Abstract
The genetic basis of hybrid vigor in plants remains largely unsolved but strong evidence suggests that variation in transcriptional regulation can explain many aspects of this phenomenon. Natural variation in transcriptional regulation is highly abundant in virtually all species and thus a potential source of heterotic variability. Allele Specific Expression (ASE), which is tightly linked to parent of origin effects and modulated by complex interactions in cis and in trans, is generally considered to play a key role in explaining the differences between hybrids and parental lines. Here we discuss the recent developments in elucidating the role of transcriptional variation in a number of aspects of hybrid vigor, thereby bridging old paradigms and hypotheses with contemporary research in various species.
Highlights
Hybrid vigor is the phenomenon of an improved performance of the progeny of a cross between two different parental genotypes over these genotypes
One way through which hybrid vigor is naturally fixed occurs in admixed populations, where optimal allele frequencies of heterotic loci are maintained by increased natural intercrossing of heterogeneous individuals with higher fitness (Oakley et al, 2015)
Changes in genome dosage involve an increase in chromosome numbers, usually caused by an abnormal meiosis leading to unreduced gametes
Summary
Hybrid vigor is the phenomenon of an improved performance of the progeny of a cross between two different parental genotypes over these genotypes. Many of the improved characteristics are directly related to plant physiology and adaptation or agriculturally important developmental and reproductive traits, such as growth vigor or seed yield. The mechanism of hybrid vigor has a major impact, both in evolution and agriculture. Hybrid vigor may lead to the formation of new species. Similar to intraspecific crosses, increased vigor in performance and reproductive traits is frequently observed after hybridization events between different allogamous species. Because phenotypic changes are caused by increased genetic heterogeneity in both cases, it is hypothesized that regulatory mechanisms may be similar. Some recently reported invasive plant species derived from combinations of heterozygous polyploids, and domesticated species such as wheat emerged from interspecific crosses and fixation by ploidy changes (Chen, 2010; Storme and Mason, 2014)
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