Specific mRNA 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 encoding 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 catalyses the terminal step in pisatin phytoalexin biosynthesis. Comparison of this almond sequence, with amino acid sequences of described OMTs, identified regions of similarity which probably contribute to the binding site of S-adenosyl-L-methionine. Southern blot analysis suggests that PAB14B may be encoded by more than one gene in the almond genome. Flower-specific expression was shown by RNA blot analysis and the OMT transcript was detected in epidermal and vascular floral tissues by in situ hybridization. The available data suggest that this enzyme may be involved in the flavonoid biosynthesis pathway in almond floral tissues. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.