Biosensors Used for Quantification of Nitrates in Plants

Table 1

Advantages and disadvantages of gene promoters that can be used as a sensing element of any nitrogen source.

Gene	Enzyme	Advantages	Disadvantages
glnA	Synthetase glutamine	It could detect a wide range of concentration of ammonium in plants	A disadvantage is that it can respond to amino acids and other nitrogenous compounds
nirA	p-Hydroxyphenylpyruvate dioxygenase	It is induced in the presence of nitrate	It is repressed in the presence of ammonium
GifA	Synechocystis NtcA	It is induced in the presence of ammonium	It is repressed in the presence of combined nitrogen
nitA	Nitrilase	It is activated by combining a source of nitrogen ammonium nitrate	Change of the nitrogen source disrupts the growth and development
pyeaR	NsrR	It is activated in the presence of nitric oxide, nitrate, and nitrite	It is repressed by two repressors, Nar-regulated by nitrates and nitrites, and NsrR-regulated by nitric oxide