GENETICS OF THE TUBULIN GENE FAMILIES OF PHYSARUM

Abstract

ABSTRACT The organization of the α- and β-tubulin gene families in Physarum was investigated by Mendelian analysis. Restriction endonuclease-generated DNA fragments homologous to α- and β-tubulin show length polymorphisms that can be used as markers for genetic mapping. Analysis of meiotic assortment among progeny of heterozygotes allowed α- and β-tubulin sequence loci to be defined. There are four unlinked α-tubulin sequence loci (altA, altB, altC and altD) and at least three unlinked β-tubulin sequence loci (betA, betB and betC). The α-tubulin loci are not linked to the β-tubulin loci. —Segregation of tubulin sequence loci with respect to ben mutations that confer resistance to antitubulin benzimidazole drugs was used to investigate whether any members of the α- or β-tubulin gene families are allelic to ben loci. The β-tubulin sequence locus betB is allelic to the resistance locus benD, the betA locus is probably allelic to benA and the α-tubulin sequence locus altC may be allelic to benC. The molecular implications of benzimidazole resistance phenotypes when only one of the expressed β-tubulin gene family members mutates to drug resistance are discussed in relation to tubulin function.