Heat Shock at an Elevated Temperature Improves Transformation Efficiency of Protoplasts from Podospora anserina

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Abstract
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.degree.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 .mu.g of plasmid DNA containing the P. anserina ura5 gene. This should allow direct cloning of P. anserina genes from a cosmid library.