A possible dose-dependent inactivation of mutator (Mu) in maize

Summary

The maize mutator system (Mu) has previously been shown to increase the mutation frequency about 50-fold in plants that have been propagated by outcrossing. In this report, a series of Mu stocks has been produced in which there is a putative 2, 4, 8, 16-fold increases in Mu.

As the putative doses of Mu increase the mutation frequency first shows a dramatic increase, then levels off. In plants with a putative 8-fold increase in Mu, the mutation frequency drops dramatically. An even more precipitous drop is observed at the putative 16-fold level, which has a mutation frequency close to that of non-Mu stocks.

Hypotheses explaining these observations are considered, and tests of these hypotheses are proposed.