RRC ID 31334
Author Satou Y, Hirayama K, Mita K, Fujie M, Chiba S, Yoshida R, Endo T, Sasakura Y, Inaba K, Satoh N.
Title Sustained heterozygosity across a self-incompatibility locus in an inbred ascidian.
Journal Mol. Biol. Evol.
Abstract Because self-incompatibility loci are maintained heterozygous and recombination within self-incompatibility loci would be disadvantageous, self-incompatibility loci are thought to contribute to structural and functional differentiation of chromosomes. Although the hermaphrodite chordate, Ciona intestinalis, has two self-incompatibility genes, this incompatibility system is incomplete and self-fertilization occurs under laboratory conditions. Here, we established an inbred strain of C. intestinalis by repeated self-fertilization. Decoding genome sequences of sibling animals of this strain identified a 2.4-Mbheterozygous region on chromosome 7. A self-incompatibility gene, Themis-B, was encoded within this region. This observation implied that this self-incompatibility locus and the linkage disequilibrium of its flanking region contribute to the formation of the 2.4-Mb heterozygous region, probably through recombination suppression. We showed that different individuals in natural populations had different numbers and different combinations of Themis-B variants, and that the rate of self-fertilization varied among these animals. Our result explains why self-fertilization occurs under laboratory conditions. It also supports the concept that the Themis-B locus is preferentially retained heterozygous in the inbred line and contributes to the formation of the 2.4-Mb heterozygous region. High structural variations might suppress recombination, and this long heterozygous region might represent a preliminary stage of structural differentiation of chromosomes.
Volume 32(1)
Pages 81-90
Published 2015-1
DOI 10.1093/molbev/msu268
PII msu268
PMID 25234703
MeSH Animals Animals, Inbred Strains / genetics* Animals, Inbred Strains / physiology Chromosomes Ciona intestinalis / genetics* Ciona intestinalis / physiology Genetic Loci Genetic Variation Heterozygote* Self-Fertilization Sequence Analysis, DNA
IF 10.217
Times Cited 1
C.intestinalis / (O.japonicus) Wild C. int