Biosynthesis of avenacins and phytosterols in roots of Avena sativa cv. Image

In keeping with the proposal that avenacin biosynthesis is restricted to th e tips of primary roots of oat seedlings, the incorporation of radioactivit y from R-[2-C-14]mevalonic acid (MVA) into avenacins and beta-amyrin by ser ial sections of primary roots was found to be more-or-less restricted to ro ot tip sections. Squalene synthase (SQS) (EC 2.5.1.21) and 2,3-oxidosqualen e:beta-amyrin cyclase (OS beta AC) (EC 5.4.99) were also most active in the se sections. The incorporation of radiolabel from R-[2-C-14]MVA into cycloa rtenol and 24-methylene cycloartanol by, and the 2,3-oxidosqualene:cycloart enol cyclase (OSCC) (EC 5.4.99) activity in, the various serial sections we re consistent with phytosterol biosynthesis occurring in all the sections o f the root with some tailing-off in the rate of synthesis in the more dista l sections. (C) 2000 Elsevier Science Ltd. All rights reserved.