Selfing mutants link Ku proteins to mating type determination in Tetrahymena
Open Access
- 3 August 2020
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLoS Biology
- Vol. 18 (8), e3000756
- https://doi.org/10.1371/journal.pbio.3000756
Abstract
Recognition of self and nonself is important for outcrossing organisms, and different mating types establish the barrier against self-mating. In the unicellular ciliate T. thermophila, mating type determination requires complex DNA rearrangements at a single mat locus during conjugation to produce a type-specific gene pair (MTA and MTB) for 1 of 7 possible mating types. Surprisingly, we found that decreased expression of the DNA breakage-repair protein Ku80 at late stages of conjugation generated persistent selfing phenotype in the progeny. DNA analysis revealed multiple mating-type gene pairs as well as a variety of mis-paired, unusually arranged mating-type genes in these selfers that resemble some proposed rearrangement intermediates. They are found also in normal cells during conjugation and are lost after 10 fissions but are retained in Ku mutants. Silencing of TKU80 or TKU70-2 immediately after conjugation also generated selfing phenotype, revealing a hidden DNA rearrangement process beyond conjugation. Mating reactions between the mutant and normal cells suggest a 2-component system for self–nonself-recognition through MTA and MTB genes.Funding Information
- Ministry of Science and Technology, Taiwan (MOST 105-2311-B-001-057)
- Academia Sinica (Institute of Molecular Biology)
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