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Bente H, Köhler C. Molecular basis and evolutionary drivers of endosperm-based hybridization barriers. PLANT PHYSIOLOGY 2024; 195:155-169. [PMID: 38298124 PMCID: PMC11060687 DOI: 10.1093/plphys/kiae050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 01/05/2024] [Accepted: 01/06/2024] [Indexed: 02/02/2024]
Abstract
The endosperm, a transient seed tissue, plays a pivotal role in supporting embryo growth and germination. This unique feature sets flowering plants apart from gymnosperms, marking an evolutionary innovation in the world of seed-bearing plants. Nevertheless, the importance of the endosperm extends beyond its role in providing nutrients to the developing embryo by acting as a versatile protector, preventing hybridization events between distinct species and between individuals with different ploidy. This phenomenon centers on growth and differentiation of the endosperm and the speed at which both processes unfold. Emerging studies underscore the important role played by type I MADS-box transcription factors, including the paternally expressed gene PHERES1. These factors, along with downstream signaling pathways involving auxin and abscisic acid, are instrumental in regulating endosperm development and, consequently, the establishment of hybridization barriers. Moreover, mutations in various epigenetic regulators mitigate these barriers, unveiling a complex interplay of pathways involved in their formation. In this review, we discuss the molecular underpinnings of endosperm-based hybridization barriers and their evolutionary drivers.
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Affiliation(s)
- Heinrich Bente
- Department of Plant Reproductive Biology and Epigenetics, Max Planck Institute of Molecular Plant Physiology, Potsdam 14476, Germany
| | - Claudia Köhler
- Department of Plant Reproductive Biology and Epigenetics, Max Planck Institute of Molecular Plant Physiology, Potsdam 14476, Germany
- Department of Plant Biology, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala 75007, Sweden
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Zhang D, Li YY, Zhao X, Zhang C, Liu DK, Lan S, Yin W, Liu ZJ. Molecular insights into self-incompatibility systems: From evolution to breeding. PLANT COMMUNICATIONS 2024; 5:100719. [PMID: 37718509 PMCID: PMC10873884 DOI: 10.1016/j.xplc.2023.100719] [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: 03/29/2023] [Revised: 08/18/2023] [Accepted: 09/13/2023] [Indexed: 09/19/2023]
Abstract
Plants have evolved diverse self-incompatibility (SI) systems for outcrossing. Since Darwin's time, considerable progress has been made toward elucidating this unrivaled reproductive innovation. Recent advances in interdisciplinary studies and applications of biotechnology have given rise to major breakthroughs in understanding the molecular pathways that lead to SI, particularly the strikingly different SI mechanisms that operate in Solanaceae, Papaveraceae, Brassicaceae, and Primulaceae. These best-understood SI systems, together with discoveries in other "nonmodel" SI taxa such as Poaceae, suggest a complex evolutionary trajectory of SI, with multiple independent origins and frequent and irreversible losses. Extensive exploration of self-/nonself-discrimination signaling cascades has revealed a comprehensive catalog of male and female identity genes and modifier factors that control SI. These findings also enable the characterization, validation, and manipulation of SI-related factors for crop improvement, helping to address the challenges associated with development of inbred lines. Here, we review current knowledge about the evolution of SI systems, summarize key achievements in the molecular basis of pollen‒pistil interactions, discuss potential prospects for breeding of SI crops, and raise several unresolved questions that require further investigation.
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Affiliation(s)
- Diyang Zhang
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yuan-Yuan Li
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Xuewei Zhao
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China; College of Forestry, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Cuili Zhang
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Ding-Kun Liu
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China; College of Forestry, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Siren Lan
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Weilun Yin
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China; College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China.
| | - Zhong-Jian Liu
- Key Laboratory of National Forestry and Grassland Administration for Orchid Conservation and Utilization, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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Tezuka T, Nagai S, Matsuo C, Okamori T, Iizuka T, Marubashi W. Genetic Cause of Hybrid Lethality Observed in Reciprocal Interspecific Crosses between Nicotiana simulans and N. tabacum. Int J Mol Sci 2024; 25:1226. [PMID: 38279225 PMCID: PMC10817076 DOI: 10.3390/ijms25021226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 01/17/2024] [Accepted: 01/17/2024] [Indexed: 01/28/2024] Open
Abstract
Hybrid lethality, a type of postzygotic reproductive isolation, is an obstacle to wide hybridization breeding. Here, we report the hybrid lethality that was observed in crosses between the cultivated tobacco, Nicotiana tabacum (section Nicotiana), and the wild tobacco species, Nicotiana simulans (section Suaveolentes). Reciprocal hybrid seedlings were inviable at 28 °C, and the lethality was characterized by browning of the hypocotyl and roots, suggesting that hybrid lethality is due to the interaction of nuclear genomes derived from each parental species, and not to a cytoplasmic effect. Hybrid lethality was temperature-sensitive and suppressed at 36 °C. However, when hybrid seedlings cultured at 36 °C were transferred to 28 °C, all of them showed hybrid lethality. After crossing between an N. tabacum monosomic line missing one copy of the Q chromosome and N. simulans, hybrid seedlings with or without the Q chromosome were inviable and viable, respectively. These results indicated that gene(s) on the Q chromosome are responsible for hybrid lethality and also suggested that N. simulans has the same allele at the Hybrid Lethality A1 (HLA1) locus responsible for hybrid lethality as other species in the section Suaveolentes. Haplotype analysis around the HLA1 locus suggested that there are at least six and two haplotypes containing Hla1-1 and hla1-2 alleles, respectively, in the section Suaveolentes.
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Affiliation(s)
- Takahiro Tezuka
- Graduate School of Agriculture, Osaka Metropolitan University, Sakai 599-8531, Osaka, Japan;
- Education and Research Field, School of Agriculture, Osaka Metropolitan University, Sakai 599-8531, Osaka, Japan
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai 599-8531, Osaka, Japan;
- School of Life and Environmental Sciences, Osaka Prefecture University, Sakai 599-8531, Osaka, Japan
| | - Shota Nagai
- Graduate School of Agriculture, Osaka Metropolitan University, Sakai 599-8531, Osaka, Japan;
| | - Chihiro Matsuo
- School of Life and Environmental Sciences, Osaka Prefecture University, Sakai 599-8531, Osaka, Japan
| | - Toshiaki Okamori
- School of Life and Environmental Sciences, Osaka Prefecture University, Sakai 599-8531, Osaka, Japan
| | - Takahiro Iizuka
- Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai 599-8531, Osaka, Japan;
| | - Wataru Marubashi
- School of Agriculture, Meiji University, Kawasaki 214-8571, Kanagawa, Japan;
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4
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Coughlan JM. The role of hybrid seed inviability in angiosperm speciation. AMERICAN JOURNAL OF BOTANY 2023; 110:1-14. [PMID: 36801827 DOI: 10.1002/ajb2.16135] [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: 08/27/2022] [Revised: 01/05/2023] [Accepted: 01/05/2023] [Indexed: 05/11/2023]
Abstract
Understanding which reproductive barriers contribute to speciation is essential to understanding the diversity of life on earth. Several contemporary examples of strong hybrid seed inviability (HSI) between recently diverged species suggest that HSI may play a fundamental role in plant speciation. Yet, a broader synthesis of HSI is needed to clarify its role in diversification. Here, I review the incidence and evolution of HSI. Hybrid seed inviability is common and evolves rapidly, suggesting that it may play an important role early in speciation. The developmental mechanisms that underlie HSI involve similar developmental trajectories in endosperm, even between evolutionarily deeply diverged incidents of HSI. In hybrid endosperm, HSI is often accompanied by whole-scale gene misexpression, including misexpression of imprinted genes which have a key role in endosperm development. I explore how an evolutionary perspective can clarify the repeated and rapid evolution of HSI. In particular, I evaluate the evidence for conflict between maternal and paternal interests in resource allocation to offspring (i.e., parental conflict). I highlight that parental conflict theory generates explicit predictions regarding the expected hybrid phenotypes and genes responsible for HSI. While much phenotypic evidence supports a role of parental conflict in the evolution of HSI, an understanding of the underlying molecular mechanisms of this barrier is essential to test parental conflict theory. Lastly, I explore what factors may influence the strength of parental conflict in natural plant populations as an explanation for why rates of HSI may differ between plant groups and the consequences of strong HSI in secondary contact.
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Affiliation(s)
- Jenn M Coughlan
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06511, USA
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Runge P, Ventura F, Kemen E, Stam R. Distinct Phyllosphere Microbiome of Wild Tomato Species in Central Peru upon Dysbiosis. MICROBIAL ECOLOGY 2023; 85:168-183. [PMID: 35041070 PMCID: PMC9849306 DOI: 10.1007/s00248-021-01947-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 12/15/2021] [Indexed: 06/14/2023]
Abstract
Plants are colonized by myriads of microbes across kingdoms, which affect host development, fitness, and reproduction. Hence, plant microbiomes have been explored across a broad range of host species, including model organisms, crops, and trees under controlled and natural conditions. Tomato is one of the world's most important vegetable crops; however, little is known about the microbiota of wild tomato species. To obtain insights into the tomato microbiota occurring in natural environments, we sampled epiphytic microbes from leaves of four tomato species, Solanum habrochaites, S. corneliomulleri, S. peruvianum, and S. pimpinellifolium, from two geographical locations within the Lima region of Peru over 2 consecutive years. Here, a high-throughput sequencing approach was applied to investigate microbial compositions including bacteria, fungi, and eukaryotes across tomato species and geographical locations. The phyllosphere microbiome composition varies between hosts and location. Yet, we identified persistent microbes across tomato species that form the tomato microbial core community. In addition, we phenotypically defined healthy and dysbiotic samples and performed a downstream analysis to reveal the impact on microbial community structures. To do so, we compared microbial diversities, unique OTUs, relative abundances of core taxa, and microbial hub taxa, as well as co-occurrence network characteristics in healthy and dysbiotic tomato leaves and found that dysbiosis affects the phyllosphere microbial composition in a host species-dependent manner. Yet, overall, the present data suggests an enrichment of plant-promoting microbial taxa in healthy leaves, whereas numerous microbial taxa containing plant pathogens occurred in dysbiotic leaves.Concluding, we identify the core phyllosphere microbiome of wild tomato species, and show that the overall phyllosphere microbiome can be impacted by sampling time point, geographical location, host genotype, and plant health. Future studies in these components will help understand the microbial contribution to plant health in natural systems and can be of use in cultivated tomatoes.
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Affiliation(s)
- Paul Runge
- Department of Microbial Interactions, IMIT/ZMBP, University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829, Köln, Germany
| | - Freddy Ventura
- Plant Pathology and Bacteriology, International Potato Centre, Avenida La Molina 1895, La Molina, Lima, Peru
| | - Eric Kemen
- Department of Microbial Interactions, IMIT/ZMBP, University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| | - Remco Stam
- Chair of Phytopathology, TUM School of Life Science, Emil-Ramann-Str. 2, 85354, Freising-Weihenstephan, Germany.
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Fei CH, Tang SS, Shang SH, Dai J, Wang XY, Wang S, Liu WQ, Wang XF. Conspecific pollen advantage mediated by the extragynoecial compitum and its potential to resist interspecific reproductive interference between two Sagittaria species. FRONTIERS IN PLANT SCIENCE 2022; 13:956193. [PMID: 35937372 PMCID: PMC9354020 DOI: 10.3389/fpls.2022.956193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 06/27/2022] [Indexed: 06/15/2023]
Abstract
The extragynoecial compitum formed by the incomplete fusion of carpel margins, while allowing intercarpellary growth of pollen tubes in apocarpous angiosperms, may also increase the risk of reproductive interference caused by heterospecific pollen (HP) deposition. In Sagittaria, congeneric HP tubes grow via different paths and enter the ovules later than conspecific pollen (CP) tubes. However, it is unclear how the growth advantage of the CP tube helps ensure reproductive success when HP is deposited on the stigmas. We performed molecular characterization of interspecies-pollinated seeds to examine the consequences of interspecific pollen deposition between Sagittaria pygmaea and S. trifolia. We also conducted CP-HP (1:1) mixed pollination and delayed CP pollination treatments to explore the seed-siring abilities of CP and HP. Our results showed that although HP could trigger the development of fruits, the interspecies-pollinated seeds contained partially developed embryos and could not germinate. More than 70% of the embryos in these seeds were molecularly identified as hybrids of both species, suggesting that HP tubes could enter the ovules and fertilize the egg cells. Moreover, CP could sire more offspring (≥70%) after the CP-HP (1:1) mixed pollination treatment, even when HP reached the stigma 0.5-1 h earlier than CP (≥50%). Following adequate CP vs. HP (1:1) pollination on carpels on two sides of the apocarpous gynoecium, both species produced > 70% conspecific seeds, indicating that the CP tubes could occupy ovules that should be occupied by HP via the extragynoecial compitum. Our results reveal that in Sagittaria, pollen deposition from co-existing congeneric heterospecies leads to interspecific seed discounting. However, the CP advantage mediated by the extragynoecial compitum is an effective strategy to mitigate the effects of interspecific pollen deposition. This study improves our understanding of how apocarpous angiosperms with an extragynoecial compitum can maintain species stability and mitigate the negative reproductive interference effect from sympatrically distributed related species.
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Affiliation(s)
- Cai-Hong Fei
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Sha-Sha Tang
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Shu-He Shang
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Jie Dai
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Xin-Yi Wang
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Shuai Wang
- College of Life Science, Hengyang Normal University, Hengyang, China
| | - Wei-Qi Liu
- College of Life Sciences, Wuhan University, Wuhan, China
| | - Xiao-Fan Wang
- College of Life Sciences, Wuhan University, Wuhan, China
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Gustafsson ALS, Gussarova G, Borgen L, Ikeda H, Antonelli A, Marie-Orleach L, Rieseberg LH, Brochmann C. Rapid evolution of post-zygotic reproductive isolation is widespread in Arctic plant lineages. ANNALS OF BOTANY 2022; 129:171-184. [PMID: 34643673 PMCID: PMC8796670 DOI: 10.1093/aob/mcab128] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 10/05/2021] [Indexed: 05/03/2023]
Abstract
BACKGROUND AND AIMS The Arctic tundra, with its extreme temperatures and short growing season, is evolutionarily young and harbours one of the most species-poor floras on Earth. Arctic species often show little phenotypic and genetic divergence across circumpolar ranges. However, strong intraspecific post-zygotic reproductive isolation (RI) in terms of hybrid sterility has frequently evolved within selfing Arctic species of the genus Draba. Here we assess whether incipient biological species are common in the Arctic flora. METHODS We conducted an extensive crossing experiment including six species representing four phylogenetically distant families collected across the circumpolar Arctic. We crossed conspecific parental populations representing different spatial scales, raised 740 F1 hybrids to maturity and measured fertility under laboratory conditions. We examined genetic divergence between populations for two of these species (Cardamine bellidifolia and Ranunculus pygmaeus). KEY RESULTS In five of the six species, we find extensive reduction in pollen fertility and seed set in F1 hybrids; 219 (46 %) of the 477 F1 hybrids generated between parents separated by ≥427 km had <20 % pollen fertility. Isolation with migration (IM) and *BEAST analyses of sequences of eight nuclear genes in C. bellidifolia suggests that reproductively isolated populations of this species diverged during, or even after, the last glaciation. Likewise, Arctic populations of R. pygmaeus were genetically very similar despite exhibiting strongly reduced fertility in crosses, suggesting that RI evolved recently also in this species. CONCLUSION We show that post-zygotic RI has developed multiple times within taxonomically recognized Arctic species belonging to several distantly related lineages, and that RI may have developed over just a few millennia. Rapid and widespread evolution of incipient biological species in the Arctic flora might be associated with frequent bottlenecks due to glacial cycles, and/or selfing mating systems, which are common in the harsh Arctic environment where pollinators are scarce.
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Affiliation(s)
| | - Galina Gussarova
- Natural History Museum, University of Oslo, Oslo, Norway
- Botany Department, Faculty of Biology and Soil Science, St Petersburg, Russia
- Tromsø University Museum, University of Tromsø, Tromsø, Norway
| | - Liv Borgen
- Natural History Museum, University of Oslo, Oslo, Norway
| | - Hajime Ikeda
- Institute of Plant Science and Resources, Okayama University, Okayama, Japan
| | - Alexandre Antonelli
- Royal Botanic Gardens, Kew, Richmond, UK
- Gothenburg Global Biodiversity Centre, Department of Biological and Environmental Sciences, University of Gothenburg, Sweden
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Lucas Marie-Orleach
- Natural History Museum, University of Oslo, Oslo, Norway
- ECOBIO—Écosystèmes, Biodiversité, Évolution, Rennes, France
| | - Loren H Rieseberg
- Botany Department, University of British Columbia, Vancouver, Canada
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Abstract
Pollen-pistil interactions serve as important prezygotic reproductive barriers that play a critical role in mate selection in plants. Here, we highlight recent progress toward understanding the molecular basis of pollen-pistil interactions as reproductive isolating barriers. These barriers can be active systems of pollen rejection, or they can result from a mismatch of required male and female factors. In some cases, the barriers are mechanistically linked to self-incompatibility systems, while others represent completely independent processes. Pollen-pistil reproductive barriers can act as soon as pollen is deposited on a stigma, where penetration of heterospecific pollen tubes is blocked by the stigma papillae. As pollen tubes extend, the female transmitting tissue can selectively limit growth by producing cell wall-modifying enzymes and cytotoxins that interact with the growing pollen tube. At ovules, differential pollen tube attraction and inhibition of sperm cell release can act as barriers to heterospecific pollen tubes.
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Affiliation(s)
- Amanda K Broz
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA; ,
| | - Patricia A Bedinger
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA; ,
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Städler T, Florez-Rueda AM, Roth M. A revival of effective ploidy: the asymmetry of parental roles in endosperm-based hybridization barriers. CURRENT OPINION IN PLANT BIOLOGY 2021; 61:102015. [PMID: 33639340 DOI: 10.1016/j.pbi.2021.102015] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 01/15/2021] [Accepted: 01/25/2021] [Indexed: 05/15/2023]
Abstract
Interest in understanding hybrid seed failure (HSF) has mushroomed, both in terms of identifying underlying molecular processes and their evolutionary drivers. We review phenotypic and molecular advances with a focus on the 'effective ploidy' concept, witnessing a recent revival after long obscurity. Endosperm misdevelopment has now been shown to underlie HSF in many inter-specific, homoploid crosses. The consistent asymmetries in seed size and developmental trajectories likely reflect parental divergence in key, dosage-sensitive processes. Transcriptomic and epigenomic studies reveal genome-wide, polarized expression perturbations and shifts in parental expression proportions, consistent with small-RNA imbalances between parental roles. Among-species differences in levels of parental conflict over resource allocation enjoy strong support in explaining why differences in effective ploidy may evolve.
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Affiliation(s)
- Thomas Städler
- Institute of Integrative Biology, ETH Zurich & Zurich-Basel Plant Science Center, Universitätstrasse 16, 8092 Zurich, Switzerland.
| | - Ana M Florez-Rueda
- Department of Plant and Microbial Biology, University of Zurich and Zurich-Basel Plant Science Center, Zollikerstrasse 107, 8008 Zurich, Switzerland
| | - Morgane Roth
- GAFL INRAE, Allée des Chênes 67, 84140 Montfavet, France
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Florez-Rueda AM, Fiscalini F, Roth M, Grossniklaus U, Städler T. Endosperm and Seed Transcriptomes Reveal Possible Roles for Small RNA Pathways in Wild Tomato Hybrid Seed Failure. Genome Biol Evol 2021; 13:6278300. [PMID: 34009298 PMCID: PMC8358227 DOI: 10.1093/gbe/evab107] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/10/2021] [Indexed: 01/10/2023] Open
Abstract
Crosses between the wild tomato species Solanum peruvianum and Solanum chilense result in hybrid seed failure (HSF), characterized by endosperm misdevelopment and embryo arrest. We previously showed that genomic imprinting, the parent-of-origin–dependent expression of alleles, is perturbed in the hybrid endosperm, with many of the normally paternally expressed genes losing their imprinted status. Here, we report transcriptome-based analyses of gene and small RNA (sRNA) expression levels. We identified 2,295 genes and 387 sRNA clusters as differentially expressed when comparing reciprocal hybrid seed to seeds and endosperms from the two within-species crosses. Our analyses uncovered a pattern of overdominance in endosperm gene expression in both hybrid cross directions, in marked contrast to the patterns of sRNA expression in whole seeds. Intriguingly, patterns of increased gene expression resemble the previously reported increased maternal expression proportions in hybrid endosperms. We identified physical clusters of sRNAs; differentially expressed sRNAs exhibit reduced transcript abundance in hybrid seeds of both cross directions. Moreover, sRNAs map to genes coding for key proteins involved in epigenetic regulation of gene expression, suggesting a regulatory feedback mechanism. We describe examples of genes that appear to be targets of sRNA-mediated gene silencing; in these cases, reduced sRNA abundance is concomitant with increased gene expression in hybrid seeds. Our analyses also show that S. peruvianum dominance impacts gene and sRNA expression in hybrid seeds. Overall, our study indicates roles for sRNA-mediated epigenetic regulation in HSF between closely related wild tomato species.
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Affiliation(s)
- Ana Marcela Florez-Rueda
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, 8008 Zurich, Switzerland.,Institute of Integrative Biology & Zurich-Basel Plant Science Center, ETH Zurich, 8092 Zurich, Switzerland
| | - Flurin Fiscalini
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, 8008 Zurich, Switzerland
| | - Morgane Roth
- Institute of Integrative Biology & Zurich-Basel Plant Science Center, ETH Zurich, 8092 Zurich, Switzerland
| | - Ueli Grossniklaus
- Department of Plant and Microbial Biology & Zurich-Basel Plant Science Center, University of Zurich, 8008 Zurich, Switzerland
| | - Thomas Städler
- Institute of Integrative Biology & Zurich-Basel Plant Science Center, ETH Zurich, 8092 Zurich, Switzerland
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11
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Köhler C, Dziasek K, Del Toro-De León G. Postzygotic reproductive isolation established in the endosperm: mechanisms, drivers and relevance. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200118. [PMID: 33866810 DOI: 10.1098/rstb.2020.0118] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The endosperm is a developmental innovation of angiosperms that supports embryo growth and germination. Aside from this essential reproductive function, the endosperm fuels angiosperm evolution by rapidly establishing reproductive barriers between incipient species. Specifically, the endosperm prevents hybridization of newly formed polyploids with their non-polyploid progenitors, a phenomenon termed the triploid block. Furthermore, recently diverged diploid species are frequently reproductively isolated by endosperm-based hybridization barriers. Current genetic approaches have revealed a prominent role for epigenetic processes establishing these barriers. In particular, imprinted genes, which are expressed in a parent-of-origin-specific manner, underpin the interploidy barrier in the model species Arabidopsis. We will discuss the mechanisms establishing hybridization barriers in the endosperm, the driving forces for these barriers and their impact for angiosperm evolution. This article is part of the theme issue 'How does epigenetics influence the course of evolution?'
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Affiliation(s)
- Claudia Köhler
- Department of Plant Biology, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala 75007, Sweden
| | - Katarzyna Dziasek
- Department of Plant Biology, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala 75007, Sweden
| | - Gerardo Del Toro-De León
- Department of Plant Biology, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala 75007, Sweden
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12
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Florez-Rueda AM, Scharmann M, Roth M, Städler T. Population Genomics of the "Arcanum" Species Group in Wild Tomatoes: Evidence for Separate Origins of Two Self-Compatible Lineages. FRONTIERS IN PLANT SCIENCE 2021; 12:624442. [PMID: 33815438 PMCID: PMC8018279 DOI: 10.3389/fpls.2021.624442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Accepted: 02/24/2021] [Indexed: 05/07/2023]
Abstract
Given their diverse mating systems and recent divergence, wild tomatoes (Solanum section Lycopersicon) have become an attractive model system to study ecological divergence, the build-up of reproductive barriers, and the causes and consequences of the breakdown of self-incompatibility. Here we report on a lesser-studied group of species known as the "Arcanum" group, comprising the nominal species Solanum arcanum, Solanum chmielewskii, and Solanum neorickii. The latter two taxa are self-compatible but are thought to self-fertilize at different rates, given their distinct manifestations of the morphological "selfing syndrome." Based on experimental crossings and transcriptome sequencing of a total of 39 different genotypes from as many accessions representing each species' geographic range, we provide compelling evidence for deep genealogical divisions within S. arcanum; only the self-incompatible lineage known as "var. marañón" has close genealogical ties to the two self-compatible species. Moreover, there is evidence under multiple inference schemes for different geographic subsets of S. arcanum var. marañón being closest to S. chmielewskii and S. neorickii, respectively. To broadly characterize the population-genomic consequences of these recent mating-system transitions and their associated speciation events, we fit demographic models indicating strong reductions in effective population size, congruent with reduced nucleotide and S-locus diversity in the two independently derived self-compatible species.
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He H, Yokoi S, Tezuka T. A high maternal genome excess causes severe seed abortion leading to ovary abscission in Nicotiana interploidy-interspecific crosses. PLANT DIRECT 2020; 4:e00257. [PMID: 32821875 PMCID: PMC7430375 DOI: 10.1002/pld3.257] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 07/21/2020] [Accepted: 07/23/2020] [Indexed: 05/05/2023]
Abstract
Seed abortion and ovary abscission, two types of postzygotic reproductive barriers, are often observed in interspecific and/or interploidy crosses in plants. However, the mechanisms underlying these reproductive barriers remain unclear. Here, we show that the distinct types of seed developmental abnormalities (type I and type II seed abortion) occur in a phased manner as maternal to paternal genome dosage increases and that type II seed abortion is followed by ovary abscission. We revealed that these two types of seed developmental abnormalities are observed during seed development in the interploidy-interspecific crosses of Nicotiana suaveolens and N. tabacum. Moreover, in the cross showing type II seed abortion, several events, such as changes in abscission-related gene expression and lignin deposition, occurred in the ovary abscission zone, eventually leading to ovary abscission. Notably, successive increases in maternal ploidy using ploidy manipulated lines resulted in successive type I and type II seed abortions, and the latter was accompanied by ovary abscission. Conversely, both types of seed abortion and ovary abscission could be overcome with a ploidy manipulation technique that balances parental ploidy levels. We thus concluded that a high maternal genome excess cross may cause severe seed developmental defects and ovary abscission. Based on our findings, we propose a model explaining the abortion phenomena, where an interaction between the promotive and inhibitive effects of the parental genomes determines the developmental destiny of seeds. SIGNIFICANCE STATEMENT We demonstrate that a stepwise increase in maternal ploidy results in a stepwise increase in seed abortion severity, leading to ovary abscission in plants. We propose a model explaining the abortion phenomena, where an interaction between the promotive and inhibitive effects of the parental genomes determines the developmental destiny of seeds.
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Affiliation(s)
- Hai He
- Graduate School of Life and Environmental SciencesOsaka Prefecture UniversitySakaiJapan
| | - Shuji Yokoi
- Graduate School of Life and Environmental SciencesOsaka Prefecture UniversitySakaiJapan
- Education and Research FieldCollege of Life, Environment, and Advanced SciencesOsaka Prefecture UniversitySakaiJapan
- Bioeconomy Research InstituteResearch Center for the 21st CenturyOsaka Prefecture UniversitySakaiJapan
| | - Takahiro Tezuka
- Graduate School of Life and Environmental SciencesOsaka Prefecture UniversitySakaiJapan
- Education and Research FieldCollege of Life, Environment, and Advanced SciencesOsaka Prefecture UniversitySakaiJapan
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14
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Flores-Vergara MA, Oneal E, Costa M, Villarino G, Roberts C, De Luis Balaguer MA, Coimbra S, Willis J, Franks RG. Developmental Analysis of Mimulus Seed Transcriptomes Reveals Functional Gene Expression Clusters and Four Imprinted, Endosperm-Expressed Genes. FRONTIERS IN PLANT SCIENCE 2020; 11:132. [PMID: 32161609 PMCID: PMC7052496 DOI: 10.3389/fpls.2020.00132] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 01/28/2020] [Indexed: 05/15/2023]
Abstract
The double fertilization of the female gametophyte initiates embryogenesis and endosperm development in seeds via the activation of genes involved in cell differentiation, organ patterning, and growth. A subset of genes expressed in endosperm exhibit imprinted expression, and the correct balance of gene expression between parental alleles is critical for proper endosperm and seed development. We use a transcriptional time series analysis to identify genes that are associated with key shifts in seed development, including genes associated with secondary cell wall synthesis, mitotic cell cycle, chromatin organization, auxin synthesis, fatty acid metabolism, and seed maturation. We relate these genes to morphological changes in Mimulus seeds. We also identify four endosperm-expressed transcripts that display imprinted (paternal) expression bias. The imprinted status of these four genes is conserved in other flowering plants, suggesting that they are functionally important in endosperm development. Our study explores gene regulatory dynamics in a species with ab initio cellular endosperm development, broadening the taxonomic focus of the literature on gene expression in seeds. Moreover, it is the first to validate genes with imprinted endosperm expression in Mimulus guttatus, and will inform future studies on the genetic causes of seed failure in this model system.
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Affiliation(s)
- Miguel A. Flores-Vergara
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, United States
| | - Elen Oneal
- Department of Biology, Duke University, Durham, NC, United States
- *Correspondence: Elen Oneal,
| | - Mario Costa
- GreenUPorto, Sustainable Agrifood Production Research Centre, Biology Department, Faculty of Sciences, University of Porto, Porto, Portugal
| | - Gonzalo Villarino
- Biology Department, San Diego State University, San Diego, CA, United States
| | - Caitlyn Roberts
- Department of Biology, Berea College, Berea, KY, United States
| | | | - Sílvia Coimbra
- GreenUPorto, Sustainable Agrifood Production Research Centre, Biology Department, Faculty of Sciences, University of Porto, Porto, Portugal
| | - John Willis
- Department of Biology, Duke University, Durham, NC, United States
| | - Robert G. Franks
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, United States
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15
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Callaway TD, Singh-Cundy A. HD-AGPs as Speciation Genes: Positive Selection on a Proline-Rich Domain in Non-Hybridizing Species of Petunia, Solanum, and Nicotiana. PLANTS (BASEL, SWITZERLAND) 2019; 8:E211. [PMID: 31288469 PMCID: PMC6681252 DOI: 10.3390/plants8070211] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/18/2019] [Accepted: 07/04/2019] [Indexed: 11/16/2022]
Abstract
Transmitting tissue-specific proteins (TTS proteins) are abundant in the extracellular matrix of Nicotiana pistils, and vital for optimal pollen tube growth and seed set. We have identified orthologs from several species in the Solanaceae, including Petunia axillaris axillaris and Petunia integrifolia. We refer to TTS proteins and their orthologs as histidine domain-arabinogalactan proteins (HD-AGPs). HD-AGPs have distinctive domains, including a small histidine-rich region and a C-terminal PAC domain. Pairwise comparisons between HD-AGPs of 15 species belonging to Petunia, Nicotiana, and Solanum show that the his-domain and PAC domain are under purifying selection. In contrast, a proline-rich domain (HV2) is conserved among cross-hybridizing species, but variant in species-pairs that are reproductively isolated by post-pollination pre-fertilization reproductive barriers. In particular, variation in a tetrapeptide motif (XKPP) is systematically correlated with the presence of an interspecific reproductive barrier. Ka/Ks ratios are not informative at the infrageneric level, but the ratios reveal a clear signature of positive selection on two hypervariable domains (HV1 and HV2) when HD-AGPs from five solanaceous genera are compared. We propose that sequence divergence in the hypervariable domains of HD-AGPs reinforces sympatric speciation in incipient species that may have first diverged as a consequence of pollinator preferences or other ecological factors.
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Affiliation(s)
- Tara D Callaway
- Biology Department, Western Washington University, Bellingham, WA 98225, USA
| | - Anu Singh-Cundy
- Biology Department, Western Washington University, Bellingham, WA 98225, USA.
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16
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Roda F, Hopkins R. Correlated evolution of self and interspecific incompatibility across the range of a Texas wildflower. THE NEW PHYTOLOGIST 2019; 221:553-564. [PMID: 29992588 DOI: 10.1111/nph.15340] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 06/10/2018] [Indexed: 06/08/2023]
Abstract
Selection to prevent interspecific mating can cause an increase or a decrease in self-pollination in sympatric populations. Characterizing the geographical variation in self and interspecific incompatibilities within a species can reveal if and how the evolution of self and interspecific mate choice are linked. We used controlled pollinations to characterize the variation in self and interspecific incompatibility across 29 populations of Phlox drummondii. We evaluated seed set from these pollinations and described the developmental timing of variation in pollen-pistil compatibility. There is extensive quantitative variation in self-incompatibility and interspecific-incompatibility with its close congener P. cuspidata. Phlox drummondii populations that co-occur and hybridize with P. cuspidata have significantly higher interspecific incompatibility and self-incompatibility than geographically isolated P. drummondii populations. The strength of self and interspecific incompatibility is significantly correlated among individuals and the strength of both incompatibilities is explained by the success of pollen adhesion to the stigma. The correlated strength of self and interspecific incompatibility across the range of P. drummondii and the concurrent developmental timing of the pollen-pistil interaction, suggests these incompatibilities have an overlapping molecular mechanism. The geographical distribution of variation in incompatibilities indicates that this mechanistic link between incompatibilities may affect the evolution of mate choice in plants.
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Affiliation(s)
- Federico Roda
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
- The Arnold Arboretum, Harvard University, 1300 Centre St, Boston, MA, 02131, USA
| | - Robin Hopkins
- Department of Organismic and Evolutionary Biology, Harvard University, 22 Divinity Avenue, Cambridge, MA, 02138, USA
- The Arnold Arboretum, Harvard University, 1300 Centre St, Boston, MA, 02131, USA
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17
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Roth M, Florez-Rueda AM, Paris M, Städler T. Wild tomato endosperm transcriptomes reveal common roles of genomic imprinting in both nuclear and cellular endosperm. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 95:1084-1101. [PMID: 29953688 DOI: 10.1111/tpj.14012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 06/01/2018] [Accepted: 06/20/2018] [Indexed: 05/06/2023]
Abstract
Genomic imprinting is a conspicuous feature of the endosperm, a triploid tissue nurturing the embryo and synchronizing angiosperm seed development. An unknown subset of imprinted genes (IGs) is critical for successful seed development and should have highly conserved functions. Recent genome-wide studies have found limited conservation of IGs among distantly related species, but there is a paucity of data from closely related lineages. Moreover, most studies focused on model plants with nuclear endosperm development, and comparisons with properties of IGs in cellular-type endosperm development are lacking. Using laser-assisted microdissection, we characterized parent-specific expression in the cellular endosperm of three wild tomato lineages (Solanum section Lycopersicon). We identified 1025 candidate IGs and 167 with putative homologs previously identified as imprinted in distantly related taxa with nuclear-type endosperm. Forty-two maternally expressed genes (MEGs) and 17 paternally expressed genes (PEGs) exhibited conserved imprinting status across all three lineages, but differences in power to assess imprinted expression imply that the actual degree of conservation might be higher than that directly estimated (20.7% for PEGs and 10.4% for MEGs). Regardless, the level of shared imprinting status was higher for PEGs than for MEGs, indicating dissimilar evolutionary trajectories. Expression-level data suggest distinct epigenetic modulation of MEGs and PEGs, and gene ontology analyses revealed MEGs and PEGs to be enriched for different functions. Importantly, our data provide evidence that MEGs and PEGs interact in modulating both gene expression and the endosperm cell cycle, and uncovered conserved cellular functions of IGs uniting taxa with cellular- and nuclear-type endosperm.
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Affiliation(s)
- Morgane Roth
- Plant Ecological Genetics, Institute of Integrative Biology & Zurich-Basel Plant Science Center, ETH Zurich, 8092, Zurich, Switzerland
| | - Ana M Florez-Rueda
- Plant Ecological Genetics, Institute of Integrative Biology & Zurich-Basel Plant Science Center, ETH Zurich, 8092, Zurich, Switzerland
| | - Margot Paris
- Plant Ecological Genetics, Institute of Integrative Biology & Zurich-Basel Plant Science Center, ETH Zurich, 8092, Zurich, Switzerland
| | - Thomas Städler
- Plant Ecological Genetics, Institute of Integrative Biology & Zurich-Basel Plant Science Center, ETH Zurich, 8092, Zurich, Switzerland
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18
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Qin X, Li W, Liu Y, Tan M, Ganal M, Chetelat RT. A farnesyl pyrophosphate synthase gene expressed in pollen functions in S-RNase-independent unilateral incompatibility. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 93:417-430. [PMID: 29206320 DOI: 10.1111/tpj.13796] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 11/22/2017] [Accepted: 11/24/2017] [Indexed: 05/25/2023]
Abstract
Multiple independent and overlapping pollen rejection pathways contribute to unilateral interspecific incompatibility (UI). In crosses between tomato species, pollen rejection usually occurs when the female parent is self-incompatible (SI) and the male parent self-compatible (SC) (the 'SI × SC rule'). Additional, as yet unknown, UI mechanisms are independent of self-incompatibility and contribute to UI between SC species or populations. We identified a major quantitative trait locus on chromosome 10 (ui10.1) which affects pollen-side UI responses in crosses between cultivated tomato, Solanum lycopersicum, and Solanum pennelliiLA0716, both of which are SC and lack S-RNase, the pistil determinant of S-specificity in Solanaceae. Here we show that ui10.1 is a farnesyl pyrophosphate synthase gene (FPS2) expressed in pollen. Expression is about 18-fold higher in pollen of S. pennellii than in S. lycopersicum. Pollen with the hypomorphic S. lycopersicum allele is selectively eliminated on pistils of the F1 hybrid, leading to transmission ratio distortion in the F2 progeny. CRISPR/Cas9-generated knockout mutants (fps2) in S. pennelliiLA0716 are self-sterile due to pollen rejection, but mutant pollen is fully functional on pistils of S. lycopersicum. F2 progeny of S. lycopersicum × S. pennellii (fps2) show reversed transmission ratio distortion due to selective elimination of pollen bearing the knockout allele. Overexpression of FPS2 in S. lycopersicum pollen rescues the pollen elimination phenotype. FPS2-based pollen selectivity does not involve S-RNase and has not been previously linked to UI. Our results point to an entirely new mechanism of interspecific pollen rejection in plants.
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Affiliation(s)
- Xiaoqiong Qin
- Department of Plant Sciences (ms #3), One Shields Ave., University of California, Davis, CA, 95616, USA
| | - Wentao Li
- Department of Plant Sciences (ms #3), One Shields Ave., University of California, Davis, CA, 95616, USA
| | - Yang Liu
- Department of Plant Sciences (ms #3), One Shields Ave., University of California, Davis, CA, 95616, USA
| | - Meilian Tan
- Department of Plant Sciences (ms #3), One Shields Ave., University of California, Davis, CA, 95616, USA
| | - Martin Ganal
- Trait Genetics GmbH, Am Schwabeplan 1B, 06466, Gatersleben, Germany
| | - Roger T Chetelat
- Department of Plant Sciences (ms #3), One Shields Ave., University of California, Davis, CA, 95616, USA
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19
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Roth M, Florez-Rueda AM, Griesser S, Paris M, Städler T. Incidence and developmental timing of endosperm failure in post-zygotic isolation between wild tomato lineages. ANNALS OF BOTANY 2018; 121:107-118. [PMID: 29280998 PMCID: PMC5786209 DOI: 10.1093/aob/mcx133] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 10/04/2017] [Indexed: 05/19/2023]
Abstract
BACKGROUND AND AIMS Defective hybrid seed development in angiosperms might mediate the rapid establishment of intrinsic post-zygotic isolation between closely related species. Extensive crosses within and among three lineages of wild tomatoes (Solanum section Lycopersicon) were performed to address the incidence, developmental timing and histological manifestations of hybrid seed failure. These lineages encompass different, yet fairly recent, divergence times and both allopatric and partially sympatric pairs. METHODS Mature seeds were scored visually 2 months after hand pollinations, and viable-looking seeds were assessed for germination success. Using histological sections from early-developing seeds from a sub-set of crosses, the growth of three major seed compartments (endosperm, embryo and seed coat) was measured at critical developmental stages up to 21 d after pollination, with a focus on the timing and histological manifestations of endosperm misdevelopment in abortive hybrid seeds. KEY RESULTS For two of three interspecific combinations including the most closely related pair that was also studied histologically, almost all mature seeds appeared 'flat' and proved inviable; histological analyses revealed impaired endosperm proliferation at early globular embryo stages, concomitant with embryo arrest and seed abortion in both cross directions. The third interspecific combination yielded a mixture of flat, inviable and plump, viable seeds; many of the latter germinated and exhibited near-normal juvenile phenotypes or, in some instances, hybrid necrosis and impaired growth. CONCLUSIONS The overall results suggest that near-complete hybrid seed failure can evolve fairly rapidly and without apparent divergence in reproductive phenology/biology. While the evidence accrued here is largely circumstantial, early-acting disruptions of normal endosperm development are most probably the common cause of seed failure regardless of the type of endosperm (nuclear or cellular).
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Affiliation(s)
- Morgane Roth
- Plant Ecological Genetics, Institute of Integrative Biology & Zurich–Basel Plant Science Center, ETH Zurich, Zurich, Switzerland
| | - Ana M Florez-Rueda
- Plant Ecological Genetics, Institute of Integrative Biology & Zurich–Basel Plant Science Center, ETH Zurich, Zurich, Switzerland
| | - Stephan Griesser
- Plant Ecological Genetics, Institute of Integrative Biology & Zurich–Basel Plant Science Center, ETH Zurich, Zurich, Switzerland
| | - Margot Paris
- Plant Ecological Genetics, Institute of Integrative Biology & Zurich–Basel Plant Science Center, ETH Zurich, Zurich, Switzerland
| | - Thomas Städler
- Plant Ecological Genetics, Institute of Integrative Biology & Zurich–Basel Plant Science Center, ETH Zurich, Zurich, Switzerland
- For correspondence. Email
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20
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Markova DN, Petersen JJ, Yam SE, Corral A, Valle MJ, Li W, Chetelat RT. Evolutionary history of two pollen self-incompatibility factors reveals alternate routes to self-compatibility within Solanum. AMERICAN JOURNAL OF BOTANY 2017; 104:1904-1919. [PMID: 29212768 DOI: 10.3732/ajb.1700196] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 10/26/2017] [Indexed: 05/23/2023]
Abstract
PREMISE OF THE STUDY Self-incompatibility (SI) prevents self-fertilization and reduces inbreeding. While SI is common in plants, transitions to self-compatibility (SC) occur frequently. Little is known about the genetic changes and evolutionary steps underlying these shifts. METHODS In the Solanaceae, SI is gametophytic, with specificity determined by S-RNases in the pistil and S-locus F-box proteins (SLFs) in pollen. We examined the role of two pollen factors, Cullin1 (CUL1) and SLF-23, in SI → SC transitions in wild tomato species from the Arcanum species group (Solanum arcanum, S. neorickii, and S. chmielewskii). Pollen compatibility was assessed on tester lines that reject pollen lacking functional SLF-23 or CUL1. Complementation tests, gene sequencing, and phylogenetic analyses were used to characterize both functional and nonfunctional alleles. KEY RESULTS We found evidence for multiple independent SI → SC transitions. In S. arcanum and S. chmielewskii, SC is caused by loss of pistil S-RNase activity, while in S. neorickii SC is associated with expression of a functional SLF-23 that recognizes the S9 type S-RNase expressed in its pistils. Interestingly, we found identical deletion mutations in CUL1 exon 7 of S. chmielewskii as previously seen in S. habrochaites. CONCLUSIONS Mating system transitions in the Arcanum group have occurred via both pistil loss-of-function and pollen gain-of-function SC mutations. Mutations common to S. chmielewskii and S. habrochaites must have arisen in a common ancestor, possibly to the entire tomato clade, then became fixed in different lineages after loss of pistil-side SI function.
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Affiliation(s)
- Dragomira N Markova
- C. M. Rick Tomato Genetics Resource Center, Department of Plant Sciences (ms 3), University of California, One Shields Avenue, Davis, California 95616 USA
| | | | - Sarah E Yam
- C. M. Rick Tomato Genetics Resource Center, Department of Plant Sciences (ms 3), University of California, One Shields Avenue, Davis, California 95616 USA
| | - Adryanna Corral
- C. M. Rick Tomato Genetics Resource Center, Department of Plant Sciences (ms 3), University of California, One Shields Avenue, Davis, California 95616 USA
| | - Matthew J Valle
- C. M. Rick Tomato Genetics Resource Center, Department of Plant Sciences (ms 3), University of California, One Shields Avenue, Davis, California 95616 USA
| | | | - Roger T Chetelat
- C. M. Rick Tomato Genetics Resource Center, Department of Plant Sciences (ms 3), University of California, One Shields Avenue, Davis, California 95616 USA
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21
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Xie Y, Zhu X, Ma Y, Zhao J, Li L, Li Q. Natural hybridization and reproductive isolation between two Primula species. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2017; 59:526-530. [PMID: 28429397 DOI: 10.1111/jipb.12546] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 04/17/2017] [Indexed: 06/07/2023]
Abstract
Natural hybridization frequently occurs in plants and can facilitate gene flow between species, possibly resulting in species refusion. However, various reproductive barriers block the formation of hybrids and maintain species integrity. Here, we conducted a field survey to examine natural hybridization and reproductive isolation (RI) between sympatric populations of Primula secundiflora and P. poissonii using ten nuclear simple sequence repeat (SSR) loci. Although introgressive hybridization occurred, species boundaries between P. secundiflora and P. poissonii were maintained through nearly complete reproductive isolation. These interfertile species provide an excellent model for studying the RI mechanisms and evolutionary forces that maintain species boundaries.
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Affiliation(s)
- Yanping Xie
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China
- Graduate University of Chinese Academy of Sciences, Beijing 10049, China
| | - Xingfu Zhu
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China
| | - Yongpeng Ma
- Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China
| | - Jianli Zhao
- Laboratory of Ecology and Evolutionary Biology, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming 650091, China
| | - Li Li
- Graduate University of Chinese Academy of Sciences, Beijing 10049, China
| | - Qingjun Li
- Laboratory of Ecology and Evolutionary Biology, State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan University, Kunming 650091, China
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