Molecular cloning of complementary DNA encoding maize nitrite reductase: molecular analysis and nitrate induction

Area of Science:

• Plant Molecular Biology
• Plant Biochemistry
• Genetics

Background:

• Nitrite reductase (NiR) is a key enzyme in nitrate assimilation.
• Understanding NiR gene regulation is crucial for plant nitrogen metabolism.

Purpose of the Study:

• To isolate and characterize the complementary DNA (cDNA) encoding maize nitrite reductase (NiR).
• To investigate the induction of NiR mRNA in maize seedlings by nitrate and nitrite.

Main Methods:

• Heterologous probing using spinach NiR gene to isolate maize NiR cDNA.
• Hydroponic cultivation of maize seedlings.
• Nitrate and nitrite induction experiments.
• Analysis of NiR mRNA levels via Northern blotting (implied).
• Genomic DNA analysis.

Main Results:

• Maize NiR cDNA was isolated, showing 66% DNA and 86% amino acid homology with spinach NiR.
• Maize NiR gene exhibits a strong G/C bias in the third codon position.
• Nitrate rapidly induced NiR mRNA in both roots and leaves of maize seedlings.
• Nitrite also induced NiR mRNA in roots, though to a lesser extent than nitrate.
• A low level of NiR mRNA was detected in leaves pre-induction, but not in roots.
• Genomic DNA analysis suggests the presence of at least two NiR genes in maize.

Conclusions:

• The study successfully isolated maize NiR cDNA and provided insights into its sequence characteristics.
• Nitrate is a potent inducer of NiR mRNA in maize, highlighting its role in nitrogen assimilation regulation.
• The findings suggest a complex genetic regulation of NiR in maize, potentially involving multiple genes.