Biosynthetic pathway of insect juvenile hormone III in cell suspension cultures of the sedge Cyperus iria

In most insect species, juvenile hormones regulate critical physiological p rocesses such as metamorphosis and reproduction. In insects, these sesquite rpenoids are synthesized by retrocerebral endocrine organs, the corpora all ata, via the classical mevalonate (MVA) pathway. One of these compounds, ju venile hormone III (JH 111), has also been identified in the sedge Cyperus iria. In higher plants, biosynthesis of the sesquiterpenoid backbone may pr oceed through two distinct pathways: the MVA pathway or the 2C-methyl eryth ritol 4-phosphate pathway or through a combination of both pathways. Cell s uspension cultures of C. iria were used to elucidate the biosynthetic pathw ay of JH III in the plant. Enzyme inhibition and labeling studies conclusiv ely demonstrated that the biosynthesis Of the sesquiterpenoid backbone of J H III proceeds via the MVA pathway. Inhibitor and precursor feeding studies also suggest that later steps of JH III biosynthesis in C. iria are simila r to the insect pathway and that the final enzymatic reaction in JH III bio synthesis is catalyzed by a cytochrome P-450 monooxygenase.