TABLE 4.
Transgenes introduced and their role in improving nitrogen use efficiency.
| Genes | Crop | Function | Role in improving NUE | References |
| NRT1.7 |
Arabidopsis Tobacco Rice |
Loading excess nitrate stored and facilitates nitrate allocation to sink leaves | Enhancing source-to-sink nitrate remobilization | Chen et al., 2020 |
| GS 1 | Rice | Glutamine synthetase (cytosol) | Increase in total N and A.A | Cai et al., 2009 |
| GS 2 | Rice | Glutamine synthetase (Plastid) | Increased in photorespiration | Hoshida et al., 2000 |
| TaNRT2.1 | Rice | Uptake of nitrate at post-flowering | high protein and grain yield | Taulemesse et al., 2015 |
| OsNRT2.1 | Rice | N-uptake and mobilization | Expressed during low N condition | Chen et al., 2016 |
| ARE1 | Rice | N-uptake and mobilization | increased NUE, delayed senescence, increased biomass | Zhang J. et al., 2021 |
| GOGAT | Tobacco | Glutamate synthetase | Increased in Biomass | Chichkova et al., 2001 |
| AlaAT | Mustard Rice |
Alanine amino transferase | Increased in biomass and grain yield | Good et al., 2007; Sisharmini et al., 2019 |
| GDHA | Tobacco | Glutamate dehydrogenase | High water potential during drought, Increased in biomass and dry weight, Increased in ammonium assimilation. | Ameziane et al., 2000; Mungur et al., 2005, 2006 |
| Nia1 | Lettuce | Nitrate reductase | Nitrate content | Lillo et al., 2003 |
| Nia2 | Potato | Nitrate reductase | Reduced in nitrate level | Djennane et al., 2002 |
|
AtNRT2.1
AtNRT2.2 |
Arabidopsis | Nitrate uptake | 75% high affinity under scarcity of N content | Li et al., 2007 |
| OsATG8b | Arabidopsis | N remobilization | Tolerance to nitrogen starvation | Zhen et al., 2019 |
| Gln1-3 and Gln 1-4 | Maize | Glutamate synthetase | 30% more grain yield in Low N uptake | Martin et al., 2006 |
| ASN1 | Rice | Asparagine synthetase 1 | Improve N content in grain | Lee et al., 2020 |
| DEP1 | Rice | DENSE AND ERECT PANICLES 1 | Ammonium uptake and assimilation | Sun et al., 2014 |
| TaVRN1 | Wheat | VERNALIZATION1 | Improve NUE | Lei et al., 2018 |
| Transcript factors | ||||
| ENOD93–1 | Rice | Early nodulin | Increased in biomass and seed yield | Bi et al., 2009 |
| TOND1 | Rice | Tolerance of Nitrogen deficiency | Increased the tolerance to N deficiency | Zhang Y. et al., 2015 |
| NAC | Wheat | Influence grain N content, zinc (Zn) and iron (Fe) concentration | Delaying the senescence period | Uauy et al., 2006 |
| MADS25 | Rice | Promote lateral and primary root development and improve root attributes | Increase the expression of nitrate transporter genes | Yu et al., 2015 |