Biology subjects

Nunez, C.

Publications and source records attributed to Nunez, C..

12 recordsLinked to original sources

bioRxiv2026

Avian uropygial secretions as a novel bioinsecticide for mosquito vector control

Background: Malaria control relies heavily on interventions targeting mosquito vectors, but the rapid emergence of insecticide resistance threatens the effectiveness of existing approaches. Identifying novel, effective, and environmentally sustainable insecticides is therefore a priority. Birds produce uropygial secretions with well-documented antimicrobial properties, but their potential insecticidal activity against mosquitoes, including malaria vectors, remains unexplored. Methods: We evaluated the insecticidal activity of uropygial secretions from wild house sparrows (Passer domesticus) against the malaria vector Anopheles stephensi and four additional mosquito species of medical importance (Aedes aegypti, Aedes albopictus, Culex pipiens, and Culiseta longiareolata). A total of 2,293 adult mosquitoes were tested using CDC bottle bioassays at three secretion concentrations (0.5, 0.25, and 0.125) and an untreated control. Mosquito mortality was monitored for 120 min. Results: Uropygial secretions caused substantial mosquito knockdown/mortality, with effects increasing with concentration and exposure time. Susceptibility differed significantly among species after 120 min. Notably, An. stephensi was particularly susceptible, reaching knockdown/mortality of 92%, 94%, and 83% at 0.5, 0.25, and 0.125 concentrations, respectively. Conclusions: Our findings provide the first experimental evidence that avian uropygial secretions possess direct insecticidal activity against mosquitoes and identify them as a previously overlooked source of naturally derived insecticidal compounds. The high susceptibility of An. stephensi highlights their potential relevance for developing novel bioinsecticides for malaria vector control.

ecology↗

bioRxiv2026

Immediate and carryover reproductive costs of infection in female but not male house finches

Wildlife diseases cause well-documented and often dramatic reductions in host survival. However, the impact of infectious diseases on host reproduction remains understudied, especially with respect to effects of prior and/or current pathogen exposure on reproductive development. Here we experimentally tested how prior and/or current infection with a common bacterial pathogen, Mycoplasma gallisepticum ( MG), alters reproductive development for female versus male house finches (Haemorhous mexicanus). Finches were inoculated with either MG or sterile media while in wintering condition and subsequently received one of these treatments while in breeding condition. In females, MG exposure had both immediate and carry-over effects on reproduction: controls had higher odds of laying eggs compared to females inoculated with MG in spring only, higher odds than females inoculated in both winter and spring, and higher odds than females given MG in the winter only. Conversely, breeding-condition males inoculated with MG in spring had higher testosterone levels than males receiving only control inoculations, and there were no carryover effects of winter MG inoculation or inoculations during both seasons on testosterone. Sex bias in the reproductive impacts of infectious diseases may have important knock-on effects on the epidemiology and population-regulating effects of pathogens, thereby warranting further study.

ecology↗

bioRxiv2026

Integrated heart rate variability and physiological profiling reveals autonomic phenotypes in older adults from a high-southern-latitude population

Heart rate variability (HRV) is widely used to assess autonomic regulation, but its interpretation in older adults is influenced by age, sex, body composition, and hemodynamic status, particularly in underrepresented populations living in geographically extreme environments. We analyzed 530 community-dwelling older adults from the Magallanes region in southern Chile using an integrated framework that combined HRV indices with demographic, anthropometric, and cardiovascular descriptors. After quality-controlled preprocessing, we characterized the distribution and association structure of autonomic and physiological variables and then performed a large-scale unsupervised clustering benchmark across multiple feature spaces, dimensionality-reduction strategies, and clustering algorithms. Conventional descriptors explained only a limited proportion of HRV variability, whereas integrated multivariate analysis revealed a structured continuum of autonomic heterogeneity. A six-cluster solution provided the best compromise between separation, balance, and physiological interpretability, identifying profiles that differed in HRV magnitude, blood pressure burden, body composition, sex distribution, and age structure. These findings indicate that autonomic regulation in older adults cannot be adequately summarized by isolated descriptors such as age, body mass index, or blood pressure alone. Instead, it is better represented as a multidimensional physiological organization that supports future hypothesis generation for risk stratification and longitudinal monitoring in aging populations.

neuroscience↗

bioRxiv2026

Paired in situ and molecular analyses identify mechanisms of pathogen persistence within environmental communities

Natural environments are a key reservoir for many opportunistic pathogens, yet mechanisms enabling persistence within complex microbial communities remain poorly defined. Current methods do not adequately link molecular and functional understanding of bacterial persistence to the activities of bacteria within their natural microbial community. Here we combine in situ culture-independent techniques, including metagenomics and metatranscriptomics, with isolate-level functional genomics and mutant studies to understand how opportunistic pathogens from the genera Escherichia, Klebsiella, and Enterococcus survive in urban-adjacent freshwater ecosystems. . Our results show that potential pathogens from each of these genera are both present and active within freshwater microbial communities. We further investigate a mouse-virulent isolate of the E. coli UPEC lineage ST73 isolated directly from this ecosystem, showing that this isolate persists in freshwater microcosms for at least one month. Paired transcriptomics and genome-scale fitness screening in creek water containing autochthonous microbiota identified E. coli genes required for persistence, including those involved in amino acid metabolism, nucleotide biosynthesis and biogenesis of curli. Isolate-resolved metatranscriptomics analysis supported these findings by revealing that many of these genes were highly expressed in situ. Deletion of curli structural genes resulted in reduced biofilm formation and a fitness defect specifically in the presence of freshwater microbiota, indicating that these structures promote environmental survival by improving E. coli competitiveness. Our study deepens our understanding of E. coli survival in waterways, while providing a broadly applicable framework for interrogating mechanisms of pathogen persistence in complex environments and communities.

microbiology↗

bioRxiv2025

Azotobacter vinelandii AmrZ is a global regulator linking alginate production and c-di-GMP homeostasis

Azotobacter vinelandii, a member of the Pseudomonadaceae, produces the exopolysaccharide alginate during vegetative growth; however, the circuitry linking alginate biosynthesis to lifestyle transitions remains poorly defined. Here we show that the Ribbon-Helix-Helix (RHH) transcription factor AmrZ coordinates alginate production, intracellular c-di-GMP levels, and motility. Deletion of amrZ abolished alginate synthesis, whereas chromosomal complementation restored it. A PalgD-gusA fusion and RT-qPCR demonstrated that algD, the first gene in the alginate biosynthetic cluster, depends on AmrZ for expression. Motif analysis identified multiple AmrZ sites upstream of algD, and electrophoretic mobility-shift assays (EMSAs) confirmed specific binding to these regions. AmrZ also positively autoregulates: PamrZ-gusA activity decreased in {Delta}amrZ, and purified AmrZ bound the amrZ promoter in EMSA. Moreover, PamrZ activity required the sigma factor AlgU, consistent with the presence of an AlgU promoter; this positive, AlgU-dependent feedback may stabilize AmrZ under alginate-inducing conditions. To probe AmrZ control of c-di-GMP, we implemented a riboswitch-based biosensor in A. vinelandii. The {Delta}amrZ strain showed a markedly reduced signal, similar to a diguanylate cyclase (DGC) mutant; whereas a phosphodiesterase (PDE) mutant displayed elevated output, validating the assay. RNA-seq and RT-qPCR identified two DGC genes, AVAEIV_RS11610 and AVAEIV_RS18795, as AmrZ-activated targets; EMSA verified direct binding at the RS11610 regulatory region. By contrast, transcription of the principal vegetative DGC AvGreg was not AmrZ-regulated. Lower c-di-GMP in {Delta}amrZ correlated with larger swimming halos. Collectively, these genetic, biochemical, and transcriptomic data support a model in which AmrZ directly activates algD and elevates c-di-GMP via selected DGCs, thereby promoting alginate synthesis while reducing motility. RNA-seq data also indicate that AmrZ influences broader cellular programs, including metabolism and ion homeostasis, positioning AmrZ as a central regulator that links c-di-GMP homeostasis to coordinated exopolysaccharide production in A. vinelandii.

microbiology↗

bioRxiv2025

Lysine acetylation plays a role in RNA binding protein-regulated alternative pre-mRNA splicing.

Alternative pre-mRNA splicing allows one gene to encode multiple spliced messenger RNAs and, in turn, multiple proteins from a single gene transcript. This process is tightly regulated by cis elements within the pre-mRNA and trans-acting RNA binding proteins that recognize and bind to these elements, thus influencing the spliceosome assembly at adjacent splice sites. Thus, chemical modifications in either the cis-elements or trans factors or both can significantly alter splicing patterns and, thereby, the cellular proteome. Recent studies highlight that many RNA binding proteins (RBPs) are modified at multiple lysine side chains via acetylation, which neutralizes the formal positive charge and disrupts RPBs ability to participate in RNA recognition, binding and protein-protein interactions. This suggests that lysine acetylation of RPBs may be a novel mode of eukaryotic gene regulation during pre-mRNA processing. To test this, we used the well-characterized polypyrimidine tract binding protein (which is acetylated at several lysine side chains) as a model system to investigate the role of reversible RBP acetylation in regulating alternative-pre mRNA splicing. Using multiple sequence analysis, structure-based electrostatic modeling of RNA-protein interactions, and multi-site glutamine (acetyllysine mimic) and arginine (deacetyllysine mimic) mutants, we show for the first time that for a subset of PTBP1-regulated exons, acetylation at RNA-interacting lysine side chains significantly alters PTBP1 splicing activity.

biochemistry↗

bioRxiv2024

The c-di-GMP effector FleQ controls alginate production by repressing transcription of the algD gene in Azotobacter vinelandii

Azotobacter vinelandii, belonging to the Psedomonadaceae family, produces the exopolysaccharide alginate during its vegetative growth and also during its differentiation process to form desiccation resistant cysts. The second messenger c-di-GMP regulates a vast array of cellular processes. It is produced by diguanylate cyclases (DGC) and degraded by phosphodiesterases (PDE). In A. vinelandii the absence of the AvgReg DGC impairs alginate synthesis while the absence of the PDE MucG increased alginate production. The effect of the different c-di-GMP levels was solely attributed to its essential role in activating the alginate polymerase complex. Here in we investigated the possible role of c-di-GMP in the control of algD transcription, encoding the key enzyme of the alginate biosynthetic pathway. At artificially high or reduced levels of c-di-GMP algD transcription was increased, or almost abrogated, respectively. Therefore, the role of the transcriptional regulator FleQ, one of the best characterized c-di-GMP effectors, was investigated. Alginate production increased in the {Delta}fleQ relative to the wt strain, which agreed with increased algD transcription. These phenotypes were rescued in the {Delta}fleQ/fleQ+ complemented strain indicating a FleQ repressing effect. EMSA assay showed that FleQ was able to directly bind to the regulatory region of algD which agreed with the presence of a FleQ binding site overlapping its RpoS-dependent promoter. In A. vinelandii the c-di-GMP is also necessary for expression of alginate C-5 epimerase genes, essential for structuring mature cysts. Out data revealed that FleQ is not an intermediary in this regulation since its absence did not impair mature cyst formation nor affected expression of algE1-6 genes. Collectively, our results support a model in which FleQ is the intermediary in the regulation of algD by c-di-GMP, exerting a direct repressing effect and reveal the existence of a FleQ-independent regulatory mechanism for the control of A. vinelandii encystment.

microbiology↗

bioRxiv2023

The Azotobacter vinelandii AlgU Regulon During Vegetative Growth and Encysting Conditions: A Proteomic Approach

In the Pseduomonadacea family, the extracytoplasmic function sigma factor AlgU is crucial to withstand adverse conditions. Azotobacter vinelandii, a closed relative of Pseudomonas aeruginosa, has been a model for cellular differentiation in Gram-negative bacteria since it forms desiccation-resistant cysts. Previous work demonstrated the essential role of AlgU to withstand oxidative stress and on A. vinelandii differentiation, particularly for the positive control of alginate production. In this study, the AlgU regulon was dissected by a proteomic approach under vegetative growing conditions and upon encystment induction. Our results revealed several molecular targets that explained the requirement of this sigma factor during oxidative stress and extended its role in alginate production. Furthermore, we demonstrate that AlgU was necessary to produce alkyl resorcinols, a type of aromatic lipids that conform the cell membrane of the differentiated cell. AlgU was also found to positively regulate stress resistance proteins such as OsmC, LEA-1, or proteins involved in trehalose synthesis. A position-specific scoring-matrix (PSSM) was generated based on the consensus sequence recognized by AlgU in P. aeruginosa, which allowed the identification of direct AlgU targets in the A. vinelandii genome. This work further expands our knowledge about the function of the ECF sigma factor AlgU in A. vinelandii and contributes to explains its key regulatory role under adverse conditions.

microbiology↗

bioRxiv2022

Viroscope: plant viral diagnosis from NGS data using biologically-informed genome assembly coverage

Next-generation sequencing (NGS) methods are transforming our capacity to detect pathogens and perform disease diagnosis. Although sequencing advances have enabled accessible and point-of-care NGS, data analysis pipelines have yet to provide robust tools for precise and certain diagnosis, particularly in cases of low sequencing coverage. Lack of standardized metrics and harmonized detection thresholds confound the problem further, impeding the adoption and implementation of these solutions in real-world applications. In this work, we tackle these issues and propose biologically-informed viral genome assembly coverage as a method to improve diagnostic certainty. We use the identification of viral replicases, an essential function of viral life cycles, to define genome coverage thresholds in which biological functions can be described. We validate the analysis pipeline, Viroscope, using field samples, synthetic and published datasets and demonstrate that it provides sensitive and specific viral detection. Furthermore, we developed Viroscope.io a web-service to provide on-demand NGS data viral diagnosis to facilitate adoption and implementation by phytosanitary agencies to enable precise viral diagnosis.

microbiology↗

bioRxiv2022

Differential role of dopamine D3 receptor through balanced modulation of Akt/mTOR and ERK1/2 activity in the reactivation of cocaine rewarding memories evoked by psychological versus physiological stress

Stress is an important trigger of relapses in cocaine use. These relapses engage the activity of memory-related nuclei, such as the basolateral amygdala (BLA) and the dentate gyrus (DG). Further, preclinical research signals D3 receptor (D3R) antagonists as promising therapeutic tools to attenuate cocaine reward and relapse. Therefore, we assessed the effect of SB-277011-A, a D3R antagonist, in the activity of Akt/mTOR and MEK/ERK1/2 pathways in these areas during the reinstatement of cocaine-induced conditioned place preference (CPP) evoked by psychological (restraint) and physiological (tail pinch) stress. Both stimuli reactivated the extinguished cocaine-CPP, but only restrained animals decreased their locomotor activity during reinstatement. Moreover, p-Akt, p-mTOR and p-ERK1/2 activity in the BLA and DG of restrained animals decreased during the reactivation of cocaine memories, contrasting to tail-pinched mice. While D3R blockade prevented stress-induced CPP reactivation and plasmatic corticosterone enhancement, SB-277011-A distinctly modulated Akt, mTOR and ERK1/2 activities in the BLA and DG based on the stressor and the dose of antagonist. Corticosterone may be partially responsible for these variations as we found high correlations among its levels and mTOR and/or Akt activity in the BLA and DG of restrained animals receiving SB-277011-A. Besides, locomotor activity of animals receiving 48 mg/kg of the antagonist highly correlated with p-mTOR/mTOR and p-ERK1/2 /ERK1/2 in the BLA during restraint- and tail pinch-induced relapse in cocaine-CPP, respectively. Hence, our study endorses D3R antagonists as therapeutic tools to prevent stress-induced relapses in drug use through a complex balance of Akt/mTOR and MEK/ERK1/2 pathways in memory-processing brain nuclei.

neuroscience↗

bioRxiv2022

Disentangling the molecular mechanisms underlying the retrieval and extinction of morphine withdrawal-associated memories in the basolateral amygdala and dentate gyrus.

Despite their indisputable efficacy for pain management, opiates prescription remains highly controversial due to their elevated addictive potential. Relapse in drug use is one of the principal problems for addiction treatment, being drug-associated memories among its main triggers. Consequently, the extinction of these memories has been proposed as a useful therapeutic tool. Hence, by using the conditioned place aversion (CPA) paradigm in rats we investigated some of the molecular mechanisms that occurred during the retrieval and extinction of morphine withdrawal memories in the basolateral amygdala (BLA) and the hippocampal dentate gyrus (DG), which control emotional and episodic memories, respectively. The retrieval of aversive memories associated with the abstinence syndrome paralleled with decreased mTOR activity and increased Arc and GluN1 expressions in the DG. Additionally, Arc mRNA levels in this nucleus very strongly correlated with the CPA score exhibited by the opiate-treated rats. On the other hand, despite the unaltered mTOR phosphorylation Arc augmented in the BLA. After the extinction test, Arc and GluN1 expressions raised in both the DG and BLA of control and morphine-treated animals. Remarkably, Homer1 expression in both areas correlated almost perfectly with the extinction showed by morphinedependent animals. Also, Arc expression in the DG correlated strongly with the extinction of the CPA manifested by the group treated with the opiate. Finally, our results support coordinated activity of some of these neuroplastic proteins for the extinction of morphine activity in a regional-dependent manner. Present data provide evidence of differential expression and activity of synaptic molecules during the retrieval and extinction of aversive memories of opiate withdrawal in amygdalar and hippocampal regions that will likely permit the development of therapeutic strategies able to minimize relapses induced by drug-associated aversive memories.

pharmacology and toxicology↗

bioRxiv2021

Distinct regulation of dopamine D3 receptor in the basolateral amygdala and dentate gyrus during the reinstatement of cocaine CPP induced by drug priming and social stress

Relapse in cocaine seeking and intake is one of the main challenges when treating its addiction. Among the triggering factors for recurrence of cocaine use are the re-exposure to the drug and stressful events. Cocaine relapse engages the activity of memory-related nuclei, such as the basolateral amygdala (BLA) and the hippocampal dentate gyrus (DG), which are responsible for emotional and episodic memories. Besides, D3 receptor (D3R) antagonists have recently arisen as a potential treatment for preventing drug relapse. Thus, we have assessed the impact of D3R blockade in the expression of some dopaminergic markers and in the activity of the mTOR pathway, that is modulated by D3R, in the BLA and DG during the reinstatement of cocaine-induced CPP evoked by drug priming and social stress. Reinstatement of cocaine-CPP paralleled with a trend to increase of D3R and dopamine transporter (DAT) levels in the BLA. Social stress-but not drug-induced reactivation of cocaine memories was prevented by systemic administration of SB-277011-A (a selective D3R antagonist), that was able, however, to impede D3R and DAT up-regulation in the BLA during CPP reinstatement evoked by both stress and cocaine. Concomitantly with cocaine-CPP reactivation occurred a diminution of mTOR phosphorylation (activation) in the BLA and DG that was inhibited by D3R blockade in both nuclei before the social stress episode, and only in the BLA when CPP reinstatement was provoked by a cocaine prime. Our data, while support a main role for D3R signalling in the BLA in the reactivation of cocaine memories evoked by social stress, indicates that different neural circuits and signalling mechanisms might mediate in the reinstatement of cocaine-seeking behaviours depending upon the triggering stimuli.

neuroscience↗