SPATIALLY DISTINCT EXPRESSION OF 2 NEW CYTOCHROME P450S IN LEAVES OF NEPETA-RACEMOSA - IDENTIFICATION OF A TRICHOME-SPECIFIC ISOFORM

Using a PCR-based approach, two novel cytochrome P450 cDNAs were isola ted from a catmint (Nepeta racemosa) leaf cDNA library. The cDNAs (pBS K3C7 and pBSK4C3) were 76.9% identical in their nucleotide sequences, indicating that they are the products of two closely-related genes. A comparison of the sequence of these cDNAs with database sequences indi cated that they represent new members of the CYP71 gene family of plan t cytochrome P450s. Clone pBSK3C7 contains the full-length coding sequ ence of a cytochrome P450, whilst pBSK4C3 lacks ca. 6 codons at the 5' end. The cytochromes P450 encoded by these clones were designated CYP 71A5 and CYP71A6 (pBSK3C7 and pBSK4C3, respectively). Southern blot an alysis indicated that the corresponding genes were present as single c opies in the genome of N. racemosa. Northern blot analysis showed that a gene homologous with CYP71A5 was expressed in the related species N . cataria, but no homologue of CYP71A6 was detected in this species. E xpression of CYP71A5 in N. racemosa was maximal in flowers, tissues wi thin the apical bud, and young expanded leaves. That of CYP71A6 was ma ximal in older leaves. Expression of CYP71A5 occurred exclusively in t richomes present on the leaf surfaces, in contrast to that of CYP71A6, which occurred predominantly within the leaf blade tissues.