DIVERSITY OF STEROL BIOSYNTHETIC CAPACITY IN THE CARYOPHYLLIDAE

The order Caryophyllales, along with its two associated orders, the Polygonales and Plumbaginales, comprise the angiosperm subclass Caryophyllidae. We have now characterized the sterol composition of 231 members of this subclass. This includes 210 species and 21 cultivars in 108 genera within the 14 families of these three orders. From these data, clear differences in biosynthetic capability and putative relationships between taxa have been established. Members of the two monofamilial orders (Polygonales and Plumbaginales) contain DELTA-5-sterols in ratios typical of "main line" angiosperms. Members of families in the Caryophyllales contain DELTA-5-sterols, or DELTA-7-sterols or mixtures of DELTA-5- and DELTA-7-sterols. In the majority of species where DELTA-7-sterols are the dominant sterols produced, trace amounts to almost equal amounts of DELTA-5-sterols are also present. Replicate samples of many of these species have shown that the ratio of DELTA-5-sterol to DELTA-7-sterol in these species is stable over time and/or location. From these data, it appears that the conversion of DELTA-7-sterols to DELTA-5-sterols is highly regulated in the majority of species within this order. In these families, similarities in sterol composition correlate well with taxonomic relatedness. Relationships between these taxa with respect to biosynthetic capability can now be postulated.