Non-Oak Ridge RFLP patterns in the Neurospora crassa multicent-2 strains

S.D. Haedo, M.R. Mautino and A.L. Rosa - Dept. Quimica Biológica (CIQUIBIC- CONICET), Fac. Ciencias Quimicas, Universidad Nacional de Córdoba, 5016 Córdoba, Argentina.

The N. crassa strain multicent-2 (FGSC 4488) is widely used for RFLP mapping (Metzenberg et al. 1984 Neurospora Newsl. 31:35-39). The genetic background of multicent- 2 is considered as being largely "Oak Ridge". However, by studying RFLP patterns, we have recently found that a region in the multicent-2 linkage group VII differs considerably from that of the standard wild type "Oak Ridge" 74-OR23-1A (FGSC 987) (Haedo et al. 1992 Genetics, in press). We extend here this observation to a 40 kb region on the left arm of linkage group I. Table I shows that the analyzed region on chromosome I is largely "Oak Ridge" both in multicent-2 and, as expected, the Mauriceville-1c genome.

Table I RFLP types found in different N. crassa strains*

RFLP                          Strain
type
                Oak Ridge     multicent-2     Mauriceville-1c
                FGSC 987      FGSC 4488       FGSC 4416

ClaI     a          I             I               III
         b          I            II                I

EcoRI    a          I             I               III
         b          I            II                I

EcoRV    a          I            II               III
         b          I            II                I
         c          I            II                I

XbaI     a          I            II               III

* - For simplicity the length of restriction fragments is not indicated. RFLPs are arbitrarily defined as I (Oak Ridge), II (Non-Oak Ridge) and III (Mauriceville-1c). a, b and c indicate different RFLPs for the corresponding enzyme.

Although this finding does not modify any conclusion based on the use of multicent-2 in RFLP mapping experiments, it indicates that a multicent-2 RFLP or, in general, the length of a multicent-2 restriction fragment is not necessarily "Oak Ridge", and would not be expected in either Southern blots or DNA clones originating from the current standard wild type "Oak Ridge" strains or libraries, respectively.

METHODS: N. crassa DNA was purified, restricted and subjected to Southern blot analysis as described (Haedo et al. 1992 Genetics, in press). A pMOcosX cosmid clone containing a 40 kb insert closely linked to the arg-3 locus (M. Mautino, S. Haedo and A.L. Rosa, unpublished), on the left arm of linkage group I, was 32P-dATP-labelled and used as a probe. The N. crassa wild-type pMOcosX library was constructed by Drs. M. Sachs and M. Orbach and is distributed by FGSC.

We are grateful for the financial support of Fundación Antorchas (Argentina), CONICET (National Research Council Argentina, and TWAS (Third World Academy of Sciences, Italy).