Functional Analysis of Deletion Derivatives of the Maize Transposon MuDR Delineates Roles for the MURA and MURB Proteins

The regulatory transposon of the Mutator system of transposable elements in maize is MuDR. MuDR elements produce two transcripts, from genes mudrA and mudrB, encoding proteins MURA and MURB, respectively. Like many other transposons, MuDR elements often undergo deletions, usually of internal sequences. Analysis of a deletion that is restricted to the region encoding MURB demonstrates that this gene is not required to cause excisions of a reporter element, although it may be required for transposition or suppression of suppressible alleles. Conversely, a derivative that lacks the region encoding MURA but that produces MURB is nonfunctional for all aspects of Mutator activity. Northern analysis of these derivatives reveals that each of the two transcripts can be independently transcribed, and analysis using an antibody specific for MURB reveals that mudrB transcript can also be successfully translated and its product appropriately localized in the absence of mudrA. A third deletion derivative provides evidence for a source of previously reported antisense transcript.