PMID- 34739049
OWN - NLM
STAT- MEDLINE
DCOM- 20220216
LR  - 20221007
IS  - 1943-2631 (Electronic)
IS  - 0016-6731 (Print)
IS  - 0016-6731 (Linking)
VI  - 219
IP  - 4
DP  - 2021 Dec 10
TI  - Overt and concealed genetic loads revealed by QTL mapping of genotype-dependent 
      viability in the Pacific oyster Crassostrea gigas.
LID - 10.1093/genetics/iyab165 [doi]
LID - iyab165
AB  - Understanding the genetic bases of inbreeding depression, heterosis, and genetic 
      load is integral to understanding how genetic diversity is maintained in natural 
      populations. The Pacific oyster Crassostrea gigas, like many long-lived plants, 
      has high fecundity and high early mortality (type-III survivorship), manifesting 
      a large, overt, genetic load; the oyster harbors an even greater concealed 
      genetic load revealed by inbreeding. Here, we map viability QTL (vQTL) in six 
      interrelated F2 oyster families, using high-density linkage maps of single 
      nucleotide polymorphisms generated by genotyping-by-sequencing (GBS) methods. 
      Altogether, we detect 70 vQTL and provisionally infer 89 causal mutations, 11 to 
      20 per family. Genetic mortality caused by independent (unlinked) vQTL ranges 
      from 94.2% to 97.8% across families, consistent with previous reports. 
      High-density maps provide better resolution of genetic mechanisms, however. 
      Models of one causal mutation present in both identical-by-descent (IBD) 
      homozygotes and heterozygotes fit genotype frequencies at 37 vQTL; consistent 
      with the mutation-selection balance theory of genetic load, 20 are highly 
      deleterious, completely recessive mutations and 17 are less deleterious, 
      partially dominant mutations. Another 22 vQTL require pairs of recessive or 
      partially dominant causal mutations, half showing selection against recessive 
      mutations linked in repulsion, producing pseudo-overdominance. Only eight vQTL 
      appear to support the overdominance theory of genetic load, with deficiencies of 
      both IBD homozygotes, but at least four of these are likely caused by 
      pseudo-overdominance. Evidence for epistasis is absent. A high mutation rate, 
      random genetic drift, and pseudo-overdominance may explain both the oyster's 
      extremely high genetic diversity and a high genetic load maintained primarily by 
      mutation-selection balance.
CI  - (c) The Author(s) 2021. Published by Oxford University Press on behalf of Genetics 
      Society of America. All rights reserved. For permissions, please email: 
      journals.permissions@oup.com.
FAU - Yin, Xiaoshen
AU  - Yin X
AUID- ORCID: 0000-0002-2687-4473
AD  - Department of Biological Sciences, University of Southern California, Los 
      Angeles, CA 90089, USA.
FAU - Hedgecock, Dennis
AU  - Hedgecock D
AUID- ORCID: 0000-0002-3995-646X
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Genetics
JT  - Genetics
JID - 0374636
SB  - IM
MH  - Animals
MH  - Chromosome Mapping
MH  - Crassostrea/*genetics
MH  - Genetic Drift
MH  - *Genetic Load
MH  - Genotype
MH  - Genotyping Techniques
MH  - Homozygote
MH  - Mutation
MH  - Polymorphism, Single Nucleotide
MH  - Quantitative Trait Loci/*genetics
MH  - Selection, Genetic
PMC - PMC8664565
OTO - NOTNLM
OT  - classical and balance models of population genetic structure
OT  - mutation load
OT  - pseudo-overdominance
OT  - quantitative-trait loci
OT  - segregation load
EDAT- 2021/11/06 06:00
MHDA- 2022/02/17 06:00
PMCR- 2022/10/06
CRDT- 2021/11/05 12:16
PHST- 2021/06/23 00:00 [received]
PHST- 2021/09/19 00:00 [accepted]
PHST- 2021/11/06 06:00 [pubmed]
PHST- 2022/02/17 06:00 [medline]
PHST- 2021/11/05 12:16 [entrez]
PHST- 2022/10/06 00:00 [pmc-release]
AID - 6382310 [pii]
AID - iyab165 [pii]
AID - 10.1093/genetics/iyab165 [doi]
PST - ppublish
SO  - Genetics. 2021 Dec 10;219(4):iyab165. doi: 10.1093/genetics/iyab165.