COLD SPRING HARBOR, NEW YORK

Cold Spring Harbor Lab

BERKELEY, CALIFORNIA1

University of California

A new Mu-induced suppressible mutation --J. Colasanti, M. Freeling1 and V. Sundaresan Recently a Mu-induced mutation at the hcf106 locus has been described which appears to be suppressed when Mu-activity is lost (Martienssen et al., EMBO J. 8:1633-1639, 1989). This raises the possibility that other Mu-induced mutations may also be suppressible by Mu inactivation. We have now found that this appears to be the case with a dwarf mutation isolated in a Mu stock. This mutant (MF 6316-21) arose in a self of a Mu outcross ear and was observed to segregate at less than 1 in 4 in this ear. In subsequent generations of selfing, the mutation disappeared altogether. DNA from the later generations was analyzed and the Mu1 elements were found to be methylated, suggesting that Mu activity was lost (Chandler and Walbot, PNAS 83:1761-1771, 1986; Bennetzen, MGG 208:45-51, 1987). During the winter of 1988, plants from this line were crossed to active Mu lines and the progeny were selfed this summer. The seeds from these selfs were planted. One out of 5 selfs screened so far have been found to segregate dwarf plants, at ratios of 1 in 4, suggesting that the mutation has been rescued by crossing to active Mu stocks. Therefore, the suppression phenomenon described for hcf106 may be representative of a whole class of Mu-induced mutations.

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