Strains for identifying and studying individual vegetative ( heterokaryon ) incompatibility loci in Neurospora crassa

Genetic and molecular studies of vegetative incompatibility are proceeding in several Neurospora labs. The purpose of this note is to present an expanded list of strains in the Fungal Genetics Stock Center that are potentially useful when partial diploids are employed to identify different alleles at any of the 11 known het loci of N. crassa. Some of the strains are newly deposited in FGSC. Others have previously been listed under other categories in the stock list. Creative Commons License This work is licensed under a Creative Commons Attribution-Share Alike 4.0 License. This regular paper is available in Fungal Genetics Reports: http://newprairiepress.org/fgr/vol40/iss1/28 Strains for identifying and studying individual vegetative (heterokaryon) incompatibility loci in Neurospora crassa. D. D. Perkins, J. F. Leslie and D. J. Jacobson Department of Biological Sciences, Stanford University, Stanford, California 94305-5020; Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506-5502; and Department of Botany and Plant Pathology, Michigan State University, East Lansing, Michigan 48824-1312 Genetic and molecular studies of vegetative incompatibility are proceeding in several Neurospora labs. The purpose of this note is to present an expanded list of strains in the Fungal Genetics Stock Center that are potentially useful when partial diploids are employed to identify different alleles at any of the 11 known het loci of N. crassa. Some of the strains are newly deposited in FGSC. Others have previously been listed under other categories in the stock list. Wild populations of N. crassa are polymorphic for het genes (Mylyk 1976 Genetics 83:275-284). Laboratory strains, which have come from varied lineages, frequently differ from one another in het genotype. This polymorphism and the multiplicity of het loci often make it difficult to use heterokaryon tests for genetic analysis, because failure to complement may result from allelic differences at any one of numerous het loci. Extraneous het genes other than at the locus of interest will usually not be a problem when duplications (partial diploids) are used. Duplications of known content can be obtained for defined chromosomal segments in progeny of crosses heterozygous for insertional or terminal translocations (see Perkins and Barry 1977 Advan. Genet. 19:133-295). Because the duplications exist in an otherwise haploid genome, they make it possible to identify individual vegetative incompatibility (het) genes and to study them one by one without the necessity of making strains isogenic or homozygous for other het genes located outside the duplicated segment. If the translocation and normal-sequence parents differ with respect to alleles at a het locus within the duplication, then duplication progeny heterozygous for the included incompatible allelic combination display a characteristic inhibited growth with abnormal morphology and pigment (Newmeyer and Taylor 1967 Genetics 56:771791; Perkins 1975 Genetics 80:87-105; Mylyk 1975 Genetics 80:107-124, 83:275-284). These heterozygous (hetx/het) duplications are clearly distinguishable from homozygous (het/het) or (het/het) duplication strains, which are usually phenotypically normal or nearly so. Heterokaryon incompatibility has been shown to correspond with phenotypic abnormality of heterozygous duplications for het genes at seven loci (mating type [Newmeyer 1970 Can. J. Genet. Cytol. 12:914-926], het-c, d, -e, -5, and -8 [see Mylyk 1976 Genetics 83:275-284], and het-6 [D. J. Jacobson unpublished]). Three loci, het-7, -9, and -10, have been defined solely on the basis of their behavior in duplications. Presumably unlike alleles at these three loci are also heterokaryon incompatible, although this has not been tested because strains are not available that are known to differ only at the het locus in question but not at other loci. het-i has been defined only by behavior in heterokaryons; it differs from other het genes in such a way that incompatibility of different het-i alleles may not be detectable in duplications (Pittenger and Brawner 1961 Genetics 46:1645-1663). Stocks with forcing markers are available for heterokaryon tests of het-c, -d, and -e in eight genotype combinations (prepared by L. Garnjobst and J. Wilson). These are listed in part VII.D.1 of the FGSC Stock List. Strains in this set are Published by New Prairie Press, 2017 probably identical to the Oak Ridge (OR) wild type and its derivatives at het loci other than hetc, -d, and -e. OR strains are het-C het-d het-e het-i het-5 het-6 het-7 het-8 het-9 het10. A few wild strains carry tol, a recessive suppressor of the het incompatibility associated with mating type, but OR and most other N. crassa strains are tol. Genetic evidence suggests the existence of multiple alleles at two loci-het-c and het-8 (Howlett, Leslie, and Perkins, 1993 Fungal Genet. Newsl. 40). However, multiple allelism could be simulated by two alleles at each of two closely linked het loci, and this alternative has not been ruled out. The listing that follows (Table 1) is comprised of reference strains and strains with relevant linked markers, both in normal sequence and in the sequence of rearrangements capable of generating duplications that include the locus in question. Different het alleles are denoted by superscripts based on the wild strains of origin or on a laboratory reference strain, for example AD Adiopodoumé, CR Costa Rica, HO Houma, LI Liberia, OR Oak Ridge, PA Panama. Symbols for het-c, -d, -e, and -i are exceptions, with unraised capital or small letters used to specify the first two alleles, e.g. het-D, het-d. These, together with mating type, were the first het loci to be identified. Map relations of the markers and loci are shown in Figure 1. Updated versions of the list will appear in the FGSC Stock List (Part VII.D, Special-Purpose Stocks). (Contribution No. 93-355-A from the Kansas Agricultural Experimental Station, Manhattan.) Table 1. Strains for studying individual het-loci of N. crassa FGSC No. Genotype A a het-c (IIL) (all are het-6OR) het-C (OR wild types) 2489 4200 het-c 7335 7336 het-C pyr-4 4030 4031 het-c pyr-4 7145 7146 cot-5 het-C 3560 3561 cot-5 het-c 7447 cot-5 het-C pyr-4 thr-2 7355 7356 T(IIL VR)NM149 het-C 3879 3880 T(IIL VR)NM149 het-c 1483 1482 T(IIL VR)NM149 het-C pyr-4 3136 T(IIL VR)NM149 het-C ro-3 2011 2012 het-cAD 43


Strains for identifying and studying individual vegetative (heterokaryon) incompatibility loci in
Genetic and molecular studies of vegetative incompatibility are proceeding in several Neurospora labs.The purpose of this note is to present an expanded list of strains in the Fungal Genetics Stock Center that are potentially useful when partial diploids are employed to identify different alleles at any of the 11 known het loci of N. crassa.Some of the strains are newly deposited in FGSC.Others have previously been listed under other categories in the stock list.
Wild populations of N. crassa are polymorphic for het genes (Mylyk 1976 Genetics 83:275-284).Laboratory strains, which have come from varied lineages, frequently differ from one another in het genotype.This polymorphism and the multiplicity of het loci often make it difficult to use heterokaryon tests for genetic analysis, because failure to complement may result from allelic differences at any one of numerous het loci.Extraneous het genes other than at the locus of interest will usually not be a problem when duplications (partial diploids) are used.
Duplications of known content can be obtained for defined chromosomal segments in progeny of crosses heterozygous for insertional or terminal translocations (see Perkins and Barry 1977 Advan.Genet.19:133-295).Because the duplications exist in an otherwise haploid genome, they make it possible to identify individual vegetative incompatibility (het) genes and to study them one by one without the necessity of making strains isogenic or homozygous for other het genes located outside the duplicated segment.If the translocation and normal-sequence parents differ with respect to alleles at a het locus within the duplication, then duplication progeny heterozygous for the included incompatible allelic combination display a characteristic inhibited growth with abnormal morphology and pigment (Newmeyer and Taylor 1967 Genetics 56:771-791; Perkins 1975 Genetics 80:87-105; Mylyk 1975 Genetics 80:107-124, 83:275-284).These heterozygous (hetx/het y ) duplications are clearly distinguishable from homozygous (het x /het x ) or (het y /het y ) duplication strains, which are usually phenotypically normal or nearly so.
Heterokaryon incompatibility has been shown to correspond with phenotypic abnormality of heterozygous duplications for het genes at seven loci -(mating type [Newmeyer 1970 Can.J. Genet.Cytol.12:914-926], het-c, d, -e, -5, and -8 [see Mylyk 1976 Genetics 83:275-284], and het-6 [D.J. Jacobson unpublished]).Three loci, het-7, -9, and -10, have been defined solely on the basis of their behavior in duplications.Presumably unlike alleles at these three loci are also heterokaryon incompatible, although this has not been tested because strains are not available that are known to differ only at the het locus in question but not at other loci.het-i has been defined only by behavior in heterokaryons; it differs from other het genes in such a way that incompatibility of different het-i alleles may not be detectable in duplications (Pittenger and Brawner 1961 Genetics 46:1645-1663).Stocks with forcing markers are available for heterokaryon tests of het-c, -d, and -e in eight genotype combinations (prepared by L. Garnjobst and J. Wilson).These are listed in part VII.D.1 of the FGSC Stock List.Strains in this set are probably identical to the Oak Ridge (OR) wild type and its derivatives at het loci other than hetc, -d, and -e.OR strains are het-C het-d het-e het-i het-5 OR het-6 OR het-7 OR het-8 OR het-9 OR het-10 OR .A few wild strains carry tol, a recessive suppressor of the het incompatibility associated with mating type, but OR and most other N. crassa strains are tol + .
Genetic evidence suggests the existence of multiple alleles at two loci-het-c and het-8 (Howlett, Leslie, and Perkins, 1993 Fungal Genet.Newsl.40).However, multiple allelism could be simulated by two alleles at each of two closely linked het loci, and this alternative has not been ruled out.
The listing that follows (Table 1) is comprised of reference strains and strains with relevant linked markers, both in normal sequence and in the sequence of rearrangements capable of generating duplications that include the locus in question.Different het alleles are denoted by superscripts based on the wild strains of origin or on a laboratory reference strain, for example AD -Adiopodoumé, CR -Costa Rica, HO -Houma, LI -Liberia, OR -Oak Ridge, PA -Panama.Symbols for het-c, -d, -e, and -i are exceptions, with unraised capital or small letters used to specify the first two alleles, e.g.het-D, het-d.These, together with mating type, were the first het loci to be identified.Map relations of the markers and loci are shown in Figure 1 Neurospora crassa.D. D. Perkins 1 , J. F. Leslie 2 and D. J. Jacobson 3 -1 Department of Biological Sciences, Stanford University, Stanford, California 94305-5020; 2 Department of Plant Pathology, Kansas State University, Manhattan, Kansas 66506-5502; and 3 Department of Botany and Plant Pathology, Michigan State University, East Lansing, Michigan 48824-1312

Figure 1 .
Figure 1.N. crassa linkage groups showing the sequence of markers and rearrangements relevant to known het loci.Dashed lines below the linkage groups show the extent of duplications