THE PLANT CELL, Vol 8, Issue 2 323-332, Copyright © 1996 by American Society of Plant Biologists
kurkku, a Phenotype of Acetabularia acetabulum That Is Arrested in Vegetative Growth, Can Be Rescued with Wild-Type Cytoplasm
D. F. Mandoli and B. E. Hunt
Department of Botany, Box 355325, University of Washington, Seattle, Washington 98195-5325
We isolated several spontaneous phenotypes in the giant unicell
Acetabularia acetabulum that have vegetative terminal morphologies. Because
they arrest in vegetative development, these cell lines are effectively
immortalized. However, they had to be rescued before they could be studied
via classical genetics because no heterozygotes from the original
self-crosses were found, that is, the wild-type siblings yielded only
wild-type progeny. We attempted to rescue these phenotypes in three ways:
by amputating the cell apex, by "piggybacking" the mutant nucleus through
development in a binucleate heterokaryon, and by replacing the abnormal
apex with a wild-type apex. We used one of our immortal cell lines, kurkku,
which has a terminal phenotype consistent with arrest early in the juvenile
phase of vegetative development, as a prototype for these rescue methods.
The kurkku phenotype segregated 1:3 in the original self-cross in which it
arose as if it were a single, recessive Mendelian trait. Although
amputation failed to rescue kurkku, we succeeded in compensating for the
defect both in binucleate heterokaryons and in apical grafts to wild-type
cells. kurkku was always recovered in the progeny of the self-crosses of
these grafts. These unique ways of analyzing vegetative mutants, combined
with the ability to then perform classical genetics, may make A. acetabulum
a powerful unicellular model system for the study of vegetative phase
change in plants.
