Changes in the Pathway of Ethylene Production Following Citrus Exocortis Viroid Infection in Tomato Plants

Abstract

Ethylene production was stimulated during the systemic reaction of Rutgers tomato to citrus exocortis viroid (CEV) infection. The increase in ethylene production of CEV-infected leaf discs was parallel to the increase in 1-aminocyclopropane-1-carboxylic acid (ACC) production, and content. Moreover, the capacity to convert ACC into ethylene (ethylene forming enzyme activity) in CEV-infected leaves also increased. The blockage of ACC synthase with aminooxyacetic acid (AOA) completely prevented the viroid-induced production of ethylene, thus indicating that this enzyme is the primary controlling step of ethylene biosynthesis acted upon in viroid infection. The increased ethylene-forming enzyme (EFE) activity acts as a secondary contributor to the enhanced production of ethylene.