The Fusarium solani-Induced Expression of a Pea Gene Family Encoding High Cysteine Content Proteins. Chin C. Chiang. Program in Genetics and Cell Biology and Department of Plant Pathology, Washington State University, Pullman 99164-6430 U.S.A. Lee A. Hadwiger. Program in Genetics and Cell Biology and Department of Plant Pathology, Washington State University, Pullman 99164-6430 U.S.A. MPMI 4:324-331. Accepted 4 March 1991. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1991.

Two pea genes, pI39 and pI230, which are specifically induced by two forma speciales of Fusarium solani, encode closely related proteins with predicted molecular masses (M_r) of 8.2 and 8 kDa, respectively. Both proteins contain a signal sequence and are cleaved to mature proteins of M_r 5 kDa as indicated by an in vitro translation system. The mature proteins contain about 17% cysteine residues and have the potential to form four disulfide bonds. The two proteins share extensive homology in their signal sequences but much less homology as mature proteins. The cysteine residues of the mature proteins are highly conserved, suggesting functional importance. Southern hybridization suggests these genes belong to a multigene family. The relative accumulations of mRNA levels indicate that the two genes are expressed somewhat differentially. In both the compatible (susceptible) and incompatible reactions between F. solani and pea tissue, pI39 mRNA accumulates more slowly than pI230 mRNA and accumulates to relatively high levels after 24 hr of inoculation. The increase in accumulation of pI230 mRNA occurs within 6 hr and thus correlates with an initial suppression of the growth of both the compatible and incompatible pathogen, which is cytologically observable at 6 hr. pI39 and pI230 belong to a distinct class of pathogenesis-related proteins characterized previously, which are associated with and thus may contribute to nonhost resistance in plants.