Order of the aro-6 and cpl-1 loci on linkage group VI of Neurospora.
FGN 47:111

Thomas J. Schmidhauser-Department of Biology, The University of Louisiana at Lafayette, Lafayette, LA.

The results reported here locate the cpl-1 locus 5.5 centimorgans to the left of the aro-6 locus on linkage group VIL of Neurospora.

The aro-6 (Halsall and Doy 1969 Biochim. Biophys. Acta 185:432-446), and cpl-1 (Chalmers 1973 Genetics 74s:43), loci have been mapped to the left arm of linkage group VI of Neurospora between the ad-8 and lys-5 loci. The order of aro-6 and cpl-1 on LGVIL has not been determined.

The cpl-1 lesion increases the sensitivity of Neurospora to chloramphenicol and is scored on medium supplemented with 1 mg/ml chloramphenicol. The wild type is resistant to 4 mg/ml chloramphenicol. The aro-6 locus encodesone of three Neurospora 3-deoxy-D-arabinoheptulosonic acid-7-phosphate synthase isozymes in the aromatic amino acid biosynthetic pathway. The aro-6 lesion prevents growth on minimal medium supplemented with inhibitors, tryptophan and phenylalanine, of the alternate two isozymes of the synthase.

The double mutant ad-8 1-152-7(E6), cpl-1 ANTAS6(s) A was isolated from a preliminary cross and crossed to aro-6 a DH1 (FGSC 1713) on solid synthetic crossing medium using aro-6 a as the female parent. Random ascospores were isolated onto 1 ml slants of Vogel's minimal medium supplemented with adenine in 75 mm tubes. Scoring was by transfer to slants of minimal medium with appropriate supplements. No double recombinants were observed.

Data obtained from random ascospore isolates from aro-6 a x ad-8, cpl-1 A
Zygote genotype Parental
Recombination Total and
percent germination
ad-8 cpl-1   + 
12 9 163
   +    +    aro-6
70 (82%)

12 recombinants in region 1 out of 163 progeny yields an interval of 7.4 centimorgans.
9 recombinants in region 2 out of 163 progeny yields an interval of 5.5 centimorgans. The data is consistent with the order shown in Figure 1; of the three loci tested aro-6 is proximal to the LGVI centromere and the ad-8 locus is distal.

Figure 1. Relevant region of linkage group VI of Neurospora showing the locations of the aro-6 and cpl-1 loci.

Anya Alleman, Felica Eichler and Marcus Louis contributed to this work.

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