Genetic and molecular analysis of a three-component transposable-element system in maize.
Two different factors control the mutability of an unstable allele (c2-m881058Y) of the C2 gene of maize. Both an autonomous En/Spm element and an unrelated independent factor, named Mediator, are coordinately required for the excision of the insert in c2-m881058Y. According to genetic analysis, Mediator does not have the suppressor (S) function or mutator (M) function of En/Spm. Mediator has no effect on the timing or frequency of excision of En1, En-low, or various I/dSpm elements. Hence, Mediator only mediates a specific interaction between En and the insert at c2-m881058Y. Molecular analysis of c2-m881058Y has revealed a 3.3 kb, complex, En-related receptor element inserted into the second exon of the C2 gene. The ends of this element are homologous to the ends of En/Spm, but an internal 1.7 kb region shows no En/Spm homology. A great degree (11-14%) of nucleotide changes, relative to En1, occur within and between the 12 bp TNPA binding motifs. Alterations of these critical cis-determinants may account for the need for a "helper" factor for excision. This element is named Irma, for Inhibitor that requires Mediator also, and represents a unique, low copy number class of receptor element.
Department of Agronomy, Iowa State University, Ames 50011.
M G
MG
Muszynski
A
A
Gierl
P A
PA
Peterson
D000483:Alleles; D001483:Base Sequence; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D004251:DNA Transposable Elements / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid; D003313:Zea mays / Q000235:genetics*
D004251:DNA Transposable Elements