Cloning and expression of a ferredoxin gene in rice roots in response to nitrate and ammonium

A ferredoxin cDNA was isolated from a lambda gt 1] cDNA library constructed from nitrate-induced rice (Oryza sativa L.) roots. The root Ed cDNA clone (pFDRR) was 603 bp long which contained 261-bp 5' region encoding the C-terminal 72 amino acid residues and 342-bp 3' noncoding region. A genomic clone was isolated from a lambda EMBL3 rice genomic library using pFDRR as a probe and its nucleotide sequence was identical with that of the cDNA clone in their overlapping region. The root Fd gene contained 1091-bp 5' upstream, 444-bp coding and 294-bp 3' noncoding regions. The transcription start site locates 46 bp upstream of the ATG translation initiation codon. In the 5' flanking region, two GATA elements and a TCCGCGGA-like sequence are located in addition to TATA box-like and CAAT sequences. Homology between the rice root and leaf Fds showed 60%, while the former protein shared much higher identity with other nonphotosynthetic Fds (66-88%). Southern blot analysis using pFDRR and the rice leaf Fd cDNA (pFDRL) as a DNA probe identified their corresponding genomic Fd DNA. Expression of the root Fd gene was induced in response to nitrate and ammonium. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.