--Richard M. Walko and Sarah Hake
A knotted mutation has arisen in a Robertson's Mutator line. This mutant exhibited mild to severe knotting as well as ligule displacement when homozygous. When outcrossed to a non-Mutator line, however, the heterozygotes exhibited very mild knotting on the first and second leaves, and then did not exhibit any knotting or ligule displacement until the last one to three leaves below the tassel. These upper leaves exhibited additional ligules displaced outward on the leaf blade and generally severe knotting.
Southern analysis indicates the insertion of an element into the Kn1
locus. The insertion is approximately 1.4kb in length with HinFI
sites close to its ends in the inverted repeat regions as indicated by
probing Southern blots with a probe for Mu ends, pDTE1 (V. Chandler,
C. Rivin, and V. Walbot, Genetics 114:1007, 1986). While this insertion
is similar to Mu1 in size and HinFI restriction pattern,
this insertion contains a PvuII restriction site and does not exhibit
homology to an internal fragment of Mu1 (pA/B5; Chandler et al.,
1986) as indicated by Southern analysis. The insertion appears to be located
in the Kn1 locus within 250 bases of the site where a Ds2
insertion occurs to cause the knotted phenotype in another mutation, Kn1-2F11
(Hake et al., EMBO in press). The insertion and its flanking sequences
have been cloned and further analysis is in progress.
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