TABLE 3.
Genes directly or indirectly involved in nitrogen use efficiency.
| Genes | Direct/Indirect functions | References |
| GS2 | Increased the photorespiration and biomass production | Migge et al., 2000 |
| NiR | NO2– assimilation | Takahashi et al., 2001 |
| GOGAT | Improved plant biomass and seed weight | Yamaya et al., 2002 |
| AtDUR3 | Upregulation of AtDUR3 plays a putative role in organic N uptake |
Liu and Tsay, 2003
|
| GDHA | Increased ammonium assimilation, biomass, and dry weight | Mungur et al., 2006 |
| GS1 | A glutamine synthetase gene had higher grain yield, NUtE, and kernel number upon overexpression | Gallais et al., 2006 |
| AlaAT | Increased plant biomass and seed yield | Good et al., 2007 |
| AMT genes (AMT 1.1, 1.3, 1.5) | Help in ammonium uptake and its transport in plants | Yuan et al., 2007 |
| HvAlaAT | As alanine aminotransferase gene increased biomass and grain yield | Shrawat et al., 2008 |
| AtNRT1.1 | It can result in better nitrate uptake when acting as a nitrate sensor | Ho et al., 2009 |
| ENOD93–1 | Increased plant biomass and seed weight |
Bi et al., 2009
|
| NIA (Nia1 and Nia2) | As nitrate reductase genes significantly increased grain weight, dry biomass, and protein contents when overexpressed in model crops | Lillo et al., 2003; Zhao et al., 2013 |
| DOF1 | Promoted the growth and N uptake | Wang et al., 2013 |
| AGL21 | Increased plant biomass and seed weight | Yu et al., 2014 |
| Gln1-3 and Gln1-4 | Overexpression of these genes improved the yields and enhanced NUE | He et al., 2014 |
| OsAMT1;1 | As an ammonium transporter gene, helped in enhancing NUE | Ranathunge et al., 2014 |
| OsAMT1;1GS1 | Facilitate in achieving higher seed yield, NUE, and more numbers of seeds | Ranathunge et al., 2014 |
| TOND1 | Enhanced tolerance under N deficit condition | Zhang et al., 2015 |
| OsNRT2.1 | Increased biomass production | Chen et al., 2016 |
| NRT1.1B and OsNRT2.3b | As nitrate transporter genes helped in increasing the biomass production and seed yield to help in enhancing NUE | Gallais et al., 2006; Hu et al., 2015; Fan et al., 2016b |
| OsNRT2.3b and NRT1.1B | Worked as nitrate transporter genes to enhance NUE | Hu et al., 2015; Fan et al., 2016a |
| NLP7, ZmNLP6, and ZmNLP8 | NLP7 regulates the nitrate content, and ZmNLP6 and ZmNLP8 are helped in nitrate signaling to increase the productivity of model plants | Castaings et al., 2009; Cao et al., 2017 |
| GLN1 and GLN2 | GLN2 nuclear gene involved in the assimilation and re-assimilation of ammonium produced by nitrate reduction and from photorespiration, respectively. GLN1 helped in the recycling of ammonium during leaf senescence. | Bernard and Habash, 2009; Ranjan and Yadav, 2019 |