title: Overexpression of CYP710A1 and CYP710A4 in transgenic Arabidopsis plants increases the level of stigmasterol at the expense of sitosterol.
abstract: Sitosterol and stigmasterol are major sterols in vascular plants. An altered stigmasterol:sitosterol ratio has been proposed to influence the properties of cell membranes, particularly in relation to various stresses, but biosynthesis of stigmasterol is poorly understood. Recently, however, Morikawa et al. (Plant Cell 18:1008-1022, 2006) showed in Arabidopsis thaliana that synthesis of stigmasterol and brassicasterol is catalyzed by two separate sterol C-22 desaturases, encoded by the genes CYP710A1 and CYP710A2, respectively. The proteins belong to a small cytochrome P450 subfamily having four members, denoted by CYP710A1-A4, and are related to the yeast sterol C-22 desaturase Erg5p acting in ergosterol synthesis. Here, we report on our parallel investigation of the Arabidopsis CYP710A family. To elucidate the function of CYP710A proteins, transgenic Arabidopsis plants were generated overexpressing CYP710A1 and CYP710A4. Compared to wild-type plants, both types of transformant displayed a normal phenotype, but contained increased levels of free stigmasterol and a concomitant decrease in the level of free sitosterol. CYP710A1 transformants also displayed higher levels of esterified forms of stigmasterol, cholesterol, 24-methylcholesterol and isofucosterol. The results confirm the findings of Morikawa et al. (Plant Cell 18:1008-1022, 2006) regarding the function of CYP710A1 in stigmasterol synthesis, and show that CYP710A4 also has this capacity. Furthermore, our results suggest that an increased stigmasterol level alone is sufficient to stimulate esterification of other major sterols.
authors.affiliation: Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, P.O. Box 7080, 75007, Uppsala, Sweden.
authors.forename: Lisa
authors.initials: L
authors.lastname: Arnqvist
authors.forename: Mattias
authors.initials: M
authors.lastname: Persson
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Jonsson
authors.forename: Paresh C
authors.initials: PC
authors.lastname: Dutta
authors.forename: Folke
authors.initials: F
authors.lastname: Sitbon
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D030821:Plants, Genetically Modified; D012855:Sitosterols / Q000737:chemistry / Q000378:metabolism*; D013265:Stigmasterol / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D012855:Sitosterols; C025473:gamma-sitosterol; D003577:Cytochrome P-450 Enzyme System; D013265:Stigmasterol; D010088:Oxidoreductases; C527746:CYP710A1 protein, Arabidopsis; C527747:CYP710A4 protein, Arabidopsis