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

Abstract

A ferredoxin cDNA was isolated from a λgt 11 cDNA library constructed from nitrate-induced rice ( Oryza sativa L.) roots. The root Fd 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 λEMBL3 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.