall outside the other groups.<sup>[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC12112388/)</sup><sup> • </sup><sup>[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10815832/)</sup>

Several historical steps fixed the current nomenclature. The ERF subfamily was first isolated from tobacco by Ohme-Takagi and colleagues in 1995, and the DREB subfamily was initially identified in *Arabidopsis thaliana* by Stockinger and colleagues.<sup>[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC12112388/)</sup> Beyond the AP2 domain itself, the proteins carry four functional regions: the [DNA-binding domain](https://www.edgepedia.org/dna-binding-domain), a transcription regulation domain, an oligomerisation site, and a nuclear localization signal.<sup>[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10815832/)</sup> At the C-terminal end of the domain, the RAYD element of about 42 to 43 residues mediates protein-protein interactions through α-helices.<sup>[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10815832/)</sup>

**DNA-binding specificity.** DREBs typically recognize the dehydration-responsive or C-repeat element (DRE/CRT), whose A/GCCGAC core sequence appears in promoters of genes conferring drought, cold, and heat resistance, while ERFs bind the ethylene-response element, also called the GCC box, with the core AGCCGCC.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup> The division is not strict: many Arabidopsis DREBs and ERFs, including TINY, CBF1, ERF53, RAP2.4, ERF1, and ERF4, bind both elements, which implies potential roles in both abiotic and biotic stress.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup> Some members recognize elements that diverge substantially from these motifs, such as the coupling element CE1 (TGCCACCG) and the hypoxia-responsive promoter element.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup>

## Subfamilies and their stress functions

**DREB.** The dehydration-responsive element-binding proteins are central regulators of plant responses to environmental stimuli, and the subfamily splits functionally into DREB1 (CBF-like) factors, which mediate cold responses, and DREB2 factors, which mediate osmotic and thermal stress.<sup>[7](https://doi.org/10.1007/s10343-026-01401-2)</sup> DREB proteins also contribute to salinity and alkaline-stress tolerance through regulation of ion homeostasis, such as the Na⁺/K⁺ ratio, and activation of antioxidant systems that scavenge reactive oxygen species.<sup>[7](https://doi.org/10.1007/s10343-026-01401-2)</sup> In Arabidopsis, DREB2A is strongly induced by dehydration and heat, and its expression is controlled by heat shock factor A1 and ABA-response binding factors acting on heat shock element and ABRE motifs in its promoter.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup>

**ERF.** Ethylene-responsive factors act in defense against microbial pathogens, integrating pathogen signals downstream of mitogen-activated protein kinase (MAPK) cascades and mediating salicylic acid, jasmonic acid, and ethylene pathways; they activate defense genes, enhance reactive oxygen species production, and modulate cell wall defenses.<sup>[6](https://journalajaar.com/index.php/AJAAR/article/view/573)</sup> A subset called ERF-VIIs regulates flooding and hypoxia tolerance, and their stability is controlled by the oxygen-dependent [N-end rule](https://www.edgepedia.org/n-end-rule) pathway, in which the N-terminal cysteine is oxidized and the proteins are ubiquitinated by the E3 ligase PRT6 under normal oxygen conditions.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup>

**AP2, RAV, and Soloist.** The AP2 subfamily regulates developmental processes such as floral organ identity, with the Arabidopsis AP2 protein binding T/A-rich sequences, and WRI4 positively regulating cuticular wax biosynthesis.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup> RAV proteins bind CAACA and CACCTG elements and participate in ABA signaling during seed germination and leaf senescence.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup> Soloist members are few and unclassified, and rice has lost Soloist members while the ERF subfamily expanded in tobacco, showing that subfamily sizes vary considerably across lineages.<sup>[8](https://academic.oup.com/hr/article/13/1/uhaf280/8293156)</sup>

## Regulation of AP2/ERF activity

AP2/ERF genes are usually expressed at low levels under normal conditions and induced or repressed by hormones and stress stimuli, with promoter cis-elements such as the heat shock element, low-temperature responsive element, ABRE, and ethylene-responsive motifs determining responsiveness.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup> Regulation operates at several levels:

- **Alternative splicing** produces functional isoforms for some DREB genes in rice, maize, wheat, and barley; under normal conditions an inactive form with a premature stop codon is produced, and under stress the stop-codon exon is excluded to yield a functional transcription factor.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup>
- **microRNA silencing**: miRNA172 targets Arabidopsis AP2 messenger RNA to inhibit its translation, and miRNA156 and miRNA838 regulate AP2/ERFs in common bean.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup>
- **Ubiquitin-mediated degradation**: E3 ligases including DRIP1/2, RGLG1/2, SINAT2, and PRT6 direct DREB2A, ERF53, RAP2.2, and ERF-VII proteins to 26S proteasome degradation under non-stress conditions.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup>
- **Phosphorylation**: mitogen-activated protein kinases phosphorylate ERF104 and ERF6 to positively regulate pathogen responses, while SnRK kinases phosphorylate RAV1 to inhibit its repressive function.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup>

At the protein level, activation domains drive target-gene expression, and the EDLL motif identified from Arabidopsis ERF98 is strong enough to override repression by the ERF-associated amphiphilic repression (EAR) motif, whose consensus LxLxL or DLNxxP sequences mark repressive members.<sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup>

## Hormone cross-talk

AP2/ERF factors sit at the junction of stress and hormone signaling. Many respond to abscisic acid (ABA) and ethylene and activate stress-responsive genes that are dependent on or independent of these hormones, and they also participate in gibberellin, auxin, brassinosteroid, and cytokinin-mediated stress responses.<sup>[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10815832/)</sup><sup> • </sup><sup>[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)</sup> In rice, the AP2/ERF genes OsDREB2B, OsRPH1, OsEATB, and OsAP2-39 affect plant height by regulating the expression of gibberellin metabolic genes, and overexpression phenotypes such as reduced height can be mitigated by exogenous GA3 application.<sup>[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10815832/)</sup><sup> • </sup><sup>[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC11990802/)</sup> This coupling of stress tolerance to growth is a recurring theme: because stress responses compete with growth, the family's regulation must balance survival against development.<sup>[3](https://www.sciencedirect.com/science/article/pii/S0098847224001217)</sup>

## Other functions and evolution

Beyond stress, AP2/ERF factors perform diverse roles in cell proliferation, vegetative and reproductive development, and plant hormone responses.<sup>[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC4943945/)</sup> They also regulate the biosynthesis of major classes of plant secondary metabolites, including terpenoids, phenolic compounds, and alkaloids, through direct, indirect, co-regulation, and self-regulation mechanisms across roughly 40 phylogenetically diverse plant species.<sup>[8](https://academic.oup.com/hr/article/13/1/uhaf280/8293156)</sup>

Genome-wide analyses indicate that the family is highly conserved during plant evolution, and its high structural similarity among members can produce substantial gene redundancy.<sup>[10](https://pubmed.ncbi.nlm.nih.gov/32522044/)</sup><sup> • </sup><sup>[2](https://pmc.ncbi.nlm.nih.gov/articles/PMC10815832/)</sup> One evolutionary hypothesis, based on the lack of introns in the majority of plant AP2/ERF transcription factors, proposes lateral gene transfer of the domain from bacterial or viral origin, with putative HNH endonucleases aligning with plant AP2 subfamily members outside the AP2 domain.<sup>[11](https://pmc.ncbi.nlm.nih.gov/articles/PMC520932/)</sup>

## Application in crop improvement

Because abiotic stresses limit arable land and crop yield, AP2/ERF genes are prominent targets for transgenic breeding.<sup>[3](https://www.sciencedirect.com/science/article/pii/S0098847224001217)</sup> Overexpression of DREB genes in transgenic crops enhances tolerance to drought, salt, cold, and heat, but constitutive overexpression carries a physiological trade-off: severe vegetative growth penalties such as dwarfism.<sup>[7](https://doi.org/10.1007/s10343-026-01401-2)</sup> The strategic use of stress-inducible promoters, notably the rd29A promoter, is the main molecular strategy used to uncouple stress resilience from growth retardation.<sup>[7](https://doi.org/10.1007/s10343-026-01401-2)</sup> Functional studies continue to add members: silencing LbAP2/ERF32 in the recretohalophyte *Limonium bicolor* decreased its salt tolerance, and MhERF113-like from *Malus hupehensis* positively regulates drought tolerance in transgenic tomato and apple.<sup>[12](https://www.sciencedirect.com/science/article/abs/pii/S0981942824007034)</sup><sup> • </sup><sup>[13](https://www.sciencedirect.com/science/article/abs/pii/S0981942825001263)</sup>

## References

1. [Su Z-L, et al. (2025). The Role of AP2/ERF Transcription Factors in Plant Responses to Biotic Stress. International Journal of Molecular Sciences.](https://pmc.ncbi.nlm.nih.gov/articles/PMC12112388/)
2. [Ma Z, Hu L, Jiang W (2024). Understanding AP2/ERF Transcription Factor Responses and Tolerance to Various Abiotic Stresses in Plants: A Comprehensive Review. International Journal of Molecular Sciences 25(2):893.](https://pmc.ncbi.nlm.nih.gov/articles/PMC10815832/)
3. [Wang K, Guo H, Yin Y (2024). AP2/ERF transcription factors and their functions in Arabidopsis responses to abiotic stresses. Environmental and Experimental Botany 222:105763.](https://www.sciencedirect.com/science/article/pii/S0098847224001217)
4. [Xie Z, Nolan TM, Jiang H, Yin Y (2019). AP2/ERF Transcription Factor Regulatory Networks in Hormone and Abiotic Stress Responses in Arabidopsis. Frontiers in Plant Science 10:228.](https://pmc.ncbi.nlm.nih.gov/articles/PMC6403161/)
5. [Rashid et al. coverage in: Transcription Factors and Plants Response to Drought Stress: Current Understanding and Future Directions.](https://pmc.ncbi.nlm.nih.gov/articles/PMC4943945/)
6. [Saxesena RR, Yadav OP, Gaur LB (2024). AP2/ERF Transcription Factors in Crop Plants' Disease Resistance Response. Asian Journal of Advances in Agricultural Research 24(12):65-74.](https://journalajaar.com/index.php/AJAAR/article/view/573)
7. [Hakeem A, et al. (2026). Functional Divergence of DREB Transcription Factors in Crop Abiotic Stress Tolerance: A Mini-Review. Journal of Crop Health 78:129.](https://doi.org/10.1007/s10343-026-01401-2)
8. [AP2/ERF transcription factors regulate the biosynthesis of terpenoids, phenolics, and alkaloids in plants. Horticulture Research 13(1):uhaf280.](https://academic.oup.com/hr/article/13/1/uhaf280/8293156)
9. [Plant Signaling Hormones and Transcription Factors: Key Regulators of Plant Responses to Growth, Development, and Stress.](https://pmc.ncbi.nlm.nih.gov/articles/PMC11990802/)
10. [Feng K, et al. (2020). Advances in AP2/ERF super-family transcription factors in plant. Critical Reviews in Biotechnology 40:750-776.](https://pubmed.ncbi.nlm.nih.gov/32522044/)
11. [From Endonucleases to Transcription Factors: Evolution of the AP2 DNA Binding Domain in Plants.](https://pmc.ncbi.nlm.nih.gov/articles/PMC520932/)
12. [Genome-wide identification of the AP2/ERF gene family from Limonium bicolor and functional characterization of LbAP2/ERF32 under salt stress. Plant Physiology and Biochemistry 215:109035 (2024).](https://www.sciencedirect.com/science/article/abs/pii/S0981942824007034)
13. [The AP2/ERF transcription factor MhERF113-like positively regulates drought tolerance in transgenic tomato and apple. Plant Physiology and Biochemistry (2025).](https://www.sciencedirect.com/science/article/abs/pii/S0981942825001263)

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*Topic: Encyclopedia › Life and health › Biological foundations › RNA and gene regulation › Transcription and gene regulation › Transcription factor families and specific factors › Plant transcription factor families*

*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 11, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*

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