Structure and expression of a root-specific rice gene.

Two rice cDNA clones (COS6 and COS9) were isolated, corresponding to genes that were highly expressed in roots from seedlings and mature plants. A genomic clone (GOS9) corresponding to cDNA clone COS9 was isolated and the intron/exon structure was determined by comparing the nucleotide sequences of the mRNA and the genomic clone. 5' ends and 3' ends of the mRNA were determined by primer extension and S1-nuclease mapping respectively. The open reading frame present in GOS9 potentially encodes a protein (14 kDa) that does not show any significant homology to other proteins in databases.