The scent of roses (Rosa x hybrida) is composed of hundreds of volatile molecules. Monoterpenes represent up to 70% percent of the scent content in some cultivars, such as the Papa Meilland rose. Monoterpene biosynthesis in plants relies on plastid-localized terpene synthases. Combining transcriptomic and genetic approaches, we show that the Nudix hydrolase RhNUDX1, localized in the cytoplasm, is part of a pathway for the biosynthesis of free monoterpene alcohols that contribute to fragrance in roses. The RhNUDX1 protein shows geranyl diphosphate diphosphohydrolase activity in vitro and supports geraniol biosynthesis in planta.

Monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are the main lipids in photosynthetic membranes in plant cells. They are synthesized in the envelope surrounding plastids by MGD and DGD galactosyltransferases. These galactolipids are critical for the biogenesis of photosynthetic membranes, and they act as a source of polyunsaturated fatty acids for the whole cell and as phospholipid surrogates in phosphate shortage. Based on a high-throughput chemical screen, we have characterized a new compound, galvestine-1, that inhibits MGDs in vitro by competing with diacylglycerol binding. Consistent effects of galvestine-1 on Arabidopsis thaliana include root uptake, circulation in the xylem and mesophyll, inhibition of MGDs in vivo causing a reduction of MGDG content and impairment of chloroplast development. The effects on pollen germination shed light on the contribution of galactolipids to pollen-tube elongation. The whole-genome transcriptional response of Arabidopsis points to the potential benefits of galvestine-1 as a unique tool to study lipid homeostasis in plants.