Programmed Minichromosome Elimination as a Mechanism for Somatic Genome Reduction in Tetrahymena thermophila.
The maintenance of chromosome integrity is crucial for genetic stability. However, programmed chromosome fragmentations are known to occur in many organisms, and in the ciliate Tetrahymena the five germline chromosomes are fragmented into hundreds of minichromosomes during somatic nuclear differentiation. Here, we showed that there are different fates of these minichromosomes after chromosome breakage. Among the 326 somatic minichromosomes identified using genomic data, 50 are selectively eliminated from the mature somatic genome. Interestingly, many and probably most of these minichromosomes are eliminated during the growth period between 6 and 20 doublings right after conjugation. Genes with potential conjugation-specific functions are found in these minichromosomes. This study revealed a new mode of programmed DNA elimination in ciliates similar to those observed in parasitic nematodes, which could play a role in developmental gene regulation.
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.|Genome and Systems Biology Degree Program, National Taiwan University, Taipei, Taiwan.
Chih-Yi Gabriela
http://orcid.org/0000-0003-0377-168X
CG
Lin
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
I-Ting
http://orcid.org/0000-0002-5458-4676
IT
Lin
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.|Genome and Systems Biology Degree Program, National Taiwan University, Taipei, Taiwan.
Meng-Chao
MC
Yao
D000818:Animals; D002467:Cell Nucleus / Q000235:genetics; D043171:Chromosomal Instability / Q000235:genetics; D019457:Chromosome Breakage; D002875:Chromosomes / Q000235:genetics*; D030541:Databases, Genetic; D015870:Gene Expression / Q000235:genetics; D015698:Genomic Library; D005854:Germ Cells / Q000254:growth & development; D016615:Telomere / Q000235:genetics*; D016808:Tetrahymena thermophila / Q000235:genetics* / Q000254:growth & development