Radiation of the Nod‐independent <i>Aeschynomene</i> relies on multiple allopolyploid speciation events

Arrighi, Jean-François; Chaintreuil, Clémence; Cartieaux, Fabienne; Cardi, Céline; Rodier-Goud, Marguerite; Brown, Spencer; Boursot, Marc; D’Hont, Angélique; Dreyfus, B; Giraud, Éric

doi:10.1111/nph.12594

Cited by 12 publications

(42 citation statements)

References 46 publications

(76 reference statements)

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“…Interpreting variation in rDNA loci number and localisation in closely related species within a phylogenetic framework and in an evolutionary context has provided valuable information about relationships between diploids and polyploids when genetic knowledge is limited (e.g., Prospero [6]; Aeschynomene [7]; Hepatica [9]; Heliophila [34]; Nicotiana [46]). The Glechoma species investigated here show micro- and macromorphological similarity, a uniform basic chromosome number and the same level of polyploidy [15–16, 21, 23].…”

Section: Discussionmentioning

confidence: 99%

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rDNA Loci Evolution in the Genus Glechoma (Lamiaceae)

et al. 2016

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Glechoma L. (Lamiaceae) is distributed in eastern Asia and Europe. Understanding chromosome evolution in Glechoma has been strongly hampered by its small chromosomes, constant karyotype and polyploidy. Here phylogenetic patterns and chromosomal variation in Glechoma species are considered, using genome sizes, chromosome mapping of 5S and 35S rDNAs by fluorescence in situ hybridisation (FISH), and phylogenetic analyses of internal transcribed spacers (nrITS) of 35S rDNA and 5S rDNA NTS sequences. Species and populations of Glechoma are tetraploid (2n = 36) with base chromosome number of x = 9. Four chromosomes carry pericentric 5S rDNA sites in their short arms in all the species. Two to four of these chromosomes also carry 35S rDNA in subterminal regions of the same arms. Two to four other chromosomes have 35S rDNA sites, all located subterminally within short arms; one individual possessed additional weak pericentric 35S rDNA signals on three other chromosomes. Five types of rDNA locus distribution have been defined on the basis of 35S rDNA variation, but none is species-specific, and most species have more than one type. Glechoma hederacea has four types. Genome size in Glechoma ranges from 0.80 to 0.94 pg (1C), with low levels of intrapopulational variation in all species. Phylogenetic analyses of ITS and NTS sequences distinguish three main clades coinciding with geographical distribution: European (G. hederacea–G. hirsuta), Chinese and Korean (G. longituba), and Japanese (G. grandis). The paper presents the first comparative cytogenetic analyses of Glechoma species including karyotype structure, rDNA location and number, and genome size interpreted in a phylogenetic context. The observed variation suggests that the genus is still in genomic flux. Genome size, but not rDNA loci number and distribution, provides a character for species delimitation which allows better inferences of interspecific relationships to be made, in the absence of well-defined morphological differentiation.

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Section: Discussionmentioning

confidence: 99%

“…Glechoma is a relatively young genus (3–6 mya [61–62]) and contains possible hybrids and several ploidy levels [48]. Coincident low levels of rDNA locus variation, particularly of 35S rDNA, coupled with low amounts of morphological differentiation have been reported in other polyploid complexes [7, 55]. …”

Section: Discussionmentioning

confidence: 99%

rDNA Loci Evolution in the Genus Glechoma (Lamiaceae)

et al. 2016

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“…DNA labeling, chromosome hybridization and fluorescent image capture were performed as described in Arrighi et al . ().…”

Section: Methodsmentioning

confidence: 97%

“…PCR amplifications, cloning and sequencing of PCR products were performed as described in Arrighi et al . (, ). The DNA sequences generated in this study were deposited in GenBank under accession numbers – (Table S2).…”

Section: Methodsmentioning

confidence: 99%

The evolutionary dynamics of ancient and recent polyploidy in the African semiaquatic species of the legume genus Aeschynomene

et al. 2016

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SummaryThe legume genus Aeschynomene is notable in the ability of certain semiaquatic species to develop nitrogen-fixing stem nodules. These species are distributed in two clades. In the first clade, all the species are characterized by the use of a unique Nod-independent symbiotic process. In the second clade, the species use a Nod-dependent symbiotic process and some of them display a profuse stem nodulation as exemplified in the African Aeschynomene afraspera.To facilitate the molecular analysis of the symbiotic characteristics of such legumes, we took an integrated molecular and cytogenetic approach to track occurrences of polyploidy events and to analyze their impact on the evolution of the African species of Aeschynomene.Our results revealed two rounds of polyploidy: a paleopolyploid event predating the African group and two neopolyploid speciations, along with significant chromosomal variations. Hence, we found that A. afraspera (8x) has inherited the contrasted genomic properties and the stem-nodulation habit of its parental lineages (4x).This study reveals a comprehensive picture of African Aeschynomene diversification. It notably evidences a history that is distinct from the diploid Nod-independent clade, providing clues for the identification of the specific determinants of the Nod-dependent and Nodindependent symbiotic processes, and for comparative analysis of stem nodulation.

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“…serrulata, which is diploid, contrary to A. indica and A. afraspera, which are allopolyploids (Renard et al, 1983;Arrighi et al, 2014). A BLAST search using MtDNF1 allowed the identification in the A. evenia ssp.…”

Section: Ncr-like Peptides Target Bacteroids In Aeschynomene Spp Nodmentioning

confidence: 99%

Convergent Evolution of Endosymbiont Differentiation in Dalbergioid and Inverted Repeat-Lacking Clade Legumes Mediated by Nodule-Specific Cysteine-Rich Peptides

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Cartieaux³

et al. 2015

Plant Physiol.

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Nutritional symbiotic interactions require the housing of large numbers of microbial symbionts, which produce essential compounds for the growth of the host. In the legume-rhizobium nitrogen-fixing symbiosis, thousands of rhizobium microsymbionts, called bacteroids, are confined intracellularly within highly specialized symbiotic host cells. In Inverted Repeat-Lacking Clade (IRLC) legumes such as Medicago spp., the bacteroids are kept under control by an arsenal of nodulespecific cysteine-rich (NCR) peptides, which induce the bacteria in an irreversible, strongly elongated, and polyploid state. Here, we show that in Aeschynomene spp. legumes belonging to the more ancient Dalbergioid lineage, bacteroids are elongated or spherical depending on the Aeschynomene spp. and that these bacteroids are terminally differentiated and polyploid, similar to bacteroids in IRLC legumes. Transcriptome, in situ hybridization, and proteome analyses demonstrated that the symbiotic cells in the Aeschynomene spp. nodules produce a large diversity of NCR-like peptides, which are transported to the bacteroids. Blocking NCR transport by RNA interference-mediated inactivation of the secretory pathway inhibits bacteroid differentiation. Together, our results support the view that bacteroid differentiation in the Dalbergioid clade, which likely evolved independently from the bacteroid differentiation in the IRLC clade, is based on very similar mechanisms used by IRLC legumes.

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Radiation of the Nod‐independent Aeschynomene relies on multiple allopolyploid speciation events

Cited by 12 publications

References 46 publications

rDNA Loci Evolution in the Genus Glechoma (Lamiaceae)

rDNA Loci Evolution in the Genus Glechoma (Lamiaceae)

The evolutionary dynamics of ancient and recent polyploidy in the African semiaquatic species of the legume genus Aeschynomene

Convergent Evolution of Endosymbiont Differentiation in Dalbergioid and Inverted Repeat-Lacking Clade Legumes Mediated by Nodule-Specific Cysteine-Rich Peptides

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