Genetic mapping of the A. nidulans xprE gene

M.E. Katz - Department of Molecular and Cellular Biology, University of New England, Armidale, NSW 2351, AUSTRALIA.

Strains carrying the xprE1 mutation produce very little or no extracellular proteases in response to carbon and nitrogen limitation and have reduced levels of extracellular protease in response to sulphur limitation. Haploidization analysis has shown that the xprE gene is located on A. nidulans chromosome VI (Katz et al. 1996, Mol. Gen. Genet., in press). In order to isolate the xprE gene using the A. nidulans physical map a more accurate position of the gene has now been determined. The gene order on chromosome VI is lysA, xprE, sB, sbA .

Table 1. Genetic mapping of xprEa

               Genotype      No. of                   Genotype      No. of    
                             progeny                                progeny   
Parentals   xprE   +    +      56      Parentals    +    xprE   +      105     
             1                                            1                    
A464         +    sB3  sbA     73      A350        lysA   +    sB3      0      
                        3                           1                          
Region I    xprE  sB3  sbA     10      Region I     +     +    sB3     12      
             1          3                                                      
crossovers   +     +    +      17      crossovers  lysA  xprE   +       0      
                                                    1     1                    
Region II   xprE   +   sbA     36      Region II    +    xprE  sB3     13      
             1          3                                 1                    
crossovers   +    sB3   +      43      crossovers  lysA   +     +       0      
Double      xprE  sB3   +       5      Double       +     +     +       6      
crossovers   +     +   sbA      5      crossovers  lysA  xprE  sB3      0      
                        3                           1     1                    
   Region I map distance: 15.1 cM       Region I map distance:  13.2 cM     
  Region II map distance:  36.3 cM      Region II map distance:  14.0 cM    

aData from crosses between xprE1 strain MK43 (biA1;xprE1;niiA4) and A464 (suA1-adE20 pabaA1 yA2 adE20; acrA1; lacA1 bwA1 sB3 sbA3) and MK55 (suA-adE20 yA1 adE20; pyroA4; xprE1; riboB2) with A350 (biA1; phenA2; lysA1 (Inv1(VI)-lysA1) sB3) are shown. Only lys+phen+ segregants from the cross to A350 were scored as the addition of lysine or phenylalanine to the medium represses extracellular protease production and prevents scoring of the xprE1 mutation.



Figure 1.Position of the xprE gene on A. nidulans chromsome VI. The upper map shows the genetic distances from the linkage map of A. nidulans (A.J. Clutterbuck 1993 In: O'Brien SJ (ed) Genetic Maps, vol 6. Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, pp 3.71-3.84). The lower map is based on the recombination frequencies listed in Table 1.

*The observed recombination frequency may be affected by the Inv1(VI)-lysA1 rearrangement.

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Last modified 7/25/96 KMC