LAUSR

Abstract The natural rubber producing plant guayule ( Parthenium argentatum Gray) stores carbohydrates mainly in the form of fructans, synthesized and stored in the same tissues at the same time as the rubber polymer, and a potential source of carbon for rubber biosynthesis. The first committed step to fructan synthesis is catalyzed by sucrose:sucrose-1-fructosyltransferase (1-SST), which was downregulated to test whether reduction of carbohydrate synthesis would divert carbon instead to rubber biosynthesis. Guayule leaf strips were transformed by Agrobacterium -mediated technology, and plants with downregulated 1-SST were evaluated in the laboratory and greenhouse. The plant tissue fructan concentration was reduced significantly, and sucrose concentration increased, especially in root tissues of greenhouse-grown plants. However, increased natural rubber production did not result.