Cytochrome P450 CYP710A encodes the sterol C-22 desaturase in plants

Abstract

Delta 22-unsaturated sterols, containing a double bond at the C-22 position in the side chain, occur specifically in fungi and plants. In yeast, cytochrome P450 (CYP61) has been known as the sterol Δ²²-desaturase in the ergosterol biosynthetic pathway. In this study, we performed a comprehensive sterol profiling to identify functional homologues of CYP61 in plants. Thus, we prepared a series of P450 transgenic lines of Arabidopsis and studied differential effects on the sterol profiles in planta. In the overexpression lines of either CYP710A1 from Arabidopsis or CYP710A11 from tomato, stigmasterol accumulated to 6- to 32-fold higher levels compared with wild type. The promoter::GUS reporter assays suggested strict tissue specific expression patterns of the Δ²²-desaturase genes in Arabidopsis, implicating developmental stage specific involvement of the Δ²²-sterols.