title: The convergent evolution of defensive polyacetylenic fatty acid biosynthesis genes in soldier beetles.
abstract: The defensive and bioactive polyacetylenic fatty acid, 8Z-dihydromatricaria acid, is sequestered within a wide range of organisms, including plants, fungi and soldier beetles. The 8Z-dihydromatricaria acid is concentrated in the defence and accessory glands of soldier beetles to repel avian predators and protect eggs. In eukaryotes, acetylenic modifications of fatty acids are catalysed by acetylenases, which are desaturase-like enzymes that act on existing double bonds. Here we obtained acyl Coenzyme A-linked desaturases from soldier beetle RNA and functionally expressed them in yeast. We show that three genes were sufficient for the conversion of a common monounsaturated fatty acid, oleic acid, to the 18 carbon precursor of 8Z-dihydromatricaria acid, that is, 9Z,16Z-octadecadiene-12,14-diynoic acid. These are the first eukaryotic genes reported to produce conjugated polyacetylenic fatty acids. Phylogenetic analysis shows that the genes responsible for 8Z-dihydromatricaria acid synthesis in soldier beetles evolved de novo and independently of the acetylenases of plants and fungi.
authors.affiliation: CSIRO Ecosystem Sciences, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia. victoria.haritos@csiro.au
authors.forename: Victoria S
authors.initials: VS
authors.lastname: Haritos
authors.forename: Irene
authors.initials: I
authors.lastname: Horne
authors.forename: Katherine
authors.initials: K
authors.lastname: Damcevski
authors.forename: Karen
authors.initials: K
authors.lastname: Glover
authors.forename: Nerida
authors.initials: N
authors.lastname: Gibb
authors.forename: Shoko
authors.initials: S
authors.lastname: Okada
authors.forename: Mats
authors.initials: M
authors.lastname: Hamberg
mesh_terms: D000480:Alkynes / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D005075:Biological Evolution; D003001:Cloning, Molecular; D001517:Coleoptera / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D019143:Evolution, Molecular; D044943:Fatty Acid Desaturases / Q000235:genetics; D005227:Fatty Acids / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D017344:Genes, Insect / Q000235:genetics* / Q000502:physiology; D007313:Insecta / Q000235:genetics; D008297:Male; D010802:Phylogeny; D053279:Polyynes / Q000737:chemistry
chemical_list: D000480:Alkynes; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D053279:Polyynes; D044943:Fatty Acid Desaturases