Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2000
Publication Date: N/A
Interpretive Summary: Fusarium solani f. sp. glycines, a soilborne fungus, is the causal agent of sudden death syndrome of soybean. The fungus has been isolated from soybean roots and occasionally from lower stems, but has not been found in leaves. The most conspicuous symptoms occur in leaves and it is believed to be caused by a translocated fungal toxin produced by the fungus in roots and translocated to leaves. As part of our effort toward understanding the interaction between soybean and F. solani f. sp. glycines, a stress-induced protein in stem exudates of soybean seedlings root-infected with F. solani f. sp. glycines was identified. This is the first report of the presence of a stress-induced protein in stem exudates of soybean root-infected with F. solani f. sp. glycines. This information is important to other researchers studying host-pathogen interactions and may provide a better understanding of what compounds are produced by the host plant after pathogen infection.
Technical Abstract: Sudden death syndrome of soybean (Glycine max) is caused by the soilborne fungus, Fusarium solani f. sp. glycines, that infects soybean roots. Besides root necrosis, symptoms include interveinal leaf chlorosis, necrosis and premature defoliation. It is proposed that a fungal toxin is produced in soybean roots and translocated to foliage. In this study, compounds were isolated from soybean stem exudates from plants that were either inoculated or not inoculated with F. solani f. sp. glycines. A protein with an estimated molecular mass of 17 kDa and designated as FISP 17 for F. solani f. sp. glycines-induced stress protein was identified using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This protein occurred only in F. solani f. sp. glycines-infected soybean stem exudates. The N-terminal amino acid sequence of the purified protein had 100% identity with a starvation-associated message 22 protein, and 80 and 78% identity with purified bean pathogenesis-related proteins, PvPR1 and PvPR2, respectively. To determine if the protein was of plant or fungal origin, a synthetic peptide was designed based on the N-terminal sequence and used to raise a polyclonal antibody from rabbit. Western blot analysis showed that the antibody only reacted with a 17-kDa protein in F. solani f. sp. glycines-infected plant exudates, but no reaction occurred with healthy plant exudates or with culture filtrates of F. solani f. sp. glycines. This is the first report of the presence of a stress-induced protein in stem exudates of soybean seedlings root-infected with F. solani f. sp. glycines.