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Ekrt L, Férová A, Koutecký P, Vejvodová K, Hori K, Hornych O. An adventurous journey toward and away from fern apomixis: Insights from genome size and spore abortion patterns. AMERICAN JOURNAL OF BOTANY 2024; 111:e16332. [PMID: 38762794 DOI: 10.1002/ajb2.16332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Revised: 03/14/2024] [Accepted: 03/15/2024] [Indexed: 05/20/2024]
Abstract
PREMISE Apomixis in ferns is relatively common and obligatory. Sterile hybrids may restore fertility via apomixis at a cost of long-term genetic stagnation. In this study, we outlined apomixis as a possible temporary phase leading to sexuality and analyzed factors relating to transitioning to and away from apomixis, such as unreduced and reduced spore formation in apomict and apo-sex hybrid ferns. METHODS We analyzed the genome size of 15 fern species or hybrids ("taxa") via flow cytometry. The number of reduced and unreduced gametophytes was established as a proxy for viable spore formation of either type. We also calculated the spore abortion ratio (sign of reduced spores) in several taxa, including the apo-sex hybrid Dryopteris × critica and its 16 apomictically formed offspring. RESULTS Four of 15 sampled taxa yielded offspring variable in genome size. Specifically, each variable taxon formed one viable reduced plant among 12-451 sampled gametophytes per taxon. Thus, haploid spore formation in the studied apomicts was very rare but possible. Spore abortion analyses indicated gradually decreasing abortion (haploid spore formation) over time. In Dryopteris × critica, abortion decreased from 93.8% to mean 89.5% in one generation. CONCLUSIONS Our results support apomixis as a transitionary phase toward sexuality. Newly formed apomicts hybridize with sexual relatives and continue to form haploid spores early on. Thus, they may get the genomic content necessary for regular meiosis and restore sexuality. If the missing relative goes extinct, the lineage gets locked into apomixis as may be the case with the Dryopteris affinis complex.
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Affiliation(s)
- Libor Ekrt
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Alžběta Férová
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Petr Koutecký
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Kateřina Vejvodová
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Kiyotaka Hori
- The Kochi Prefectural Makino Botanical Garden, Godaisan 4200-6, Kochi, 781-8125, Japan
| | - Ondřej Hornych
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
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Wefferling KM, Castro M, Castro S, Holmlund H, Loureiro J, Rothfels CJ, Schuettpelz E. Polyploid goldback and silverback ferns (Pentagramma) occupy a wider, colder, and wetter bioclimatic niche than diploid counterparts. AMERICAN JOURNAL OF BOTANY 2024; 111:e16305. [PMID: 38517199 DOI: 10.1002/ajb2.16305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 01/22/2024] [Accepted: 01/22/2024] [Indexed: 03/23/2024]
Abstract
PREMISE The western North American fern genus Pentagramma (Pteridaceae) is characterized by complex patterns of ploidy variation, an understanding of which is critical to comprehending both the evolutionary processes within the genus and its current diversity. METHODS We undertook a cytogeographic study across the range of the genus, using a combination of chromosome counts and flow cytometry to infer ploidy level. Bioclimatic variables and elevation were used to compare niches. RESULTS We found that diploids and tetraploids are common and widespread, and triploids are rare and sporadic; in contrast with genome size inferences in earlier studies, no hexaploids were found. Diploids and tetraploids show different geographic ranges: only tetraploids were found in the northernmost portion of the range (Washington, Oregon, and British Columbia) and only diploids were found in the Sierra Nevada of California. Diploid, triploid, and tetraploid cytotypes were found to co-occur in relatively few localities: in the southern (San Diego County, California) and desert Southwest (Arizona) parts of the range, and along the Pacific Coast of California. CONCLUSIONS Tetraploids occupy a wider bioclimatic niche than diploids both within P. triangularis and at the genus-wide scale. It is unknown whether the wider niche of tetraploids is due to their expansion upon the diploid niche, if diploids have contracted their niche due to competition or changing abiotic conditions, or if this wider niche occupancy is due to multiple origins of tetraploids.
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Affiliation(s)
- Keir M Wefferling
- Department of Biology, Gary A. Fewless Herbarium, Cofrin Center for Biodiversity, University of Wisconsin-Green Bay, Green Bay, 54311, Wisconsin, USA
| | - Mariana Castro
- Department of Life Sciences, Centre for Functional Ecology, University of Coimbra, Coimbra, Portugal
| | - Sílvia Castro
- Department of Life Sciences, Centre for Functional Ecology, University of Coimbra, Coimbra, Portugal
| | - Helen Holmlund
- Natural Science Division, Pepperdine University, Malibu, 90263, California, USA
| | - João Loureiro
- Department of Life Sciences, Centre for Functional Ecology, University of Coimbra, Coimbra, Portugal
| | - Carl J Rothfels
- Department of Biology, Ecology Center, and Intermountain Herbarium, Utah State University, Logan, 84322, Utah, USA
| | - Eric Schuettpelz
- Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, 20560, DC, USA
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Ptáček J, Ekrt L, Hornych O, Urfus T. Interploidy gene flow via a 'pentaploid bridge' and ploidy reduction in Cystopteris fragilis fern complex (Cystopteridaceae: Polypodiales). PLANT REPRODUCTION 2023; 36:321-331. [PMID: 37532893 DOI: 10.1007/s00497-023-00476-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 07/15/2023] [Indexed: 08/04/2023]
Abstract
KEY MESSAGE Our results indicate the existence of interploidy gene flow in Cystopteris fragilis, resulting in sexual triploid and diploid gametophytes from pentaploid parents. Similar evolutionary dynamics might operate in other fern complexes and need further investigation. Polyploidization and hybridization are a key evolutionary processes in ferns. Here, we outline an interploidy gene flow pathway operating in the polyploid Cystopteris fragilis complex. The conditions necessary for the existence of this pathway were tested. A total of 365 C. fragilis individuals were collected covering representatives of all three predominant ploidy levels (tetraploid, pentaploid, and hexaploid), cultivated, had their ploidy level estimated by flow cytometry, and their spores collected. The spores, as well as gametophytes and sporophytes established from them, were analysed by flow cytometry. Spore abortion rate was also estimated. In tetraploids, we observed the formation of unreduced (tetraploid) spores (ca 2%). Collected pentaploid individuals indicate ongoing hybridization between ploidy levels. Pentaploids formed up to 52% viable spores, ca 79% of them reduced, i.e. diploid and triploid. Reduced spores formed viable gametophytes, and, in the case of triploids, filial hexaploid sporophytes, showing evidence of sexual reproduction. Some tetraploid sporophytes reproduce apomictically (based on uniform ploidy of their metagenesis up to filial sporophytes). Triploid and diploid gametophytes from pentaploid parents are able to mate among themselves, or with "normal" reduced gametophytes from the sexual tetraploid sporophytes (the dominant ploidy level in the sporophytes in this populations), to produce tetraploid, pentaploid, and hexaploid sporophytes, allowing for geneflow from the pentaploids to both the tetraploid and hexaploid populations. Similar evolutionary dynamics might operate in other fern complexes and need further investigation.
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Affiliation(s)
- Jan Ptáček
- Department of Botany, Faculty of Science, Charles University, Benátská 2, , 128 00, Praha, Czech Republic
| | - Libor Ekrt
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic
| | - Ondřej Hornych
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czech Republic
| | - Tomáš Urfus
- Department of Botany, Faculty of Science, Charles University, Benátská 2, , 128 00, Praha, Czech Republic.
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Hornych O, Férová A, Hori K, Košnar J, Ekrt L. Apomictic fern fathers: an experimental approach to the reproductive characteristics of sexual, apomict, and hybrid fern gametophytes. AMERICAN JOURNAL OF BOTANY 2022; 109:628-644. [PMID: 35072270 DOI: 10.1002/ajb2.1817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 01/05/2022] [Accepted: 01/13/2022] [Indexed: 06/14/2023]
Abstract
PREMISE Apomixis and hybridization are two essential and complementary factors in the evolution of plants, including ferns. Hybridization combines characteristics from different species, while apomixis conserves features within a lineage. When combined, these two processes result in apo-sex hybrids. The conditions leading to the formation of these hybrids are poorly understood in ferns. METHODS We cultivated spores from 66 fern samples (43 apomicts, 7 apo-sex hybrids, and 16 sexuals), and measured their development in vitro over 16 weeks. We evaluated germination, lateral meristem formation rates, sexual expression, and production of sporophytes and then compared ontogenetic patterns among the three groups. RESULTS The three examined groups formed antheridia (male gametangia) but differed in overall gametophyte development. Sexual species created archegonia (female, 86% of viable samples), but no sporophytes. Apomicts rarely created nonfunctional archegonia (8%) but usually produced apogamous sporophytes (75%). Surprisingly, apomictic and sexual species showed similar development speed. The sexually reproducing parents of viable studied hybrids formed about twice as many meristic gametophytes as the apomictic parents (39% vs. 20%, respectively). CONCLUSIONS We present the most thorough comparison of gametangial development of sexual and apomictic ferns, to date. Despite expectations, apomictic reproduction might not lead to earlier sporophyte formation. Apomicts produce functional sperm and thus can contribute this type of gamete to their hybrids. The development patterns found in the parents of hybrids indicate a possible increase of hybridization rates by antheridiogens. The apo-sex hybrids always inherit the apomictic reproductive strategy and are thus capable of self-perpetuation.
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Affiliation(s)
- Ondřej Hornych
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Alžběta Férová
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Kiyotaka Hori
- The Kochi prefectural Makino Botanical Garden, Godaisan 4200-6, Kochi, 781-8125, Japan
| | - Jiří Košnar
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Libor Ekrt
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
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Hornych O, Černochová L, Lisner A, Ekrt L. An experimental assessment of competitive interactions between sexual and apomictic fern gametophytes using Easy Leaf Area. APPLICATIONS IN PLANT SCIENCES 2022; 10:e11466. [PMID: 35495190 PMCID: PMC9039791 DOI: 10.1002/aps3.11466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 01/25/2022] [Accepted: 01/31/2022] [Indexed: 05/14/2023]
Abstract
PREMISE Few studies have explored competition in fern gametophyte populations. One limiting factor is the tedious measurement of gametophyte size as a proxy for biomass in these small plants. Here, an alternative approach of estimating the number of green pixels from photos was employed to measure the competitive interactions among apomictic and sexual Dryopteris gametophytes. METHODS We cultivated the gametophytes of two apomictic (diploid and triploid) and one sexual (tetraploid) Dryopteris species in monocultures and in two-species mixtures in the ratios 1 : 1 and 1 : 3. The total gametophyte cover of each population originating from 20 spores was assessed using Easy Leaf Area. Assessments were performed weekly between weeks 4 and 10 of cultivation. Additionally, during week 5, the cover of each species in each mixture was estimated separately. RESULTS We identified a positive correlation between gametophyte size and ploidy level as well as sexual reproduction. The performance of the tested species in mixtures was dependent on the competitor species identity, indicating the importance of competition between gametophytes. DISCUSSION The methods outlined can be used for a rapid assessment of fern gametophyte cover in large gametophyte populations. Ploidy level and reproduction type seem to play a major role in the competitive abilities of fern gametophytes, but more research is needed on this topic.
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Affiliation(s)
- Ondřej Hornych
- Department of Botany, Faculty of ScienceUniversity of South BohemiaBranišovská 1760, České Budějovice, CZ‐37005Czech Republic
| | - Lucie Černochová
- Department of Botany, Faculty of ScienceUniversity of South BohemiaBranišovská 1760, České Budějovice, CZ‐37005Czech Republic
| | - Aleš Lisner
- Department of Botany, Faculty of ScienceUniversity of South BohemiaBranišovská 1760, České Budějovice, CZ‐37005Czech Republic
| | - Libor Ekrt
- Department of Botany, Faculty of ScienceUniversity of South BohemiaBranišovská 1760, České Budějovice, CZ‐37005Czech Republic
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Fernández H, Grossmann J, Gagliardini V, Feito I, Rivera A, Rodríguez L, Quintanilla LG, Quesada V, Cañal MJ, Grossniklaus U. Sexual and Apogamous Species of Woodferns Show Different Protein and Phytohormone Profiles. FRONTIERS IN PLANT SCIENCE 2021; 12:718932. [PMID: 34868105 PMCID: PMC8633544 DOI: 10.3389/fpls.2021.718932] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 09/23/2021] [Indexed: 06/13/2023]
Abstract
The gametophyte of ferns reproduces either by sexual or asexual means. In the latter, apogamy represents a peculiar case of apomixis, in which an embryo is formed from somatic cells. A proteomic and physiological approach was applied to the apogamous fern Dryopteris affinis ssp. affinis and its sexual relative D. oreades. The proteomic analysis compared apogamous vs. female gametophytes, whereas the phytohormone study included, in addition to females, three apogamous stages (filamentous, spatulate, and cordate). The proteomic profiles revealed a total of 879 proteins and, after annotation, different regulation was found in 206 proteins of D. affinis and 166 of its sexual counterpart. The proteins upregulated in D. affinis are mostly associated to protein metabolism (including folding, transport, and proteolysis), ribosome biogenesis, gene expression and translation, while in the sexual counterpart, they account largely for starch and sucrose metabolism, generation of energy and photosynthesis. Likewise, ultra-performance liquid chromatography-tandem spectrometry (UHPLC-MS/MS) was used to assess the levels of indol-3-acetic acid (IAA); the cytokinins: 6-benzylaminopurine (BA), trans-Zeatine (Z), trans-Zeatin riboside (ZR), dyhidrozeatine (DHZ), dyhidrozeatin riboside (DHZR), isopentenyl adenine (iP), isopentenyl adenosine (iPR), abscisic acid (ABA), the gibberellins GA3 and GA4, salicylic acid (SA), and the brassinosteroids: brassinolide (BL) and castasterone (CS). IAA, the cytokinins Z, ZR, iPR, the gibberellin GA4, the brassinosteoids castasterone, and ABA accumulated more in the sexual gametophyte than in the apogamous one. When comparing the three apogamous stages, BA and SA peaked in filamentous, GA3 and BL in spatulate and DHRZ in cordate gametophytes. The results point to the existence of large metabolic differences between apogamous and sexual gametophytes, and invite to consider the fern gametophyte as a good experimental system to deepen our understanding of plant reproduction.
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Affiliation(s)
- Helena Fernández
- Area of Plant Physiology, Department of Organisms and Systems Biology, Oviedo University, Oviedo, Spain
| | - Jonas Grossmann
- Functional Genomics Center, Zurich, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Valeria Gagliardini
- Department of Plant and Microbial Biology & Zurich and Basel Plant Science Center, University of Zurich, Zurich, Switzerland
| | - Isabel Feito
- Servicio Regional de Investigación y Desarrollo Agroalimentario (SERIDA), Finca Experimental La Mata, Grado, Spain
| | - Alejandro Rivera
- Area of Plant Physiology, Department of Organisms and Systems Biology, Oviedo University, Oviedo, Spain
| | - Lucía Rodríguez
- Servicio Regional de Investigación y Desarrollo Agroalimentario (SERIDA), Finca Experimental La Mata, Grado, Spain
| | - Luis G. Quintanilla
- Department of Biology and Geology, Physics and Inorganic Chemistry, Rey Juan Carlos University, Móstoles, Spain
| | - Víctor Quesada
- Department of Biochemistry and Molecular Biology, Institute of Oncology of the Principality of Asturias, Oviedo University, Móstoles, Spain
| | - Mª Jesús Cañal
- Area of Plant Physiology, Department of Organisms and Systems Biology, Oviedo University, Oviedo, Spain
| | - Ueli Grossniklaus
- Department of Plant and Microbial Biology & Zurich and Basel Plant Science Center, University of Zurich, Zurich, Switzerland
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Grusz AL, Windham MD, Picard KT, Pryer KM, Schuettpelz E, Haufler CH. A drought-driven model for the evolution of obligate apomixis in ferns: evidence from pellaeids (Pteridaceae). AMERICAN JOURNAL OF BOTANY 2021; 108:263-283. [PMID: 33624306 DOI: 10.1002/ajb2.1611] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 01/20/2021] [Indexed: 06/12/2023]
Abstract
PREMISE Xeric environments impose major constraints on the fern life cycle, yet many lineages overcome these limitations by evolving apomixis. Here, we synthesize studies of apomixis in ferns and present an evidence-based model for the evolution and establishment of this reproductive strategy, focusing on genetic and environmental factors associated with its two defining traits: the production of "unreduced" spores (n = 2n) and the initiation of sporophytes from gametophyte tissue (i.e., diplospory and apogamy, respectively). METHODS We evaluated existing literature in light of the hypothesis that abiotic characteristics of desert environments (e.g., extreme diurnal temperature fluctuations, high light intensity, and water limitation) drive the evolution of obligate apomixis. Pellaeid ferns (Cheilanthoideae: Pteridaceae) were examined in detail, as an illustrative example. We reconstructed a plastid (rbcL, trnG-trnR, atpA) phylogeny for the clade and mapped reproductive mode (sexual versus apomictic) and ploidy across the resulting tree. RESULTS Our six-stage model for the evolution of obligate apomixis in ferns emphasizes the role played by drought and associated abiotic conditions in the establishment of this reproductive approach. Furthermore, our updated phylogeny of pellaeid ferns reveals repeated origins of obligate apomixis and shows an increase in the frequency of apomixis, and rarity of sexual reproduction, among taxa inhabiting increasingly dry North American deserts. CONCLUSIONS Our findings reinforce aspects of other evolutionary, physiological, developmental, and omics-based studies, indicating a strong association between abiotic factors and the establishment of obligate apomixis in ferns. Water limitation, in particular, appears critical to establishment of this reproductive mode.
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Affiliation(s)
- Amanda L Grusz
- Department of Biology, University of Minnesota Duluth, Duluth, MN, 55812, USA
| | | | - Kathryn T Picard
- Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, D.C., 20013, USA
| | | | - Eric Schuettpelz
- Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, D.C., 20013, USA
| | - Christopher H Haufler
- Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, 66045, USA
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Hornych O, Testo WL, Sessa EB, Watkins JE, Campany CE, Pittermann J, Ekrt L. Insights into the evolutionary history and widespread occurrence of antheridiogen systems in ferns. THE NEW PHYTOLOGIST 2021; 229:607-619. [PMID: 32740926 PMCID: PMC7754499 DOI: 10.1111/nph.16836] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 07/21/2020] [Indexed: 05/23/2023]
Abstract
Sex expression of homosporous ferns is controlled by multiple factors, one being the antheridiogen system. Antheridiogens are pheromones released by sexually mature female fern gametophytes, turning nearby asexual gametophytes precociously male. Nevertheless, not all species respond. It is still unknown how many fern species use antheridiogens, how the antheridiogen system evolved, and whether it is affected by polyploidy and/or apomixis. We tested the response of 68 fern species to antheridiogens in cultivation. These results were combined with a comprehensive review of literature to form the largest dataset of antheridiogen interactions to date. Analyzed species also were coded as apomictic or sexual and diploid or polyploid. Our final dataset contains a total of 498 interactions involving 208 species (c. 2% of all ferns). About 65% of studied species respond to antheridiogen. Multiple antheridiogen types were delimited and their evolution is discussed. Antheridiogen responsiveness was not significantly affected by apomixis or polyploidy. Antheridiogens are widely used by ferns to direct sex expression. The antheridiogen system likely evolved multiple times and provides homosporous ferns with the benefits often associated with heterospory, such as increased rates of outcrossing. Despite expectations, antheridiogens may be beneficial to polyploids and apomicts.
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Affiliation(s)
- Ondřej Hornych
- Department of BotanyFaculty of ScienceUniversity of South BohemiaBranišovská 1760České BudějoviceCZ37005Czech Republic
| | - Weston L. Testo
- Department of BiologyUniversity of FloridaBox 118525GainesvilleFL32611USA
| | - Emily B. Sessa
- Department of BiologyUniversity of FloridaBox 118525GainesvilleFL32611USA
| | - James E. Watkins
- Department of BiologyColgate University13 Oak Drive HamiltonHamiltonNY13346USA
| | | | - Jarmila Pittermann
- Department of Ecology and Evolutionary BiologyUniversity of CaliforniaSanta CruzCA95060USA
| | - Libor Ekrt
- Department of BotanyFaculty of ScienceUniversity of South BohemiaBranišovská 1760České BudějoviceCZ37005Czech Republic
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Barrington DS, Patel NR, Southgate MW. Inferring the impacts of evolutionary history and ecological constraints on spore size and shape in the ferns. APPLICATIONS IN PLANT SCIENCES 2020; 8:e11339. [PMID: 32351800 PMCID: PMC7186895 DOI: 10.1002/aps3.11339] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 02/03/2020] [Indexed: 05/27/2023]
Abstract
PREMISE In the ferns, cell size has been explored with spores, which are largely uniform within species, produced in abundance, and durable. However, spore size and shape have been variously defined, and the relationship of these traits to genome size has not been well established. Here, we explore the variation in fern spore size and shape by ploidy level and genome size. METHODS Measurements of spore dimensions for two study sets of ferns, Polystichum and Adiantum, both including diploid and tetraploid taxa, provided the basis for computing estimates of shape and size as defined here. These traits were compared between and within ploidy levels and regressed with genome size estimates from flow cytometry analysis. RESULTS All size traits were strongly correlated with genome size; the shape trait was weakly correlated. Tetraploids were larger than diploids as expected; the spores of some closely related diploid species were also significantly different in size. DISCUSSION Researchers with access to a student-grade compound microscope can develop a valid estimate of relative genome size for ferns. These estimates provide enough resolution to infer ploidy level and explore the relationship between genome size, habitat, and physiological constraints for species within ploidy level.
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Affiliation(s)
- David S. Barrington
- Pringle HerbariumUniversity of Vermont111 Jeffords HallBurlingtonVermont05405‐1737USA
| | - Nikisha R. Patel
- Ecology and Evolutionary BiologyUniversity of Connecticut75 North Eagleville RoadStorrsConnecticut06269USA
| | - Morgan W. Southgate
- Pringle HerbariumUniversity of Vermont111 Jeffords HallBurlingtonVermont05405‐1737USA
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Wyder S, Rivera A, Valdés AE, Cañal MJ, Gagliardini V, Fernández H, Grossniklaus U. Differential gene expression profiling of one- and two-dimensional apogamous gametophytes of the fern Dryopteris affinis ssp. affinis. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2020; 148:302-311. [PMID: 32000107 DOI: 10.1016/j.plaphy.2020.01.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 12/16/2019] [Accepted: 01/15/2020] [Indexed: 05/01/2023]
Abstract
Apomixis was originally defined as the replacement of sexual reproduction by an asexual process that does not involve fertilization but, in angiosperms, it is often used in the more restricted sense of asexual reproduction through seeds. In ferns, apomixis combines the production of unreduced spores (diplospory) and the formation of sporophytes from somatic cells of the prothallium (apogamy). The genes that control the onset of apogamy in ferns are largely unknown. In this study, we describe the gametophyte transcriptome of the apogamous fern Dryopteris affinis ssp. affinis using an RNA-Seq approach to compare the gene expression profiles of one- and two-dimensional gametophytes, the latter containing apogamic centers. After collapsing highly similar de novo transcripts, we obtained 166,191 unigenes, of which 30% could be annotated using public databases. Multiple quality metrics indicate a good quality of the de novo transcriptome with a low level of fragmentation. Our data show a total of 10,679 genes (6% of all genes) to be differentially expressed between gametophytes of filamentous (one-dimensional) and prothallial (two-dimensional) architecture. 6,110 genes were up-regulated in two-dimensional relative to one-dimensional gametophytes, some of which are implicated in the regulation of meristem growth, auxin signaling, reproduction, and sucrose metabolism. 4,570 genes were down-regulated in two-dimensional versus one-dimensional gametophytes, which are enriched in stimulus and defense genes, as well as genes involved in epigenetic gene regulation and ubiquitin degradation. Our results provide insights into free-living gametophyte development, focusing on the filamentous-to-prothallus growth transition, and provide a useful resource for further investigations of asexual reproduction.
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Affiliation(s)
- Stefan Wyder
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, CH-8008, Zurich, Switzerland
| | - Alejandro Rivera
- Area of Plant Physiology, Department of Organisms and Systems Biology, University of Oviedo, c) Catedrático R Uría s/n, 33071, Oviedo, Spain
| | - Ana E Valdés
- Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91, Stockholm, Sweden
| | - María Jesús Cañal
- Area of Plant Physiology, Department of Organisms and Systems Biology, University of Oviedo, c) Catedrático R Uría s/n, 33071, Oviedo, Spain
| | - Valeria Gagliardini
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, CH-8008, Zurich, Switzerland
| | - Helena Fernández
- Area of Plant Physiology, Department of Organisms and Systems Biology, University of Oviedo, c) Catedrático R Uría s/n, 33071, Oviedo, Spain.
| | - Ueli Grossniklaus
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, Zollikerstrasse 107, CH-8008, Zurich, Switzerland
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Hornych O, Ekrt L, Riedel F, Koutecký P, Košnar J. Asymmetric hybridization in Central European populations of the Dryopteris carthusiana group. AMERICAN JOURNAL OF BOTANY 2019; 106:1477-1486. [PMID: 31634425 DOI: 10.1002/ajb2.1369] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 08/30/2019] [Indexed: 06/10/2023]
Abstract
PREMISE Hybridization is a key process in plant speciation. Despite its importance, there is no detailed study of hybridization rates in fern populations. A proper estimate of hybridization rates is needed to understand factors regulating hybridization. METHODS We studied hybridization in the European Dryopteris carthusiana group, represented by one diploid and two tetraploid species and their hybrids. We sampled ~100 individuals per population in 40 mixed populations of the D. carthusiana group across Europe. All plants were identified by measuring genome size (DAPI staining) using flow cytometry. To determine the maternal parentage of hybrids, we sequenced the chloroplast region trnL-trnF of all taxa involved. RESULTS We found hybrids in 85% of populations. Triploid D. ×ambroseae occurred in every population that included both parent species and is most abundant when the parent species are equally abundant. By contrast, tetraploid D. ×deweveri was rare (15 individuals total) and triploid D. ×sarvelae was absent. The parentage of hybrid taxa is asymmetric. Despite expectations from previous studies, tetraploid D. dilatata is the predominant male parent of its triploid hybrid. CONCLUSIONS This is a thorough investigation of hybridization rates in natural populations of ferns. Hybridization rates differ greatly even among closely related fern taxa. In contrast to angiosperms, our data suggest that hybridization rates are highest in balanced parent populations and support the notion that some ferns possess very weak barriers to hybridization. Our results from sequencing cpDNA challenge established notions about the correlation of ploidy level and mating tendencies.
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Affiliation(s)
- Ondřej Hornych
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Libor Ekrt
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Felix Riedel
- Botanischer Garten der Universität Potsdam, Maulbeerallee 3, Potsdam, D-14469, Germany
- Arboretum der Humboldt-Universität zu Berlin, Späthstrasse 80/81, Berlin, D-12437, Germany
| | - Petr Koutecký
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
| | - Jiří Košnar
- Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic
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Hanušová K, Čertner M, Urfus T, Koutecký P, Košnar J, Rothfels CJ, Jarolímová V, Ptáček J, Ekrt L. Widespread co-occurrence of multiple ploidy levels in fragile ferns (Cystopteris fragilis complex; Cystopteridaceae) probably stems from similar ecology of cytotypes, their efficient dispersal and inter-ploidy hybridization. ANNALS OF BOTANY 2019; 123:845-855. [PMID: 30541055 PMCID: PMC6526313 DOI: 10.1093/aob/mcy219] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Accepted: 11/09/2018] [Indexed: 05/13/2023]
Abstract
BACKGROUND AND AIMS Polyploidy has played an important role in the evolution of ferns. However, the dearth of data on cytotype diversity, cytotype distribution patterns and ecology in ferns is striking in comparison with angiosperms and prevents an assessment of whether cytotype coexistence and its mechanisms show similar patterns in both plant groups. Here, an attempt to fill this gap was made using the ploidy-variable and widely distributed Cystopteris fragilis complex. METHODS Flow cytometry was used to assess DNA ploidy level and monoploid genome size (Cx value) of 5518 C. fragilis individuals from 449 populations collected over most of the species' global distributional range, supplemented with data from 405 individuals representing other related species from the complex. Ecological preferences of C. fragilis tetraploids and hexaploids were compared using field-recorded parameters and database-extracted climate data. KEY RESULTS Altogether, five different ploidy levels (2x, 4x, 5x, 6x, 8x) were detected and three species exhibited intraspecific ploidy-level variation: C. fragilis, C. alpina and C. diaphana. Two predominant C. fragilis cytotypes, tetraploids and hexaploids, co-occur over most of Europe in a diffuse, mosaic-like pattern. Within this contact zone, 40 % of populations were mixed-ploidy and most also contained pentaploid hybrids. Environmental conditions had only a limited effect on the distribution of cytotypes. Differences were found in the Cx value of tetraploids and hexaploids: between-cytotype divergence was higher in uniform-ploidy than in mixed-ploidy populations. CONCLUSIONS High ploidy-level diversity and widespread cytotype coexistence in the C. fragilis complex match the well-documented patterns in some angiosperms. While ploidy coexistence in C. fragilis is not driven by environmental factors, it could be facilitated by the perennial life-form of the species, its reproductive modes and efficient wind dispersal of spores. Independent origins of hexaploids and/or inter-ploidy gene flow may be expected in mixed-ploidy populations according to Cx value comparisons.
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Affiliation(s)
- Kristýna Hanušová
- Department of Botany, Faculty of Science, Charles University, Benátská, Praha, Czech Republic
| | - Martin Čertner
- Department of Botany, Faculty of Science, Charles University, Benátská, Praha, Czech Republic
- Institute of Botany, The Czech Academy of Sciences, Zámek, Průhonice, Czech Republic
| | - Tomáš Urfus
- Department of Botany, Faculty of Science, Charles University, Benátská, Praha, Czech Republic
| | - Petr Koutecký
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, Czech Republic
| | - Jiří Košnar
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, Czech Republic
| | - Carl J Rothfels
- University Herbarium and Department of Integrative Biology, University of California, Berkeley, CA, USA
| | - Vlasta Jarolímová
- Institute of Botany, The Czech Academy of Sciences, Zámek, Průhonice, Czech Republic
| | - Jan Ptáček
- Department of Botany, Faculty of Science, Charles University, Benátská, Praha, Czech Republic
| | - Libor Ekrt
- Department of Botany, Faculty of Science, University of South Bohemia, Branišovská, České Budějovice, Czech Republic
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Saggoo MIS, Kaur M. An Infertile Triploid Population of <i>Polystichum squarrosum</i> from Himachal Pradesh. CYTOLOGIA 2018. [DOI: 10.1508/cytologia.83.181] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Yakimowski SB, Barrett SCH. The role of hybridization in the evolution of sexual system diversity in a clonal, aquatic plant. Evolution 2016; 70:1200-11. [PMID: 27150128 DOI: 10.1111/evo.12941] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 04/21/2016] [Accepted: 04/26/2016] [Indexed: 01/25/2023]
Abstract
The stable coexistence within populations of females, males, and hermaphrodites (subdioecy) is enigmatic because theoretical models indicate that maintenance of this sexual system involves highly restricted conditions. Subdioecy is more commonly interpreted as a transitory stage along the gynodioecious pathway from hermaphroditism to dioecy. The widespread, North American, aquatic plant Sagittaria latifolia is largely composed of monoecious or dioecious populations; however, subdioecious populations with high frequencies of hermaphrodites (mean frequency = 0.50) characterize the northern range boundary of dioecy in eastern North America. We investigated two hypotheses for the origin of subdioecy in this region. Using polymorphic microsatellite loci, we evaluated whether subdioecy arises through selection on standing genetic variation for male sex inconstancy in dioecious populations, or results from hybridization between monoecious and dioecious populations. We found evidence for both pathways to subdioecy, although hybridization was the more common mechanism, with genetic evidence of admixture in nine of 14 subdioecious populations examined. Hybridization has also played a role in the origin of androdioecious populations in S. latifolia, a mechanism not often considered in the evolution of this rare sexual system. Our study demonstrates how hybridization has the potential to play a role in the diversification of plant sexual systems.
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Affiliation(s)
- Sarah B Yakimowski
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, M5S 3B2, Canada. .,Current Address: Department of Biology, Queen's University, 116 Barrie Street, Kingston, Ontario, K7L 3N6, Canada.
| | - Spencer C H Barrett
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, M5S 3B2, Canada
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