title: Functional characterisation of two cytochrome b5-fusion desaturases from Anemone leveillei: the unexpected identification of a fatty acid Delta6-desaturase.
abstract: The Ranunculaceae are known to accumulate a wide range of unusual fatty acids in their seed lipids, and this variability has been advocated as a taxonomic marker. The Anemone species, Anemone leveillei L. and Anemone rivularis Buch.-Ham., have previously been reported to accumulate Delta5-desaturated fatty acids in their seed tissue [K. Aitzetmüller (1995) Plant Syst Evol 9:229-240]. Two cDNAs, AL1 and AL2, with similarity to plant cytochrome b5-fusion "front-end" desaturases were isolated from developing seeds of A. leveillei and their function identified by expression in Saccharomyces cerevisiae. AL2 was characterised as a sphingolipid long-chain-base Delta8-desaturase, while AL1 acted as a fatty acid desaturase. However, AL1 did not produce Delta5-desaturated fatty acids as expected; instead, when expressed in transgenic S. cerevisiae or Arabidopsis thaliana this enzyme was functionally characterised as a Delta6-desaturase. Northern analysis confirmed the expression of this gene in seed tissue and leaf tissue of A. leveillei, though Delta6-desaturated fatty acids were found to accumulate only in the leaf tissue. The unexpected characterisation of a Delta6-desaturase in A. leveillei has implications for the use of fatty acids in chemotaxonomic studies. This is also the first report of a higher-plant Delta6-desaturase from a family other than the Boraginaceae.
authors.affiliation: Long Ashton Research Station, Long Ashton, Bristol, BS41 9AF, UK.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Whitney
authors.forename: Louise V
authors.initials: LV
authors.lastname: Michaelson
authors.forename: Olga
authors.initials: O
authors.lastname: Sayanova
authors.forename: John A
authors.initials: JA
authors.lastname: Pickett
authors.forename: Johnathan A
authors.initials: JA
authors.lastname: Napier
mesh_terms: D000595:Amino Acid Sequence; D031883:Anemone / Q000201:enzymology* / Q000235:genetics; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D015786:Cytochromes b5 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D050602:Linoleoyl-CoA Desaturase; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D015786:Cytochromes b5; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase