Abstract

[Gregory May]

The following is an abstract of a paer that is in press.  It will appear in
the Journal of Cell Biology Volume 128, No. 4, February 1995.

myoA of Aspergillus nidulans encodes an essential myosin I 
required for secretion and polarized growth.

Carol A. McGoldrick, Carol Gruver and Gregory S. May

ABSTRACT 
	We have identified and cloned a novel essential myosin I in 
Aspergillus nidulans, called myoA. The 1249 amino acid predicted 
polypeptide encoded by myoA is most similar to the amoeboid myosins
 I. Using affinity purified antibodies against the unique myosin I carboxyl
 terminus, we have determined that MYOA is enriched at growing 
hyphal tips. Disruption of myoA, by homologous recombination, resulted
 in a diploid strain heterozygous for the myoA gene disruption. We can 
recover haploids with an intact myoA gene from these strains but never 
haploids that are myoA disrupted. These data indicate that myoA 
encodes an essential myosin I and this has allowed us to use a unique 
approach to studying myosin I function. We have developed conditionally 
null myoA strains in which myoA expression is regulated by the alcA 
alcohol dehydrogenase promoter. A conditionally lethal strain germinated 
on inducing medium grows as wild type, displaying polarized growth by 
apical extension. However, growth of the same myoA mutant strain on 
repressing medium results in enlarged cells incapable of hyphal extension 
and these cells eventually die. Under repressing conditions, this strain 
also displays reduced levels of secreted acid phosphatase. The mutant 
phenotype indicates that myoA plays a critical role in polarized growth 
and secretion.

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  Gregory S. May			      	
  Department of Cell Biology			
  Baylor College of Medicine			
  One Baylor Plaza				
  Houston, TX  77030				
  Tel.  713-798-4756				
  FAX.  713-798-7799				
  E-mail gsmay at bcm.tmc.edu			
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