The bouquet of grapevine (Vitis vinifera L. cv. Cabernet Sauvignon) flowers arises from the biosynthesis of sesquiterpene volatiles in pollen grains

Abstract

Terpenoid volatiles are important information molecules that enable pollinators to locate flowers and may protect reproductive tissues against pathogens or herbivores. Inflorescences of grapevine (Vitis vinifera L.) are composed of tiny green flowers that produce an abundance of sesquiterpenoid volatiles. We demonstrate that male flower parts of grapevines are responsible for sesquiterpenoid floral scent formation. We describe temporal and spatial patterns of biosynthesis and release of floral volatiles throughout the blooming of V. vinifera L. cv. Cabernet Sauvignon. The biosynthesis of sesquiterpene volatiles, which are emitted with a light-dependent diurnal pattern early in the morning at prebloom and bloom, is localized to anthers and, more specifically, within the developing pollen grains. Valencene synthase (VvValCS) enzyme activity, which produces the major sesquiterpene volatiles of grapevine flowers, is present in anthers. VvValCS transcripts are most abundant in flowers at prebloom stages. Western blot analysis identified VvValCS protein in anthers, and in situ immunolabeling located VvValCS protein in pollen grains during bloom. Histochemical staining, as well as immunolabeling analysis by fluorescent microscopy and transmission electron microscopy, indicated that VvValCS localizes close to lipid bodies within the maturing microspore.