Rapid and Transient lnduction of a Parsley Microsomal A12 Fatty Acid Desaturase mRNA by Funga1 Elicitor'

Treatment of cultured parsley (Petroselinum crispum L.) cells with a structurally defined peptide elicitor (Pep25) of fungal origin has previously been shown to cause rapid and large changes in the levels of various desaturated fatty acids. We isolated two distinct parsley cDNAs sharing high sequence similarity with microsomal w-6 fatty acid desaturases (FADs). One of them was functionally identified as a A1 2 FAD by expression in the yeast Saccharomyces cerevisiae. Two dienoic fatty acids, hexadecadienoic and linoleic, which were not detectable in control cells, together constituted up to 12% of the total fatty acids in the transformed yeast cells. A12 FAD mRNA accumulated rapidly and transiently in elicitor-treated parsley cells, protoplasts, and leaves. These and previous results indicate that fatty acid desaturation is an important early component of the complex defense response of parsley to attempted fungal infection.