Fructan reduction by downregulation of 1-SST in guayule

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.