Abstract
The plant pyrethrum (Tanacetum cinerariifolium) synthesizes highly effective natural pesticides known as pyrethrins. Pyrethrins are esters consisting of an irregular monoterpenoid acid and an alcohol derived from jasmonic acid (JA). These alcohols, referred to as rethrolones, can be jasmolone, pyrethrolone, or cinerolone. We recently showed that jasmolone is synthesized from jasmone, a degradation product of JA, in a single hydroxylation step catalyzed by jasmone hydroxylase (TcJMH). TcJMH belongs to the CYP71 clade of the cytochrome P450 oxidoreductase family. Here, we used coexpression analysis, heterologous gene expression, and in vitro biochemical assays to identify the enzyme responsible for conversion of jasmolone to pyrethrolone. A further T cinerariifolium cytochrome P450 family member, CYP82Q3 (designated Pyrethrolone Synthase; TcPYS), appeared to catalyze the direct desaturation of the C1-C2 bond in the pentyl side chain of jasmolone to produce pyrethrolone. TcPYS is highly expressed in the trichomes of the ovaries in pyrethrum flowers, similar to TcJMH and other T cinerariifolium genes involved in JA biosynthesis. Thus, as previously shown for biosynthesis of the monoterpenoid acid moiety of pyrethrins, rethrolones are synthesized in the trichomes. However, the final assembly of pyrethrins occurs in the developing achenes. Our data provide further insight into pyrethrin biosynthesis, which could ultimately be harnessed to produce this natural pesticide in a heterologous system.