COLD SPRING HARBOR, NEW YORK

Cold Spring Harbor Laboratory

Mu1-associated hm1alleles --Guri Johal and Steven P. Briggs A collection of hm1 mutants from a Mutator background (Briggs, Curr. Topics Plant Biochem. Physiol. 6:59-67, 1987) was assayed for co-segregation of the mutant alleles with Mu1 homologous sequences. The mutant alleles were characterized by hybridization with the Pioneer RFLP probes PIO200644 and PIO200044, which are 5 cM proximal and distal, respectively, to hm1. Both probes could distinguish the alleles in our material, restricting our error in classification to double crossovers (estimated to occur in less than 1% of the progeny). For Mu1 hybridizations, the DNA was cut with either SstI, BamHI, or HindIII, none of which cut Mu1. Southern blots were probed with the AvaI-BstNI fragment of Mu1, isolated from pAB-5 (pAB-5 was obtained from Loverine Taylor). Analysis was simplified by outcrossing progeny in which the Mutator system was inactive, to reduce the number of Mu1-homologous fragments. Two mutants were identified in which a unique Mu1-homologous fragment co-segregated with the mutant hm1 allele. No recombination between the co-segregating Mu1-homologous fragments and the hm1-flanking RFLP probes has been observed in studies of 74 progeny for the hm1-6561 allele and 91 for the hm1-10621 allele. Our tentative conclusion is that these co-segregating fragments are Mu1 insertions in the Hm1 gene.

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