Mutator-suppressible alleles of rough sheath1 and liguleless3 in maize reveal multiple mechanisms for suppression

Insertions of Mutator transposons into maize genes can generate suppressibl e alleles. Mu suppression is when, in the absence of Mu activity, the pheno type of a mutant allele reverts to that of its progenitor. Here we present the characterization of five dominant Mu-suppressible alleles of the knox ( knotted1-like homeobox) genes liguleless and rough sheath1, which exhibit n eomorphic phenotypes in the leaves. RNA blot analysis suggests that Mu supp ression affects only the neomorphic aspect of the allele, not the wild-type aspect. Additionally, Mu suppression appears to be exerting its effects at the level of transcription or transcript accumulation. We show that trunca ted transcripts are produced by three alleles, implying a mechanism for Mu suppression of 5' untranslated region insertion alleles distinct fr om that which has been described previously. Additionally, it is found that Mu sup pression can be caused by at least three different types of Mutator element s. Evidence preserved here suggests that whether an allele is suppressible or not may depend upon the site of insertion. We rite precious work on the knox gene kn1, and discuss our results in the context of inter-actions betw een Mu-encoded products and the inherently negative regulation of neomorphi c liguleless3 and rough sheath1 transcription.