1
|
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.
Collapse
Affiliation(s)
- Jenn M Coughlan
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06511, USA
| |
Collapse
|
2
|
Muyle A, Marais GAB, Bačovský V, Hobza R, Lenormand T. Dosage compensation evolution in plants: theories, controversies and mechanisms. Philos Trans R Soc Lond B Biol Sci 2022; 377:20210222. [PMID: 35306896 PMCID: PMC8935305 DOI: 10.1098/rstb.2021.0222] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In a minority of flowering plants, separate sexes are genetically determined by sex chromosomes. The Y chromosome has a non-recombining region that degenerates, causing a reduced expression of Y genes. In some species, the lower Y expression is accompanied by dosage compensation (DC), a mechanism that re-equalizes male and female expression and/or brings XY male expression back to its ancestral level. Here, we review work on DC in plants, which started as early as the late 1960s with cytological approaches. The use of transcriptomics fired a controversy as to whether DC existed in plants. Further work revealed that various plants exhibit partial DC, including a few species with young and homomorphic sex chromosomes. We are starting to understand the mechanisms responsible for DC in some plants, but in most species, we lack the data to differentiate between global and gene-by-gene DC. Also, it is unknown why some species evolve many dosage compensated genes while others do not. Finally, the forces that drive DC evolution remain mysterious, both in plants and animals. We review the multiple evolutionary theories that have been proposed to explain DC patterns in eukaryotes with XY or ZW sex chromosomes. This article is part of the theme issue 'Sex determination and sex chromosome evolution in land plants'.
Collapse
Affiliation(s)
- Aline Muyle
- Laboratoire 'Biométrie et Biologie Evolutive', CNRS/Université Lyon 1, Lyon, France
| | - Gabriel A B Marais
- Laboratoire 'Biométrie et Biologie Evolutive', CNRS/Université Lyon 1, Lyon, France.,CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Campus de Vairão, Universidade do Porto, 4485-661 Vairão, Portugal.,Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, 4099-002 Porto, Portugal.,BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, 4485-661 Vairão, Portugal
| | - Václav Bačovský
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska 135, Brno, Czech Republic
| | - Roman Hobza
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Kralovopolska 135, Brno, Czech Republic
| | - Thomas Lenormand
- CEFE, University of Montpellier, CNRS, EPHE, IRD, Montpellier, France
| |
Collapse
|
3
|
Rivera-Vega LJ, Grunseich JM, Aguirre NM, Valencia CU, Sword GA, Helms AM. A Beneficial Plant-Associated Fungus Shifts the Balance toward Plant Growth over Resistance, Increasing Cucumber Tolerance to Root Herbivory. PLANTS 2022; 11:plants11030282. [PMID: 35161264 PMCID: PMC8838125 DOI: 10.3390/plants11030282] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/28/2021] [Accepted: 01/18/2022] [Indexed: 11/21/2022]
Abstract
Plants allocate their limited resources toward different physiological processes, dynamically adjusting their resource allocation in response to environmental changes. How beneficial plant-associated microbes influence this allocation is a topic that continues to interest plant biologists. In this study, we examined the effect of a beneficial fungus, Phialemonium inflatum, on investment in growth and anti-herbivore resistance traits in cucumber plants (Cucumis sativus). We inoculated cucumber seeds with P. inflatum spores and measured several growth parameters, including germination rate, above and belowground biomass, and number of flowers. We also examined plant resistance to adult and larval striped cucumber beetles (Acalymma vitattum), and quantified levels of defense hormones in leaves and roots. Our results indicate that P. inflatum strongly enhances cucumber plant growth and reproductive potential. Although fungus treatment did not improve plant resistance to cucumber beetles, inoculated plants were more tolerant to root herbivory, experiencing less biomass reduction. Together, these findings document how a beneficial plant-associated fungus shifts plant investment in growth over herbivore resistance, highlighting the importance of microbes in mediating plant-herbivore interactions. These findings also have important implications for agricultural systems, where beneficial microbes are often introduced or managed to promote plant growth or enhance resistance.
Collapse
Affiliation(s)
- Loren J. Rivera-Vega
- Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060, USA;
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA; (J.M.G.); (C.U.V.); (G.A.S.)
| | - John M. Grunseich
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA; (J.M.G.); (C.U.V.); (G.A.S.)
| | - Natalie M. Aguirre
- Ecology and Evolutionary Biology Program, Texas A&M University, College Station, TX 77843, USA;
| | - Cesar U. Valencia
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA; (J.M.G.); (C.U.V.); (G.A.S.)
| | - Gregory A. Sword
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA; (J.M.G.); (C.U.V.); (G.A.S.)
- Ecology and Evolutionary Biology Program, Texas A&M University, College Station, TX 77843, USA;
| | - Anjel M. Helms
- Department of Entomology, Texas A&M University, College Station, TX 77843, USA; (J.M.G.); (C.U.V.); (G.A.S.)
- Ecology and Evolutionary Biology Program, Texas A&M University, College Station, TX 77843, USA;
- Correspondence:
| |
Collapse
|
4
|
Tateyama H, Chimura K, Tsuchimatsu T. Evolution of seed mass associated with mating systems in multiple plant families. J Evol Biol 2021; 34:1981-1987. [PMID: 34662478 PMCID: PMC9298147 DOI: 10.1111/jeb.13949] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 09/30/2021] [Accepted: 10/10/2021] [Indexed: 11/28/2022]
Abstract
In flowering plants, the evolution of self‐fertilization (selfing) from obligate outcrossing is regarded as one of the most prevalent evolutionary transitions. The evolution of selfing is often accompanied by various changes in genomic, physiological and morphological properties. In particular, a set of reproductive traits observed typically in selfing species is called the “selfing syndrome”. A mathematical model based on the kinship theory of genetic imprinting predicted that seed mass should become smaller in selfing species compared with outcrossing congeners, as a consequence of the reduced conflict between maternally and paternally derived alleles in selfing plants. Here, we test this prediction by examining the association between mating system and seed mass across a wide range of taxa (642 species), considering potential confounding factors: phylogenetic relationships and growth form. We focused on three plant families—Solanaceae, Brassicaceae and Asteraceae—where information on mating systems is abundant, and the analysis was performed for each family separately. When phylogenetic relationships were controlled, we consistently observed that selfers (represented by self‐compatible species) tended to have a smaller seed mass compared with outcrossers (represented by self‐incompatible species) in these families. In summary, our analysis suggests that small seeds should also be considered a hallmark of the selfing syndrome, although we note that mating systems have relatively small effects on seed mass variation.
Collapse
Affiliation(s)
- Hirofumi Tateyama
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.,Graduate School of Science and Technology, Chiba University, Chiba, Japan
| | - Kaori Chimura
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Takashi Tsuchimatsu
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
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?'
Collapse
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
| |
Collapse
|
7
|
Tonnabel J, David P, Janicke T, Lehner A, Mollet JC, Pannell JR, Dufay M. The Scope for Postmating Sexual Selection in Plants. Trends Ecol Evol 2021; 36:556-567. [PMID: 33775429 DOI: 10.1016/j.tree.2021.02.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 02/22/2021] [Accepted: 02/24/2021] [Indexed: 11/27/2022]
Abstract
Sexual selection is known to shape plant traits that affect access to mates during the pollination phase, but it is less well understood to what extent it affects traits relevant to interactions between pollen and pistils after pollination. This is surprising, because both of the two key modes of sexual selection, male-male competition and female choice, could plausibly operate during pollen-pistil interactions where physical male-female contact occurs. Here, we consider how the key processes of sexual selection might affect traits involved in pollen-pistil interactions, including 'Fisherian runaway' and 'good-genes' models. We review aspects of the molecular and cellular biology of pollen-pistil interactions on which sexual selection could act and point to research that is needed to investigate them.
Collapse
Affiliation(s)
- Jeanne Tonnabel
- CEFE, Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France.
| | - Patrice David
- CEFE, Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
| | - Tim Janicke
- CEFE, Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France; Applied Zoology, Technical University Dresden, Zellescher Weg 20b, 01062 Dresden, Germany
| | - Arnaud Lehner
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire Végétale (GlycoMEV), SFR 4377 NORVEGE, IRIB, Carnot I2C, 76000 Rouen, France
| | - Jean-Claude Mollet
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire Végétale (GlycoMEV), SFR 4377 NORVEGE, IRIB, Carnot I2C, 76000 Rouen, France
| | - John R Pannell
- Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland
| | - Mathilde Dufay
- CEFE, Univ Montpellier, CNRS, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France
| |
Collapse
|
8
|
Gianella M, Balestrazzi A, Pagano A, Müller JV, Kyratzis AC, Kikodze D, Canella M, Mondoni A, Rossi G, Guzzon F. Heteromorphic seeds of wheat wild relatives show germination niche differentiation. PLANT BIOLOGY (STUTTGART, GERMANY) 2020; 22:191-202. [PMID: 31639249 DOI: 10.1111/plb.13060] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 10/12/2019] [Indexed: 05/12/2023]
Abstract
Crop wild relatives are fundamental genetic resources for crop improvement. Wheat wild relatives often produce heteromorphic seeds that differ in morphological and physiological traits. Several Aegilops and Triticum species possess, within the same spikelet, a dimorphic seed pair, with one seed being larger than the other. A comprehensive analysis is needed to understand which traits are involved in seed dimorphism and if these aspects of variation in dimorphic pairs are functionally related. To this end, dispersal units of Triticum urartu and five Aegilops species were X-rayed and the different seed morphs weighed. Germination tests were carried out on seeds, both dehulled and left in their dispersal units. Controlled ageing tests were performed to detect differences in seed longevity among seed morphs, and the antioxidant profile was assessed in terms of antioxidant compounds equipment and expression of selected antioxidant genes. We used PCA to group seed morphs sharing similar patterns of germination traits, longevity estimates and antioxidant profile. Different seed morphs differed significantly in terms of mass, final germination, germination timing, longevity estimates and antioxidant profile in most of the tested species. Small seeds germinated slower, had lower germination when left in their dispersal units, a higher antioxidant potential and were longer-lived than large seeds. The antioxidant gene expression varied between morphs, with different patterns across species but not clearly reflecting the phenotypic observations. The results highlight different trait trade-offs in dimorphic seeds of Aegilops and T. urartu, affecting their germination phenology and longevity, thereby resulting in recruitment niche differentiation.
Collapse
Affiliation(s)
- M Gianella
- Department of Biology and Biotechnology "L. Spallanzani", University of Pavia, Pavia, Italy
| | - A Balestrazzi
- Department of Biology and Biotechnology "L. Spallanzani", University of Pavia, Pavia, Italy
| | - A Pagano
- Department of Biology and Biotechnology "L. Spallanzani", University of Pavia, Pavia, Italy
| | - J V Müller
- Millennium Seed Bank, Conservation Science Department, Royal Botanic Gardens Kew, Wakehurst Place, UK
| | - A C Kyratzis
- Vegetable Crops Sector, Agricultural Research Institute of Cyprus, Nicosia, Cyprus
| | - D Kikodze
- Institute of Botany, Ilia State University, Tbilisi, Georgia
| | - M Canella
- Department of Earth and Environmental Sciences, University of Pavia, Pavia, Italy
| | - A Mondoni
- Department of Earth and Environmental Sciences, University of Pavia, Pavia, Italy
| | - G Rossi
- Department of Earth and Environmental Sciences, University of Pavia, Pavia, Italy
| | - F Guzzon
- International Maize and Wheat Improvement Center (CIMMYT), Texcoco, Estado de Mexico, Mexico
| |
Collapse
|
9
|
Coughlan JM, Wilson Brown M, Willis JH. Patterns of Hybrid Seed Inviability in the Mimulus guttatus sp. Complex Reveal a Potential Role of Parental Conflict in Reproductive Isolation. Curr Biol 2020; 30:83-93.e5. [PMID: 31883810 PMCID: PMC7017923 DOI: 10.1016/j.cub.2019.11.023] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/01/2019] [Accepted: 11/06/2019] [Indexed: 11/19/2022]
Abstract
Genomic conflicts may play a central role in the evolution of reproductive barriers. Theory predicts that early-onset hybrid inviability may stem from conflict between parents for resource allocation to offspring. Here, we describe M. decorus: a group of cryptic species within the M. guttatus species complex that are largely reproductively isolated by hybrid seed inviability (HSI). HSI between M. guttatus and M. decorus is common and strong, but populations of M. decorus vary in the magnitude and directionality of HSI with M. guttatus. Patterns of HSI between M. guttatus and M. decorus, as well as within M. decorus, conform to the predictions of parental conflict: first, reciprocal F1s exhibit size differences and parent-of-origin-specific endosperm defects; second, the extent of asymmetry between reciprocal F1 seed size is correlated with asymmetry in HSI; and third, inferred differences in the extent of conflict predict the extent of HSI between populations. We also find that HSI is rapidly evolving, as populations that exhibit the most HSI are each others' closest relative. Lastly, although all populations appear largely outcrossing, we find that the differences in the inferred strength of conflict scale positively with π, suggesting that demographic or life history factors other than transitions to self-fertilization may influence the rate of parental-conflict-driven evolution. Overall, these patterns suggest the rapid evolution of parent-of-origin-specific resource allocation alleles coincident with HSI within and between M. guttatus and M. decorus. Parental conflict may therefore be an important evolutionary driver of reproductive isolation.
Collapse
Affiliation(s)
- Jenn M Coughlan
- Biological Sciences, Duke University, 25 Science Drive, Durham, NC 27708, USA; Biology Department, University of North Carolina, Chapel Hill, 120 South Road, Chapel Hill, NC 27599, USA.
| | - Maya Wilson Brown
- Biological Sciences, Duke University, 25 Science Drive, Durham, NC 27708, USA
| | - John H Willis
- Biological Sciences, Duke University, 25 Science Drive, Durham, NC 27708, USA
| |
Collapse
|
10
|
Yule KJ, Burns KC. Parasite-offspring competition for female resources can explain male-biased parasitism in plants. Biol Lett 2019; 15:20180761. [PMID: 30836880 DOI: 10.1098/rsbl.2018.0761] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Male-biased susceptibility to parasites is common in dioecious plants. However, why males have higher parasite loads than females is unclear. Unlike males, females must subsidize post-fertilization costs of reproduction (e.g. seed and fruit development). As a result, females may have smaller pools of resources potentially available to parasites, thus leading to lower parasite loads. We tested this prediction in New Zealand's largest native moth ( Aenetus virescens: Lepidoptera), whose larvae parasitize Aristotelia serrata (Elaeocarpaceae), an endemic species of dioecious tree. We measured parasite loads in male and female trees, as well as annual seed set in females. We then derived a technique to equate the energetic cost of seed set in females to an equivalent number of parasitic larvae. Our results showed evidence for male-biased parasitism: male trees harboured more larval parasites than female trees. However, when parasite loads in males were compared with parasite loads in females, plus the energetic cost of seed production calculated as an equivalent number of parasitic larvae, differences in parasitism between the sexes disappeared. We conclude that male-biased parasitism in plants could arise from parasite-offspring (i.e. herbivore-seed) competition for female resources.
Collapse
Affiliation(s)
- Kirsty J Yule
- School of Biological Sciences, Victoria University of Wellington , PO Box 600, Wellington 6012 , New Zealand
| | - Kevin C Burns
- School of Biological Sciences, Victoria University of Wellington , PO Box 600, Wellington 6012 , New Zealand
| |
Collapse
|
11
|
Itagaki T, Mochizuki J, Aoyagi Blue Y, Ito M, Sakai S. Evolution towards minimum ovule size? Ovule size variations and the relative sizes of ovules to seeds. ANNALS OF BOTANY 2019; 123:1253-1256. [PMID: 30918957 PMCID: PMC6612939 DOI: 10.1093/aob/mcz031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 02/14/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND AND AIMS Is there selection minimizing the costs of ovule production? Such selection should lead to a smaller ovule size in relation to seed size and, at the same time, smaller variation in ovule size within plants, the latter because the minimum structures and resources for functioning of ovules should be the same among ovules. Additionally, within species, ovule size should not depend on the plant's resource status. METHODS To confirm these predictions, we examined ovule and seed production for a variety of species. KEY RESULTS Among the 27 species studied, we found a significant negative dependence of the species mean of the coefficient of variation for plant ovule size on the ratio of the mean species seed size/mean species ovule size. Thus, the smaller the ovule size as compared with seed size, the smaller the degree of variation in ovule size. Among the 49 species studied, only two species showed significant positive dependence of mean ovule size on plant size. Although larger plants should have greater resources for ovule production, selection has not enhanced the production of large ovules in most species. CONCLUSIONS These results suggest that there is selection minimizing the costs of ovule production.
Collapse
Affiliation(s)
- Tomoyuki Itagaki
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Japan
| | - Jun Mochizuki
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Japan
| | - Yuta Aoyagi Blue
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Japan
| | - Masaya Ito
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Japan
| | - Satoki Sakai
- Graduate School of Life Sciences, Tohoku University, Aoba, Sendai, Japan
| |
Collapse
|
12
|
Abstract
Evolutionary conflict can drive rapid adaptive evolution, sometimes called an arms race, because each party needs to respond continually to the adaptations of the other. Evidence for such arms races can sometimes be seen in morphology, in behavior, or in the genes underlying sexual interactions of host-pathogen interactions, but is rarely predicted a priori. Kin selection theory predicts that conflicts of interest should usually be reduced but not eliminated among genetic relatives, but there is little evidence as to whether conflict within families can drive rapid adaptation. Here we test multiple predictions about how conflict over the amount of resources an offspring receives from its parent would drive rapid molecular evolution in seed tissues of the flowering plant Arabidopsis As predicted, there is more adaptive evolution in genes expressed in Arabidopsis seeds than in other specialized organs, more in endosperms and maternal tissues than in embryos, and more in the specific subtissues involved in nutrient transfer. In the absence of credible alternative hypotheses, these results suggest that kin selection and conflict are important in plants, that the conflict includes not just the mother and offspring but also the triploid endosperm, and that, despite the conflict-reducing role of kinship, family members can engage in slow but steady tortoise-like arms races.
Collapse
|