abstract

[Nora Plesofsky-Vig]

Abstract of paper in Proceedings of the National Academy of Science  
92:5032-5036, 1995. 

  Disruption of the gene for hsp30, an alpha-crystallin-related
  heat shock protein of Neurospora crassa, causes defects in 

  thermotolerance

Nora Plesofsky-Vig and Robert Brambl

Departments of Genetics and Cell Biology and Plant Biology and
  Plant Molecular Genetics Institute
The University of Minnesota

ABSTRACT
The alpha-crystallin-related heat shock proteins are produced by all  
eukaryotes, but the role of these proteins in thermoprotection  
remains unclear. To investigate the function of one of these  
proteins, we disrupted expression of the single-copy hsp30 gene of  
Neurospora crassa, using RIP (Repeat-Induced Point) mutagenesis, and  
we generated and characterized mutant strains that were deficient in  
hsp30 synthesis. These strains grew well at high temperature and they  
acquired heat shock-induced thermotolerance. However, the  
hsp30-defective strains proved to be extremely sensitive to the  
combined stresses of high temperature and carbohydrate limitation,  
enforced by the addition of a glucose analogue. Under these  
conditions, their survival was reduced to as low as 10% that of  
wild-type cells. This sensitive phenotype was reversed by  
reintroduction of a functional hsp30 gene into the mutant strains.  
The mutant cells showed altered localization of a 22 kDa protein,  
which was easily solubilized from their mitochondria, in contrast to  
its retention by the mitochondria of wild-type cells. Antibodies  
against hsp30 coimmunoprecipitated a protein of approximately 22 kDa  
from wild-type cells. These results suggest that hsp30 may be  
important for efficient carbohydrate utilization during high  
temperature stress and that it may function as a protein chaperone in  
vivo.