Fig. 6.

Monoterpene biosynthesis in wild rose petals. The methylerythritol phosphate (MEP) pathway in plastids and the newly elucidated NUDIX hydrolase pathway in cytosol are responsible for monoterpene synthesis in rose petals. Geraniol-poor Type C roses likely possess only the conventional MEP pathway, which makes all kinds of monoterpenes at low levels. In geraniol-rich Type A and B roses, floral maturity coincides with geraniol enrichment by cytosolic NUDIX hydrolase pathway, which is likely absent in Type C roses. Cytokinins (isoprenoid zeatins and their conjugates Fig. S1), cyclic monoterpenes, and linalool are made by the MEP pathway during early floral development in most roses