Chantha SC(1), Herman AC(1,2), Castric V(3), Vekemans X(3), Marande W(4), Schoen DJ(1).

 Author information

(1) Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montreal, QC, Canada,H3A1B1.

(2) Department of Plant Biology, University of Minnesota, St Paul, MN, 55108, USA.

(3) Unité Evo-Eco-Paléo (EEP) - UMR 8198, CNRS/Université de Lille - Sciences et Technologies, Villeneuve d'Ascq Cedex, F-59655, France

(4) Institut National de la Recherche Agronomique, 31326, Castanet Tolosan Cedex, France. 

Journal: New Phytologist

DOI:   10.1111/nph.14764

Abstract

The Leavenworthia self-incompatibility locus (S locus) consists of paralogs (Lal2, SCRL) of the canonical Brassicaceae S locus genes (SRK, SCR), and is situated in a genomic position that differs from the ancestral one in the Brassicaceae. Unexpectedly, in a small number of Leavenworthia alabamica plants examined, sequences closely resembling exon 1 of SRK have been found, but the function of these has remained unclear. BAC cloning and expression analyses were employed to characterize these SRK-like sequences. An SRK-positive Bacterial Artificial Chromosome clone was found to contain complete SRK and SCR sequences located close by one another in the derived genomic position of the Leavenworthia S locus, and in place of the more typical Lal2 and SCRL sequences. These sequences are expressed in stigmas and anthers, respectively, and crossing data show that the SRK/SCR haplotype is functional in self-incompatibility. Population surveys indicate that < 5% of Leavenworthia S loci possess such alleles. An ancestral translocation or recombination event involving SRK/SCR and Lal2/SCRL likely occurred, together with neofunctionalization of Lal2/SCRL, and both haplotype groups now function as Leavenworthia S locus alleles. These findings suggest that S locus alleles can have distinctly different evolutionary origins.

Link: http://onlinelibrary.wiley.com/doi/10.1111/nph.14764/full

Link: http://onlinelibrary.wiley.com/doi/10.1111/tpj.13450/abstract

Rizzolatti C, Bury P, Tatara E, Pin PA, Rodde N, Berges H, Budar F, Mireau H, Gielen JJL.

Journal: Euphytica

DOI: 213: 276.

Abstract

Hybridization technology has proven valuable in enhancing yields in many crops, but was only recently adopted in the small grain cereals. Hybrid varieties in barley (Hordeum vulgare) rely on the cytoplasmic male sterility (CMS) system msm1 derived from Hordeum vulgare ssp. spontaneum. The major restorer gene described for the msm1 system is known as Rfm1 and maps to the top of chromosome 6H. To gain further insight into mechanisms underlying male fertility restoration in barley, we used a map-based cloning approach to identify the nuclear gene involved in the restoration mechanism of this hybridization system. Taking advantage of the available genomic resources in barley in combination with a custom-made non-gridded BAC library developed from a restorer line, we cloned and sequenced the Rfm1 restorer locus. The characterization and annotation of the nucleotide sequence for the Rfm1 restorer allele allowed for the identification of the candidate gene for Rfm1. The Rfm1 locus carries a tandem repeat of a gene encoding a pentatricopeptide repeat (PPR) protein. Surprisingly, Rfm1 belongs to the PLS-DYW subfamily of PPR genes known for their involvement in RNA editing in plants organelles, but that to date have not been identified as restorer genes.

Link: https://link.springer.com/article/10.1007%2Fs10681-017-2056-4

Novikova PY, Tsuchimatsu T, Simon S, Nizhynska V, Voronin V, Burns R, Fedorenko OM, Holm S, Saell T, Prat E, Marande W, Castric V, Nordborg M.

Journal: Molecular Biology and Evolution

DOI: 34: 957-968.

Abstract

Polyploidy is an example of instantaneous speciation when it involves the formation of a new cytotype that is incompatible with the parental species. Because new polyploid individuals are likely to be rare, establishment of a new species is unlikely unless polyploids are able to reproduce through self-fertilization (selfing), or asexually. Conversely, selfing (or asexuality) makes it possible for polyploid species to originate from a single individual—a bona fide speciation event. The extent to which this happens is not known. Here, we consider the origin of Arabidopsis suecica, a selfing allopolyploid between Arabidopsis thaliana and Arabidopsis arenosa, which has hitherto been considered to be an example of a unique origin. Based on whole-genome re-sequencing of 15 natural A. suecica accessions, we identify ubiquitous shared polymorphism with the parental species, and hence conclusively reject a unique origin in favor of multiple founding individuals. We further estimate that the species originated after the last glacial maximum in Eastern Europe or central Eurasia (rather than Sweden, as the name might suggest). Finally, annotation of the self-incompatibility loci in A. suecica revealed that both loci carry non-functional alleles. The locus inherited from the selfing A. thaliana is fixed for an ancestral non-functional allele, whereas the locus inherited from the outcrossing A. arenosa is fixed for a novel loss-of-function allele. Furthermore, the allele inherited from A. thaliana is predicted to transcriptionally silence the allele inherited from A. arenosa, suggesting that loss of self-incompatibility may have been instantaneous.

Link: https://academic.oup.com/mbe/article/34/4/957/2838775

Demars J, Cano M, Drouilhet L, Plisson-Petit F, Bardou P, Fabre S, Servin B, Sarry J, Woloszyn F, Mulsant P, Foulquier D, Carriere F, Aletru M, Rodde N, Cauet S, Bouchez O, Pirson M, Tosser-Klopp G, Allain D.

Journal: Molecular Biology and Evolution

DOI: 34: 1722-1729.

Abstract

The composition and structure of fleece variation observed in mammals is a consequence of a strong selective pressure for fiber production after domestication. In sheep, fleece variation discriminates ancestral species carrying a long and hairy fleece from modern domestic sheep (Ovis aries) owning a short and woolly fleece. Here, we report that the “woolly” allele results from the insertion of an antisense EIF2S2 retrogene (called asEIF2S2) into the 3′ UTR of the IRF2BP2 gene leading to an abnormal IRF2BP2 transcript. We provide evidence that this chimeric IRF2BP2/asEIF2S2 messenger 1) targets the genuine sense EIF2S2 RNA and 2) creates a long endogenous double-stranded RNA which alters the expression of both EIF2S2 and IRF2BP2 mRNA. This represents a unique example of a phenotype arising via a RNA-RNA hybrid, itself generated through a retroposition mechanism. Our results bring new insights on the sheep population history thanks to the identification of the molecular origin of an evolutionary phenotypic variation.

Link: https://academic.oup.com/mbe/article/34/7/1722/3091105

Holušová K, Vrána J, Šafář J, Šimková H, Balcárková B, Frenkel Z, Darrier B, Paux E, Cattonaro F, Berges H, Letellier T, Alaux M, Doležel J, Bartoš J.

Journal : Plant Genome.
DOI: 10.3835/plantgenome2017.03.0021

Abstract

Bread wheat ( L.) is one of the most important crops worldwide. Although a reference genome sequence would represent a valuable resource for wheat improvement through genomics-assisted breeding and gene cloning, its generation has long been hampered by its allohexaploidy, high repeat content, and large size. As a part of a project coordinated by the International Wheat Genome Sequencing Consortium (IWGSC), a physical map of the short arm of wheat chromosome 3D (3DS) was prepared to facilitate reference genome assembly and positional gene cloning. It comprises 869 contigs with a cumulative length of 274.5 Mbp and represents 85.5% of the estimated chromosome arm size. Eighty-six Mbp of survey sequences from chromosome arm 3DS were assigned in silico to physical map contigs via next-generation sequencing of bacterial artificial chromosome pools, thus providing a high-density framework for physical map ordering along the chromosome arm. About 60% of the physical map was anchored in this single experiment. Finally, 1393 high-confidence genes were anchored to the physical map. Comparisons of gene space of the chromosome arm 3DS with genomes of closely related species [ (L.) P.Beauv., rice ( L.), and sorghum [ (L.) Moench] and homeologous wheat chromosomes provided information about gene movement on the chromosome arm.

Hélène Badouin, Jérôme Gouzy, Christopher J. Grassa, Florent Murat, S. Evan Staton, Ludovic Cottret, Christine Lelandais-Brière, Gregory L. Owens, Sébastien Carrère, Baptiste Mayjonade, Ludovic Legrand, Navdeep Gill, Nolan C. Kane, John E. Bowers, Sariel Hubner, Arnaud Bellec, Aurélie Bérard, Hélène Bergès, Nicolas Blanchet, Marie-Claude Boniface, Dominique Brunel, Olivier Catrice, Nadia Chaidir, Clotilde Claudel, Cécile Donnadieu, Thomas Faraut, Ghislain Fievet, Nicolas Helmstetter, Matthew King, Steven J. Knapp, Zhao Lai, Marie-Christine Le Paslier, Yannick Lippi, Lolita Lorenzon, Jennifer R. Mandel, Gwenola Marage, Gwenaëlle Marchand, Elodie Marquand, Emmanuelle Bret-Mestries, Evan Morien, Savithri Nambeesan, Thuy Nguyen, Prune Pegot-Espagnet, Nicolas Pouilly, Frances Raftis, Erika Sallet, Thomas Schiex, Justine Thomas, Céline Vandecasteele, Didier Varès, Felicity Vear, Sonia Vautrin, Martin Crespi, Brigitte Mangin, John M. Burke, Jérôme Salse, Stéphane Muños, Patrick Vincourt, Loren H. Rieseberg & Nicolas B. Langlade  

Abstract

The domesticated sunflower, Helianthus annuus L., is a global oil crop that has promise for climate change adaptation, because it can maintain stable yields across a wide variety of environmental conditions, including drought. Even greater resilience is achievable through the mining of resistance alleles from compatible wild sunflower relatives, including numerous extremophile species. Here we report a high-quality reference for the sunflower genome (3.6 gigabases), together with extensive transcriptomic data from vegetative and floral organs. The genome mostly consists of highly similar, related sequences and required single-molecule real-time sequencing technologies for successful assembly. Genome analyses enabled the reconstruction of the evolutionary history of the Asterids, further establishing the existence of a whole-genome triplication at the base of the Asterids II clade and a sunflower-specific whole-genome duplication around 29 million years ago. An integrative approach combining quantitative genetics, expression and diversity data permitted development of comprehensive gene networks for two major breeding traits, flowering time and oil metabolism, and revealed new candidate genes in these networks. We found that the genomic architecture of flowering time has been shaped by the most recent whole-genome duplication, which suggests that ancient paralogues can remain in the same regulatory networks for dozens of millions of years. This genome represents a cornerstone for future research programs aiming to exploit genetic diversity to improve biotic and abiotic stress resistance and oil production, while also considering agricultural constraints and human nutritional needs.

The sunflower genome provides insights into oil metabolism, flowering and Asterid evolution

https://www.nature.com/nature/journal/v546/n7656/full/nature22380.html

Authors :

Tsuchimatsu T, Goubet PM, Gallina S, Holl AC, Fobis-Loisy I, Bergès H, Marande W, Prat E, Meng D, Long Q, Platzer A, Nordborg M, Vekemans X, Castric V.

Mol Biol Evol. doi: 10.1093/molbev/msx122.

Abstract :

Although the transition to selfing in the model plant Arabidopsis thaliana involved the loss of the self-incompatibility (SI) system, it clearly did not occur due to the fixation of a single inactivating mutation at the locus determining the specificities of SI (the S-locus). At least three groups of divergent haplotypes (haplogroups), corresponding to ancient functional S-alleles, have been maintained at this locus, and extensive functional studies have shown that all three carry distinct inactivating mutations. However, the historical process of loss of SI is not well understood, in particular its relation with the last glaciation. Here, we took advantage of recently published genomic re-sequencing data in 1,083 Arabidopsis thaliana accessions that we combined with BAC sequencing to obtain polymorphism information for the whole S-locus region at a species-wide scale. The accessions differed by several major rearrangements including large deletions and inter-haplogroup recombinations, forming a set of haplogroups that are widely distributed throughout the native range and largely overlap geographically. 'Relict' A. thaliana accessions that directly derive from glacial refugia are polymorphic at the S-locus, suggesting that the three haplogroups were already present when glacial refugia from the last Ice Age became isolated. Inter-haplogroup recombinant haplotypes were highly frequent, and detailed analysis of recombination breakpoints suggested multiple independent origins. These findings suggest that the complete loss of SI in A. thaliana involved independent self-compatible mutants that arose prior to the last Ice Age, and experienced further rearrangements during post-glacial colonization.

Authors :

Hyles J, Vautrin S, Pettolino F, MacMillan C, Stachurski Z, Breen J, Berges H, Wicker T, Spielmeyer W.

J Exp Bot. doi: 10.1093/jxb/erx051

Abstract :

The tiller inhibition gene (tin) that reduces tillering in wheat (Triticum aestivum) is also associated with large spikes, increased grain weight, and thick leaves and stems. In this study, comparison of near-isogenic lines (NILs) revealed changes in stem morphology, cell wall composition, and stem strength. Microscopic analysis of stem cross-sections and chemical analysis of stem tissue indicated that cell walls in tin lines were thicker and more lignified than in free-tillering NILs. Increased lignification was associated with stronger stems in tin plants. A candidate gene for tin was identified through map-based cloning and was predicted to encode a cellulose synthase-like (Csl) protein with homology to members of the CslA clade. Dinucleotide repeat-length polymorphism in the 5'UTR region of the Csl gene was associated with tiller number in diverse wheat germplasm and linked to expression differences of Csl transcripts between NILs. We propose that regulation of Csl transcript and/or protein levels affects carbon partitioning throughout the plant, which plays a key role in the tin phenotype.

Link : https://www.ncbi.nlm.nih.gov/pubmed/28369427

Authors :

Cauz Santos LA, Freitas Munhoz C, Rodde N, Cauet S, Azevedo Santos A, Alves Penha H, Carnier Dornelas M, de Mello Varani A, Conde Xavier Oliveira G, Bergès H, Carneiro Vieira ML (2017)

Front. Plant Sci. 8:334. DOI: 10.3389/fpls.2017.00334

Abstract :

The family Passifloraceae consists of some 700 species classified in around 16 genera. Almost all its members belong to the genus Passiflora. In Brazil, the yellow passion fruit (Passiflora edulis) is of considerable economic importance, both for juice production and consumption as fresh fruit. The availability of chloroplast genomes (cp genomes) and their sequence comparisons has led to a better understanding of the evolutionary relationships within plant taxa. In this study, we obtained the complete nucleotide sequence of the P. edulis chloroplast genome, the first entirely sequenced in the Passifloraceae family. We determined its structure and organization, and also performed phylogenomic studies on the order Malpighiales and the Fabids clade. The P. edulis chloroplast genome is characterized by the presence of two copies of an inverted repeat sequence (IRA and IRB) of 26,154 bp, each separating a small single copy region of 13,378 bp and a large single copy (LSC) region of 85,720 bp. The annotation resulted in the identification of 105 unique genes, including 30 tRNAs, 4 rRNAs, and 71 protein coding genes. Also, 36 repetitive elements and 85 SSRs (microsatellites) were identified. The structure of the complete cp genome of P. edulis differs from that of other species because of rearrangement events detected by means of a comparison based on 22 members of the Malpighiales. The rearrangements were three inversions of 46,151, 3,765 and 1,631 bp, located in the LSC region. Phylogenomic analysis resulted in strongly supported trees, but this could also be a consequence of the limited taxonomic sampling used. Our results have provided a better understanding of the evolutionary relationships in the Malpighiales and the Fabids, confirming the potential of complete chloroplast genome sequences in inferring evolutionary relationships and the utility of long sequence reads for generating very accurate biological information.

Link : https://www.ncbi.nlm.nih.gov/pubmed/28344587

Authors :

Gilles LM, Khaled A, Laffaire JB, Chaignon S, Gendrot G, Laplaige J, Bergès H, Beydon G, Bayle V, Barret P, Comadran J, Martinant JP, Rogowsky PM, Widiez T.

EMBO J. 2017 Mar 15;36(6):707-717. doi: 10.15252/embj.201796603.

Abstract :

Gynogenesis is an asexual mode of reproduction common to animals and plants, in which stimuli from the sperm cell trigger the development of the unfertilized egg cell into a haploid embryo. Fine mapping restricted a major maize QTL (quantitative trait locus) responsible for the aptitude of inducer lines to trigger gynogenesis to a zone containing a single gene NOT LIKE DAD (NLD) coding for a patatin-like phospholipase A. In all surveyed inducer lines, NLD carries a 4-bp insertion leading to a predicted truncated protein. This frameshift mutation is responsible for haploid induction because complementation with wild-type NLD abolishes the haploid induction capacity. Activity of the NLD promoter is restricted to mature pollen and pollen tube. The translational NLD::citrine fusion protein likely localizes to the sperm cell plasma membrane. In Arabidopsis roots, the truncated protein is no longer localized to the plasma membrane, contrary to the wild-type NLD protein. In conclusion, an intact pollen-specific phospholipase is required for successful sexual reproduction and its targeted disruption may allow establishing powerful haploid breeding tools in numerous crops

Links :

Jackson - 2017 - No sex please, we're (in)breeding

https://www.ncbi.nlm.nih.gov/pubmed/28228439
http://emboj.embopress.org/content/36/6.cover-expansion
http://emboj.embopress.org/

Authors :

Yousfi FE, Makhloufi E, Marande W, Ghorbel AW., Bouzayen M and Bergès H  

Front Plant Sci  7:2034. doi: 10.3389/fpls.2016.02034

Abstract :

WRKY transcription factors are involved in multiple aspects of plant growth, development and responses to biotic stresses. Although they have been found to play roles in regulating plant responses to environmental stresses, these roles still need to be explored, especially those pertaining to crops. Durum wheat is the second most widely produced cereal in the world. Complex, large and unsequenced genomes, in addition to a lack of genomic resources, hinder the molecular characterization of tolerance mechanisms. This paper describes the isolation and characterization of five TdWRKY genes from durum wheat (Triticum turgidum L. ssp. durum). A PCR-based screening of a T. turgidum BAC genomic library using primers within the conserved region of WRKY genes resulted in the isolation of five BAC clones. Following sequencing fully the five BACs, fine annotation through Triannot pipeline revealed 74.6% of the entire sequences as transposable elements and a 3.2% gene content with genes organized as islands within oceans of TEs. Each BAC clone harbored a TdWRKY gene. The study showed a very extensive conservation of genomic structure between TdWRKYs and their orthologs from Brachypodium, barley, and T. aestivum. The structural features of TdWRKY proteins suggested that they are novel members of the WRKY family in durum wheat. TdWRKY1/2/4, TdWRKY3, and TdWRKY5 belong to the group Ia, IIa, and IIc, respectively. Enrichment of cis-regulatory elements related to stress responses in the promoters of some TdWRKY genes indicated their potential roles in mediating plant responses to a wide variety of environmental stresses. TdWRKY genes displayed different expression patterns in response to salt stress that distinguishes two durum wheat genotypes with contrasting salt stress tolerance phenotypes. TdWRKY genes tended to react earlier with a down-regulation in sensitive genotype leaves and with an up-regulation in tolerant genotype leaves. The TdWRKY transcripts levels in roots increased in tolerant genotype compared to sensitive genotype. The present results indicate that these genes might play some functional role in the salt tolerance in durum wheat.

Link
https://www.ncbi.nlm.nih.gov/pubmed/28197152

Authors :

Rousseau-Gueutin M, Morice J, Coriton O, Huteau V, Trotoux G, Nègre S, Falentin C, Deniot G, Gilet M, Eber F, Pelé A, Vautrin S, Fourment J, Lodé M, Bergès H, Chèvre AM.

G3 (Bethesda). pii: g3.116.036517. doi: 10.1534/g3.116.036517.

Abstract :

Allopolyploidy, which results from the merger and duplication of two divergent genomes, has played a major role in the evolution and diversification of flowering plants. The genomic changes that occur in resynthesized or natural neopolyploids have been extensively studied, but little is known about the effects of the reproductive mode in the initial generations that may precede its successful establishment. To truly reflect the early generations of a nascent polyploid, two resynthesized allotetraploid Brassica napus populations were obtained for the first time by open pollination. In these populations, we detected a much lower level of aneuploidy (3rd generation) compared with those previously published populations obtained by controlled successive selfing. We specifically studied 33 resynthesized B. napus individuals from our two open pollinated populations and showed that meiosis was affected in both populations. Their genomes were deeply shuffled after allopolyploidization: up to 8.5% and 3.5% of the C and A subgenomes were deleted in only two generations. The identified deletions occurred mainly at the distal part of the chromosome and to a significantly greater extent on the C rather than the A subgenome. Using Fluorescent In Situ Hybridization (BAC-FISH), we demonstrated that four of these deletions corresponded to fixed translocations (via homoeologous exchanges). We were able to evaluate the size of the structural variations and their impact on the whole genome size, gene content and allelic diversity. In addition, the evolution of fertility was assessed to better understand the difficulty encountered by novel polyploid individuals before the putative formation of a novel stable species.

Link : https://www.ncbi.nlm.nih.gov/pubmed/28007837