scholarly journals A segregating inversion generates fitness variation in a yellow monkeyflower (Mimulus guttatus) population

2015 ◽  
Author(s):  
John Kelly ◽  
John Willis ◽  
Young Wha Lee ◽  
Lila Fishman
Keyword(s):  
Inbreeding Depression ◽  
Pollen Viability ◽  
Chromosomal Rearrangements ◽  
Intermediate Frequency ◽  
Population Divergence ◽  
Mimulus Guttatus ◽  
Female Fitness ◽  
Recombination Suppression ◽  
F1 Hybrid ◽  
Divergence With Gene Flow

Polymorphic chromosomal rearrangements, which can bind together hundreds of genes into single genetic loci with diverse effects, are increasingly associated with local adaptation and speciation. They may also be an important component of genetic variation within populations. We genetically and phenotypically characterized a novel segregating inversion (inv6) in the Iron Mountain (IM) population of Mimulus guttatus (yellow monkeyflower). We first identified a region of recombination suppression in three F2 mapping populations resulting from crosses among IM plants; in each case, the F1 hybrid parent was heterozygous for a homogenous derived haplotype (inv6) across markers spanning over 4.2 Mb of Linkage Group 6. Genotype-phenotype associations in the three F2 populations demonstrated negative inv6 effects on male and female fitness components. In addition, inv6 carriers suffered a ~30% loss of pollen viability in the field. Despite these costs, inv6 exists at moderate and apparently stable frequency (~7%) in the natural population, suggesting counter-balancing fitness benefits that maintain the polymorphism. Across four years of monitoring in the field, inv6 had an overall significant positive effect on the seed production (lifetime female fitness) of carriers. This benefit was particularly strong in harsh years and may be mediated (in part) by strong positive inv6 effects on flower production. These data suggest that opposing fitness effects maintain an intermediate frequency, and as a consequence, inv6 generates inbreeding depression and high genetic variance. We discuss these findings in the context of theory about the genetic basis of inbreeding depression and the role for chromosomal rearrangements in population divergence with gene flow.

scholarly journals Quantifying the gender load: can population crosses reveal interlocus sexual conflict?

2006 ◽  
Vol 361 (1466) ◽  
pp. 363-374 ◽  
Author(s):  
Tristan A.F Long ◽  
Robert Montgomerie ◽  
Adam K Chippindale
Keyword(s):  
Sperm Competition ◽  
Sexual Conflict ◽  
Population Differentiation ◽  
Population Divergence ◽  
Mating Frequency ◽  
Female Reproduction ◽  
Female Fitness ◽  
Antagonistic Coevolution ◽  
The Cost ◽  
Sexually Antagonistic Coevolution

Six sister populations of Drosophila melanogaster kept under identical environmental conditions for greater than 600 generations were reciprocally crossed to investigate the incidence of population divergence in allopatry. Population crosses directly influenced fitness, mating frequency, and sperm competition patterns. Changes in both female remating rate and the outcome of male sperm competition (P 1 , P 2 ) in response to foreign males were consistent with intersexual coevolution. Moreover, seven of the 30 crosses between foreign mates resulted in significant reductions in female fitness, whereas two resulted in significant increases, compared to local matings. This tendency for foreign males to reduce female fitness may be interpreted as evidence for either sexually antagonistic coevolution or the disruption of mutualistic interactions. However, instances in which female fitness improved via cohabitation with foreign males may better reveal sexual conflict, signalling release from the cost of interacting with locally adapted males. By this metric, female reproduction in D. melanogaster is strongly constrained by local adaptation by males, a situation that would promote antagonistic coevolution between the sexes. We conclude that sexual selection can promote population differentiation in allopatry and that sexual conflict is likely to have played a role in population differentiation in this study system.

scholarly journals Evidence for the partial dominance of viability genes contributing to inbreeding depression in Mimulus guttatus.

Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 323-331
Author(s):  
Y B Fu ◽  
K Ritland
Keyword(s):  
Inbreeding Depression ◽  
Wild Plant ◽  
Mimulus Guttatus ◽  
Selfed Progeny ◽  
Partial Dominance ◽  
Complete Dominance ◽  
Model Free ◽  
Segregation Ratios ◽  
Marker Loci ◽  
In The Wild

Abstract The relative importance of different modes of gene expression of viability genes contributing to inbreeding depression was investigated in the wild plant, Mimulus guttatus. Viability genes were identified by self-fertilizing 31 outbred plants, each heterozygous for three to nine unlinked allozyme markers, and analyzing segregation ratios of selfed progeny at maturity for deviations from 1:2:1 ratios. In this study, 24 linkages of viability genes to marker loci were detected. To infer the nature of gene action for these viability genes, a "model-free" graphical method was developed that examines the "space" of segregation ratios allowed by each of seven selection models (i.e., overdominance, complete recessivity, partial recessivity, additivity, partial dominance, complete dominance and underdominance). Using this method, we found that, of 24 linkages detected, 18 were consistent with either partial dominance, complete dominance or underdominance. Six were consistent with either partial recessivity, complete recessivity or overdominance. This finding indicates that, in these chromosomal segments identified by allozyme markers, partial dominance plays the predominant role in inbreeding depression. This is inconsistent with either the dominance or overdominance hypotheses proposed to account for inbreeding depression.

scholarly journals Reproductive Cold Stress Tolerance in Sorghum F1 Hybrids is a Heterotic Trait

Agronomy ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 508
Author(s):  
André Schaffasz ◽  
Steffen Windpassinger ◽  
Rod Snowdon ◽  
Benjamin Wittkop
Keyword(s):  
Cold Stress ◽  
Cold Tolerance ◽  
Combining Ability ◽  
Pollen Viability ◽  
Field Trials ◽  
Hybrid Breeding ◽  
F1 Hybrids ◽  
F1 Hybrid ◽  
Poor Seed ◽  
High Heritability

The sensitivity of sorghum to pre-flowering cold stress, resulting in reduced pollen viability and poor seed set, is a major constraint for expanding growing areas into higher altitudes and latitudes. Nevertheless, compared to juvenile cold tolerance, reproductive cold tolerance in sorghum has received much less attention so far, and very little is known about its inheritance in F1-hybrids. We have composed a representative factorial (n = 49 experimental F1-hybrids) for a comprehensive study on heterosis and combining ability for crucial tolerance traits as spikelet fertility (panicle harvest index), seed yield and pollen viability, using field trials in stress- and control environments in Germany and Mexico as well as climate chamber experiments. Our results indicate a heterotic and rather dominant inheritance of reproductive cold tolerance in sorghum, with strong effects of female general combining ability (GCA) on F1-hybrid performance in our material. These findings, together with the comparatively low contribution of specific combining ability (SCA) effects and high heritability estimates, suggest that robust and efficient enhancement of reproductive cold tolerance is feasible via hybrid breeding.

scholarly journals The Saccharomyces cerevisiae Rad6 Postreplication Repair and Siz1/Srs2 Homologous Recombination-Inhibiting Pathways Process DNA Damage That Arises in asf1 Mutants

2009 ◽  
Vol 29 (19) ◽  
pp. 5226-5237 ◽  
Author(s):  
Ellen S. Kats ◽  
Jorrit M. Enserink ◽  
Sandra Martinez ◽  
Richard D. Kolodner
Keyword(s):  
Homologous Recombination ◽  
Genome Stability ◽  
Chromosomal Rearrangements ◽  
Nuclear Antigen ◽  
Recombination Suppression ◽  
Postreplication Repair ◽  
Gross Chromosomal Rearrangements ◽  
Translesion Bypass ◽  
The Relationship ◽  
Proliferating Cell

ABSTRACT The Asf1 and Rad6 pathways have been implicated in a number of common processes such as suppression of gross chromosomal rearrangements (GCRs), DNA repair, modification of chromatin, and proper checkpoint functions. We examined the relationship between Asf1 and different gene products implicated in postreplication repair (PRR) pathways in the suppression of GCRs, checkpoint function, sensitivity to hydroxyurea (HU) and methyl methanesulfonate (MMS), and ubiquitination of proliferating cell nuclear antigen (PCNA). We found that defects in Rad6 PRR pathway and Siz1/Srs2 homologous recombination suppression (HRS) pathway genes suppressed the increased GCR rates seen in asf1 mutants, which was independent of translesion bypass polymerases but showed an increased dependency on Dun1. Combining an asf1 deletion with different PRR mutations resulted in a synergistic increase in sensitivity to chronic HU and MMS treatment; however, these double mutants were not checkpoint defective, since they were capable of recovering from acute treatment with HU. Interestingly, we found that Asf1 and Rad6 cooperate in ubiquitination of PCNA, indicating that Rad6 and Asf1 function in parallel pathways that ubiquitinate PCNA. Our results show that ASF1 probably contributes to the maintenance of genome stability through multiple mechanisms, some of which involve the PRR and HRS pathways.

Marker-based inferences about fecundity genes contributing to inbreeding depression in Mimulus guttatus

Genome ◽  
1994 ◽  
Vol 37 (6) ◽  
pp. 1005-1010 ◽  
Author(s):  
Yong-Bi Fu ◽  
Kermit Ritland
Keyword(s):  
Genetic Markers ◽  
Inbreeding Depression ◽  
Phenotypic Variation ◽  
Mimulus Guttatus ◽  
Selfed Progeny ◽  
Partial Dominance ◽  
Number Of Genes ◽  
Isozyme Loci ◽  
Deleterious Genes

Eight unlinked isozyme loci were used as genetic markers to characterize fecundity genes contributing to inbreeding depression in two selfed progeny arrays of Mimulus guttatus. Five fecundity traits were measured. Six of eight marked chromosomal segments were significantly associated with the expression of these traits. The number of genes detected for five traits in two progeny arrays varied, with an average of 2.8 genes per trait. Individual segments explained 1.44–9.29%, and together accounted for 3.85–11.32%, of phenotypic variation. Of 20 significant associations, 10 could be interpreted as exhibiting partial dominance, 7 overdominance, 3 partial recessivity, and 0 underdominance. Significant pairwise epistasis was rare. The results of this study suggest that inbreeding depression is caused by many deleterious genes of relatively small, partially dominant effects.Key words: linkage, isozymes, QTLs, inbreeding depression, Mimulus guttatus.

scholarly journals Combining capacity and heterosis in eggplant hybrids under high temperatures

2019 ◽  
Vol 37 (3) ◽  
pp. 348-353
Author(s):  
Ricardo de N Valadares ◽  
Danieli A Nóbrega ◽  
Lilian B de Lima ◽  
Jordana Antônia dos S Silva ◽  
Ana Maria M dos Santos ◽  
...  
Keyword(s):  
High Temperatures ◽  
Combining Ability ◽  
Phenotypic Variability ◽  
Pollen Viability ◽  
Fixation Index ◽  
Gene Effects ◽  
F1 Hybrid ◽  
Fruit Length ◽  
Additive Gene Effects ◽  
Additive Gene

ABSTRACT The objective of this work was to estimate the combinatorial capacity and heterosis of eggplant hybrids under high temperature conditions. Seven genitors, twelve hybrid combinations, originated from a partial diallel, and the Ciça F1 hybrid, as control, were evaluated. The experiment was conducted under greenhouse conditions in randomized block design with four replications, from April to December 2017. The assessed traits related to high temperatures were pollen viability (PV) and fruit fixation index (FFI); the morphoagronomic traits were number of fruits per plant (NFP), fruit weight (FWe), production per plant (PP), fruit length (FL), fruit width (FWi), fruit length/width ratio (FLWR) and plant height (PH). The variance analysis showed greater participation of the additive gene effects in relation to the non-additive gene effects in most traits, except for PV. The genitors CNPH 141, CNPH 135, CNPH 109 and CNPH 51 stood out with favorable gene effects to obtain genotypes tolerant to high temperatures, since they present good general combining ability (GCA) for the traits FFI, NFP and PP. The 1x4 and 3x4 hybrids presented positive estimates for both GCA and specific combining ability (SCA), demonstrating a greater potential to be used in breeding to increase the FFI, NFP and PP, under high temperatures. The 1x4, 1x5 and 1x6 hybrids expressed positive heterosis for most analyzed traits. The 1x4 hybrid stood out for the highest averages for PV, FFI, NFP and PP. For FWe, FL, FWi and FLWR, both positive and negative heterosis were observed, as consequence of the phenotypic variability of the genitors for these traits and suggests the possibility of selection for different sizes and formats.

scholarly journals Extensive Recombination Suppression and Epistatic Selection Causes Chromosome-Wide Differentiation of a Selfish Sex Chromosome in Drosophila pseudoobscura

Genetics ◽  
2020 ◽  
Vol 216 (1) ◽  
pp. 205-226 ◽  
Author(s):  
Zachary L. Fuller ◽  
Spencer A. Koury ◽  
Christopher J. Leonard ◽  
Randee E. Young ◽  
Kobe Ikegami ◽  
...  
Keyword(s):  
Population Genetic ◽  
Sex Chromosome ◽  
Chromosomal Rearrangements ◽  
Comparative Genomic ◽  
Recombination Suppression ◽  
Mendelian Segregation ◽  
Multiple Alleles ◽  
Chromosome Inversions ◽  
Combined Action ◽  
The Right

Sex-Ratio (SR) chromosomes are selfish X-chromosomes that distort Mendelian segregation and are commonly associated with inversions. These chromosomal rearrangements suppress recombination with Standard (ST) X-chromosomes and are hypothesized to maintain multiple alleles important for distortion in a single large haplotype. Here, we conduct a multifaceted study of the multiply inverted Drosophila pseudoobscura SR chromosome to understand the evolutionary history, genetic architecture, and present-day dynamics that shape this enigmatic selfish chromosome. The D. pseudoobscura SR chromosome has three nonoverlapping inversions of the right arm of the metacentric X-chromosome: basal, medial, and terminal. We find that 23 of 29 Mb of the D. pseudoobscuraX-chromosome right arm is highly differentiated between the Standard and SR arrangements, including a 6.6 Mb collinear region between the medial and terminal inversions. Although crossing-over is heavily suppressed on this chromosome arm, we discover it is not completely eliminated, with measured rates indicating recombination suppression alone cannot explain patterns of differentiation or the near-perfect association of the three SR chromosome inversions in nature. We then demonstrate the ancient basal and medial inversions of the SR chromosome contain genes sufficient to cause weak distortion. In contrast, the younger terminal inversion cannot distort by itself, but contains at least one modifier gene necessary for full manifestation of strong sex chromosome distortion. By parameterizing population genetic models for chromosome-wide linkage disequilibrium with our experimental results, we infer that strong selection acts to maintain the near-perfect association of SR chromosome inversions in present-day populations. Based on comparative genomic analyses, direct recombination experiments, segregation distortion assays, and population genetic modeling, we conclude the combined action of suppressed recombination and strong, ongoing, epistatic selection shape the D. pseudoobscura SR arrangement into a highly differentiated chromosome.

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