CONJUGATION-SPECIFIC GENES IN THE CILIATE EUPLOTES-CRASSUS - GENE-EXPRESSION FROM THE OLD MACRONUCLEUS

Following mating or conjugation, the hypotrichous ciliate Euplotes cra ssus undergoes a massive genome reorganization process. While the natu re of the rearrangement events has been well studied, little is known concerning proteins that carry out such processes. As a means of ident ifying such proteins, differential screening of a developmental cDNA l ibrary, as well as construction of a cDNA subtraction library, was use d to isolate genes expressed only during sexual reproduction. Five dif ferent conjugation-specific genes have been identified that are maxima lly expressed early in conjugation, during the period of micronuclear meiosis, which is just prior to macronuclear development and the DNA r earrangement process. All five genes are retained in the mature macron ucleus. Micronuclear, macronuclear, and cDNA clones of one gene (conZA 7) have been sequenced, and the results indicate that the gene encodes a putative DNA binding protein. In addition, the presence of an inter nal eliminated sequence in the micronuclear copy of the conZA7 gene in dicates that this conjugation-specific gene is transcribed from the ol d macronucleus.