Unraveling the genetic basis of hybrid vigor

Division of Biological Sciences, University of Missouri, Columbia, 65211, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 09/2006; 103(35):12957-8. DOI: 10.1073/pnas.0605627103
Source: PubMed
Download full-text


Available from: James A Birchler,
24 Reads
  • Source
    • "A third genetic model, referred to as " pseudo-overdominance, " is actually a simple case of dominance complementation in which the two genes are linked and the increasing alleles are inherited in repulsion, i.e. each parent contributes one of the two increasing alleles at two different but genetically linked genes to the hybrid. This type of complementation in the hybrid resembles overdominance , because of the tight chromosomal linkage and the co-inheritance of these genes as a single one [1]. In fact, distinction between the overdominance and dominance models should give an indication of how much the specific heterozygosity, as opposed to overall heterozygosity (proportional to the genetic distance between parents of the hybrids), causes heterosis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The genomic makeup and phenotypes of plants are diversifying, in part due to artificial or natural selection in agricultural and natural environments. Utilization of these variations to enhance crop productivity requires an understanding of the relationships between genotype and phenotype in inbreds and hybrids derived from crosses between these populations. This review highlights recent studies on hybrid vigor (heterosis) and the related phenomenon of hybrid weakness - two types of non-additive inheritance. Heterosis is a phenomenon whereby the phenotype of first-generation hybrids is superior to that of their parents. Intralocus interactions between alleles, complementation of dominant alleles, or inter-loci epistatic interactions are genetic mechanisms that may cause non-additive phenotypic inheritance in hybrids. However, there are different views on what portion of the heterotic variation is modulated by each of these mechanisms. Another aspect of plant vigor is phenotypic stability or robustness in different environments and how this is influenced by gene heterozygosity. Hybrids are not necessarily more phenotypically stable than inbreds since local heterozygosity might be associated with negative effects on biochemical activities. This review integrates genetic and biochemical considerations to illustrate how these relationships may be tightly linked with breeding system and sequence divergence.
    Plant Science 12/2014; 232C. DOI:10.1016/j.plantsci.2014.11.014 · 3.61 Impact Factor
  • Source
    • "If overdominant loci are common, they should cause substantial reductions in fitness when organisms are inbred, and indeed, inbreeding depression is very common (Charlesworth & Charlesworth , 1987). However, data returning from long-term genetic studies of corn began to suggest that heterosis is caused more by pseudo-overdominance than genuine heterozygote advantage (Gardner, 1963; Moll et al., 1964; Crow, 1987; but also see Birchler et al., 2006). Here, pseudo-overdominance refers to elevated fitness in hybrids owing to complementation of recessive deleterious alleles at two closely linked genes (see Table 1 for definitions of some relevant terms). "
    [Show abstract] [Hide abstract]
    ABSTRACT: I. II. III. IV. V. VI. VII. VIII. References SUMMARY: Balancing selection refers to a variety of selective regimes that maintain advantageous genetic diversity within populations. We review the history of the ideas regarding the types of selection that maintain such polymorphism in flowering plants, notably heterozygote advantage, negative frequency-dependent selection, and spatial heterogeneity. One shared feature of these mechanisms is that whether an allele is beneficial or detrimental is conditional on its frequency in the population. We highlight examples of balancing selection on a variety of discrete traits. These include the well-referenced case of self-incompatibility and recent evidence from species with nuclear-cytoplasmic gynodioecy, both of which exhibit trans-specific polymorphism, a hallmark of balancing selection. We also discuss and give examples of how spatial heterogeneity in particular, which is often thought unlikely to allow protected polymorphism, can maintain genetic variation in plants (which are rooted in place) as a result of microhabitat selection. Lastly, we discuss limitations of the protected polymorphism concept for quantitative traits, where selection can inflate the genetic variance without maintaining specific alleles indefinitely. We conclude that while discrete-morph variation provides the most unambiguous cases of protected polymorphism, they represent only a fraction of the balancing selection at work in plants.
    New Phytologist 08/2013; 201(1). DOI:10.1111/nph.12441 · 7.67 Impact Factor
  • Source
    • "bred parents in more than one dimension ; for example , the hybrid may have an extended period of expres - sion , broader spatial distribution , or more adapted environ - ments than its inbred parents . The cumulative effects from such an allelic diversity may result in an overall non - allelic additive effect on hybrid performance and heterosis ( Birchler et al . 2006 ) . Vergeer et al . ( 2012 ) have recently provided intriguing results that may change our understanding of inbreeding depression and challenge the classical theory of how inbreeding depression evolves , and might give us clues to further studies ; the details are discussed in " Regulatory mechanism of ASE " ."
    [Show abstract] [Hide abstract]
    ABSTRACT: Although the majority of genes are expressed equally from both alleles, some genes are differentially expressed. Organisms possess characteristics to preferentially express a particular allele under regulatory factors, which is termed allele-specific expression (ASE). It is one of the important genetic factors that lead to phenotypic variation and can be used to identify the variance of gene regulation factors. ASE indicates mechanisms such as DNA methylation, histone modifications, and non-coding RNAs function. Here, we review a broad survey of progress in ASE studies, and what this simple yet very effective approach can offer in functional genomics, and possible implications toward our better understanding of the underlying mechanisms of complex traits.
    Journal of applied genetics 04/2013; 54(3). DOI:10.1007/s13353-013-0148-y · 1.48 Impact Factor
Show more