A semi-dominant allele, niv-525, acts in trans to inhibit expression of its wild-type homologue in Antirrhinum majus.
Niv-525 is a semi-dominant allele of the nivea locus, which encodes the enzyme chalcone synthase required for flower pigment biosynthesis in Antirrhinum majus. Plants heterozygous for niv-525 and wild-type (Niv+) allele, have flowers with a reduced intensity and novel spatial pattern of pigmentation compared with Niv+ homozygotes. In heterozygotes, niv-525 acts in trans to reduce the steady-state level of nivea transcript produced by its Niv+ homologue and hence the quantity of chalcone synthase protein. Niv-525 carries an inverted duplication of 207 bp in its promoter region which has arisen following excision of the transposable element Tam 3. This structure can be explained by a model of plant transposable element excision that involves resolution of two hairpin DNA molecules. Possible mechanisms for the trans-acting effect of niv-525 and its relationship to other examples of allelic interactions, such as transvection in Drosophila melanogaster, are discussed.
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AFRC, Institute of Plant Science Research, John Innes Institute, Norwich, UK.
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D000217:Acyltransferases / Q000235:genetics; D000483:Alleles; D001483:Base Sequence; D005786:Gene Expression Regulation; D005796:Genes; D005799:Genes, Dominant; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010944:Plants / Q000201:enzymology / Q000235:genetics*; D014158:Transcription, Genetic
D000217:Acyltransferases; C020141:flavanone synthetase