Expression of a delta 9 14:0-acyl carrier protein fatty acid desaturase gene is necessary for the production of omega 5 anacardic acids found in pest-resistant geranium (Pelargonium xhortorum).
Anacardic acids, a class of secondary compounds derived from fatty acids, are found in a variety of dicotyledonous families. Pest resistance (e.g., spider mites and aphids) in Pelargonium xhortorum (geranium) is associated with high levels (approximately 81%) of unsaturated 22:1 omega 5 and 24:1 omega 5 anacardic acids in the glandular trichome exudate. A single dominant locus controls the production of these omega 5 anacardic acids, which arise from novel 16:1 delta 11 and 18:1 delta 13 fatty acids. We describe the isolation and characterization of a cDNA encoding a unique delta 9 14:0-acyl carrier protein fatty acid desaturase. Several lines of evidence indicated that expression of this desaturase leads to the production of the omega 5 anacardic acids involved in pest resistance. First, its expression was found in pest-resistant, but not suspectible, plants and its expression followed the production of the omega 5 anacardic acids in segregating populations. Second, its expression and the occurrence of the novel 16:1 delta 11 and 18:1 delta 13 fatty acids and the omega 5 anacardic acids were specific to tall glandular trichomes. Third, assays of the recombinant protein demonstrated that this desaturase produced the 14:1 delta 9 fatty acid precursor to the novel 16:1 delta 11 and 18:1 delta 13 fatty acids. Based on our genetic and biochemical studies, we conclude that expression of this delta 9 14:0-ACP desaturase gene is required for the production of omega 5 anacardic acids that have been shown to be necessary for pest resistance in geranium.
Schultz
D J
DJ
Intercollege Graduate Degree Program in Genetics, Pennsylvania State University, University Park 16802, USA.
Cahoon
E B
EB
Shanklin
J
J
Craig
R
R
Cox-Foster
D L
DL
Mumma
R O
RO
Medford
J I
JI
D000595:Amino Acid Sequence; D048729:Anacardic Acids; D002849:Chromatography, Gas; D018076:DNA, Complementary / Q000235:genetics; D004926:Escherichia coli; D044943:Fatty Acid Desaturases / Q000235:genetics*; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis; D015870:Gene Expression; D017343:Genes, Plant; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology; D006899:Mixed Function Oxygenases / Q000235:genetics*; D008969:Molecular Sequence Data; D010944:Plants / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins; D012459:Salicylates / Q000378:metabolism*
D048729:Anacardic Acids; D018076:DNA, Complementary; D005231:Fatty Acids, Unsaturated; D012333:RNA, Messenger; D011994:Recombinant Proteins; D012459:Salicylates; C088115:anacardic acid; D006899:Mixed Function Oxygenases; D044943:Fatty Acid Desaturases; C018747:acyl-(acyl-carrier-protein)desaturase