A PUTATIVE O-METHYLTRANSFERASE FROM BARLEY IS INDUCED BY FUNGAL PATHOGENS AND UV-LIGHT

A cDNA clone, pBH72-F1 (F1), was isolated from a cDNA library prepared from barley leaves 72 h after inoculation with Erysiphe graminis f. s p. hordei. The 1388 bp nucleotide sequence of pBH72-F1 contains an ope n reading frame encoding a 42.3 kDa polypeptide of 390 amino acids whi ch shows sequence similarity to O-methyltransferases (OMTs) from diffe rent plant species; the highest identity (41%) was observed with a put ative OMT expressed in roots of maize. A phylogenetic analysis shows t hat the barley and maize sequences are distinctly different from the o rtho-diphenol-OMTs involved in lignin formation. A putative S-adenosyl -L-methionine-binding motif (KELVDDSITN) determined for a rabbit prote in-carboxyl OMT is partially conserved in the encoded amino acid seque nce. Genomic Southern blot hybridization shows that pBH72-F1 probably represents a single copy gene. The F1 clone corresponds to a gene tran script exhibiting a relatively late accumulation in mildew-infected ba rley leaves compared to other pathogen-induced transcripts, such as tr anscripts encoding PR proteins, a peroxidase, and transcripts homologo us to a maize caffeic acid OMT. No transcript was detected in plants e xhibiting papilla resistance at time points when resistance is thought to be manifested. The atypical transcript accumulation pattern for Fl was also observed after infection by other pathogens and after UV-lig ht treatment.