AN INNER CELL-WALL PROTEIN (CWP1) FROM CONIDIA OF THE ENTOMOPATHOGENIC FUNGUS BEAUVERIA-BASSIANA

Following the removal of the rodlet layer from aerial or submerged con idia of the entomopathogenic deuteromycetous fungus Beauveria bassiana , SDS-insoluble, formic-acid-extractable proteins were found in the re sidual cell wall material. Two major proteins (12.8 and 14.0 kDa) were extracted with formic acid from fractured aerial and submerged conidi a but not from blastospores. Oxidation of the sample extracted by form ic acid resulted in a single protein band (15.4 kDa) as judged by SDS- PAGE. Antibodies against this cell wall protein (cwp1) did not cross-r eact with cell wall extracts from the entomopathogenic deuteromycetous fungi Verticillium lecanii or Metarhizium anisopliae. Western blot an alysis of two-dimensional gels revealed at least three acidic isoforms (pI 4.0-4.8) of cwp1. Immunohistological studies revealed that the cw p1 was primarily localized in the cell wall of aerial and submerged co nidia but not in blastospores. Immunolocalization was possible only if the conidia were previously boiled in 5% (v/v) beta-mercaptoethanol. The N-terminal sequence of cwp1 showed no similarities with other publ ished sequences. Our results suggest that at least two major species o f SDS-insoluble, formic-acid-extractable proteins exist in cell walls of B. bassiana aerial or submerged conidia; one is the hydrophobin whi ch occurs in the outermost rodlet layer and the other, cwp1, occurs pr imarily next to the rodlet layer.