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Nodulation in Dimorphandra wilsonii Rizz. (Caesalpinioideae), a threatened species native to the Brazilian Cerrado.

ABSTRACT: The threatened caesalpinioid legume Dimorphandra wilsonii, which is native to the Cerrado biome in Brazil, was examined for its nodulation and N(2)-fixing ability, and was compared with another, less-threatened species, D. jorgei. Nodulation and potential N(2) fixation was shown on seedlings that had been inoculated singly with five bradyrhizobial isolates from mature D. wilsonii nodules. The infection of D. wilsonii by two of these strains (Dw10.1, Dw12.5) was followed in detail using light and transmission electron microscopy, and was compared with that of D. jorgei by Bradyrhizobium strain SEMIA6099. The roots of D. wilsonii were infected via small transient root hairs at 42 d after inoculation (dai), and nodules were sufficiently mature at 63 dai to express nitrogenase protein. Similar infection and nodule developmental processes were observed in D. jorgei. The bacteroids in mature Dimorphandra nodules were enclosed in plant cell wall material containing a homogalacturonan (pectic) epitope that was recognized by the monoclonal antibody JIM5. Analysis of sequences of their rrs (16S rRNA) genes and their ITS regions showed that the five D. wilsonii strains, although related to SEMIA6099, may constitute five undescribed species of genus Bradyrhizobium, whilst their nodD and nifH gene sequences showed that they formed clearly separated branches from other rhizobial strains. This is the first study to describe in full the N(2)-fixing symbiotic interaction between defined rhizobial strains and legumes in the sub-family Caesalpinioideae. This information will hopefully assist in the conservation of the threatened species D. wilsonii.

SUBMITTER: Fonseca MB

PROVIDER: S-EPMC3501520 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Nodulation in Dimorphandra wilsonii Rizz. (Caesalpinioideae), a threatened species native to the Brazilian Cerrado.

Fonseca Márcia Bacelar MB Peix Alvaro A de Faria Sergio Miana SM Mateos Pedro F PF Rivera Lina P LP Simões-Araujo Jean L JL França Marcel Giovanni Costa MG Isaias Rosy Mary dos Santos RM Cruz Cristina C Velázquez Encarna E Scotti Maria Rita MR Sprent Janet I JI James Euan K EK

PloS one 20121119 11

The threatened caesalpinioid legume Dimorphandra wilsonii, which is native to the Cerrado biome in Brazil, was examined for its nodulation and N(2)-fixing ability, and was compared with another, less-threatened species, D. jorgei. Nodulation and potential N(2) fixation was shown on seedlings that had been inoculated singly with five bradyrhizobial isolates from mature D. wilsonii nodules. The infection of D. wilsonii by two of these strains (Dw10.1, Dw12.5) was followed in detail using light and ...[more]

PMID: 23185349

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Project description:Backgrounds and aimsDimorphandra wilsonii Rizzini, a critically endangered and protected tree, has a restricted distribution in the ecotone between the Cerrado and the Atlantic Forest in south-eastern Brazil. In this area, it co-occurs with D. mollis Benth., a common tree from the Cerrado, and D. exaltata Schott., a rare tree from the Atlantic Forest. Previous studies of D. wilsonii indicated heterozygosity excess at the individual level. Field observation of some intermediate phenotypes between D. wilsonii and both congeners suggests hybridization of D. wilsonii with D. mollis and/or D. exaltata. Here, we tested the hypothesis that D. wilsonii may have originated from hybridization between D. exaltata and D. mollis. We also performed cytogenetic analysis to examine if the heterozygosity excess could be explained by polyploidy in D. wilsonii.MethodsWe evaluated the genetic diversity and population structure of D. wilsonii using 11 nuclear simple sequence repeats (SSRs) genotyped in 152 individuals sampled across the taxon's range. We performed comparative genetic analyses using overlapping SSR markers between D. wilsonii and previously published SSR data in D. mollis and D. exaltata to subsequently perform a series of allelic comparisons, multivariate and Bayesian analysis.Key resultsOur results suggest that D. wilsonii individuals are most likely to correspond to F1 hybrids between D. exaltata and D. mollis. Cytogenetic analysis indicated that D. wilsonii is diploid with the same chromosome number as D. mollis (2n = 2x = 28).ConclusionsOur study raises questions about the taxonomic status and the evolutionary future of D. wilsonii. We suggest that the conservation and management strategy for D. wilsonii should be revised and that it should take into account both parental Dimorphandra species in the ecotone, with special emphasis on the threatened D. exaltata. Finally, this study highlights the value of genetic information for the design of conservation strategies.

Dataset Information

Nodulation in Dimorphandra wilsonii Rizz. (Caesalpinioideae), a threatened species native to the Brazilian Cerrado.

Publications

Nodulation in Dimorphandra wilsonii Rizz. (Caesalpinioideae), a threatened species native to the Brazilian Cerrado.

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