cDNA cloning and differential expression of three caffeic acid O-methyltransferase homologues from perennial ryegrass (Lolium perenne)

Three caffeic acid O-methyltransferase (COMT) cDNA homologues (LpOMT1, LpOMT2, LpOMT3) from perennial ryegrass (Lolium perenne) were isolated. The nucleotide sequence analysis revealed open reading frames of 1080 bp for LpOMT 1, 1053 bp for LpOMT2 and 1083 bp for LpOMT3. The estimated molecular masses of the predicted proteins were 38,748, 38,235 and 39,138 u, respectively. LpOMT 1 is 92 % identical to LpOMT3 and 75 % identical to LpOMT2. The perennial ryegrass COMT cDNAs are most closely related to the caffeic acid 3-O-methyltransferase from maize involved in lignin biosynthesis. Genomic DNA blot analysis suggests that LpOMT1 and LpOMT3 are highly homologous members of a small gene family, while LpOMT2 is from a different single copy class. Northern blot analysis with perennial ryegrass and tall fescue (Festuca arundinacea) RNA showed that the LpOMT1 and LpOMT3 transcripts were present in both roots and shoots of young seedlings and in mature roots and stems, while LpOMT2 transcripts accumulated to high levels in shoots of young seedlings but were not present in roots or mature leaves. The corresponding transcripts do not appear to be significantly induced by wounding or fungal infection.