Table 2.
Summary of regulation of GA metabolism and signaling genes with respect to abiotic stress and seed germination in different plant species.
| Gene | Protein encoded | Genotype | Plant studied | Effect on abiotic stress and/ or germination | Altered compound/pathways/processes | References | |
|---|---|---|---|---|---|---|---|
| I. GA METABOLISM AND REGULATORS OF GA SIGNALING | |||||||
| 1. | GAI, RGA, RGL1, and RGL2 | DELLA Protein | DELLA quadruple-mutant gai-t6 rga-t2 rgl1-1 rgl2-1 | Arabidopsis | Salt sensitivity, Early flowering | DELLA-dependent reduced accumulation of bioactive GAs | Achard et al., 2006 |
| 2. | GA-INSENSITIVE (GAI) | DELLA Protein | Mutant (gai) | Arabidopsis | Salinity tolerance | DELLA-dependent growth restraint | Achard et al., 2006 |
| 3. | GA-deficient GA1-3 | DELLA Protein | Mutant (ga1-3) | Arabidopsis | Salinity tolerance | DELLA-dependent growth restraint | Achard et al., 2006 |
| 4. | PROCERA | DELLA Protein | Mutant (pro) | Tomato | Enhanced stomatal conductance and rapid wilting under drought stress | Negative regulator of GA signaling | Nir et al., 2017 |
| 5. | NUCLEAR FACTOR Y C proteins (NF-YC) homologs NF-YC3, NF-YC4 and NF-YC9 Nuclear factor Y (NF-Y) family proteins | Mutant nf-yc3 nf-yc4 nf-yc9 (nf-ycT) | Arabidopsis | Higher germination rates than the wild type in the presence of a of paclobutrazol PAC (GA biosynthesis inhibitor) | Altered GA and ABA signaling | Liu et al., 2016 | |
| Overexpression (35S:NF-YC3 and 35S:NF-YC9) | Arabidopsis | Lower germination rates than the wild type in the presence of a of PAC | |||||
| 6. | GA1-3 and GA2 | GA biosynthesis genes | Mutant (ga1-3 and ga2) | Arabidopsis | Unable to germinate in the absence of exogenous GA | Absence or the changed composition of endogenous GA's | Koornneef and Van Der Veen, 1980 |
| 7. | GIB-1 | Gibberellin biosynthesis gene | Mutant (gib-1) | Tomato | Unable to germinate without exogenous GA | Lack of GA | Karssen et al., 1989; Benson and Zeevaart, 1990 |
| 8. | GID1, GID2, and GID3 | GA INSENSITIVE DWARF (GID) GA receptor | Mutant (gid1a gid1b gid1c) | Arabidopsis | Unable to germinate | The absence of DELLAs destruction by gibberellins | Willige et al., 2007 |
| 9. | DAG1 | Transcription factor DOF AFFECTING GERMINATION 1 (DAG1) | dag1 | Arabidopsis | Reduced GA requirement for the seeds to germinate | Negative regulation GA biosynthesis by acting downstream of PIL5 (PHYTOCHROME INTERACTING FACTOR 3-LIKE 5) | Gabriele et al., 2010 |
| 10. | SPY-1 and SPY-3 | O-linked N-acetylglucosamine transf Erase | Mutants (spy-1 and spy-3) | Arabidopsis | Drought and salinity tolerance | Altered environmental stress signals via Gibberellin and Cytokinin cross talk | Qin et al., 2011 |
| Overexpression | Arabidopsis | Drought sensitive | |||||
| 11. | KYP/SUVH4 | Histone methyltransferase | Mutant | Arabidopsis | Increased seed dormancy and sensitivity to ABA | Altered ABA and GA regulation, and altered expression of dormancy-related genes | Zheng et al., 2012 |
| Overexpression | Arabidopsis | Reduced seed dormancy and sensitivity to ABA | |||||
| II. GA-RELATED TFS | |||||||
| 1. | DDF1 | AP2 transcription factor of the DREB1/CBF subfamily | Overexpression | Arabidopsis | Salinity tolerance | Upregulates expression of a gibberellin-deactivating gene, GA2ox7 | Magome et al., 2008 |
| 2. | ERF6 | Ethylene response factor (ERF) | Gain-of-function | Arabidopsis | Hypersensitive to osmotic stress | Inhibits growth through a GA/DELLA dependent mechanism | Dubois et al., 2013 |
| 3. | CBF1 | C-repeat/drought-responsive element binding factor | Overexpression | Arabidopsis | Cold tolerance, Inhibit seed germination | Accumulation of DELLAs | Achard et al., 2008 |
| 4. | PIL5 | PHYTOCHROME INTERACTING FACTOR 3-LIKE 5 | Overexpression | Arabidopsis | Inhibits seed germination | Activation of a GA catabolic gene (GA2ox2) and repression of GA biosynthesis genes GA3ox1 and GA3ox2 | Oh et al., 2007 |
| 5. | CHOTTO1 | Double APETALA2 Repeat Transcription Factor | Overexpression | Arabidopsis | Sensitive to ABA during seed germination processes | Inactivates GA biosynthesis | Yano et al., 2009; Shu et al., 2018 |
| 6. | SNORKEL1 and SNORKEL2 | Ethylene response factor (ERF) domain proteins | Overexpression | Rice | Submergence-tolerance | Increases in bioactive GA levels | Hattori et al., 2009 |
| 7. | SUB1A | Ethylene response factor (ERF) domain proteins | Overexpression | Rice | Submergence-tolerance | Negatively regulates GA responses by accumulation of the GA signaling repressors Slender Rice-1 (SLR1) and SLR1 Like-1 (SLRL1) | Fukao and Bailey-Serres, 2008 |