Cloning, characterization, and expression of two cDNA clones for a rice ferulate-5-hydroxylase gene, a cytochrome P450-dependent monooxygenase

Abstract

Ferulate-5-hydroxylase (F5H) is a cytochrome P450-dependent monooxygenase that catalyses the hydroxylation of ferulic acid, coniferaldehyde, and coniferyl alcohol in the pathways leading to sinapic acid and the syringyl unit of lignin. We have isolated twoF5H genes,OsF5HL andOsF5HL2, from a japonica-type rice (Oryza sativa L. cv. llpoombyeo). They are the firstF5H genes experimentally identified in monocotyledonous plants. Phylogenetic analysis indicated that both genes are closely related to dicotF5H genes fromArabidopsis thaliana andBrassica napus. Southern blot analysis showed that these genes exist as single copies in the rice genome. Alignments of theOsF5HL andOsF5HL2 cDNAs to their genomic DNAs revealed thatOsF5HL has an open reading frame (ORF) of 1590 b from four exons, whileOsF5HL2 has an ORF of 1560 b from two exons. Expression ofOsFSHL is highest in young leaves, whereas that ofOsF5HL2 is greatest in mature leaves. In the roots and stems, transcription levels for both genes are markedly low. These data suggest that theOsF5HL andOsF5HL2 genes belong to theCYP84 subfamily and that their expressions are tissue-specific.