SPECIFIC MESSENGER-RNA ACCUMULATION OF A GENE CODING FOR AN O-METHYLTRANSFERASE IN ALMOND (PRUNUS-AMYGDALUS, BATSCH) FLOWER TISSUES

A cDNA clone, PAB14B, was isolated from an almond flower cDNA library. The 1245 bp nucleotide sequence contains an open reading frame encodi ng a polypeptide of 356 amino acids which shows sequence similarity to O-methyltransferases (OMTs) from different plant species. The highest identity (49%) was observed with a methyltransferase from pea that ca talyses the terminal step in pisatin phytoalexin biosynthesis. Compari son of this almond sequence, with amino acid sequences of described OM Ts, identified regions of similarity which probably contribute to the binding site of S-adenosyl-L-methionine. Southern blot analysis sugges ts that PAB14B may be encoded by more than one gene in the almond geno me. Flower-specific expression was shown by RNA blot analysis and the OMT transcript was detected in epidermal and vascular floral tissues b y in situ hybridization. The available data suggest that this enzyme m ay be involved in the flavonoid biosynthesis pathway in almond floral tissues. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.