1
|
Melton AE, Novak SJ, Buerki S. Utilizing a comparative approach to assess genome evolution during diploidization in Artemisia tridentata, a keystone species of western North America. AMERICAN JOURNAL OF BOTANY 2024:e16353. [PMID: 38826031 DOI: 10.1002/ajb2.16353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 04/03/2024] [Accepted: 04/03/2024] [Indexed: 06/04/2024]
Abstract
PREMISE Polyploidization is often followed by diploidization. Diploidization is generally studied using synthetic polyploid lines and/or crop plants, but rarely using extant diploids or nonmodel plants such as Artemisia tridentata. This threatened western North American keystone species has a large genome compared to congeneric Artemisia species; dominated by diploid and tetraploid cytotypes, with multiple origins of tetraploids with genome size reduction. METHODS The genome of an A. tridentata sample was resequenced to study genome evolution and compared to that of A. annua, a diploid congener. Three diploid genomes of A. tridentata were compared to test for multiple diploidization events. RESULTS The A. tridentata genome had many chromosomal rearrangements relative to that of A. annua, while large-scale synteny of A. tridentata chromosome 3 and A. annua chromosome 4 was conserved. The three A. tridentata genomes had similar sizes (4.19-4.2 Gbp), heterozygosity (2.24-2.25%), and sequence (98.73-99.15% similarity) across scaffolds, and in k-mer analyses, similar patterns of diploid heterozygous k-mers (AB = 41%, 47%, and 47%), triploid heterozygous k-mers (AAB = 18-21%), and tetraploid k-mers (AABB = 13-17%). Biallelic SNPs were evenly distributed across scaffolds for all individuals. Comparisons of transposable element (TE) content revealed differential enrichment of TE clades. CONCLUSIONS Our findings suggest population-level TE differentiation after a shared polyploidization-to-diploidization event(s) and exemplify the complex processes of genome evolution. This research approached provides new resources for exploration of abiotic stress response, especially the roles of TEs in response pathways.
Collapse
Affiliation(s)
- Anthony E Melton
- Department of Biological Sciences, Boise State University, Boise, 83725, ID, USA
| | - Stephen J Novak
- Department of Biological Sciences, Boise State University, Boise, 83725, ID, USA
| | - Sven Buerki
- Department of Biological Sciences, Boise State University, Boise, 83725, ID, USA
| |
Collapse
|
2
|
de Tomás C, Vicient CM. The Genomic Shock Hypothesis: Genetic and Epigenetic Alterations of Transposable Elements after Interspecific Hybridization in Plants. EPIGENOMES 2023; 8:2. [PMID: 38247729 PMCID: PMC10801548 DOI: 10.3390/epigenomes8010002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 12/21/2023] [Accepted: 12/24/2023] [Indexed: 01/23/2024] Open
Abstract
Transposable elements (TEs) are major components of plant genomes with the ability to change their position in the genome or to create new copies of themselves in other positions in the genome. These can cause gene disruption and large-scale genomic alterations, including inversions, deletions, and duplications. Host organisms have evolved a set of mechanisms to suppress TE activity and counter the threat that they pose to genome integrity. These includes the epigenetic silencing of TEs mediated by a process of RNA-directed DNA methylation (RdDM). In most cases, the silencing machinery is very efficient for the vast majority of TEs. However, there are specific circumstances in which TEs can evade such silencing mechanisms, for example, a variety of biotic and abiotic stresses or in vitro culture. Hybridization is also proposed as an inductor of TE proliferation. In fact, the discoverer of the transposons, Barbara McClintock, first hypothesized that interspecific hybridization provides a "genomic shock" that inhibits the TE control mechanisms leading to the mobilization of TEs. However, the studies carried out on this topic have yielded diverse results, showing in some cases a total absence of mobilization or being limited to only some TE families. Here, we review the current knowledge about the impact of interspecific hybridization on TEs in plants and the possible implications of changes in the epigenetic mechanisms.
Collapse
Affiliation(s)
| | - Carlos M. Vicient
- Centre for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Cerdanyola del Vallès, 08193 Barcelona, Spain
| |
Collapse
|
3
|
Hartig N, Seibt KM, Heitkam T. How to start a LINE: 5' switching rejuvenates LINE retrotransposons in tobacco and related Nicotiana species. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2023. [PMID: 36965091 DOI: 10.1111/tpj.16208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 02/10/2023] [Accepted: 02/19/2023] [Indexed: 06/18/2023]
Abstract
By contrast to their conserved mammalian counterparts, plant long interspersed nuclear elements (LINEs) are highly variable, splitting into many low-copy families. Curiously, LINE families from the retrotransposable element (RTE) clade retain a stronger sequence conservation and hence reach higher copy numbers. The cause of this RTE-typical property is not yet understood, but would help clarify why some transposable elements are removed quickly, whereas others persist in plant genomes. Here, we bring forward a detailed study of RTE LINE structure, diversity and evolution in plants. For this, we argue that the nightshade family is the ideal taxon to follow the evolutionary trajectories of RTE LINEs, given their high abundance, recent activity and partnership to non-autonomous elements. Using bioinformatic, cytogenetic and molecular approaches, we detect 4029 full-length RTE LINEs across the Solanaceae. We finely characterize and manually curate a core group of 458 full-length LINEs in allotetraploid tobacco, show an integration event after polyploidization and trace hybridization by RTE LINE composition of parental genomes. Finally, we reveal the role of the untranslated regions (UTRs) as causes for the unique RTE LINE amplification and evolution pattern in plants. On the one hand, we detected a highly conserved motif at the 3' UTR, suggesting strong selective constraints acting on the RTE terminus. On the other hand, we observed successive rounds of 5' UTR cycling, constantly rejuvenating the promoter sequences. This interplay between exchangeable promoters and conserved LINE bodies and 3' UTR likely allows RTE LINEs to persist and thrive in plant genomes.
Collapse
Affiliation(s)
- Nora Hartig
- Faculty of Botany, Technische Universität Dresden, 01069, Dresden, Germany
| | - Kathrin M Seibt
- Faculty of Botany, Technische Universität Dresden, 01069, Dresden, Germany
| | - Tony Heitkam
- Faculty of Botany, Technische Universität Dresden, 01069, Dresden, Germany
| |
Collapse
|
4
|
Chase MW, Samuel R, Leitch AR, Guignard MS, Conran JG, Nollet F, Fletcher P, Jakob A, Cauz-Santos LA, Vignolle G, Dodsworth S, Christenhusz MJM, Buril MT, Paun O. Down, then up: non-parallel genome size changes and a descending chromosome series in a recent radiation of the Australian allotetraploid plant species, Nicotiana section Suaveolentes (Solanaceae). ANNALS OF BOTANY 2023; 131:123-142. [PMID: 35029647 PMCID: PMC9904355 DOI: 10.1093/aob/mcac006] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 01/11/2022] [Indexed: 05/25/2023]
Abstract
BACKGROUND AND AIMS The extent to which genome size and chromosome numbers evolve in concert is little understood, particularly after polyploidy (whole-genome duplication), when a genome returns to a diploid-like condition (diploidization). We study this phenomenon in 46 species of allotetraploid Nicotiana section Suaveolentes (Solanaceae), which formed <6 million years ago and radiated in the arid centre of Australia. METHODS We analysed newly assessed genome sizes and chromosome numbers within the context of a restriction site-associated nuclear DNA (RADseq) phylogenetic framework. KEY RESULTS RADseq generated a well-supported phylogenetic tree, in which multiple accessions from each species formed unique genetic clusters. Chromosome numbers and genome sizes vary from n = 2x = 15 to 24 and 2.7 to 5.8 pg/1C nucleus, respectively. Decreases in both genome size and chromosome number occur, although neither consistently nor in parallel. Species with the lowest chromosome numbers (n = 15-18) do not possess the smallest genome sizes and, although N. heterantha has retained the ancestral chromosome complement, n = 2x = 24, it nonetheless has the smallest genome size, even smaller than that of the modern representatives of ancestral diploids. CONCLUSIONS The results indicate that decreases in genome size and chromosome number occur in parallel down to a chromosome number threshold, n = 20, below which genome size increases, a phenomenon potentially explained by decreasing rates of recombination over fewer chromosomes. We hypothesize that, more generally in plants, major decreases in genome size post-polyploidization take place while chromosome numbers are still high because in these stages elimination of retrotransposons and other repetitive elements is more efficient. Once such major genome size change has been accomplished, then dysploid chromosome reductions take place to reorganize these smaller genomes, producing species with small genomes and low chromosome numbers such as those observed in many annual angiosperms, including Arabidopsis.
Collapse
Affiliation(s)
- Mark W Chase
- Royal Botanic Gardens, Kew, Richmond TW9 3DS, UK
- Department of Environment and Agriculture, Curtin University, Perth, Western Australia, Australia
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| | - Rosabelle Samuel
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| | - Andrew R Leitch
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | | | - John G Conran
- ACEBB & SGC, School of Biological Sciences, The University of Adelaide, SA 5005Australia
| | - Felipe Nollet
- Universidade Federal Rural de Pernambuco, Centro de Ciências Biológicas, Departamento de Botânica, Rua Manuel de Medeiros, S/N, Dois Irmãos, 52171-900 Recife, Pernambuco, Brazil
| | - Paul Fletcher
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Aljaž Jakob
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| | - Luiz A Cauz-Santos
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| | - Gabriel Vignolle
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| | - Steven Dodsworth
- School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK
| | - Maarten J M Christenhusz
- Department of Environment and Agriculture, Curtin University, Perth, Western Australia, Australia
| | - Maria Teresa Buril
- ACEBB & SGC, School of Biological Sciences, The University of Adelaide, SA 5005Australia
| | - Ovidiu Paun
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| |
Collapse
|
5
|
Fukai E, Yoshikawa M, Shah N, Sandal N, Miyao A, Ono S, Hirakawa H, Akyol TY, Umehara Y, Nonomura KI, Stougaard J, Hirochika H, Hayashi M, Sato S, Andersen SU, Okazaki K. Widespread and transgenerational retrotransposon activation in inter- and intraspecies recombinant inbred populations of Lotus japonicus. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 111:1397-1410. [PMID: 35792830 DOI: 10.1111/tpj.15896] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Accepted: 06/30/2022] [Indexed: 06/15/2023]
Abstract
Transposable elements (TEs) constitute a large proportion of genomes of multicellular eukaryotes, including flowering plants. TEs are normally maintained in a silenced state and their transpositions rarely occur. Hybridization between distant species has been regarded as a 'shock' that stimulates genome reorganization, including TE mobilization. However, whether crosses between genetically close parents that result in viable and fertile offspring can induce TE transpositions has remained unclear. Here, we investigated the activation of long terminal repeat (LTR) retrotransposons in three Lotus japonicus recombinant inbred line (RIL) populations. We found that at least six LTR retrotransposon families were activated and transposed in 78% of the RILs investigated. LORE1a, one of the transposed LTR retrotransposons, showed transgenerational epigenetic activation, indicating the long-term effects of epigenetic instability induced by hybridization. Our study highlights TE activation as an unexpectedly common event in plant reproduction.
Collapse
Affiliation(s)
- Eigo Fukai
- Graduate School of Science and Technology, Niigata University, Ikarashi-ninocho, 950-2181, Niigata, Japan
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2, Oowashi, Tsukuba, Ibaraki, 305-8634, Japan
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark
- Plant Cytogenetics, Department of Gene Function and Phenomics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan
- Department of Technology Development, Kazusa DNA Research Institute, Kisarazu, Chiba, 292-0818, Japan
| | - Manabu Yoshikawa
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2, Oowashi, Tsukuba, Ibaraki, 305-8634, Japan
| | - Niraj Shah
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark
| | - Niels Sandal
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark
| | - Akio Miyao
- Institute of Crop Science, National Agriculture and Food Research Organization, 2-1-2, Kannondai, Tsukuba, Ibaraki, 305-8518, Japan
| | - Seijiro Ono
- Plant Cytogenetics, Department of Gene Function and Phenomics, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan
| | - Hideki Hirakawa
- Department of Technology Development, Kazusa DNA Research Institute, Kisarazu, Chiba, 292-0818, Japan
| | - Turgut Yigit Akyol
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark
| | - Yosuke Umehara
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2, Oowashi, Tsukuba, Ibaraki, 305-8634, Japan
| | - Ken-Ichi Nonomura
- Department of Technology Development, Kazusa DNA Research Institute, Kisarazu, Chiba, 292-0818, Japan
| | - Jens Stougaard
- Department of Molecular Biology and Genetics, Aarhus University, 8000, Aarhus, Denmark
| | - Hirohiko Hirochika
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2, Oowashi, Tsukuba, Ibaraki, 305-8634, Japan
| | - Makoto Hayashi
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2, Oowashi, Tsukuba, Ibaraki, 305-8634, Japan
- Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa, 230-0045, Japan
| | - Shusei Sato
- Department of Technology Development, Kazusa DNA Research Institute, Kisarazu, Chiba, 292-0818, Japan
- Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai, Miyagi, 980-8577, Japan
| | | | - Keiichi Okazaki
- Graduate School of Science and Technology, Niigata University, Ikarashi-ninocho, 950-2181, Niigata, Japan
| |
Collapse
|
6
|
Eriksson MC, Mandáková T, McCann J, Temsch EM, Chase MW, Hedrén M, Weiss-Schneeweiss H, Paun O. Repeat dynamics across timescales: a perspective from sibling allotetraploid marsh orchids (Dactylorhiza majalis s.l.). Mol Biol Evol 2022; 39:6651906. [PMID: 35904928 PMCID: PMC9366187 DOI: 10.1093/molbev/msac167] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
To provide insights into the fate of transposable elements (TEs) across timescales in a post-polyploidization context, we comparatively investigate five sibling Dactylorhiza allotetraploids (Orchidaceae) formed independently and sequentially between 500 and 100K generations ago by unidirectional hybridization between diploids D. fuchsii and D. incarnata. Our results first reveal that the paternal D. incarnata genome shows a marked increased content of LTR retrotransposons compared to the maternal species, reflected in its larger genome size and consistent with a previously hypothesized bottleneck. With regard to the allopolyploids, in the youngest D. purpurella both genome size and TE composition appear to be largely additive with respect to parents, whereas for polyploids of intermediate ages we uncover rampant genome expansion on a magnitude of multiple entire genomes of some plants such as Arabidopsis. The oldest allopolyploids in the series are not larger than the intermediate ones. A putative tandem repeat, potentially derived from a non-autonomous miniature inverted-repeat TE (MITE) drives much of the genome dynamics in the allopolyploids. The highly dynamic MITE-like element is found in higher proportions in the maternal diploid, D. fuchsii, but is observed to increase in copy number in both subgenomes of the allopolyploids. Altogether, the fate of repeats appears strongly regulated and therefore predictable across multiple independent allopolyploidization events in this system. Apart from the MITE-like element, we consistently document a mild genomic shock following the allopolyploidizations investigated here, which may be linked to their relatively large genome sizes, possibly associated with strong selection against further genome expansions.
Collapse
Affiliation(s)
- Mimmi C Eriksson
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria.,Vienna Graduate School of Population Genetics, Veterinärplatz 1, A-1210 Vienna, Austria
| | - Terezie Mandáková
- Plant Cytogenomics Research Group, CEITEC-Central - European Institute of Technology, Masaryk University, Brno 62500, Czech Republic
| | - Jamie McCann
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| | - Eva M Temsch
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| | - Mark W Chase
- Royal Botanic Gardens Kew, London TW9 3AE, United Kingdom.,Department of Environment and Agriculture, Curtin University, Perth, Western Australia, Australia
| | - Mikael Hedrén
- Department of Biology, University of Lund, Sölvegatan 37, SE-223 62 Lund, Sweden
| | - Hanna Weiss-Schneeweiss
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| | - Ovidiu Paun
- Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030 Vienna, Austria
| |
Collapse
|
7
|
de Tomás C, Bardil A, Castanera R, Casacuberta JM, Vicient CM. Absence of major epigenetic and transcriptomic changes accompanying an interspecific cross between peach and almond. HORTICULTURE RESEARCH 2022; 9:uhac127. [PMID: 35928404 PMCID: PMC9343919 DOI: 10.1093/hr/uhac127] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
Hybridization has been widely used in breeding of cultivated species showing low genetic variability, such as peach (Prunus persica). The merging of two different genomes in a hybrid often triggers a so-called "genomic shock" with changes in DNA methylation and in the induction of transposable element expression and mobilization. Here, we analysed the DNA methylation and transcription levels of transposable elements and genes in leaves of Prunus persica and Prunus dulcis and in an F1 hybrid using high-throughput sequencing technologies. Contrary to the "genomic shock" expectations, we found that the overall levels of DNA methylation in the transposable elements in the hybrid are not significantly altered compared with those of the parental genomes. We also observed that the levels of transcription of the transposable elements in the hybrid are in most cases intermediate as compared with that of the parental species and we have not detected cases of higher transcription in the hybrid. We also found that the proportion of genes whose expression is altered in the hybrid compared with the parental species is low. The expression of genes potentially involved in the regulation of the activity of the transposable elements is not altered. We can conclude that the merging of the two parental genomes in this Prunus persica x Prunus dulcis hybrid does not result in a "genomic shock" with significant changes in the DNA methylation or in the transcription. The absence of major changes may facilitate using interspecific peach x almond crosses for peach improvement.
Collapse
Affiliation(s)
- Carlos de Tomás
- Centre for Research in Agricultural Genomics CSIC-IRTA-UAB-UB, Campus UAB, Edifici CRAG, Bellaterra, Barcelona 08193, Spain
| | - Amélie Bardil
- Institut écologie et environnement (INEE), CNRS, Montpelier, France
| | - Raúl Castanera
- Centre for Research in Agricultural Genomics CSIC-IRTA-UAB-UB, Campus UAB, Edifici CRAG, Bellaterra, Barcelona 08193, Spain
| | | | | |
Collapse
|
8
|
Specificities and Dynamics of Transposable Elements in Land Plants. BIOLOGY 2022; 11:biology11040488. [PMID: 35453688 PMCID: PMC9033089 DOI: 10.3390/biology11040488] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/10/2022] [Accepted: 03/18/2022] [Indexed: 01/27/2023]
Abstract
Simple Summary Transposable elements are dynamic components of plant genomes, and display a high diversity of lineages and distribution as the result of evolutionary driving forces and overlapping mechanisms of genetic and epigenetic regulation. They are now regarded as main contributors for genome evolution and function, and important regulators of endogenous gene expression. In this review, we survey recent progress and current challenges in the identification and classification of transposon lineages in complex plant genomes, highlighting the molecular specificities that may explain the expansion and diversification of mobile genetic elements in land plants. Abstract Transposable elements (TEs) are important components of most plant genomes. These mobile repetitive sequences are highly diverse in terms of abundance, structure, transposition mechanisms, activity and insertion specificities across plant species. This review will survey the different mechanisms that may explain the variability of TE patterns in land plants, highlighting the tight connection between TE dynamics and host genome specificities, and their co-evolution to face and adapt to a changing environment. We present the current TE classification in land plants, and describe the different levels of genetic and epigenetic controls originating from the plant, the TE itself, or external environmental factors. Such overlapping mechanisms of TE regulation might be responsible for the high diversity and dynamics of plant TEs observed in nature.
Collapse
|
9
|
Xiao Y, Li M, Wang J. The impacts of allopolyploidization on Methyl-CpG-Binding Domain (MBD) gene family in Brassica napus. BMC PLANT BIOLOGY 2022; 22:103. [PMID: 35255818 PMCID: PMC8900393 DOI: 10.1186/s12870-022-03485-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 02/21/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Polyploidization promotes species formation and is widespread in angiosperms. Genome changes dramatically bring opportunities and challenges to plants after polyploidy. Methyl-CpG-Binding Domain (MBD) proteins can recognize and bind to methylation sites and they play an important role in the physiological process related to methylation in animals and plants. However, research on the influence of the allopolyploidization process on the MBD gene family is still lacking, so it is necessary to conduct a comprehensive analysis. RESULTS In this study, twenty-two, ten and eleven MBD genes were identified in the genome of allotetraploid B. napus and its diploid ancestors, B. rapa and B. oleracea, respectively. Based on the clades of the MBD gene in Arabidopsis, rice and maize, we divided the new phylogenetic tree into 8 clades. Among them, the true MBD genes in Brassica existed in only 5 clades. Clade IV and Clade VI were unique in term of MBD genes in dicotyledons. Ka/Ks calculations showed that MBD genes underwent purifying selection in Brassica and may retain genes through sequence or functional differentiation early in evolution. In the process of allopolyploidization, the number of MBD gene introns increased, and the protein motifs changed. The MBD proteins had their own special motifs in each clade, and the MBD domains were only conserved in their clades. At the same time, the MBD genes were expressed in flower, leaf, silique, and stem tissues, and the expression levels of the different genes were significantly different, while the tissue specificity was not obvious. The allopolyploidization process may increase the number of cis-acting elements and activate the transposable elements. During allopolyploidization, the expression pattern of the MBD gene changes, which may be regulated by cis-acting elements and transposable elements. The number imbalance of cis-acting elements and transposable elements in An and Cn subgenomes may also lead to biased An subgenome expression of the MBD gene in B. napus. CONCLUSIONS In this study, by evaluating the number, structure, phylogeny and expression of the MBD gene in B. napus and its diploid ancestors, we increased the understanding of MBD genes in allopolyploids and provided a reference for future analysis of allopolyploidization.
Collapse
Affiliation(s)
- Yafang Xiao
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Mengdi Li
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072, China
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, 710069, China
| | - Jianbo Wang
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
| |
Collapse
|
10
|
Gantuz M, Morales A, Bertoldi MV, Ibañez VN, Duarte PF, Marfil CF, Masuelli RW. Hybridization and polyploidization effects on LTR-retrotransposon activation in potato genome. JOURNAL OF PLANT RESEARCH 2022; 135:81-92. [PMID: 34674075 DOI: 10.1007/s10265-021-01354-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Accepted: 10/13/2021] [Indexed: 06/13/2023]
Abstract
Hybridization and polyploidization are major forces in plant evolution and potatoes are not an exception. It is proposed that the proliferation of Long Terminal Repeat-retrotransposons (LTR-RT) is related to genome reorganization caused by hybridization and/or polyploidization. The main purpose of the present work was to evaluate the effect of interspecific hybridization and polyploidization on the activation of LTR-RT. We evaluated the proliferation of putative active LTR-RT in a diploid hybrid between the cultivated potato Solanum tuberosum and the wild diploid potato species S. kurtzianum, allotetraploid lines derived from this interspecific hybrid and S. kurtzianum autotetraploid lines (ktz-autotetraploid) using the S-SAP (sequence-specific amplified polymorphism) technique and normalized copy number determination by qPCR. Twenty-nine LTR-RT copies were activated in the hybrid and present in the allotetraploid lines. Major LTR-RT activity was detected in Copia-27, Copia-12, Copia-14 and, Gypsy-22. According to our results, LTR-RT copies were activated principally in the hybrid, there was no activation in allotetraploid lines and only one copy was activated in the autotetraploid.
Collapse
Affiliation(s)
- Magdalena Gantuz
- Facultad de Ciencias Agrarias, Instituto de Biología Agrícola de Mendoza, Consejo Nacional de Investigaciones Científicas y Técnicas (IBAM-CONICET), Universidad Nacional de Cuyo, A. Brown 500 (M5528AHB) Chacras de Coria, Mendoza, Argentina.
| | - Andrés Morales
- Instituto Nacional de Tecnología Agropecuaria (INTA), Luján de Cuyo, Mendoza, Argentina
| | - María Victoria Bertoldi
- Facultad de Ciencias Agrarias, Instituto de Biología Agrícola de Mendoza, Consejo Nacional de Investigaciones Científicas y Técnicas (IBAM-CONICET), Universidad Nacional de Cuyo, A. Brown 500 (M5528AHB) Chacras de Coria, Mendoza, Argentina
| | - Verónica Noé Ibañez
- Facultad de Ciencias Agrarias, Instituto de Biología Agrícola de Mendoza, Consejo Nacional de Investigaciones Científicas y Técnicas (IBAM-CONICET), Universidad Nacional de Cuyo, A. Brown 500 (M5528AHB) Chacras de Coria, Mendoza, Argentina
| | - Paola Fernanda Duarte
- Facultad de Ciencias Agrarias, Instituto de Biología Agrícola de Mendoza, Consejo Nacional de Investigaciones Científicas y Técnicas (IBAM-CONICET), Universidad Nacional de Cuyo, A. Brown 500 (M5528AHB) Chacras de Coria, Mendoza, Argentina
| | - Carlos Federico Marfil
- Facultad de Ciencias Agrarias, Instituto de Biología Agrícola de Mendoza, Consejo Nacional de Investigaciones Científicas y Técnicas (IBAM-CONICET), Universidad Nacional de Cuyo, A. Brown 500 (M5528AHB) Chacras de Coria, Mendoza, Argentina
| | - Ricardo Williams Masuelli
- Facultad de Ciencias Agrarias, Instituto de Biología Agrícola de Mendoza, Consejo Nacional de Investigaciones Científicas y Técnicas (IBAM-CONICET), Universidad Nacional de Cuyo, A. Brown 500 (M5528AHB) Chacras de Coria, Mendoza, Argentina.
| |
Collapse
|
11
|
Kozlowski DKL, Hassanaly‐Goulamhoussen R, Da Rocha M, Koutsovoulos GD, Bailly‐Bechet M, Danchin EGJ. Movements of transposable elements contribute to the genomic plasticity and species diversification in an asexually reproducing nematode pest. Evol Appl 2021; 14:1844-1866. [PMID: 34295368 PMCID: PMC8288018 DOI: 10.1111/eva.13246] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 04/12/2021] [Accepted: 04/15/2021] [Indexed: 12/14/2022] Open
Abstract
Despite reproducing without sexual recombination, Meloidogyne incognita is an adaptive and versatile phytoparasitic nematode. This species displays a global distribution, can parasitize a large range of plants, and can overcome plant resistance in a few generations. The mechanisms underlying this adaptability remain poorly known. At the whole-genome level, only a few single nucleotide variations have been observed across different geographical isolates with distinct ranges of compatible hosts. Exploring other factors possibly involved in genomic plasticity is thus important. Transposable elements (TEs), by their repetitive nature and mobility, can passively and actively impact the genome dynamics. This is particularly expected in polyploid hybrid genomes such as the one of M. incognita. Here, we have annotated the TE content of M. incognita, analyzed the statistical properties of this TE landscape, and used whole-genome pool-seq data to estimate the mobility of these TEs across twelve geographical isolates, presenting variations in ranges of compatible host plants. DNA transposons are more abundant than retrotransposons, and the high similarity of TE copies to their consensus sequences suggests they have been at least recently active. We have identified loci in the genome where the frequencies of presence of a TE showed substantial variations across the different isolates. Overall, variations in TE frequencies across isolates followed their phylogenetic divergence, suggesting TEs participate in the species diversification. Compared with the M. incognita reference genome, we detected isolate and lineage-specific de novo insertion of some TEs, including within genic regions or in the upstream regulatory regions. We validated by PCR the insertion of some of these TEs inside genic regions, confirming TE movements have possible functional impacts. Overall, we show DNA transposons can drive genomic plasticity in M. incognita and their role in genome evolution of other parthenogenetic animal deserves further investigation.
Collapse
|
12
|
Nieto Feliner G, Casacuberta J, Wendel JF. Genomics of Evolutionary Novelty in Hybrids and Polyploids. Front Genet 2020; 11:792. [PMID: 32849797 PMCID: PMC7399645 DOI: 10.3389/fgene.2020.00792] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 07/03/2020] [Indexed: 12/15/2022] Open
Abstract
It has long been recognized that hybridization and polyploidy are prominent processes in plant evolution. Although classically recognized as significant in speciation and adaptation, recognition of the importance of interspecific gene flow has dramatically increased during the genomics era, concomitant with an unending flood of empirical examples, with or without genome doubling. Interspecific gene flow is thus increasingly thought to lead to evolutionary innovation and diversification, via adaptive introgression, homoploid hybrid speciation and allopolyploid speciation. Less well understood, however, are the suite of genetic and genomic mechanisms set in motion by the merger of differentiated genomes, and the temporal scale over which recombinational complexity mediated by gene flow might be expressed and exposed to natural selection. We focus on these issues here, considering the types of molecular genetic and genomic processes that might be set in motion by the saltational event of genome merger between two diverged species, either with or without genome doubling, and how these various processes can contribute to novel phenotypes. Genetic mechanisms include the infusion of new alleles and the genesis of novel structural variation including translocations and inversions, homoeologous exchanges, transposable element mobilization and novel insertional effects, presence-absence variation and copy number variation. Polyploidy generates massive transcriptomic and regulatory alteration, presumably set in motion by disrupted stoichiometries of regulatory factors, small RNAs and other genome interactions that cascade from single-gene expression change up through entire networks of transformed regulatory modules. We highlight both these novel combinatorial possibilities and the range of temporal scales over which such complexity might be generated, and thus exposed to natural selection and drift.
Collapse
Affiliation(s)
- Gonzalo Nieto Feliner
- Department of Biodiversity and Conservation, Real Jardín Botánico, CSIC, Madrid, Spain
| | - Josep Casacuberta
- Center for Research in Agricultural Genomics, CRAG (CSIC-IRTA-UAB-UB), Barcelona, Spain
| | - Jonathan F. Wendel
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, United States
| |
Collapse
|
13
|
Heitkam T, Weber B, Walter I, Liedtke S, Ost C, Schmidt T. Satellite DNA landscapes after allotetraploidization of quinoa (Chenopodium quinoa) reveal unique A and B subgenomes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 103:32-52. [PMID: 31981259 DOI: 10.1111/tpj.14705] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 12/10/2019] [Accepted: 01/17/2020] [Indexed: 06/10/2023]
Abstract
If two related plant species hybridize, their genomes may be combined and duplicated within a single nucleus, thereby forming an allotetraploid. How the emerging plant balances two co-evolved genomes is still a matter of ongoing research. Here, we focus on satellite DNA (satDNA), the fastest turn-over sequence class in eukaryotes, aiming to trace its emergence, amplification, and loss during plant speciation and allopolyploidization. As a model, we used Chenopodium quinoa Willd. (quinoa), an allopolyploid crop with 2n = 4x = 36 chromosomes. Quinoa originated by hybridization of an unknown female American Chenopodium diploid (AA genome) with an unknown male Old World diploid species (BB genome), dating back 3.3-6.3 million years. Applying short read clustering to quinoa (AABB), C. pallidicaule (AA), and C. suecicum (BB) whole genome shotgun sequences, we classified their repetitive fractions, and identified and characterized seven satDNA families, together with the 5S rDNA model repeat. We show unequal satDNA amplification (two families) and exclusive occurrence (four families) in the AA and BB diploids by read mapping as well as Southern, genomic, and fluorescent in situ hybridization. Whereas the satDNA distributions support C. suecicum as possible parental species, we were able to exclude C. pallidicaule as progenitor due to unique repeat profiles. Using quinoa long reads and scaffolds, we detected only limited evidence of intergenomic homogenization of satDNA after allopolyploidization, but were able to exclude dispersal of 5S rRNA genes between subgenomes. Our results exemplify the complex route of tandem repeat evolution through Chenopodium speciation and allopolyploidization, and may provide sequence targets for the identification of quinoa's progenitors.
Collapse
Affiliation(s)
- Tony Heitkam
- Institute of Botany, Technische Universität Dresden, 01069, Dresden, Germany
| | - Beatrice Weber
- Institute of Botany, Technische Universität Dresden, 01069, Dresden, Germany
| | - Ines Walter
- Institute of Botany, Technische Universität Dresden, 01069, Dresden, Germany
| | - Susan Liedtke
- Institute of Botany, Technische Universität Dresden, 01069, Dresden, Germany
| | - Charlotte Ost
- Institute of Botany, Technische Universität Dresden, 01069, Dresden, Germany
- Institute of Biology, Martin-Luther-Universität Halle-Wittenberg, 06120, Halle (Saale), Germany
| | - Thomas Schmidt
- Institute of Botany, Technische Universität Dresden, 01069, Dresden, Germany
| |
Collapse
|
14
|
Borredá C, Pérez-Román E, Ibanez V, Terol J, Talon M. Reprogramming of Retrotransposon Activity during Speciation of the Genus Citrus. Genome Biol Evol 2020; 11:3478-3495. [PMID: 31710678 PMCID: PMC7145672 DOI: 10.1093/gbe/evz246] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2019] [Indexed: 12/13/2022] Open
Abstract
Speciation of the genus Citrus from a common ancestor has recently been established to begin ∼8 Ma during the late Miocene, a period of major climatic alterations. Here, we report the changes in activity of Citrus LTR retrotransposons during the process of diversification that gave rise to the current Citrus species. To reach this goal, we analyzed four pure species that diverged early during Citrus speciation, three recent admixtures derived from those species and an outgroup of the Citrus clade. More than 30,000 retrotransposons were grouped in ten linages. Estimations of LTR insertion times revealed that retrotransposon activity followed a species-specific pattern of change that could be ascribed to one of three different models. In some genomes, the expected pattern of gradual transposon accumulation was suddenly arrested during the radiation of the ancestor that gave birth to the current Citrus species. The individualized analyses of retrotransposon lineages showed that in each and every species studied, not all lineages follow the general pattern of the species itself. For instance, in most of the genomes, the retrotransposon activity of elements from the SIRE lineage reached its highest level just before Citrus speciation, while for Retrofit elements, it has been steadily growing. Based on these observations, we propose that Citrus retrotransposons may respond to stressful conditions driving speciation as a part of the genetic response involved in adaptation. This proposal implies that the evolving conditions of each species interact with the internal regulatory mechanisms of the genome controlling the proliferation of mobile elements.
Collapse
Affiliation(s)
- Carles Borredá
- Centro de Genómica, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia, Spain
| | - Estela Pérez-Román
- Centro de Genómica, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia, Spain
| | - Victoria Ibanez
- Centro de Genómica, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia, Spain
| | - Javier Terol
- Centro de Genómica, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia, Spain
| | - Manuel Talon
- Centro de Genómica, Instituto Valenciano de Investigaciones Agrarias (IVIA), Valencia, Spain
| |
Collapse
|
15
|
Eriksson MC, Szukala A, Tian B, Paun O. Current research frontiers in plant epigenetics: an introduction to a Virtual Issue. THE NEW PHYTOLOGIST 2020; 226:285-288. [PMID: 32180259 PMCID: PMC7154677 DOI: 10.1111/nph.16493] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
http://www.newphytologist.com/virtualissues
Collapse
Affiliation(s)
- Mimmi C. Eriksson
- Botany and Biodiversity ResearchUniversity of ViennaRennweg 14A‐1030ViennaAustria
- Vienna Graduate School of Population GeneticsVeterinärplatz 1A‐1210ViennaAustria
| | - Aglaia Szukala
- Botany and Biodiversity ResearchUniversity of ViennaRennweg 14A‐1030ViennaAustria
- Vienna Graduate School of Population GeneticsVeterinärplatz 1A‐1210ViennaAustria
| | - Bin Tian
- Botany and Biodiversity ResearchUniversity of ViennaRennweg 14A‐1030ViennaAustria
- Southwest Forestry UniversityKunming650224China
| | - Ovidiu Paun
- Botany and Biodiversity ResearchUniversity of ViennaRennweg 14A‐1030ViennaAustria
| |
Collapse
|
16
|
Glombik M, Bačovský V, Hobza R, Kopecký D. Competition of Parental Genomes in Plant Hybrids. FRONTIERS IN PLANT SCIENCE 2020; 11:200. [PMID: 32158461 PMCID: PMC7052263 DOI: 10.3389/fpls.2020.00200] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 02/11/2020] [Indexed: 05/17/2023]
Abstract
Interspecific hybridization represents one of the main mechanisms of plant speciation. Merging of two genomes from different subspecies, species, or even genera is frequently accompanied by whole-genome duplication (WGD). Besides its evolutionary role, interspecific hybridization has also been successfully implemented in multiple breeding programs. Interspecific hybrids combine agronomic traits of two crop species or can be used to introgress specific loci of interests, such as those for resistance against abiotic or biotic stresses. The genomes of newly established interspecific hybrids (both allopolyploids and homoploids) undergo dramatic changes, including chromosome rearrangements, amplifications of tandem repeats, activation of mobile repetitive elements, and gene expression modifications. To ensure genome stability and proper transmission of chromosomes from both parental genomes into subsequent generations, allopolyploids often evolve mechanisms regulating chromosome pairing. Such regulatory systems allow only pairing of homologous chromosomes and hamper pairing of homoeologs. Despite such regulatory systems, several hybrid examples with frequent homoeologous chromosome pairing have been reported. These reports open a way for the replacement of one parental genome by the other. In this review, we provide an overview of the current knowledge of genomic changes in interspecific homoploid and allopolyploid hybrids, with strictly homologous pairing and with relaxed pairing of homoeologs.
Collapse
Affiliation(s)
- Marek Glombik
- Institute of Experimental Botany, Czech Academy of Sciences, Centre of the Region Hana for Biotechnological and Agricultural Research, Olomouc, Czechia
| | - Václav Bačovský
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czechia
| | - Roman Hobza
- Institute of Experimental Botany, Czech Academy of Sciences, Centre of the Region Hana for Biotechnological and Agricultural Research, Olomouc, Czechia
- Department of Plant Developmental Genetics, Institute of Biophysics of the Czech Academy of Sciences, Brno, Czechia
| | - David Kopecký
- Institute of Experimental Botany, Czech Academy of Sciences, Centre of the Region Hana for Biotechnological and Agricultural Research, Olomouc, Czechia
| |
Collapse
|
17
|
Usai G, Mascagni F, Vangelisti A, Giordani T, Ceccarelli M, Cavallini A, Natali L. Interspecific hybridisation and LTR-retrotransposon mobilisation-related structural variation in plants: A case study. Genomics 2019; 112:1611-1621. [PMID: 31605729 DOI: 10.1016/j.ygeno.2019.09.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 07/13/2019] [Accepted: 09/12/2019] [Indexed: 11/30/2022]
Abstract
The dynamics of long-terminal-repeat retrotransposons in two poplar species (Populus deltoides and P. nigra) and in an interspecific hybrid, recently synthesized, were investigated by analyzing the genomic abundance and transcription levels of a collection of 828 full-length retroelements identified in the genome sequence of P. trichocarpa, all occurring also in the genomes of P. deltoides and P. nigra. Overall, genomic abundance and transcription levels of many retrotransposons in the hybrid resulted higher or lower than expected by calculating the mean of the parental values. A bioinformatics procedure was established to ascertain the occurrence of the same retrotransposon loci in the three genotypes. The results indicated that retrotransposon abundance variations between the hybrid and the mean value of the parents were due to i) co-segregation of retrotransposon high- or low-abundant haplotypes; ii) new retroelement insertions; iii) retrotransposon loss. Concerning retrotransposon expression, this was generally low, with only 14/828 elements over- or under-expressed in the hybrid than expected by calculating the mean of the parents. It is concluded that interspecific hybridisation between the two poplar species determine quantitative variation and differential expression of some retrotransposons, with possible consequences for the genetic differentiation of the hybrid.
Collapse
Affiliation(s)
- Gabriele Usai
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, I-56124 Pisa, Italy
| | - Flavia Mascagni
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, I-56124 Pisa, Italy
| | - Alberto Vangelisti
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, I-56124 Pisa, Italy
| | - Tommaso Giordani
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, I-56124 Pisa, Italy
| | - Marilena Ceccarelli
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di sotto 8, 06123 Perugia, Italy
| | - Andrea Cavallini
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, I-56124 Pisa, Italy.
| | - Lucia Natali
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, I-56124 Pisa, Italy.
| |
Collapse
|
18
|
McCarthy EW, Landis JB, Kurti A, Lawhorn AJ, Chase MW, Knapp S, Le Comber SC, Leitch AR, Litt A. Early consequences of allopolyploidy alter floral evolution in Nicotiana (Solanaceae). BMC PLANT BIOLOGY 2019; 19:162. [PMID: 31029077 PMCID: PMC6486959 DOI: 10.1186/s12870-019-1771-5] [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: 10/03/2018] [Accepted: 04/10/2019] [Indexed: 05/08/2023]
Abstract
BACKGROUND Polyploidy has played a major role in angiosperm evolution. Previous studies have examined polyploid phenotypes in comparison to their extant progenitors, but not in context of predicted progenitor phenotypes at allopolyploid origin. In addition, differences in the trends of polyploid versus diploid evolution have not been investigated. We use ancestral character-state reconstructions to estimate progenitor phenotype at allopolyploid origin to determine patterns of polyploid evolution leading to morphology of the extant species. We also compare trends in diploid versus allopolyploid evolution to determine if polyploidy modifies floral evolutionary patterns. RESULTS Predicting the ancestral phenotype of a nascent allopolyploid from reconstructions of diploid phenotypes at the time of polyploid formation generates different phenotype predictions than when extant diploid phenotypes are used, the outcome of which can alter conclusions about polyploid evolution; however, most analyses yield the same results. Using ancestral reconstructions of diploid floral phenotypes indicate that young polyploids evolve shorter, wider corolla tubes, but older polyploids and diploids do not show any detectable evolutionary trends. Lability of the traits examined (floral shape, corolla tube length, and corolla tube width) differs across young and older polyploids and diploids. Corolla length is more evolutionarily labile in older polyploids and diploids. Polyploids do not display unique suites of floral characters based on both morphological and color traits, but some suites of characters may be evolving together and seem to have arisen multiple times within Nicotiana, perhaps due to the influence of pollinators. CONCLUSIONS Young polyploids display different trends in floral evolution (shorter, wider corolla tubes, which may result in more generalist pollination) than older polyploids and diploids, suggesting that patterns of divergence are impacted by the early consequences of allopolyploidy, perhaps arising from genomic shock and/or subsequent genome stabilization associated with diploidization. Convergent evolution in floral morphology and color in Nicotiana can be consistent with pollinator preferences, suggesting that pollinators may have shaped floral evolution in Nicotiana.
Collapse
Affiliation(s)
- Elizabeth W. McCarthy
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA 92521 USA
- Present address: Department of Biological Sciences, SUNY Cortland, Cortland, NY 13045 USA
| | - Jacob B. Landis
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA 92521 USA
- Department of Biology, University of Florida, Gainesville, FL 32611 USA
- Florida Museum of Natural History, University of Florida, Gainesville, FL 32611 USA
| | - Amelda Kurti
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA 92521 USA
| | - Amber J. Lawhorn
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA 92521 USA
| | - Mark W. Chase
- Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3DS UK
- Department of Environment and Agriculture, Curtin University, Bentley, Western Australia 6102 Australia
| | | | - Steven C. Le Comber
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS UK
| | - Andrew R. Leitch
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS UK
| | - Amy Litt
- Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA 92521 USA
| |
Collapse
|