Studies of the site and mode of biosynthesis of tobacco trichome exudate components.

Detached glandular trichome head preparations and epidermal strips with and without trichome heads were used to identify glandular trichome heads as the site of sucrose ester biosynthesis in tobacco. Carbon dioxide in solution as well as sucrose, glucose, and acetate were shown to serve as precursors to both sucrose esters and duvatrienediol diterpenes in detached trichome heads or epidermal strips, and gaseous CO2 was also efficiently utilized by epidermal strips. Thus, glandular heads can biosynthesize these principal exudate components from a molecule as simple as CO2. While formation of duvatriendiols from all precursors tested and conversion of sucrose and glucose to sucrose esters was light dependent, utilization of acetate to label the 6-O-acetyl group of the glucose moiety of sucrose esters occurred equally well in light and dark. The data suggest that CO2 and/or monosaccharides produced in trichome head cells and perhaps that supplied by other epidermal cells can act as carbon sources for sucrose ester and duvatrienediol biosynthesis which occurs in the glandular trichome head.