Diversity of Δ12 fatty acid desaturases in santalaceae and their role in production of seed oil acetylenic fatty acids.
Plants in the Santalaceae family, including the native cherry Exocarpos cupressiformis and sweet quandong Santalum acuminatum, accumulate ximenynic acid (trans-11-octadecen-9-ynoic acid) in their seed oil and conjugated polyacetylenic fatty acids in root tissue. Twelve full-length genes coding for microsomal Δ12 fatty acid desaturases (FADs) from the two Santalaceae species were identified by degenerate PCR. Phylogenetic analysis of the predicted amino acid sequences placed five Santalaceae FADs with Δ12 FADs, which include Arabidopsis thaliana FAD2. When expressed in yeast, the major activity of these genes was Δ12 desaturation of oleic acid, but unusual activities were also observed: i.e. Δ15 desaturation of linoleic acid as well as trans-Δ12 and trans-Δ11 desaturations of stearolic acid (9-octadecynoic acid). The trans-12-octadecen-9-ynoic acid product was also detected in quandong seed oil. The two other FAD groups (FADX and FADY) were present in both species; in a phylogenetic tree of microsomal FAD enzymes, FADX and FADY formed a unique clade, suggesting that are highly divergent. The FADX group enzymes had no detectable Δ12 FAD activity but instead catalyzed cis-Δ13 desaturation of stearolic acid when expressed in yeast. No products were detected for the FADY group when expressed recombinantly. Quantitative PCR analysis showed that the FADY genes were expressed in leaf rather than developing seed of the native cherry. FADs with promiscuous and unique activities have been identified in Santalaceae and explain the origin of some of the unusual lipids found in this plant family.
From the Commonwealth Scientific and Industrial Research Organization (CSIRO) Ecosystem Sciences, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia.
Shoko
S
Okada
the CSIRO Plant Industry, GPO Box 1600, Canberra, Australian Capital Territory 2601, Australia.
Xue-Rong
XR
Zhou
From the Commonwealth Scientific and Industrial Research Organization (CSIRO) Ecosystem Sciences, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia.
Katherine
K
Damcevski
From the Commonwealth Scientific and Industrial Research Organization (CSIRO) Ecosystem Sciences, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia.
Nerida
N
Gibb
the CSIRO Plant Industry, GPO Box 1600, Canberra, Australian Capital Territory 2601, Australia.
Craig
C
Wood
Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
Mats
M
Hamberg
From the Commonwealth Scientific and Industrial Research Organization (CSIRO) Ecosystem Sciences, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia,. Electronic address: victoria.haritos@csiro.au.
Victoria S
VS
Haritos
D000480:Alkynes; D044943:Fatty Acid Desaturases / Q000096:biosynthesis* / Q000235:genetics; D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D018515:Plant Leaves / Q000201:enzymology* / Q000235:genetics; D010938:Plant Oils / Q000378:metabolism*; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029630:Santalaceae / Q000201:enzymology* / Q000235:genetics; D012639:Seeds / Q000201:enzymology / Q000235:genetics / Q000276:immunology
D000480:Alkynes; D005231:Fatty Acids, Unsaturated; D010938:Plant Oils; D010940:Plant Proteins; D011994:Recombinant Proteins; C031203:2-hexadecynoic acid; D044943:Fatty Acid Desaturases
Enzyme Catalysis; Gene Expression; Lipids; Membrane Enzymes; Phylogenetics; Polyunsaturated Fatty Acids