Pyrethrins are synthesized by the plant pyrethrum (), a chrysanthemum relative. These compounds possess efficient insecticidal properties and are not toxic to humans and most vertebrates. Pyrethrum flowers, and to a smaller extent leaves, synthesize six main types of pyrethrins, which are all esters of a monoterpenoid acid moiety and an alcohol moiety derived from jasmonic acid. Here, we identified and characterized the enzyme responsible for the conversion of jasmone, a derivative of jasmonic acid, to jasmolone. Feeding pyrethrum flowers with jasmone resulted in a 4-fold increase in the concentration of free jasmolone as well as smaller but significant proportional increases in free pyrethrolone and all three type I pyrethrins. We used floral transcriptomic data to identify cytochrome P450 genes whose expression patterns were most highly correlated with that of a key gene in pyrethrin biosynthesis, The candidate genes were screened for jasmone hydroxylase activity through transient expression in leaves fed with jasmone. The expression of only one of these candidate genes produced jasmolone; therefore, this gene was named () and given the CYP designation CYP71AT148. The protein encoded by localized to the endoplasmic reticulum, and microsomal preparations from leaves expressing were capable of catalyzing the hydroxylation of jasmone to jasmolone in vitro, with a value of 53.9 µm was expressed almost exclusively in trichomes of floral ovaries and was induced in leaves by jasmonate.

ORCID IDs: 0000-0001-6777-6565 (M.E.S.); 0000-0001-9917-0656 (G.W.)The glycosylation of nicotinate (NA), a key intermediate of the NAD salvage pathway, occurs widely in land plants. However, the physiological function of NA glycosylation is not well understood in planta, and no gene encoding NA glycosyltransferase has been reported to date. NA glycosylation in Arabidopsis thaliana occurs at either the N-or the O-position of the NA molecule, and O-glucosylation appears to be unique to the Brassicaceae. Using gene-enzyme correlations focused on Family 1 glycosyltransferases (GTs; EC 2.4), we identified and characterized three Arabidopsis GTs, which are likely involved in NA glycosylation. These include one NAOGT (UGT74F2; previously identified as a salicylic acid glycosyltransferases) and two NANGTs (UGT76C4 and UGT76C5). Arabidopsis mutants of UGT74F2 accumulate higher levels of free NA, but not salicylic acid, than that of the wild type, and this inversely correlated with seed germination rates under various abiotic stresses. The germination defect of the ugt74f2-1 mutant could be fully complemented by overexpression of UGT74F2. These observations, together with comprehensive chemical analysis, suggest that NA glycosylation may function to protect plant cells from the toxicity of NA overaccumulation during seed germination. Combined with phylogenetic analysis, our results suggest that NAOGTs arose recently in the Brassicaceae family and may provide a fitness benefit. The multifunctionality of UGT74F2 in Arabidopsis is also investigated and discussed.