The structure and paramutagenicity of the R-marbled haplotype of Zea mays.
Paramutation is the meiotically heritable silencing of a gene that can occur in particular heterozygous combinations. The R-marbled (R-mb) haplotype is paramutagenic: it causes paramutable r1 haplotypes like R-r to become heritably silenced. R-mb was found to comprise three distinct r1 genes arranged as direct repeats. The most distal gene of R-mb, Scm, contains a novel transposable element, Shooter (Sho). Excision of the Sho element early in aleurone development results in the characteristic "marbled" aleurone pigmentation pattern conferred by R-mb. The effect of gene copy number on the paramutagenic strength of R-mb was tested. Paramutagenic strength of R-mb is directly correlated with r1 gene copy number. Paramutagenic strength of R-mb is directly correlated with r1 gene copy number. Paramutagenic strength of R-mb was not affected by removal, through crossing over, of the Sho transposon. Finally, R-mb does not appear to contain the transposable element, Doppia, which is associated with paramutability of R-r, and has been suggested to play a role in paramutagenicity of another paramutagenic haplotype, R-stippled.
Panavas
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T
Biology Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Weir
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J
Walker
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D001483:Base Sequence; D003433:Crosses, Genetic; D017931:DNA Primers; D004251:DNA Transposable Elements; D017343:Genes, Plant; D006239:Haplotypes; D006579:Heterozygote; D008540:Meiosis; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic; D015183:Restriction Mapping; D003313:Zea mays / Q000235:genetics*
D017931:DNA Primers; D004251:DNA Transposable Elements