Table 1.
Summary of regulation of ABA metabolism and signaling genes with respect to abiotic stress and seed germination in different plant species.
| Gene/protein encoded | Mutation/Overexpression | Plant studied | Effect on abiotic stress and/ or germination | Altered compounds/pathways/processes involved | References | |
|---|---|---|---|---|---|---|
| I. ABA RELATED TRANSCRIPTION FACTORS | ||||||
| 1. | OsbZIP46CA1 | Overexpression | Rice | Drought tolerance | Positive regulator of ABA signaling | Tang et al., 2012 |
| 2. | OsbZIP71 | Overexpression | Rice | Drought tolerance | Positive regulator of ABA signaling | Liu et al., 2014 |
| 3. | OsbZIP52 | Overexpression | Rice | Cold and drought sensitivity | Negative regulator of ABA signaling | Liu et al., 2012 |
| 4. | OsbZIP23 | Overexpression | Rice | Salinity and drought tolerance | Positive regulator of ABA signaling | Xiang et al., 2008 |
| 5. | OsABF2 | Mutant | Rice | Sensitive to salinity, drought, and oxidative stress | Modulates transcript levels of abiotic stress-responsive genes | Hossain et al., 2010 |
| 6. | DIG1 (Dynamic Influencer of Gene expression 1), DIG2 | DEX Inducible expression | Arabidopsis | Salinity sensitivity | Differential ABA signaling | Song et al., 2016 |
| 7. | OsAP2-39 (AP2-domain containing Transcription) | Overexpression | Rice | Low germination rate, ABA sensitivity, increased endogenous ABA level | Direct activation of ABA biosynthesis gene OsNCED1, whereas directly activating GA-inactivating gene OsEUI (Elongated Uppermost Internode) | Yaish et al., 2010; Shu et al., 2018 |
| 8. | ORA47 (octadecanoid-responsive AP2/ERF-domain transcription factor 47) | Overexpression | Arabidopsis | Insensitive to wounding and water stress treatments, ABA insensitive | Direct regulation of ABA biosynthesis genes (NCED3 and NCED9) and the ABA-responsive gene RESPONSIVE TO DESICCATION 26 (RD26) under normal and wounding conditions but not under drought stress | Chen et al., 2016 |
| 9. | ABA-INSENSITIVE 4 (ABI4) | Mutant | Arabidopsis | Reduced primary seed dormancy, Resistant to paclobutrazol PAC (GA biosynthesis inhibitor) | ABI4 negatively regulates GA biosynthesis and by inhibits ABA catabolic genes expression (CYP707A1 and CYP707A2) | Shu et al., 2013, 2016 |
| Overexpression | Arabidopsis | Sensitive to PAC | ||||
| II. ABA METABOLISM GENES | ||||||
| 1. | AtABA2 (Encodes ABA biosynthesis gene, short-chain-dehydrogenase reductase) | Overexpression | Arabidopsis | Delayed germination, Salinity tolerance | Increased ABA level, Altered primary metabolite level upon stress | Lin et al., 2007 |
| 2. | SgNCED1 (from Stylosanthes guianensis) | Heterologous expression | Tobacco | Drought tolerance | Increase in the antioxidant enzyme activities | Bao et al., 2016 |
| 3. | LeNCED1 (from tomato) | Heterologous expression | Petunia | Drought tolerance | Decreases in stomatal conductance, transpiration, and photosynthesis and increased concentrations of proline | Estrada-Melo et al., 2015 |
| 4. | Cytochrome P450 CYP707A encodes ABA 8′- hydroxylases | Mutant (cyp707a2) | Arabidopsis | Enhanced seed dormancy | Altered ABA levels in seeds | Asano et al., 2011 |
| 5. | AtBG1 (β-glucosidase) | Mutant (atbg1) | Arabidopsis | Dehydration sensitive and early germination | Defective stomatal movement | Lee et al., 2006 |
| 6. | AtBG2 (β-glucosidase) | Mutant (atbg2) | Arabidopsis | Dehydration and salinity sensitive | Altered ABA level | Xu et al., 2012 |
| Overexpression | Arabidopsis | Dehydration and salinity tolerance | ||||
| 7. | BGLU10 (β-glucosidase) | Mutant (bglu10) | Arabidopsis | Drought sensitive | Increased rate of water loss, Reduced ABA content and expressions of ABA-and drought-responsive genes | Wang et al., 2011 |
| Overexpression | Arabidopsis | Drought tolerance | Reduced rate of water loss, Increased ABA content and expressions of ABA-and drought-responsive genes | |||
| 8. | AtDTX50 (DTX/Multidrug and Toxic Compound Extrusion (MATE) family member) | Mutant (atdtx50) | Arabidopsis | Drought tolerance | ABA efflux carrier in guard cells | Zhang et al., 2014 |
| 9. | AtPDR12/ABCG40 (a ATP-binding cassette (ABC) transporter) | Mutant (atabcg40) | Arabidopsis | Drought sensitive, Low rate of ABA-induced stomatal closer, impaired ABA regulation of seed germination and root development | Altered stomatal regulation, Altered cellular uptake of ABA | Kang et al., 2010 |
| 10. | AtABCG25 (a ATP-binding cassette (ABC) transporter) | Overexpression | Arabidopsis | less transpiration from the leaves (High leaf temperature) | AtABCG25 acts as an ABA exporter Which delivers ABA to guard cells. | Kuromori et al., 2010 |
| 11. | AtABCG22 (a ATP-binding cassette (ABC) transporter) | Mutant (atabcg22) | Arabidopsis | Drought sensitive, Increased transpiration through altered stomatal regulation | ABA signaling and ABA biosynthesis | Kuromori et al., 2011 |
| 12. | XERICO (encodes a RING-H2 zinc-finger protein) | Overexpression | Arabidopsis | Hypersensitivity to osmotic and salinity stress during germination and early seedling stage; and increased drought tolerance in the adult stage | Altered accumulation of ABA and differential expression GA, ethylene and ABA biosynthesis genes | Ko et al., 2006; Verma et al., 2016 |
| Rice | Salinity and drought tolerance | Increased ABA level and ABA-mediated stress response | Zeng et al., 2015 | |||
| III. ABA SIGNALING GENES | ||||||
| 1. | PYL8/RCAR3 | Overexpression | Arabidopsis | Hypersensitive to Salt and Osmotic Stresses | Positively regulates ABA signaling | Saavedra et al., 2010 |
| 2. | PYL5 and PYL7 (from tomato) | Heterologous expression | Arabidopsis | Drought tolerance | Not defined | González-Guzmán et al., 2014 |
| 3. | SAPK9 | Overexpression | Rice | Drought tolerance | Modulating cellular osmotic potential, stomatal closure and stress-responsive gene expression | Dey et al., 2016 |
| 4. | SnRKD,E,I | srk2d/e/i triple mutant | Arabidopsis | Drought sensitivity | Decreased expression of ABA- and stress-inducible genes | Fujita et al., 2009 |
| 5. | ZmSAPK8 (from corn) | Heterologous expression | Arabidopsis | Salinity tolerance | Proline accumulation and low relative electrolyte leakage | Ying et al., 2011 |
| 6. | Abscisic acid-insensitive(abi) | Mutant (abi3, abi4, and abi5) | Arabidopsis | ABA-mediated inhibition of seed germination and low water potential-induced ABA and proline accumulation | Altered ABA or Proline accumulation | Finkelstein, 1994; Verslues and Bray, 2006 |
| 7. | SIZ1 (SUMO E3 ligase) | Mutant (siz1–2 and siz1–3) | Arabidopsis | Increased ABA inhibition of seed germination and seedling primary root growth. | Induced expression of genes that are ABA-responsive (ABI5-dependent signaling) (e.g., RD29A, Rd29B, AtEm6, RAB18, ADH1) | Miura et al., 2009 |