Identification and characterization of a gene encoding a subtilisin-like serine protease induced during the...

In the filamentous fungi, cell fusion between unlike individuals generally triggers a cell-death reaction known as vegetative incompatibility. In Podospora anserina, it was shown that, during this cell-death reaction, there is a strong increase in proteolytic activity. Here, we report the purification of a 36-kDa protease that is induced during the incompatibility reaction. An internal peptide of this protein displayed a strong similarity with the PEPC subtilisin-like serine protease from Aspergillus niger. This led us to use the pepC gene as a probe to clone the homologous gene from P. anserina, which we called pspA. The expression of pspA is upregulated at the transcript level during the progress of the incompatibility reaction. This induction is diminished in strains bearing suppressors of the vegetative incompatibility reaction. The fact that pspA is homologous to PrB, a vacuolar protease involved in autophagy in yeast, suggests that the incompatibility cell-death reaction and autophagy might be related processes.