Biology subjects

Riva, C.

Publications and source records attributed to Riva, C..

4 recordsLinked to original sources

bioRxiv2025

Reducing Honey Bee Winter Mortality with Molybdenum Supplementation: Field Evidence Across Europe

Nutrition is key to improve honey bees resilience to environmental stress factors that threaten their health. Yet, little is known about the micronutritional needs of colonies, in particular about molybdenum, an essential trace element in biology. This study focuses on a coordination complex based on molybdenum Mo(+V) which was assessed for compatibility with standard beekeeping practices. It was found to be non-toxic for bees, stable and easy to use. Importantly, it does not leave any residues in honey produced. This study investigated how supplementation with few milligrams of this complex can improve hive performance at early spring and reduce winter mortality. Over a two-year field campaign, 283 beehives spread over 6 apiaries located in Spain, Greece and France were involved: 142 beehives supplemented with the molybdenum-based compound and 141 beehives as a control group. Supplementation resulted in a significant reduction in winter colony losses, averaging a 44% decrease, ranging between 27% and 75% in the different apiaries. The risk of death was twice lower in the Na-Mo2O4-EDTA group compared to the control group (risk ratio: 0.51). The impact on bee populations and honey production was also evaluated. A significant increase in honey reserves within the brood area of 107% was observed in the Greek apiary, whereas no comparable effect was detected in Spain, suggesting that local environmental conditions or management practices may influence this parameter. This study highlights the importance of molybdenum in the management of honey bees as an efficient tool to reduce the winter mortality of the colonies. HighlightsO_LIMolybdenum-based feed supplementation reduced honey bee winter mortality by 44% in average and up to 75% C_LIO_LIThere are no adverse effects on honey bee health or honey and wax composition. C_LIO_LISupplement showed variable effects on honey reserves and no effects on bee population. C_LIO_LIALP levels increased transiently, while the TAC was unaffected.Supplementation with Molybdenum-based compound represents a promising strategy to enhance colony overwintering success C_LI

zoology↗

bioRxiv2022

The small non-coding RNA B11 regulates multiple facets of Mycobacterium abscessus virulence

Mycobacterium abscessus causes severe, virtually incurable disease in young patients with cystic fibrosis. Little is known in M. abscessus about the roles of small regulatory RNAs (sRNA) in gene expression regulation. Here, we show that the sRNA B11 controls gene expression and virulence-associated phenotypes in this pathogen. B11 deletion from the smooth strain ATCC_19977 produced a rough colony morphology, increased pro-inflammatory signaling and virulence in in-vivo infection models, and increased resistance to clinically relevant antibiotics. Examination of clinical isolate cohorts revealed some isolates with B11 mutations or reduced expression. We used RNAseq and proteomics to investigate the effects of B11 on gene expression and test the impact of two mutations found in clinical isolates. Approximate 230 genes were differentially expressed in the B11 deletion mutant. Strains with the clinical B11 mutations showed similar expression trends to the deletion mutant but of a lesser magnitude, suggesting partial loss of function. Among genes upregulated in the B11 mutant, there was a strong enrichment for genes with B11-complementary sequences in their predicted ribosome binding sites (RBS), consistent with a model of translational repression via base-pairing of B11 to RBSs. Comparing the proteomes similarly revealed that upregulated proteins were strongly enriched for B11-complementary sequences in their RBS, consistent with B11 functioning as a negative regulator through direct binding of target mRNAs. Intriguingly, the genes upregulated in the absence of B11 included components of the ESX-4 secretion system, known to be critical for M. abscessus virulence. One of these genes had a B11-complementary sequence at its RBS, and fusing the UTR of this gene to a reporter was sufficient to make the reporter suppressible by B11. Taken together, our data show that B11 may act as either a negative or positive regulator with pleiotropic effects on gene expression and clinically important phenotypes in M. abscessus. The presence of hypomorphic B11 mutations in clinical strains supports the idea that lower B11 activity may be advantageous for M. abscessus in some clinical contexts. To our knowledge, this is the first report of the role of an sRNA in M. abscessus.

microbiology↗

bioRxiv2021

A natural transdifferentiation event involving mitosis is empowered by integrating signaling inputs with conserved plasticity factors

Transdifferentiation, or direct cell reprogramming, is the direct conversion of one fully differentiated cell type into another. Whether core mechanisms are shared between different transdifferentiation events, which can occur naturally in presence or in absence of cell division, is unclear. Our lab has previously characterized the Y-to-PDA natural transdifferentiation in Caenorhabditis elegans, which occurs without cell division and requires orthologs of vertebrates reprogramming factors. In this study, focusing on another transdifferentiation process, the K rectal cell-to-DVB GABAergic neuron, we report that the Y-to-PDA reprogramming factor SEM-4/SALL, SOX-2, CEH-6/POU are required for K-to-DVB transdifferentiation to allow the erasure of the rectal identity. In addition, cell division is necessary but not sufficient for this transdifferentiation event while the Wnt signaling plays distinct functions during the process including the selection of the daughter cell with a different fate, loss of the rectal identity and imposition of the specific neuronal subtype identity. We provide evidence that both the Wnt signaling and Y-to-PDA reprogramming factor SEM-4/SALL, SOX-2, CEH-6/POU act in parallel for the rectal identity erasure. Our results further support a model where antagonistic activities of SOX-2 and POP-1 and decreasing SOX-2 levels over time provide a timer for the acquisition of the final identity. In addition, the different levels of SOX-2 provide a mechanism for the integration of Wnt opposite dedifferentiation and re-differentiation functions during K-to-DVB transdifferentiation.

developmental biology↗

bioRxiv2020

A new model of chronic Mycobacterium abscessus lung infection in immunocompetent mice

Pulmonary infections caused by Mycobacterium abscessus (MA) have increased over recent decades affecting individuals with underlying pathologies such as chronic obstructive pulmonary disease, bronchiectasis and, especially, cystic fibrosis. The lack of a representative and standardized model of chronic infection in mice has limited steps forward in the field of MA pulmonary infection. To overcome this challenge we refined the method of agar beads to establish MA chronic infection in immunocompetent mice. We evaluated bacterial count, lung pathology and markers of inflammation and we performed longitudinal studies with magnetic resonance imaging (MRI) up to three months after MA infection. In this model, MA was able to establish a persistent lung infection up to two months and with minimal systemic spread. Lung histopathological analysis revealed granulomatous inflammation around bronchi characterized by the presence of neutrophils, lymphocytes and aggregates of vacuolated foamy cells, mimicking the damage observed in humans. Furthermore, MA lung lesions were successfully monitored for the first time by MRI. The availability of this murine model and the introduction of the successfully longitudinal monitoring of the murine lung lesions with MRI pave the way for further investigations on the impact of MA pathogenesis and the efficacy of novel treatments.

microbiology↗