TRANSMISSION OF SURFACE PATTERN THROUGH A DEDIFFERENTIATED STAGE IN THE CILIATE PARAUROSTYLA - EVIDENCE FROM THE ANALYSIS OF MICROTUBULE AND BASAL BODY DEPLOYMENT

During conjugation of the hypotrich ciliate Paraurostyla weissei, the two partners fuse to form a transient dedifferentiated stage, the zygo cyst, which later redifferentiates into a vegetative cell. Immunocytoc hemical studies have been performed to follow the deployment of microt ubules and basal bodies during the entire cycle of conjugation. They s how that a superficial lattice persists during the whole zygocyst stag e, after most of the infraciliature of the exconjugants has been disas sembled. These superficial microtubules display different immunocytoch emical properties in the mature zygocyst and during its morphogenesis, suggesting that some transient chemical modifications of the microtub ules are associated with the morphogenetic activity. In the zygocyst, the superficial microtubules retain the specific orientation character istic of the ventral and the dorsal sides of the recipient cell, respe ctively. In the course of subsequent morphogenesis of the zygocyst, th ese specific cellular territories differentiate into the ventral and d orsal sides of the new cell. Although our experiments do not resolve t he question of whether superficial microtubules play an active or mere ly a passive role in the transmission of surface pattern, they show th at no complete breakdown in cell polarity occurs, even through a profo und dedifferentiated stage. Thus, the overall surface pattern appears to be retained, in a simplified form, through the conjugation cycle.