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Paczesniak D, Pellino M, Goertzen R, Guenter D, Jahnke S, Fischbach A, Lovell JT, Sharbel TF. Seed size, endosperm and germination variation in sexual and apomictic Boechera. FRONTIERS IN PLANT SCIENCE 2022; 13:991531. [PMID: 36466233 PMCID: PMC9716183 DOI: 10.3389/fpls.2022.991531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 10/26/2022] [Indexed: 06/17/2023]
Abstract
Asexual reproduction results in offspring that are genetically identical to the mother. Among apomictic plants (reproducing asexually through seeds) many require paternal genetic contribution for proper endosperm development (pseudogamous endosperm). We examined phenotypic diversity in seed traits using a diverse panel of sexual and apomictic accessions from the genus Boechera. While genetic uniformity resulting from asexual reproduction is expected to reduce phenotypic diversity in seeds produced by apomictic individuals, pseudogamous endosperm, variable endosperm ploidy, and the deviations from 2:1 maternal:paternal genome ratio in endosperm can all contribute to increased phenotypic diversity among apomictic offspring. We characterized seed size variation in 64 diploid sexual and apomictic (diploid and triploid) Boechera lineages. In order to find out whether individual seed size was related to endosperm ploidy we performed individual seed measurements (projected area and mass) using the phenoSeeder robot system and flow cytometric seed screen. In order to test whether individual seed size had an effect on resulting fitness we performed a controlled growth experiment and recorded seedling life history traits (germination success, germination timing, and root growth rate). Seeds with triploid embryos were 33% larger than those with diploid embryos, but no average size difference was found between sexual and apomictic groups. We identified a maternal effect whereby chloroplast lineage 2 had 30% larger seeds than lineage 3, despite having broad and mostly overlapping geographic ranges. Apomictic seeds were not more uniform in size than sexual seeds, despite genetic uniformity of the maternal gametophyte in the former. Among specific embryo/endosperm ploidy combinations, seeds with tetraploid (automomous) endosperm were on average smaller, and the proportion of such seeds was highest in apomicts. Larger seeds germinated more quickly than small seeds, and lead to higher rates of root growth in young seedlings. Seed mass is under balancing selection in Boechera, and it is an important predictor of several traits, including germination probability and timing, root growth rates, and developmental abnormalities in apomictic accessions.
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Affiliation(s)
- Dorota Paczesniak
- Global Institute for Food Security (GIFS), University of Saskatchewan, Saskatoon, SK, Canada
- Breeding Research, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
| | - Marco Pellino
- Global Institute for Food Security (GIFS), University of Saskatchewan, Saskatoon, SK, Canada
- Breeding Research, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
| | - Richard Goertzen
- Global Institute for Food Security (GIFS), University of Saskatchewan, Saskatoon, SK, Canada
| | - Devan Guenter
- Global Institute for Food Security (GIFS), University of Saskatchewan, Saskatoon, SK, Canada
| | - Siegfried Jahnke
- Forschungszentrum Jülich, Institute of Bio- and Geosciences, IBG-2: Plant Sciences, Jülich, Germany
| | - Andreas Fischbach
- Forschungszentrum Jülich, Institute of Bio- and Geosciences, IBG-2: Plant Sciences, Jülich, Germany
| | - John T. Lovell
- Breeding Research, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
| | - Timothy F. Sharbel
- Global Institute for Food Security (GIFS), University of Saskatchewan, Saskatoon, SK, Canada
- Breeding Research, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany
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Rushworth CA, Wagner MR, Mitchell-Olds T, Anderson JT. The Boechera model system for evolutionary ecology. AMERICAN JOURNAL OF BOTANY 2022; 109:1939-1961. [PMID: 36371714 DOI: 10.1002/ajb2.16090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 08/27/2022] [Accepted: 08/30/2022] [Indexed: 06/16/2023]
Abstract
Model systems in biology expand the research capacity of individuals and the community. Closely related to Arabidopsis, the genus Boechera has emerged as an important ecological model owing to the ability to integrate across molecular, functional, and eco-evolutionary approaches. Boechera species are broadly distributed in relatively undisturbed habitats predominantly in western North America and provide one of the few experimental systems for identification of ecologically important genes through genome-wide association studies and investigations of selection with plants in their native habitats. The ecologically, evolutionarily, and agriculturally important trait of apomixis (asexual reproduction via seeds) is common in the genus, and field experiments suggest that abiotic and biotic environments shape the evolution of sex. To date, population genetic studies have focused on the widespread species B. stricta, detailing population divergence and demographic history. Molecular and ecological studies show that balancing selection maintains genetic variation in ~10% of the genome, and ecological trade-offs contribute to complex trait variation for herbivore resistance, flowering phenology, and drought tolerance. Microbiome analyses have shown that host genotypes influence leaf and root microbiome composition, and the soil microbiome influences flowering phenology and natural selection. Furthermore, Boechera offers numerous opportunities for investigating biological responses to global change. In B. stricta, climate change has induced a shift of >2 weeks in the timing of first flowering since the 1970s, altered patterns of natural selection, generated maladaptation in previously locally-adapted populations, and disrupted life history trade-offs. Here we review resources and results for this eco-evolutionary model system and discuss future research directions.
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Affiliation(s)
| | - Maggie R Wagner
- Department of Ecology and Evolutionary Biology, Kansas Biological Survey and Center for Ecological Research, University of Kansas, Lawrence, KS, 66045, USA
| | | | - Jill T Anderson
- Department of Genetics and Odum School of Ecology, University of Georgia, Athens, GA, 30602, USA
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Orive ME, Krueger-Hadfield SA. Sex and Asex: A Clonal Lexicon. J Hered 2020; 112:1-8. [PMID: 33336685 DOI: 10.1093/jhered/esaa058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 12/15/2020] [Indexed: 01/05/2023] Open
Abstract
Organisms across the tree of life have complex life cycles that include both sexual and asexual reproduction or that are obligately asexual. These organisms include ecologically dominant species that structure many terrestrial and marine ecosystems, as well as many pathogens, pests, and invasive species. We must consider both the evolution and maintenance of these various reproductive modes and how these modes shape the genetic diversity, adaptive evolution, and ability to persist in the species that exhibit them. Thus, having a common framework is a key aspect of understanding the biodiversity that shapes our planet. In the 2019 AGA President's Symposium, Sex and Asex: The genetics of complex life cycles, researchers investigating a wide range of taxonomic models and using a variety of modes of investigation coalesced around a common theme-understanding not only how such complex life cycles may evolve, but how they are shaped by the evolutionary and ecological forces around them. In this introduction to the Special Issue from the symposium, we give an overview of some of the key ideas and areas of investigation (a common clonal lexicon, we might say) and introduce the breadth of work submitted by symposium participants.
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Affiliation(s)
- Maria E Orive
- Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045
| | - Stacy A Krueger-Hadfield
- Department of Biology, University of Alabama, Birmingham, 1300 University Blvd., Birmingham, AL 35294
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Rushworth CA, Brandvain Y, Mitchell‐Olds T. Identifying the fitness consequences of sex in complex natural environments. Evol Lett 2020; 4:516-529. [PMID: 33312687 PMCID: PMC7719549 DOI: 10.1002/evl3.194] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 08/14/2020] [Accepted: 08/24/2020] [Indexed: 02/06/2023] Open
Abstract
In the natural world, sex prevails, despite its costs. Although much effort has been dedicated to identifying the intrinsic costs of sex (e.g., the cost of males), few studies have identified the ecological fitness consequences of sex. Furthermore, correlated biological traits that differ between sexuals and asexuals may alter these costs, or even render the typical costs of sex irrelevant. We conducted a large-scale, multisite, reciprocal transplant using multiple sexual and asexual genotypes of a native North American wildflower to show that sexual genotypes have reduced lifetime fitness, despite lower herbivory. We separated the effects of sex from those of hybridity, finding that overwinter survival is elevated in asexuals regardless of hybridity, but herbivores target hybrid asexuals more than nonhybrid asexual or sexual genotypes. Survival is lowest in homozygous sexual lineages, implicating inbreeding depression as a cost of sex. Our results show that the consequences of sex are shaped not just by sex itself, but by complex natural environments, correlated traits, and the identity and availability of mates.
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Affiliation(s)
- Catherine A. Rushworth
- Department of Evolution and EcologyUniversity of California, DavisDavisCalifornia95616
- University and Jepson HerbariaUniversity of California, BerkeleyBerkeleyCalifornia94720
- Department of Plant and Microbial BiologyUniversity of MinnesotaSt. PaulMinnesota55108
- Department of BiologyDuke UniversityDurhamNorth Carolina27708
| | - Yaniv Brandvain
- Department of Plant and Microbial BiologyUniversity of MinnesotaSt. PaulMinnesota55108
| | - Tom Mitchell‐Olds
- Department of BiologyDuke UniversityDurhamNorth Carolina27708
- Center for Genomic and Computational BiologyDuke UniversityDurhamNorth Carolina27708
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