Elicitors of Plant Defense Responses from Biocontrol Strains of Trichoderma viren

ABSTRACT Effective biocontrol strains of Trichoderma virens can induce the production of defense-related compounds in the roots of cotton. Ineffective strains do not induce these compounds to significant levels. This elicittation was found to be heat stable, insoluble in chloroform, passed through a 5K molecular weight cut-off (MWCO) filter, but not a 3K MWCO filter, and was sensitive to treatment by proteinase K. When the active material was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, several bands were present in the material from biocontrol-active strains that were lacking in inactive strains. When eluted and tested for elicitation activity, with or without renaturation, four bands stimulated cotton terpenoid production. One band showed cross-reaction with an antibody to the ethylene-inducing xylanase from T. viride. Another band of approximately 18 kDa, gave significant stimulation of cotton terpenoid production and increased peroxidase activity in cotton radicles in all tests, with or without renaturation. The 18-kDa protein was subjected to amino-terminal sequence analysis, and the first 19 amino acids at the amino terminus were determined to be DTVSYDTGYDNGSRSLNDV. A database homology search using the BLASTp algorithm showed the highest similarity to a serine proteinase from Fusarium sporotrichioides.