NUCLEOTIDE-SEQUENCE OF A RICE ROOT FERREDOXIN-NADP(+) REDUCTASE CDNA AND ITS INDUCTION BY NITRATE

A ferredoxin-NADP(+) reductase (FNR) cDNA was isolated from a lambda gt 11 cDNA library constructed from the roots of nitrate-induced rice (Oryza sativa L. cv. Kinmaze) seedlings. The nucleotide sequence of this clone contains a 1134 nucleotide open reading frame. The N-terminal 62 amino acid stretch was assigned to the transit sequence, followed by 316 residues for the mature protein. The rice root FNR shows only 49% sequence identity to that of the leaf enzyme, but the regions of the binding sites to ferredoxin, NADP-PPi and NADP(+) are highly conserved between the two enzymes. The root FNR mRNA was induced transiently by the addition of nitrate, but not by ammonia. The results support the view that the root FNR is involved in the nitrate assimilation in nonchlorophyllous tissues.