DEVELOPMENTALLY CONTROLLED REARRANGEMENT OF SURFACE PROTEIN GENES IN PARAMECIUM-TETRAURELIA

Early research on Paramecium genetics highlighted the: role of the cyt oplasm on inheritance. Today this tradition continues as recent invest igations of macronuclear development in Paramecium have revealed unusu al cytoplasmic effects that are not easily explained within current pa radigms. It is generally assumed that most programmed DNA rearrangemen ts in ciliates are regulated by cis acting signals encoded within the germline (micronuclear) DNA, but there are increasing examples in whic h the old macronucleus acts through the cytoplasm (in trans) to affect the loss and rearrangement of DNA in the developing macronucleus. The remarkable specificity of this effect has forced a reevaluation of th e standard view of macronuclear determination in Paramecium. This revi ew summarizes our knowledge of the effect of the old macronucleus on t he developmentally controlled rearrangements of the P. tetraurelia, st ock 51A and B variable surface protein genes.