The highly divergent beta-tubulins of Aspergillus nidulans are functionally interchangeable.

Abstract

An internal 1.4-kb Bst EII fragment was used to disrupt the benA gene and establish heterokaryons. The heterokaryons demonstrated that the molecular disruption of benA results in a recessive benA null mutation. Conidia from a heterokaryon swell and germinante but cannot undergo nuclear division and are thus inviable. A chimeric .beta.-tubulin gene was constructed with the benA promoter driving the tubC structural gene. This chimeric gene construction was placed on a plasmid containing a selectable marker for Aspergillus transformation and the gene disrupting fragment of benA. Integration of this plasmid at benA by the internal gene disrupting fragment of benA simultaneously disrupts the benA gene and replaces it with the chimeric .beta.-tubulin gene, rescuing the benA null generated by the integration. Strains generated by this procedure contain only tubC .beta.-tubulin functions. Strains having only tubC .beta.-tubulin are viable and exhibit no detectable microtubule dysfunction though they are more sensitive than wild-type strains to the antimicrotubule drug benomyl. It is concluded that the two .beta.-tubulin genes of Aspergillus nidulans, though highly divergent, are interchangeable.