Biology subjects

Dube, F.

Publications and source records attributed to Dube, F..

3 recordsLinked to original sources

bioRxiv2025

Soil Carbon Sequestration in Nothofagus obliqua Forests with Different Canopy Cover Levels under Silvopastoral Management

Agroforestry contributes to slowing deforestation, favouring ecosystem regeneration and improving land use sustainability. In this study, we evaluated the effect of agroforestry on the recovery of degraded soils in a native forest and its capacity to capture and stabilize carbon (C) and nitrogen (N) in the soil. We conducted the study in a native forest of Nothofagus obliqua (oak) located in Ranchillo Alto (37{degrees}04'52'' S, 71{degrees}39'14'' W), in the Nuble region, Chile. This site includes three silvopastoral systems with different levels of forest degradation: open (Op), semi- open (SOp) and semi-closed (SC), together with a control treatment without silvopastoral treatment (Ctr). The analysis was conducted at four soil depths (0-10, 10-20, 20-30 and 30-60 cm). To evaluate carbon and nitrogen sequestration and fixation in relation to the different forest cover treatments, we performed chemical, physical and biological soil analyses. We also included a physical fractionation by particle size to separate soil organic matter (SOM) into meaningful fractions with different characteristics and dynamics: particulate organic matter (POM) and organic matter associated with the mineral matrix (MAOM). Our results indicated that Op, despite being the most degraded condition, showed the highest values of C, N and non- oxidizable carbon (Cnox). This condition could be associated with the history of potato burning in this sector, which generates stable pyrogenic carbon in the soil. Analyses of C and N, as well as Cnox in the MAOM fraction, and C stock revealed that the three silvopastoral systems showed higher values than the control treatment without silvopastoral treatment. This suggests that the adoption of silvopastoral practices can improve soil quality and contribute to long-term carbon sequestration. These results support the application of sustainable practices to mitigate soil degradation and enhance carbon sequestration in degraded ecosystems.

ecology↗

bioRxiv2023

Gene co-expression network analysis reveal core responsive genes in Parascaris univalens tissues following ivermectin exposure

Anthelmintic resistance in equine parasite Parascaris univalens, compromises ivermectin (IVM) effectiveness and necessitates an in-depth understanding of its resistance mechanisms. Most research, primarily focused on holistic gene expression analyses, may overlook vital tissue-specific responses and often limit the scope of novel genes. This study leveraged gene co-expression network analysis to elucidate tissue-specific transcriptional responses and to identify core genes implicated in the IVM response in P. univalens. Adult worms (n=28) were exposed to 10-11 M and 10-9 M IVM in vitro for 24 hours. RNA-sequencing examined transcriptional changes in the anterior end and intestine. Differential expression analysis revealed pronounced tissue differences, with the intestine exhibiting substantially more IVM-induced transcriptional activity. Gene co-expression network analysis identified seven modules significantly associated with the response to IVM. Within these, 219 core genes were detected, largely expressed in the intestinal tissue and spanning diverse biological processes with unspecific patterns. After 10-11 M IVM, intestinal tissue core genes showed transcriptional suppression, cell cycle inhibition, and ribosomal alterations. Interestingly, genes PgR028_g047 (sorb-1), PgB01_g200 (gmap-1) and PgR046_g017 (col-37 & col-102) switched from downregulation at 10-11 M to upregulation at 10-9 M IVM. The 10-9 M concentration induced expression of cuticle and membrane integrity core genes in the intestinal tissue. No clear core gene patterns were visible in the anterior end after 10-11 M IVM. However, after 10-9 M IVM, the anterior end mostly displayed downregulation, indicating disrupted transcriptional regulation. One interesting finding was the non-modular calcium-signaling gene, PgR047_g066 (gegf-1), which uniquely connected 71 genes across four modules. These genes were enriched for transmembrane signaling activity, suggesting that PgR047_g066 (gegf-1) could have a key signaling role. By unveiling tissue-specific expression patterns and highlighting biological processes through unbiased core gene detection, this study reveals intricate IVM responses in P. univalens. These findings suggest alternative drug uptake of IVM and can guide functional validations to further IVM resistance mechanism understanding. Author summaryIn our study, we tackled the challenge of understanding how the equine roundworm Parascaris univalens has become resistant to ivermectin (IVM). We exposed adult worms in laboratory conditions to IVM and thereafter dissected two tissues, the frontal part and the intestine of the worm. We used gene networks and focused on how these two tissues respond at the genetic level to exposure of IVM. We discovered that the response to IVM is highly tissue-specific. The intestinal tissue, in particular, showed a much stronger reaction to the drug compared to the frontal part of the worm. We identified 219 key genes, mainly in the intestinal tissue, involved in various biological functions that play a crucial role in how the parasite deals with IVM. Interestingly, we found a decrease in gene activity leading to cellular disruptions at lower drug concentration, whereas genes responsible for maintaining the worms structural integrity were triggered at high concentration. One of our significant finding was the identification of, PgR047_g066 (gegf-1), which seems to act as a master regulator, coordinating the response of numerous other genes. This finding opens new avenues for understanding the complex ways in which P. univalens respond to drug treatment. Our research not only sheds light on the specific ways P. univalens responds to IVM, but it also demonstrates the power of looking at gene networks to uncover new and important genes. These insights can be crucial for developing new strategies to combat drug resistance in parasites, a matter of great importance in both veterinary and human medicine.

genomics↗

bioRxiv2023

Evidence of virulence and antimicrobial resistance in Streptococcus pneumoniae serotype 16F lineages

IntroductionDue to the emergence of non-vaccine serotypes in vaccinated populations, Streptococcus pneumoniae remains a major global health challenge despite advances in vaccine development. Serotype 16F is among the predominant non-vaccine serotypes identified among vaccinated infants in South Africa (SA). AimTo characterise lineages and antimicrobial resistance in 16F isolates obtained from South Africa and placed the local findings in a global context. MethodologyWe analysed 10923 S. pneumoniae carriage isolates obtained from infants recruited as part of a broader SA birth cohort. We inferred serotype, resistance profile for penicillin, chloramphenicol, cotrimoxazole, erythromycin and tetracycline, and Global Pneumococcal Sequence Clusters (GPSCs) from genomic data. To ensure global representation, we also included S. pneumoniae carriage and disease isolates from the Global Pneumococcal Sequencing (GPS) project database (n=19,607, collected from 49 countries across five continents, years covered (1995 - 2018), accessed on 17th March 2022). ResultsNine percent (934/10923) of isolates obtained from infants in the Drakenstein community in SA and 2% (419/19607) of genomes in the GPS dataset were serotype 16F. Serotype 16F isolates were from 28 different lineages of S. pneumoniae, with GPSC33 and GPSC46 having the highest proportion of serotype 16F isolates at 26% (346/1353) and 53% (716/1353), respectively. Serotype 16F isolates were identified globally, however, most isolates were collected from Africa. GPSC33 was associated with carriage [OR (95% CI) 0.24 (0.09 - 0.66); p=0.003], while GPSC46 was associated with disease [OR (95% CI) 19.9 (2.56 - 906.50); p=0.0004]. 10% (37/346) and 15% (53/346) of isolates within GPSC33 had genes associated with resistance to penicillin and co-trimoxazole, respectively, and 18% (128/716) of isolates within GPSC46 had genes associated with resistance to co-trimoxazole. Resistant isolates formed genetic clusters which may suggest emerging resistant lineages. DiscussionSerotype 16F lineages are common in Southern Africa. Some of these lineages are associated with disease, and resistance to penicillin and cotrimoxazole. We recommend continuous genomic surveillance to determine long term impact of serotype 16F lineages on vaccine efficacy and antimicrobial therapy globally. Investing in vaccine strategies that offer protection over a wide range of serotypes/lineages remains essential. DATA SUMMARYThe sequencing reads for the genomes analysed have been deposited in the European Nucleotide Archive and the accession numbers for each isolate are listed in Supplementary Table1. Phylogenetic tree of serotype 16F pneumococcal genomes and associated metadata are available for download and visualisation on the Microreact website: Phylogenies of seotype 16F, GPSC33 and GPSC46 are available on the Microreact serotype-16F, GPSC33 and GPSC46, respectively. IMPACT STATEMENTThis study shows that serotype 16F lineages are predominant in Southern Africa and are associated with disease and antimicrobial resistance. Although serotype 16F has been included in the newer formulation of the upcoming vaccine formulations of PCV21 and IVT-25, continuous surveillance to determine long term impact of serotype 16F lineages on vaccines and antimicrobial therapy remains essential.

genomics↗