Cell wall assembly of Neurospora crassa: lack of evidence for preexisting cell wall acting as primer or template.

Cell wall formation of Neurospora crassa and other filamentous fungi involves the apical extension of preexisting cell wall in a complex assembly sequence; however, it is not known if preexisting wall participates in the formation of new cell wall. It was found that temperature-sensitive protoplasts which lack detectable preexisting wall form cell wall upon a shift to a permissive temperature. Similarly, temperature-sensitive colonial mutants form morphologically normal cell wall directly from preexisting abnormal hyphae after a shift to a permissive temperature. These results are consistent with the idea that cell wall assembly occurs without the participation of preexisting cell wall as either primer or template for new cell wall assembly.