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Low cytomolecular diversification in the genus Stylosanthes Sw. (Papilionoideae, Leguminosae).

ABSTRACT: Stylosanthes (Papilionoideae, Leguminosae) is a predominantly Neotropical genus with ~48 species that include worldwide important forage species. This study presents the chromosome number and morphology of eight species of the genus Stylosanthes (S. acuminata, S. gracilis, S. grandifolia, S. guianensis, S. hippocampoides, S. pilosa, S. macrocephala, and S. ruellioides). In addition, staining with CMA and DAPI, in situ hybridization with 5S and 35S rDNA probes, and estimation of DNA content were performed. The interpretation of Stylosanthes chromosome diversification was anchored by a comparison with the sister genus Arachis and a dated molecular phylogeny based on nuclear and plastid loci. Stylosanthes species showed 2n = 20, with low cytomolecular diversification regarding 5S rDNA, 35S rDNA, and genome size. Arachis has a more ancient diversification (~7 Mya in the Pliocene) than the relatively recent Stylosanthes (~2 Mya in the Pleistocene), and it seems more diverse than its sister lineage. Our data support the idea that the cytomolecular stability of Stylosanthes in relation to Arachis could be a result of its recent origin. The recent diversification of Stylosanthes could also be related to the low morphological differentiation among species, and to the recurrent formation of allopolyploid complexes.

SUBMITTER: Franco AL

PROVIDER: S-EPMC7197990 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Low cytomolecular diversification in the genus Stylosanthes Sw. (Papilionoideae, Leguminosae).

Franco Ana Luiza AL Figueredo Amanda A Pereira Lívia de Moraes LM Sousa Saulo Marçal de SM Souza Gustavo G Carvalho Marcelo Ayres MA Simon Marcelo F MF Viccini Lyderson Facio LF

Genetics and molecular biology 20200306 1

Stylosanthes (Papilionoideae, Leguminosae) is a predominantly Neotropical genus with ~48 species that include worldwide important forage species. This study presents the chromosome number and morphology of eight species of the genus Stylosanthes (S. acuminata, S. gracilis, S. grandifolia, S. guianensis, S. hippocampoides, S. pilosa, S. macrocephala, and S. ruellioides). In addition, staining with CMA and DAPI, in situ hybridization with 5S and 35S rDNA probes, and estimation of DNA content were ...[more]

PMID: 31429856

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Project description:Allopolyploidy is widely present across plant lineages. Though estimating the correct phylogenetic relationships and origin of allopolyploids may sometimes become a hard task. In the genus Stylosanthes Sw. (Leguminosae), an important legume crop, allopolyploidy is a key speciation force. This makes difficult adequate species recognition and breeding efforts on the genus. Based on comparative analysis of nine high-throughput sequencing (HTS) samples, including three allopolyploids (S. capitata Vogel cv. "Campo Grande," S. capitata "RS024" and S. scabra Vogel) and six diploids (S. hamata Taub, S. viscosa (L.) Sw., S. macrocephala M. B. Ferreira and Sousa Costa, S. guianensis (Aubl.) Sw., S. pilosa M. B. Ferreira and Sousa Costa and S. seabrana B. L. Maass & 't Mannetje) we provide a working pipeline to identify organelle and nuclear genome signatures that allowed us to trace the origin and parental genome recognition of allopolyploids. First, organelle genomes were de novo assembled and used to identify maternal genome donors by alignment-based phylogenies and synteny analysis. Second, nuclear-derived reads were subjected to repetitive DNA identification with RepeatExplorer2. Identified repeats were compared based on abundance and presence on diploids in relation to allopolyploids by comparative repeat analysis. Third, reads were extracted and grouped based on the following groups: chloroplast, mitochondrial, satellite DNA, ribosomal DNA, repeat clustered- and total genomic reads. These sets of reads were then subjected to alignment and assembly free phylogenetic analyses and were compared to classical alignment-based phylogenetic methods. Comparative analysis of shared and unique satellite repeats also allowed the tracing of allopolyploid origin in Stylosanthes, especially those with high abundance such as the StyloSat1 in the Scabra complex. This satellite was in situ mapped in the proximal region of the chromosomes and made it possible to identify its previously proposed parents. Hence, with simple genome skimming data we were able to provide evidence for the recognition of parental genomes and understand genome evolution of two Stylosanthes allopolyploids.

Project description:Backgrounds and aimsThe genus Stylosanthes includes nitrogen-fixing and drought-tolerant species of considerable economic importance for perennial pasture, green manure and land recovery. Stylosanthes scabra is adapted to variable soil conditions, being cultivated to improve pastures and soils worldwide. Previous studies have proposed S. scabra as an allotetraploid species (2n = 40) with a putative diploid A genome progenitor S. hamata or S. seabrana (2n = 20) and the B genome progenitor S. viscosa (2n = 20). We aimed to provide conclusive evidence for the origin of S. scabra.MethodsWe performed fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH) experiments and Illumina paired-end sequencing of S. scabra, S. hamata and S. viscosa genomic DNA, to assemble and compare complete ribosomal DNA (rDNA) units and chloroplast genomes. Plastome- and genome-wide single nucleotide variation detection was also performed.Key resultsGISH and phylogenetic analyses of plastid DNA and rDNA sequences support that S. scabra is an allotetraploid formed from 0.63 to 0.52 million years ago (Mya), from progenitors with a similar genome structure to the maternal donor S. hamata and the paternal donor S. viscosa. FISH revealed a non-additive number of 35S rDNA sites in S. scabra compared with its progenitors, indicating the loss of one locus from A genome origin. In S. scabra, most 5S rDNA units were similar to S. viscosa, while one 5S rDNA site of reduced size most probably came from an A genome species as revealed by GISH and in silico analysis.ConclusionsOur approach combined whole-plastome and rDNA assembly with additional cytogenetic analysis to shed light successfully on the allotetraploid origin of S. scabra. We propose a Middle Pleistocene origin for S. scabra involving species with maternal A and paternal B genomes. Our data also suggest that variation found in rDNA units in S. scabra and its progenitors reveals differences that can be explained by homogenization, deletion and amplification processes that have occurred since its origin.

Project description:Background and aimsSpecies of the genus Burkholderia, from the Betaproteobacteria, have been isolated from legume nodules, but so far they have only been shown to form symbioses with species of Mimosa, sub-family Mimosoideae. This work investigates whether Burkholderia tuberum strains STM678 (isolated from Aspalathus carnosa) and DUS833 (from Aspalathus callosa) can nodulate species of the South African endemic papilionoid genera Cyclopia (tribe Podalyrieae) and Aspalathus (Crotalarieae) as well as the promiscuous legume Macroptilium atropurpureum (Phaseoleae).MethodsBacterial strains and the phylogeny of their symbiosis-related (nod) genes were examined via 16S rRNA gene sequencing. Seedlings were grown in liquid culture and inoculated with one of the two strains of B. tuberum or with Sinorhizobium strain NGR 234 (from Lablab purpureus), Mesorhizobium strain DUS835 (from Aspalathus linearis) or Methylobacterium nodulans (from Crotalaria podocarpa). Some nodules, inoculated with green fluorescence protein (GFP)-tagged strains, were examined by light and electron microscopy coupled with immunogold labelling with a Burkholderia-specific antibody. The presence of active nitrogenase was checked by immunolabelling of nitrogenase and by the acetylene reduction assay. B. tuberum STM678 was also tested on a wide range of legumes from all three sub-families.Key resultsNodules were not formed on any of the Aspalathus spp. Only B. tuberum nodulated Cyclopia falcata, C. galioides, C. genistoides, C. intermedia and C. pubescens. It also effectively nodulated M. atropurpureum but no other species tested. GFP-expressing inoculant strains were located inside infected cells of C. genistoides, and bacteroids in both Cyclopia spp. and M. atropurpureum were immunogold-labelled with antibodies against Burkholderia and nitrogenase. Nitrogenase activity was also shown using the acetylene reduction assay. This is the first demonstration that a beta-rhizobial strain can effectively nodulate papilioinoid legumes.ConclusionsPapilionoid legumes from widely different tribes can be nodulated by beta-rhizobia, forming both indeterminate (Cyclopia) and determinate (Macroptilium) nodules.

Dataset Information

Low cytomolecular diversification in the genus Stylosanthes Sw. (Papilionoideae, Leguminosae).

Publications

Low cytomolecular diversification in the genus Stylosanthes Sw. (Papilionoideae, Leguminosae).

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