TABLE 2.

Nitrogen use efficiency regulating enzymes and their specific roles in plants.

Enzymes	Roles	References
Plastidic isoenzyme-GS2	Involved in primary N assimilation	Masclaux et al., 2000; Hirel et al., 2001
Cytosolic GS isoenzyme-GS1	Involved in the recycling of organic N	Masclaux et al., 2000; Hirel et al., 2001
Glutamine synthetase	Increased N uptake and photorespiration	Habash et al., 2001
Nitrate reductase and nitrite reductase	NO2– assimilation and reduced the nitrate levels	Takahashi et al., 2001; Lillo et al., 2003
GS1.3 isoenzyme	Plays a putative role in controlling the yield under variable N conditions	Martin et al., 2006
Alanine aminotransferase	Increased biomass and grain yield	Good et al., 2007
NADH-GOGAT	Involved in glutamate synthesis to promote the growth of plants; promoted inorganic nitrogen assimilation notably in the roots	Tabuchi et al., 2007; Garnett et al., 2015
Cytosolic asparagine synthetase and carbamoylphosphate synthase enzymes	Increased ammonium assimilation	Lam et al., 2003; Ranjan and Yadav, 2019