ABSTRACT
The hard tick Amblyomma aureolatum (Pallas) is a vector of the bacterium Rickettsia rickettsii , the etiologic agent of Brazilian spotted fever (BSF) in parts of Brazil. Despite its wide distribution in southeastern South America and its public health importance, there is no information about genetic variation of this species that might help to understand the epidemiology of BSF. Using data from eight microsatellite markers and ticks from six localities, we used a population genetics approach to test the hypothesis that tick populations from areas with the presence of R. rickettsii are genetically different from ticks from areas without R. rickettsii . Contrary to expectations, we found low genetic structure between studied regions. Thus, the presence of R. rickettsii in the specific area is more likely correlated with ecological and the environmental conditions or due to unknown gene coding regions of A. aureolatum genome that would be related to R. rickettsii infection resistance...
Subject(s)
Animals , Ixodidae/classification , Ixodidae/growth & development , Ixodidae/genetics , Rickettsia/geneticsABSTRACT
Amblyomma aureolatum (Pallas) is the main vector of the bacterium Rickettsia rickettsii, the etiological agent of Brazilian spotted fever. This disease is the most lethal human spotted fever rickettsiosis in the world. Microsatellite loci were isolated from a dinucleotide-enriched library produced from A. aureolatum sampled in Southeastern Brazil. Eight polymorphic microsatellites were further characterized among 38 individuals sampled from São Paulo metropolitan region. The number of observed alleles ranged from 2 to 9, observed heterozygosity was 0.184-0.647, and expected heterozygosity was 0.251-0.747. Cross-species amplifications suggested that these loci will be useful for other Amblyomma species.
Subject(s)
Genetic Loci , Ixodidae/genetics , Microsatellite Repeats/genetics , Animals , Female , Polymorphism, GeneticABSTRACT
Amblyomma aureolatum (Pallas) is the main vector of the bacterium Rickettsia rickettsii, the etiological agent of Brazilian spotted fever. This disease is the most lethal human spotted fever rickettsiosis in the world. Microsatellite loci were isolated from a dinucleotide-enriched library produced from A. aureolatum sampled in Southeastern Brazil. Eight polymorphic microsatellites were further characterized among 38 individuals sampled from São Paulo metropolitan region. The number of observed alleles ranged from 2 to 9, observed heterozygosity was 0.184-0.647, and expected heterozygosity was 0.251-0.747. Cross-species amplifications suggested that these loci will be useful for other Amblyomma species...
Subject(s)
Animals , Ixodidae/genetics , Rickettsia rickettsii/growth & development , Rickettsia rickettsii/geneticsABSTRACT
The Cabreúva tree, Myroxylon peruiferum, is an endangered tropical species from Brazil used in forest restoration projects. It is known for its medicinal properties. Eleven microsatellite markers were developed for this species, from a microsatellite-enriched library. Nine of these markers, characterized in 30 individuals from a semideciduous forest remnant population in southeast Brazil, were polymorphic, with allele numbers ranging from 2 to 8 per locus; expected and observed heterozygosities ranged from 0.103 to 0.757 and 0.107 to 0.704, respectively. One locus (Mpe-C04) showed significant deviation from Hardy-Weinberg equilibrium, probably due to null alleles. Two other loci (Mpe-E09 and Mpe-H07) were monomorphic in this population. These microsatellite loci should be useful for future population genetic studies of this species.
Subject(s)
Endangered Species , Microsatellite Repeats/genetics , Myroxylon/genetics , Plants, Medicinal/genetics , Alleles , Brazil , DNA, Plant/chemistry , DNA, Plant/genetics , Forests , Gene Frequency , Genotype , Heterozygote , Linkage Disequilibrium , Molecular Sequence Data , Polymorphism, Genetic , Sequence Analysis, DNAABSTRACT
Nitrogen-fixing bacteria have been isolated from sugarcane in an endophytic and beneficial interaction that promotes plant growth. In this work, for the first time, the involvement of ethylene signalling in this interaction was investigated by molecular characterizing members of this pathway in sugarcane. The expression pattern of a putative ethylene receptor (SCER1) and two putative ERF transcription factors (SCERF1 and SCERF2) show exclusive modulation in plants inoculated with the diazotrophic endophytes. The gene expression profile of SCER1, SCERF1, and SCERF2 is differentially regulated in sugarcane genotypes that can establish efficient or inefficient associations with diazotrophic micro-organisms, exhibiting high or low biological nitrogen fixation (BNF) rates, respectively. In addition, SCER1, SCERF1, and SCERF2 expression is different in response to interactions with pathogenic and beneficial micro-organisms. Taken together, that data suggest that SCER1, SCERF1, and SCERF2 might participate in specific ethylene signalling cascade(s) that can identify a beneficial endophytic association, modulating sugarcane responses toward the diazotrophic endophytes.
Subject(s)
Ethylenes/metabolism , Gluconacetobacter/physiology , Herbaspirillum/physiology , Nitrogen Fixation , Plant Proteins/metabolism , Saccharum/microbiology , Signal Transduction , Amino Acid Sequence , Ethylenes/pharmacology , Expressed Sequence Tags , Gene Expression Regulation, Plant , Genotype , Gluconacetobacter/metabolism , Herbaspirillum/metabolism , Molecular Sequence Data , Phylogeny , Plant Proteins/chemistry , Plant Proteins/genetics , Receptors, Cell Surface/chemistry , Receptors, Cell Surface/genetics , Receptors, Cell Surface/metabolism , Saccharum/genetics , Saccharum/metabolism , Transcription Factors/chemistry , Transcription Factors/genetics , Transcription Factors/metabolismABSTRACT
Endophytic nitrogen-fixing bacteria have been isolated from graminaceous plants such as maize, rice, and sugarcane. They are thought to promote plant growth, not only by fixing nitrogen, but also by the production of plant hormones. The molecular mechanisms involved in this interaction are not yet clear. In this work, the identification of a receptor-like kinase (RLK), named SHR5, which may participate in signal transduction involved in the establishment of plant-endophytic bacteria interaction is described for the first time. SHR5 seems to be part of a novel subclass of RLKs present in a wide range of plant species. The expression of this gene is down-regulated in sugarcane plants associated exclusively with beneficial endophytic bacteria and is not a general response caused by micro-organisms or abiotic stress. In addition, more successful sugarcane-endophytic bacteria associations have a more pronounced decrease in SHR5 expression, suggesting that SHR5 mRNA levels in plant cells are inversely related to the efficiency of the association.
