Poster: Secondary Metabolism

Abs # 283: Fungal elicitor-induced fatty acid acetylenases occur widely in evolutionarily distant plant families

Presenter:	Cahoon, Edgar B., ecahoon@danforthcenter.org
Authors	Cahoon, Edgar B. (A)   Schnurr, Judy A. (B)   Huffman, Errol A. (C)   Minto, Robert E. (C)
Affiliations:	(A): USDA-ARS Plant Genetics Research Unit, Donald Danforth Plant Science Center (B): USDA-ARS Plant Science Research Unit, University of Minnesota (C): Department of Chemistry and Biochemistry, Miami (OH) University

The fungal elicitor-induced ELI12 gene from parsley has been previously shown to encode a divergent form of the D¹²-oleic acid desaturase [Kirsch et al. (1997) Plant Physiol. 115: 283-290]. In this report, we show that the ELI12 gene product is a fatty acid acetylenase or triple bond-forming enzyme. Expression of this enzyme in transgenic soybean seeds was accompanied by the accumulation of the D¹²-acetylenic fatty acids crepenynic and dehydrocrepenynic acids. Using PCR with degenerate oligonucleotides, we also show that homologs of the ELI12 gene are present in other members of the Apiaceae family. In addition, cDNAs for divergent forms of the D¹²-oleic acid desaturase were detected among ESTs from English ivy, an Araliaceae species, and sunflower, an Asteraceae species. As with the ELI12 gene, expression of these cDNAs in transgenic soybean embryos was accompanied by the accumulation of crepenynic and dehydrocrepenynic acids. Homologs of the sunflower acetylenase gene were also detected in other Asteraceae species, as revealed by PCR analysis of isolated genomic DNA. Results from Northern and EST analyses indicated that expression of the sunflower gene, like ELI12, is induced by fungal elicitation. Overall, these results demonstrate that expressed genes for D¹²-fatty acid acetylenases occur in at least three plant families and are responsive to fungal pathogenesis. Natural products derived from crepenynic and dehydrocrepenynic acids that display antifungal, insecticidal, and nematicidal properties are distributed through at least 15 plant families. The acetylenases described here provide probes for chemotaxonomists and facilitate functional genomic and molecular investigations of these defensive mechanisms.