Prohevein is poorly processed but shows enhanced resistance to a chitin-binding fungus in transgenic tomato plants

In latex of rubber tree (Hevea brasiliensis), prohevein, homologous to potato win gene-encoded proteins, is processed to yield mature hevein. This mature hevein is composed of one chitin-binding domain and the C-terminal polypeptide homologous to pathogenesis-related proteins such as tobacco PR-4 and tomato P2 proteins. In contrast, prohevein was poorly cleaved to form the C-terminal polypeptide in transgenic tomato plants expressing hevein gene (HEV1)-driven polypeptides. However, mature hevein, the N-terminal cleavage form, was not found in this system. Immunoblot analysis of extracellular and intracellular fluid proteins showed that HEV1-encoded polypeptides accumulated intracellularly. In addition, retardation of growth of Trichoderma hamatum was observed in transgenic tomatoes constitutively expressing HEV1-encoded proteins.