Heat shock at an elevated temperature improves transformation efficiency of protoplasts from Podospora anserina

We have developed an improved transformation procedure for the filamentous fungus Podospora anserina. This procedure is based on the observation that a heat shock at an elevated temperature (48 degrees C) improves the competence of P. anserina protoplasts for transformation 5- to 10-fold. This is observable only if the heat shock is applied before the addition of transforming DNA. An increase in competence is observed immediately after the heat shock, and heat-shocked cells are still competent after 20-30 min. The mechanism by which heat shock improves competence remains unclear. The modified transformation procedure gives as many as 200-500 stable transformants per microgram of plasmid DNA containing the P. anserina ura5 gene. This should allow direct cloning of P. anserina genes from a cosmid library.