Analysis of the petunia nitrate reductase apoenzyme-encoding gene: a first step for sequence modification analysis.

In this paper, we describe the gene (nia) coding for the apoenzyme of the nitrate reductase (NR) of petunia. A full-size genomic clone was isolated from a genomic library, using the tobacco nia2 cDNA as a probe, and sequenced. The open reading frame is interrupted by three introns and encodes a protein of 909 amino acids which reveals between 92% and 68% identity to the NADH NR apoenzyme from other higher plants. Southern analyses indicated that the NR apoenzyme is encoded by a single-copy gene, although another region homologous to part of nia was also identified. The analysis of the steady-state level of nia mRNA showed that the petunia nia is regulated by the nitrogen source and is under the control of the circadian rhythm.