Mimosoid Clade Research Articles

PacBio-Based Mitochondrial Genome Assembly of Leucaena trichandra (Leguminosae) and an Intrageneric Assessment of Mitochondrial RNA Editing.

Reconstructions of vascular plant mitochondrial genomes (mt-genomes) are notoriously complicated by rampant recombination that has resulted in comparatively few plant mt-genomes being available. The dearth of plant mitochondrial resources has limited our understanding of mt-genome structural diversity, complex patterns of RNA editing, and the origins of novel mt-genome elements. Here, we use an efficient long read (PacBio) iterative assembly pipeline to generate mt-genome assemblies for Leucaena trichandra (Leguminosae: Caesalpinioideae: mimosoid clade), providing the first assessment of non-papilionoid legume mt-genome content and structure to date. The efficiency of the assembly approach facilitated the exploration of alternative structures that are common place among plant mitochondrial genomes. A compact version (729 kbp) of the recovered assemblies was used to investigate sources of mt-genome size variation among legumes and mt-genome sequence similarity to the legume associated root holoparasite Lophophytum. The genome and an associated suite of transcriptome data from select species of Leucaena permitted an in-depth exploration of RNA editing in a diverse clade of closely related species that includes hybrid lineages. RNA editing in the allotetraploid, Leucaena leucocephala, is consistent with co-option of nearly equal maternal and paternal C-to-U edit components, generating novel combinations of RNA edited sites. A preliminary investigation of L. leucocephala C-to-U edit frequencies identified the potential for a hybrid to generate unique pools of alleles from parental variation through edit frequencies shared with one parental lineage, those intermediate between parents, and transgressive patterns.

Lachesiodendron, a new monospecific genus segregated from Piptadenia (Leguminosae: Caesalpinioideae: mimosoid clade): Evidence from morphology and molecules

AbstractThe widest historical circumscription of the mimosoid legume genus Piptadenia (Caesalpinioideae: mimosoid clade) previously embraced morphologically disparate species that are currently ascribed to nine different genera. Previous molecular phylogenetic studies have demonstrated that the neotropical dry forest Piptadenia viridiflora is not closely related to Piptadenia s.str. Here we plug gaps in the DNA sequence dataset of a recently published study to build a more comprehensive phylogeny of the Piptadenia group and revise morphological evidence to define the phylogenetic relationship of P. viridiflora. Both morphological and molecular data confirm that P. viridiflora is an isolated lineage, thus warranting the description of the new monospecific genus Lachesiodendron. The new genus is diagnosed by the combination of paired stipular spines (vs. stipules not modified into spines in Piptadenia s.str.), prickles absent (vs. present), flowers in axillary spikes not grouped in compound inflorescences (vs. spikes grouped in compound pseudoracemes or panicles), flowers with a cylindrical corolla long exserted from the calyx (vs. corolla campanulate with petals free or slightly joined at the base) and long green stamens (vs. shorter and white, pale yellow or pink stamens). In addition, Lachesiodendron has pollen aggregated into 8–celled polyads with a hamulate exine, which further contrasts with the 12–celled polyads with a psilate exine in Piptadenia s.str.

Brazilian species of Calliandra Benth. (tribe Ingeae) are nodulated by diverse strains of Paraburkholderia

The Chapada Diamantina in NE of Brazil is a biodiversity hotspot and a center of radiation for many Neotropical legume genera, such as Calliandra and Mimosa. The present study aimed to evaluate nodulation in Calliandra species endemic to various environments, and to characterize the diversity of their symbiotic rhizobia using housekeeping (16S rRNA, recA) and plasmid-borne, symbiosis-related (nifH and nodC) genes. The nodulation ability of selected isolates was assessed. All of the 126 bacterial isolates from 18 Calliandra species collected in six different vegetation types were identified as Paraburkholderia according to their housekeeping and symbiosis gene phylogenies. They were grouped in seven clades in relation to the dominant vegetation type in their native environments. The majority, particularly those from highland “campo rupestre” vegetation, were similar to Paraburkholderia nodosa, but had nodC genes identical to the Mimosa symbiont Paraburkholderia tuberum sv. mimosae. The other smaller groups were related to Paraburkholderia diazotrophica and Paraburkholderia sabiae, and some single strains were not close to any known species. The symbionts of Calliandra spp. in NE Brazil are Paraburkholderia strains closely-related to Mimosa symbionts from the same region. NE Brazil is a reservoir of symbiotic Paraburkholderia that have an affinity for genera in the Mimosoid clade.

Electronic supplement to: Lachesiodendron, a new monospecific genus segregated from Piptadenia (Leguminosae: Caesalpinioideae: mimosoid clade): Evidence from morphology and molecules

Electronic supplement to: Lachesiodendron, a new monospecific genus segregated from Piptadenia (Leguminosae: Caesalpinioideae: mimosoid clade): Evidence from morphology and molecules

Interdependency of efficient nodulation and arbuscular mycorrhization in Piptadenia gonoacantha, a Brazilian legume tree.

Tripartite interactions between legumes and their root symbionts (rhizobia and arbuscular mycorrhizal fungi, AMF) are poorly understood, although it is well established that only specific combinations of symbionts lead to optimal plant growth. A classic example in which to investigate such interactions is the Brazilian legume tree Piptadenia gonoacantha (Caesalpinioideae), for which efficient nodulation has been described as dependent on the presence of AMF symbiosis. In this study, we compared the nodulation behaviour of several rhizobial strains with or without AMF inoculation, and performed analyses on nodulation, nodule cytology, N-fixing efficiency, and plant growth response. Nodulation of P.gonoacantha does not rely on the presence of AMF, but mycorrhization was rhizobial strain-dependent, and nodule effectiveness and plant growth were dependent on the presence of specific combinations of rhizobial strains and AMF. The co-occurrence of both symbionts within efficient nodules and the differentiation of bacteroids within nodule cells were also demonstrated. Novel close interactions and interdependency for the establishment and/or functioning of these symbioses were also revealed in Piptadenia, thanks to immunocytochemical analyses. These data are discussed in terms of the evolutionary position of the newly circumscribed mimosoid clade within the Caesalpinioid subfamily and its relative proximity to non-nodulated (but AMF-associated) basal subfamilies.

Leguminosae clado mimosoide em um fragmento de floresta estacional semidecidual do sudeste do Brasil

Resumo A floresta estacional semidecidual, fitofisionomia que revestia quase todo o interior do estado de São Paulo, está representada atualmente por apenas 5% da sua cobertura original. Este trabalho consiste no levantamento dos representantes do clado mimosoide numa das últimas áreas de vegetação contínua do estado, a Serra do Japi. Foram registradas 24 espécies distribuídas em oito gêneros, dos quais os mais diversos são Mimosa (7 spp.), Inga (6 spp.), Senegalia (5 spp.) e Anadenanthera (2 spp.). As espécies de hábito arbóreo predominam no local e a maioria dos táxons compartilha o Cerrado e a Mata Atlântica como área de ocorrência, com exceção de Inga subnuda e Senegalia grandistipula, ambas endêmicas da Mata Atlântica. Seis são endêmicas do Brasil (Abarema langsdorffii, I. subnuda., I. sessilis, Leucochloron incuriale, Mimosa furfuracea, S. grandistipula), doze são novos registros para a Serra do Japi e uma é inédita para o estado (Senegalia tucumanensis). Os principais caracteres diagnósticos para a distinção dos gêneros foram os tipos de folha e fruto, presença de nectários extraflorais e número e fusão de estames, e para as espécies, presença de glândulas em locais específicos, presença de acúleos, tricomas e estípulas, e número de folíolos.

A new subfamily classification of the Leguminosae based on a taxonomically comprehensive phylogeny: The Legume Phylogeny Working Group (LPWG)

AbstractThe classification of the legume family proposed here addresses the long‐known non‐monophyly of the traditionally recognised subfamily Caesalpinioideae, by recognising six robustly supported monophyletic subfamilies. This new classification uses as its framework the most comprehensive phylogenetic analyses of legumes to date, based on plastid matK gene sequences, and including near‐complete sampling of genera (698 of the currently recognised 765 genera) and ca. 20% (3696) of known species. The matK gene region has been the most widely sequenced across the legumes, and in most legume lineages, this gene region is sufficiently variable to yield well‐supported clades. This analysis resolves the same major clades as in other phylogenies of whole plastid and nuclear gene sets (with much sparser taxon sampling). Our analysis improves upon previous studies that have used large phylogenies of the Leguminosae for addressing evolutionary questions, because it maximises generic sampling and provides a phylogenetic tree that is based on a fully curated set of sequences that are vouchered and taxonomically validated. The phylogenetic trees obtained and the underlying data are available to browse and download, facilitating subsequent analyses that require evolutionary trees. Here we propose a new community‐endorsed classification of the family that reflects the phylogenetic structure that is consistently resolved and recognises six subfamilies in Leguminosae: a recircumscribed Caesalpinioideae DC., Cercidoideae Legume Phylogeny Working Group (stat. nov.), Detarioideae Burmeist., Dialioideae Legume Phylogeny Working Group (stat. nov.), Duparquetioideae Legume Phylogeny Working Group (stat. nov.), and Papilionoideae DC. The traditionally recognised subfamily Mimosoideae is a distinct clade nested within the recircumscribed Caesalpinioideae and is referred to informally as the mimosoid clade pending a forthcoming formal tribal and/or clade‐based classification of the new Caesalpinioideae. We provide a key for subfamily identification, descriptions with diagnostic charactertistics for the subfamilies, figures illustrating their floral and fruit diversity, and lists of genera by subfamily. This new classification of Leguminosae represents a consensus view of the international legume systematics community; it invokes both compromise and practicality of use.

Polyploidy did not predate the evolution of nodulation in all legumes.

BackgroundSeveral lines of evidence indicate that polyploidy occurred by around 54 million years ago, early in the history of legume evolution, but it has not been known whether this event was confined to the papilionoid subfamily (Papilionoideae; e.g. beans, medics, lupins) or occurred earlier. Determining the timing of the polyploidy event is important for understanding whether polyploidy might have contributed to rapid diversification and radiation of the legumes near the origin of the family; and whether polyploidy might have provided genetic material that enabled the evolution of a novel organ, the nitrogen-fixing nodule. Although symbioses with nitrogen-fixing partners have evolved in several lineages in the rosid I clade, nodules are widespread only in legume taxa, being nearly universal in the papilionoids and in the mimosoid subfamily (e.g., mimosas, acacias) – which diverged from the papilionoid legumes around 58 million years ago, soon after the origin of the legumes.Methodology/Principal FindingsUsing transcriptome sequence data from Chamaecrista fasciculata, a nodulating member of the mimosoid clade, we tested whether this species underwent polyploidy within the timeframe of legume diversification. Analysis of gene family branching orders and synonymous-site divergence data from C. fasciculata, Glycine max (soybean), Medicago truncatula, and Vitis vinifera (grape; an outgroup to the rosid taxa) establish that the polyploidy event known from soybean and Medicago occurred after the separation of the mimosoid and papilionoid clades, and at or shortly before the Papilionoideae radiation.ConclusionsThe ancestral legume genome was not fundamentally polyploid. Moreover, because there has not been an independent instance of polyploidy in the Chamaecrista lineage there is no necessary connection between polyploidy and nodulation in legumes. Chamaecrista may serve as a useful model in the legumes that lacks a paleopolyploid history, at least relative to the widely studied papilionoid models.