This chapter addresses genetic communication, the transfer of information from one generation to the next. We focus on the model ciliate, Tetrahymena. Communication in Tetrahymena involves communication between the organism and the environment, communication between organisms, and communication within the organism to distinguish self from non-self and germline from soma. Ciliates have a unique genomic structure, with two nuclei within the same cytoplasm, a large polyploid somatic nucleus and a smaller diploid germinal nucleus, both sharing the same genetic information. We will discuss how the structure of Tetrahymena’s genomes enables the expression of all possible combinations of alleles, and how it contributes to the silencing of genetic invaders (e.g. transposons). We will discuss how the genomic structure is maintained in a process that involves the coexistence of up to five nuclei in the same cytoplasm and the destruction of unneeded nuclei in a process called programmed nuclear death (PND) with analogies to autophagy and apoptosis.
