Characterization of mRNAs encoding ethylene biosynthesis enzymes in the root holoparasitic plants Orobanche

Abstract

Total RNA samples were extracted from the non-photosynthetic root parasitic plants Orobanche minor and O. ramosa and used to synthesize cDNAs. The cDNA fragments encoding ethylene biosynthesis enzymes, 1-amino-1-cyclopropanecarboxylic acid (ACC) synthase and ACC oxidase, were amplified and characterized. ACC synthases (OmACS and OrACS) and ACC oxidases (OmACO and OrACO) were found to have high homologies with those in other plants, in particular, with SHACS2 and SHACO1 of the root hemiparasite Striga hermonthica. The expression of these genes after germination stimulation by (+)-strigol, a natural germination stimulant, was slightly increased in O. ramosa but not in O. minor, indicating the possible involvement of ethylene biosynthesis in the germination of O. ramosa. In these root parasites, however, inhibitors of ethylene biosynthesis and action did not affect seed germination elicited by (+)-strigol except for the ethylene action inhibitor silver thiosulfate in O. ramosa.