A novel hybrid of Hypericum undulatum (Wavy-leaved St. John’s-wort, Hypericaceae) and its subsequent dispersal

Andrew Jones; Fred Rumsey

doi:10.33928/bib.2020.02.207

A novel hybrid of Hypericum undulatum (Wavy-leaved St. John’s-wort, Hypericaceae) and its subsequent dispersal

British & Irish Botany ◽

10.33928/bib.2020.02.207 ◽

2020 ◽

Vol 2 (3) ◽

Author(s):

Andrew Jones ◽

Fred Rumsey

Keyword(s):

De Novo ◽

Parental Species ◽

Species Range ◽

The Novel ◽

The Core ◽

St John’S Wort ◽

St John's Wort ◽

Core Site

The novel hybrid Hypericum undulatum Schousb. ex. Willd. x H. perforatum L. is described from Cardiganshire (v.c.46) and given the name H. x cereticae R.A. Jones, F.J. Rumsey & N. Robson. Despite reduced fertility it shows indications of ongoing introgression and signs of recent dispersal up to 5 km from the core site. The hybrid has arisen recently at the northern extremes of the rarer (H. undulatum) parental species’ range, although at neither site are the parents currently sympatric and in the outlying population both are absent, supporting the belief that here it has not arisen de novo but has colonised through unknown agencies.

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Massive rhizobial genomic variations associated with partner quality in Lotus–Mesorhizobium symbiosis

10.1101/2020.03.08.983007 ◽

2020 ◽

Author(s):

Masaru Bamba ◽

Seishiro Aoki ◽

Tadashi Kajita ◽

Hiroaki Setoguchi ◽

Yasuyuki Watano ◽

...

Keyword(s):

Core Genome ◽

De Novo ◽

Lotus Japonicus ◽

The Novel ◽

Associated Bacteria ◽

Association Analyses ◽

Genomic Variations ◽

The Core ◽

Genome Variations

ABSTRACTIn diverse mutualistic relationships, genetic variations in impact on the growth of interacting partners—variations in partner quality—are common, despite the theoretical prediction that selection favoring high-quality partners should eliminate such variations. Here, we investigated how variations in partner quality could be maintained in the nitrogen-fixing mutualism between Lotus japonicus and Mesorhizobium bacteria. We reconstructed de novo assembled full-genome sequences from nine rhizobial symbionts, finding massive variations in the core genome and the contrastingly similar symbiotic islands, indicating recent horizontal gene transfer (HGT) of the symbiosis islands into diverse Mesorhizobium lineages. A cross-inoculation experiment using nine sequenced rhizobial symbionts and 15 L. japonicus accessions revealed extensive quality variations represented by plant growth phenotypes, including genotype-by-genotype interactions. Quality variations were not associated with the presence/absence variations of known symbiosis-related genes in the symbiosis island, but rather, showed significant correlations with the core genome variations, supported by SNP- and kinship matrix-based association analyses. These findings highlight the novel role of HGT of symbiosis islands, which indirectly supply mutations of core genomes into L. japonicus-associated bacteria, thereby contributing to the maintenance of variations in partner quality.

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Massive rhizobial genomic variation associated with partner quality in Lotus–Mesorhizobium symbiosis

FEMS Microbiology Ecology ◽

10.1093/femsec/fiaa202 ◽

2020 ◽

Vol 96 (12) ◽

Author(s):

Masaru Bamba ◽

Seishiro Aoki ◽

Tadashi Kajita ◽

Hiroaki Setoguchi ◽

Yasuyuki Watano ◽

...

Keyword(s):

Core Genome ◽

De Novo ◽

Lotus Japonicus ◽

Genomic Variation ◽

The Novel ◽

High Quality ◽

Cooperative Relationships ◽

The Core ◽

Quality Variation

ABSTRACT Variation in partner quality is commonly observed in diverse cooperative relationships, despite the theoretical prediction that selection favoring high-quality partners should eliminate such variation. Here, we investigated how genetic variation in partner quality could be maintained in the nitrogen-fixing mutualism between Lotus japonicus and Mesorhizobium bacteria. We reconstructed de novo assembled full-genome sequences from nine rhizobial symbionts, finding massive variation in the core genome and the similar symbiotic islands, indicating recent horizontal gene transfer (HGT) of the symbiosis islands into diverse Mesorhizobium lineages. A cross-inoculation experiment using 9 sequenced rhizobial symbionts and 15 L. japonicus accessions revealed extensive quality variation represented by plant growth phenotypes, including genotype-by-genotype interactions. Variation in quality was not associated with the presence/absence variation in known symbiosis-related genes in the symbiosis island; rather, it showed significant correlation with the core genome variation. Given the recurrent HGT of the symbiosis islands into diverse Mesorhizobium strains, local Mesorhizobium communities could serve as a major source of variation for core genomes, which might prevent variation in partner quality from fixing, even in the presence of selection favoring high-quality partners. These findings highlight the novel role of HGT of symbiosis islands in maintaining partner quality variation in the legume–rhizobia symbiosis.

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