Genetic Diversity and Population Structure Analyses of Wild Relatives and Cultivated Cowpea (Vigna unguiculata (L.) Walp.) from Senegal Using Simple Sequence Repeat Markers

Cowpea (Vigna unguiculata (L.)) is an important crop for food security in Senegal; therefore, understanding the genetic diversity of local germplasm is relevant for crop improvement and genetic maintenance in the era of climate change. For this purpose, 15 microsatellite markers were used to estimate the genetic diversity of Senegalese cowpea germplasm, including 671 accessions grown in eight regions and 66 wild relatives and intermediate forms (weedy). For the cultivated, the main expected heterozygosity (mHe) ranged between 0.317 (Fatick) and 0.439 (South). A narrow genetic variation between accessions from the different regions was observed with genetic similarity ranging from 0.861 to 0.965 and genetic differentiation indices (Fst) between 0.018 and 0.100. The accessions from southern Senegal (Kédougou, Sédhiou, and Kolda regions) are more diverse than the others. However, the accessions from the North (Saint-Louis) are genetically different from other regions. The diversity analysis in wild relatives from Senegal, which had never been performed before, revealed that the wild/weedy forms remain more diverse than the cultivated with genetic diversity values (He) of 0.389 and 0.480, respectively. STRUCTURE software divided the Senegalese germplasm into five subpopulations. Three of them (i, ii, and iii) included only cultivated accessions from several regions, one (v) mainly from Saint-Louis, and one (iv) the wild/weedy with some cultivated accessions. Our results support the hypothesis that Vigna unguiculata var. spontanea is the wild progenitor of cowpea. The accessions from the South, the northern recession accessions, and the wild/weedy could serve as sources of new genes for the genetic improvement of cowpea in Senegal.

     

Selection of antimalarial drug resistance after intermittent preventive treatment of infants and children (IPTi/c) in Senegal

Senegal has since 2003 used sulphadoxine-pyrimethamine (SP) for Intermittent Preventive Treatment (IPT) of malaria in risk groups. However, the large-scale IPT strategy may result in increasing drug resistance. Our study investigated the possible impact of SP-IPT given to infants and children on the prevalence of SP-resistant haplotypes in the Plasmodium falciparum genes Pfdhfr and Pfdhps, comparing sites with and without IPTi/c. P. falciparum positives samples (n = 352) were collected from children under 5 years of age during two cross-sectional surveys in 2010 and 2011 in three health districts (two on IPTi/c and one without IPTi/c intervention) located in the southern part of Senegal. The prevalence of SP-resistance-related haplotypes in Pfdhfr and Pfdhps was determined by nested PCR followed by sequence-specific oligonucleotide probe (SSOP)–ELISA. The prevalence of the Pfdhfr double mutant haplotypes (CNRN and CICN) was stable between years at < 10% in the control group (P = 0.69), while it rose significantly in the IPTi/c group from 2% in 2010 to 20% in 2011 (P = 0.008). The prevalence of the Pfdhfr triple mutant haplotype (CIRN) increased in both groups, but only significantly in the IPTi/c group from 41% to 65% in 2011 (P = 0.005). Conversely, the Pfdhps 437G mutation decreased in both groups from 44.6% to 28.6% (P = 0.07) and from 66.7% to 47.5% (P = 0.02) between 2010 and 2011 in the control and the IPTi/c groups, respectively. Combined with Pfdhfr, there was a weak trend for decreasing prevalence of quadruple mutants (triple Pfdhfr + Pfdhps 437G) in both groups (P = 0.15 and P = 0.34). During the two cross-sectional surveys, some significant changes were observed in the SP-resistance-related genes. However, since these changes were observed in the two groups, the IPTi/c strategy does only seem to have limited impact on resistance development and other factors as well. However, continuous monitoring will be needed, due to the up-scaling of the IPTi/c strategy in Senegal according to WHO recommendations.     

Does P-Cresylglucuronide Have the Same Impact on Mortality as Other Protein-Bound Uremic Toxins?

Background

Uremic toxins are emerging as important, non-traditional cardiovascular risk factors in chronic kidney disease (CKD). P-cresol has been defined as a prototype protein-bound uremic toxin. Conjugation of p-cresol creates p-cresylsulfate (PCS) as the main metabolite and p-cresylglucuronide (PCG), at a markedly lower concentration. The objective of the present study was to evaluate serum PCG levels, determine the latter’s association with mortality and establish whether the various protein-bound uremic toxins (i.e. PCS, PCG and indoxylsulfate (IS)) differed in their ability to predict mortality.

Methodology/Principal Findings

We studied 139 patients (mean ± SD age: 67±12; males: 60%) at different CKD stages (34.5% at CKD stages 2–3, 33.5% at stage 4–5 and 32% at stage 5D). A recently developed high-performance liquid chromatography method was used to assay PCG concentrations. Total and free PCG levels increased with the severity of CKD. During the study period (mean duration: 779±185 days), 38 patients died. High free and total PCG levels were correlated with overall and cardiovascular mortality independently of well-known predictors of survival, such as age, vascular calcification, anemia, inflammation and (in predialysis patients) the estimated glomerular filtration rate. In the same cohort, free PCS levels and free IS levels were both correlated with mortality. Furthermore, the respective predictive powers of three Cox multivariate models (free PCS+other risk factors, free IS+other risk factors and free PCS+other risk factors) were quite similar - suggesting that an elevated PCG concentration has much the same impact on mortality as other uremic toxins (such as PCS or IS) do.

Conclusions

Although PCG is the minor metabolite of p-cresol, our study is the first to reveal its association with mortality. Furthermore, the free fraction of PCG appears to have much the same predictive power for mortality as PCS and IS do.     

Phylogenetic analyses of symbiotic genes and characterization of functional traits of Mesorhizobium spp. strains associated with the promiscuous species Acacia seyal Del.

Aims: To assess the phenotypic, symbiotic and genotypic diversity scope of Mesorhizobium spp. strains associated with Acacia seyal (Del.) isolated from different agro‐ecological zones in Senegal, and uses of susceptible microbial inoculum in a reafforestation process. Methods and Results: A polyphasic approach including phenotypic and genotypic techniques was used to study the diversity and their relationships with other biovars and species of rhizobia. The geographical origins of the strains have limited effect on their phylogenetic and phenotypic classification. Nodulation tests indicated promiscuity of the strains studied, because they were capable of nodulating six woody legume species (Acacia auriculiformis, Acacia senegal, A. seyal, Acacia tortilis ssp. raddiana, Leucaena leucocephala and Prosopis juliflora). Sequencing and phylogenetic analyses of nodA, nodC and nifH genes pointed out that in contrast to nodA gene, the phylogenies of nodC and nifH genes were not consistent with that of 16S rRNA, indicating that these genes of the A. seyal‐nodulating rhizobia might have different origins. Microbial inoculation on nonsterile soil had significant effect on the nodules number and the growth of the seedlings, indicating that these strains of rhizobia might be used as inoculum. Conclusions: The results indicated that A. seyal is a nonselective host that can establish effective symbiosis with Mesorhizobium spp. strains from diverse genomic backgrounds and that the selected A. seyal‐nodulating rhizobia could enhance plant growth. Significance and Impact of the Study: These results showed the important role that A. seyal could play in the improvement of reafforestation process as a promiscuous host, which can establish effective symbiosis with rhizobia from diverse genomic backgrounds.     

Comparative study of lignins isolated from Alfa grass (Stipa tenacissima L.)

Soda lignin, dioxane lignin and milled lignin were isolated from Alfa grass (Stipatenacissima L.). The physico-chemical characterization of three different lignins: one industrial lignin precipitated from soda spent liquor and two lignin preparations isolated under laboratory conditions from Alfa grass (also know as Esparto grass) was performed. The structures of lignins were studied by three non-destructive (FT-IR, solid state ¹³C NMR and UV/visible spectroscopy) and two destructive (nitrobenzene oxidation and thermogravimetric analysis) methods. Elemental analysis and the methoxyl content determination were performed in order to determine the C₉ formulae for the studied lignins. The total antioxidant capacity of the studied lignins has been determined and compared to commercial antioxidants commonly used in thermoplastic industry.     

Genetic Diversity of <Emphasis Type="Italic">Acacia seyal</Emphasis> Del. Rhizobial Populations Indigenous to Senegalese Soils in Relation to Salinity and pH of the Sampling Sites

The occurrence and the distribution of rhizobial populations naturally associated to Acacia seyal Del. were characterized in 42 soils from Senegal. The diversity of rhizobial genotypes, as characterized by polymerase chain reaction restriction fragment length polymorphism (RFLP) analysis of 16S–23S rDNA, performed on DNA extracted from 138 nodules resulted in 15 clusters. Results indicated the widespread occurrence of compatible rhizobia associated to A. seyal in various ecogeographic areas. However, the clustering of rhizobial populations based on intergenic spacer (IGS) RFLP profiles did not reflect their geographic origin. Four genera were discriminated on the basis of 16S rRNA gene sequences of the strains representative for the IGS-RFLP profiles. The majority of rhizobia associated to A. seyal were affiliated to Mesorhizobium and Sinorhizobium 64 and 29%, respectively, of the different IGS-RFLP profiles. Our results demonstrate the coexistence inside the nodule of plant-pathogenic non-N₂-fixing Agrobacterium and Burkholderia strains, which induced the formation of ineffective nodules, with symbiotic rhizobia. Nodulation was recorded in saline soils and/or at low pH values or in alkaline soils, suggesting adaptability of natural rhizobial populations to major ecological environmental stress and their ability to establish symbiotic associations within these soil environments. These results contribute to the progressing research efforts to uncover the biodiversity of rhizobia and to improve nitrogen fixation in agroforestry systems in sub-Saharan Africa.     

Slow growth of the overexploited milk shark Rhizoprionodon acutus affects its sustainability in West Africa

Age and growth of Rhizoprionodon acutus were estimated from vertebrae age bands. From December 2009 to November 2010, 423 R. acutus between 37 and 112 cm total length (L_T) were sampled along the Senegalese coast. Marginal increment ratio was used to check annual band deposition. Three growth models were adjusted to the length at age and compared using Akaike's information criterion. The Gompertz growth model with estimated size at birth appeared to be the best and resulted in growth parameters of L_∞ = 139·55 (L_T) and K = 0·17 year^?1 for females and L_∞ = 126·52 (L_T) and K = 0·18 year^?1 for males. The largest female and male examined were 8 and 9 years old, but the majority was between 1 and 3 years old. Ages at maturity estimated were 5·8 and 4·8 years for females and males, respectively. These results suggest that R. acutus is a slow‐growing species, which render the species particularly vulnerable to heavy fishery exploitation. The growth parameters estimated in this study are crucial for stock assessments and for demographic analyses to evaluate the sustainability of commercial harvests.     

Subdomain 3 of Plasmodium falciparum VAR2CSA DBL3x Is Identified as a Minimal Chondroitin Sulfate A-binding Region

Molecular interactions between the VAR2CSA protein, expressed on the surface of Plasmodium falciparum-infected erythrocytes, and placental chondroitin sulfate A (CSA) are primarily responsible for pregnancy-associated malaria (PAM). Interrupting these interactions may prevent or ameliorate the severity of PAM. Several of the Duffy binding-like (DBL) domains of VAR2CSA, including the DBL3x domain, have been shown to bind CSA in vitro, but a more detailed understanding of how DBL domains bind CSA is needed. In this study, we demonstrate that subdomain 3 (S3), one of the three subdomains of VAR2CSA DBL3x by itself, is the major contributor toward CSA binding. NMR spectroscopy and flow cytometry analyses show that S3 and the intact DBL3x domain bind CSA similarly. Mutations within the S3 portion of DBL3x markedly affect CSA binding. Both recombinant molecules, S3 and DBL3x, are recognized by antibodies in the plasma of previously pregnant women living in malaria-endemic regions of Mali, but much less so by plasma from men of the same regions. As the S3 sequence is highly conserved in all known VAR2CSA proteins expressed by different parasite isolates obtained from various malaria endemic areas of the world, the identification of S3 as an independent CSA-binding region provides a compelling molecular basis for designing interventions against PAM.     

Ecological and human impacts on stand density and distribution of tamarind (Tamarindus indica L.) in Senegal

Indigenous fruit tree species such as tamarind (Tamarindus indica L.) in African sub‐Saharan traditionally act to build resilience into the farming system in terms of food security, income generation and ecosystem stability. Therefore, increasing our knowledge on their ecology and distribution is a priority. Tamarind is mainly grown for the fruits but is also a valuable timber species. The fruit pulp has a high content of vitamin B and is eaten fresh or made into jam, chutney, juice or sweets. Flowers, leaves and seeds are also edible and used in a variety of dishes. The main objective of this study is to evaluate actual density of tamarind in Senegal and the climate change effects on its distribution for better conservation strategies. Tamarind's distribution and density around villages were recorded and modelled in different agro‐ecological zones in Senegal using transect method and under current and future climates. Distribution under two future climate scenarios were modelled using four climate models and three time slices (2020, 2050 and 2080). Results show a decreasing gradient in tree density (from 7 to 1 trees km^?2) from the Sudano agro‐ecological zone (in the south) to the Sahel (in the north). Future climate predictions show that although tamarind distribution will increase in the north‐west and south of the country in 2020; by 2050, the area identified as suitable for its growth will be greatly reduced. Areas in the north‐west basin appear to be an important refugia for the species under future climate conditions. However, density around villages in this area was found to be relatively low indicating that this could lead to problems of poor connectivity and inbreeding depression. This region should therefore be highlighted as important conservative management and protection strategies of tamarind in this region.