Robust Stress Response Research Articles

Unveiling superior phenol detoxification and degradation ability in Candida tropicalis SHC-03: a comparative study with Saccharomyces cerevisiae BY4742.

This study examined the phenol degradation capabilities and oxidative stress responses of Candida tropicalis SHC-03, demonstrating its metabolic superiority and resilience compared to Saccharomyces cerevisiae BY4742 in a culture medium with phenol as the sole carbon source. Through comparative growth, transcriptomic, and metabolomic analyses under different phenol concentrations, this study revealed C. tropicalis SHC-03's specialized adaptations for thriving in phenol as the sole carbon source environments. These include a strategic shift from carbohydrate metabolism to enhanced phenol degradation pathways, highlighted by the significant upregulation of genes for Phenol 2-monoxygenase and Catechol 1,2-dioxygenase. Despite phenol levels reaching 1.8 g/L, C. tropicalis exhibits a robust oxidative stress response, efficiently managing ROS through antioxidative pathways and the upregulation of genes for peroxisomal proteins like PEX2, PEX13, and PMP34. Concurrently, there was significant upregulation of genes associated with membrane components and transmembrane transporters, enhancing the cell's capacity for substance exchange and signal transduction. Especially, when the phenol concentration was 1.6 g/L and 1.8 g/L, the degradation rates of C. tropicalis towards it were 99.47 and 95.91%, respectively. Conversely, S. cerevisiae BY4742 shows limited metabolic response, with pronounced growth inhibition and lack of phenol degradation. Therefore, our study not only sheds light on the molecular mechanisms underpinning phenol tolerance and degradation in C. tropicalis but also positions this yeast as a promising candidate for environmental and industrial processes aimed at mitigating phenol pollution.

Genotoxic stress impacts pre-mRNA 3'-end processing.

Genotoxic stress, arising from various environmental sources and endogenous cellular processes, pose a constant threat to genomic stability. Cells have evolved intricate mechanisms to detect and repair DNA damage, orchestrating a robust genotoxic stress response to safeguard the integrity of the genome. Recent research has shed light on the crucial role of co- and post-transcriptional regulatory mechanisms in modulating the cellular response to genotoxic stress. Here we highlight recent advances illustrating the intricate interplay between pre-mRNA processing, with a focus on 3'-end processing, and genotoxic stress response.

Effect of Creep, Fatigue and Random Vibration on the Integrity of Solder Joints in BGA Package

This study employs Finite Element Analysis (FEA) to investigate the effects of creep, fatigue, and random vibration on the integrity of solder joints in BGA packages in electronic modules. Evaluating the response of lead-based Sn63Pb37 and lead-free SnAgCu alloy solders (SAC305, SAC387, SAC396, and SAC405) to induced loads - stress, strain, strain energy density, and displacement in the joints is obtained and studied better to understand the mechanism of the joints' degradation. SAC305 and SAC405 are modelled with linear stress-temperature relationships σ = 3.152T–68.167 and σ = 1.543T–34.983, respectively. The magnitude of the strain energy density in the joints is a key failure driver. SAC387 and SAC396 solder joints display lower values of strain energy density and thus have higher durability. Displacement analysis indicates that SAC305 and Sn63Pb37 are prone to deformation-induced failure. SAC387 exhibits the highest fatigue yield stress at 58 MPa, while SAC405 displays the lowest stress at 22 MPa. Analysis of the results of random vibration shows that Sn63Pb37 developed the highest stress at 34.62 MPa and is thus susceptible to stress-induced failure. The robust stress, strain, and strain energy responses of SAC405 and SAC396 provide key insights into improving the mechanical reliability of future electronic devices towards better sustainability.

Xrp1 governs the stress response program to spliceosome dysfunction.

Co-transcriptional processing of nascent pre-mRNAs by the spliceosome is vital to regulating gene expression and maintaining genome integrity. Here, we show that the deficiency of functional U5 small nuclear ribonucleoprotein particles (snRNPs) in Drosophila imaginal cells causes extensive transcriptome remodeling and accumulation of highly mutagenic R-loops, triggering a robust stress response and cell cycle arrest. Despite compromised proliferative capacity, the U5 snRNP-deficient cells increased protein translation and cell size, causing intra-organ growth disbalance before being gradually eliminated via apoptosis. We identify the Xrp1-Irbp18 heterodimer as the primary driver of transcriptional and cellular stress program downstream of U5 snRNP malfunction. Knockdown of Xrp1 or Irbp18 in U5 snRNP-deficient cells attenuated JNK and p53 activity, restored normal cell cycle progression and growth, and inhibited cell death. Reducing Xrp1-Irbp18, however, did not rescue the splicing defects, highlighting the requirement of accurate splicing for cellular and tissue homeostasis. Our work provides novel insights into the crosstalk between splicing and the DNA damage response and defines the Xrp1-Irbp18 heterodimer as a critical sensor of spliceosome malfunction and mediator of the stress-induced cellular senescence program.

Embryonic manipulations shape life-long, heritable stress responses through complex epigenetic mechanisms: a review.

Enhancing an organism's likelihood of survival hinges on fostering a balanced and adaptable development of robust stress response systems. This critical process is significantly influenced by the embryonic environment, which plays a pivotal role in shaping neural circuits that define the stress response set-point. While certain embryonic conditions offer advantageous outcomes, others can lead to maladaptive responses. The establishment of this response set-point during embryonic development can exert life-long and inheritable effects on an organism's physiology and behavior. This review highlights the significance of multilevel epigenetic regulation and the intricate cross-talk among these layers in response to heat stress during the embryonic period, with a particular focus on insights gained from the avian model.

Divergent transcriptional response to thermal stress among life stages could constrain coral adaptation to climate change

The ability for adaptation to track environmental change depends on how efficiently selection can act on heritable genetic variation. Complex life cycles may promote or constrain adaptation depending on the integration or independence of fitness-related traits over development. Reef-building corals exhibit life cycle complexity and are sensitive to increasing temperatures, highlighting the need to understand heritable potential of the thermal stress response and its developmental regulation. We used tag-based RNA-seq to profile holobiont gene expression of inshore and offshore Porites astreoides adults and recruit offspring in response to a 16-day heat stress, and larvae in response to a 4-day heat stress. Host developmental stage affected both broad patterns of host and symbiont expression, and modulated the stress response in both partners, suggesting that symbiotic interactions could vary between host developmental stages and influence the thermal stress response. Populations also exhibited origin-specific treatment responses, but response magnitude differed among life-stages. Inshore parents and recruit offspring exhibited a more robust stress response, exhibiting greater expression profile divergence and differentially expressing more genes compared to offshore-origin corals. This suggests genetic or epigenetic inheritance of regulatory mechanisms giving rise to expression plasticity, although ontogenetic plasticity as a result of the local reef environment during larval development could also explain the origin effect. However, larval populations exhibited the opposite response, with offshore larvae exhibiting a more robust stress response, possibly due to stage-specific effects or exposure duration. Overall, these results show that putatively adaptive regulatory variation persists in thermally naïve life stages, but thermally responsive genes are stage-specific, which could complicate the evolutionary response of corals to climate change.

Does a laboratory-based CO2 challenge induce a hypothalamic-pituitary-adrenal (HPA) axis stress response in healthy adults?

A methodological limitation to studying hypothalamic-pituitary-adrenal (HPA) axis functioning is that there are few laboratory-based tasks that consistently induce a stress response. Moreover, most tasks use a socially-evaluative approach to eliciting a stress response. The aim of the current study was to test whether a CO2 inhalation challenge (originally designed to induce panic symptoms) produces a robust HPA-axis stress response. Forty-eight adults (mean age = 25.6; 69% women; 73% white) were recruited from a local university in the mid-southern part of the United States. Participants were asked to complete a 35% CO2 inhalation challenge. Six saliva samples were collected to measure cortisol responses to the task (a pre-stress baseline sample followed by 5 post-stress samples). Linear mixed effects modeling was used to examine whether there was a significant increase in cortisol following the challenge. There was substantial between-subjects variability in cortisol responses to the challenge. That said, the mean group cortisol response indicated that participants experienced an increase in cortisol 15-30 minutes post-challenge and a subsequent decrease in cortisol 45-60 minutes post-challenge (linear effect, b=0.007, p<0.001; quadratic effect, b=-0.0001, p<0.001). On average, there was a 53% increase in cortisol from baseline and nearly two-thirds of participants had at least a 45% increase in cortisol. The data suggest that a CO2 inhalation challenge can be used to induce a cortisol stress response among healthy participants and offers an alternative laboratory-based task that does not rely on socially-evaluative cues to induce stress.

Oral CBD-rich hemp extract modulates sterile inflammation in female and male rats.

Introduction: Cannabidiol (CBD) extract from the cannabis plant has biomedical and nutraceutical potential. Unlike tetrahydrocannabinol (THC), CBD products produce few psychoactive effects and pose little risk for abuse. There is emerging preclinical and clinical evidence that CBD is stress modulatory and may have anti-inflammatory properties. People across the United States legally ingest CBD-rich hemp extracts to manage mental and physical health problems, including stress and inflammation. Preclinical studies have revealed potential mechanisms for these effects; however, the impact of this prior work is diminished because many studies: 1) tested synthetic CBD rather than CBD-rich hemp extracts containing terpenes and/or other cannabinoids thought to enhance therapeutic benefits; 2) administered CBD via injection into the peritoneal cavity or the brain instead of oral ingestion; and 3) failed to examine potential sex differences. To address these gaps in the literature, the following study tested the hypothesis that the voluntary oral ingestion of CBD-rich hemp extract will attenuate the impact of stressor exposure on plasma and tissue inflammatory and stress proteins in females and males. Methods: Adult male and female Sprague Dawley rats (10-15/group) were randomly assigned to be given cereal coated with either vehicle (coconut oil) or CBD-rich hemp extract (L-M0717, CBDrx/Functional Remedies, 20.0mg/kg). After 7days, rats were exposed to a well-established acute model of stress (100, 1.5mA, 5-s, intermittent tail shocks, 90min total duration) or remained in home cages as non-stressed controls. Results: Stressor exposure induced a robust stress response, i.e., increased plasma corticosterone and blood glucose, and decreased spleen weight (a surrogate measure of sympathetic nervous system activation). Overall, stress-induced increases in inflammatory and stress proteins were lower in females than males, and oral CBD-rich hemp extract constrained these responses in adipose tissue (AT) and mesenteric lymph nodes (MLN). Consistent with previous reports, females had higher levels of stress-evoked corticosterone compared to males, which may have contributed to the constrained inflammatory response measured in females. Discussion: Results from this study suggest that features of the acute stress response are impacted by oral ingestion of CBD-rich hemp extract in female and male rats, and the pattern of changes may be sex and tissue dependent.

The Role of Long-Distance Mobile Metabolites in Plant Stress Response and Signaling.

Plants developed sophisticated mechanisms to receive environmental stimuli and generate appropriate signals to maintain optimal growth and stress responses. A fascinating strategy employed by plants is the use of long-distance mobile signals which can trigger local and distant responses across the entire plant. Some metabolites play a central role as long-distance mobile signals allowing plants to communicate across tissues and mount robust stress responses. In the review, we summarize the current state of knowledge regarding the various long-distance mobile metabolites and their function in stress response and signaling pathways. We also raise questions with respect to how can we identify new mobile metabolites and engineer them to improve plant health and resilience.

Investigating the biophysical mechanisms regulating transcription in starved Escherichia coli via single-molecule tracking.

Bacteria have a robust stress response in starvation conditions, entering a quiescent stationary phase and remaining viable despite depletion of resources. An important component of this stress response is the upregulation of DNA-binding protein from starved cells (Dps) upon entry into the stationary phase. Dps promotes nucleoid condensation, protecting genetic information from harm. Intriguingly, this condensation does not affect the ability of RNA polymerase (RNAP) to access the nucleoid and transcribe RNA. The mechanism by which RNAP accesses the nucleoid under starvation conditions remains unclear. To investigate the dynamics of stationary-phase RNAP, we are applying live-cell single-molecule tracking of RNAP tagged with a photo-activatable fluorescent protein. In living E. coli cells, we find that compared to the dynamics of RNAP in the exponential growth phase, RNAP in the stationary phase spends less time bound to DNA, reflective of an expected decline in protein synthesis. Instead, stationary-phase RNAP spends the majority of its time in an intermediate dynamic state that we hypothesize results from frequent interactions with DNA as RNAP searches for its target sequence. Unexpectedly, the diffusion coefficient of this intermediate state increases in the stationary phase, even though the nucleoid is more compact and thus has a smaller pore size that could restrict motion. To isolate how Dps upregulation leads to changes in the dynamics of RNAP throughout the cell cycle, we over-expressed Dps and found that the RNAP dynamics were nearly identical to those measured with native Dps expression. Ultimately, these studies suggest that the interactions between RNAP and DNA are primarily biochemically driven, and do not depend on nucleoid pore size. Additionally, our results may indicate that Dps can be rapidly displaced by RNAP such that it does not interfere with target searching.

Characterizing the structural rearrangement of the bacterial nucleoid by Dps.

Bacteria are subject to a wide variety of environmental stresses which requires a robust stress response system to protect the cell. A key protein in Escherichia coli known for its numerous functions in stress response and cell maintenance is the DNA-binding protein from starved cells (Dps). The Dps protein protects DNA via two different mechanisms. First, Dps oxidizes iron to prevent the generation of hydroxyl radicals. Second, in response to stress and throughout the stationary phase of the growth cycle, Dps oligomers bind to DNA and multimerize further to create a Dps-DNA complex that compacts. To access how Dps affects this structural change of DNA to afford protection of the cell's genome, photoactivatable localization microscopy is employed to generate nanometer-scale maps of the nucleoid structure throughout the E. coli growth phases. These maps are attained by super-resolving the localizations of single molecules of the nucleoid-associated protein HUα, which non-specifically binds to DNA, tagged with the photoactivatable fluorescent protein PAmCherry. Super-resolution maps of the nucleoid structure are compared to maps of the nucleoid in E. coli strains with dps deleted. Tagging Dps and other major nucleoid associated proteins with PAmCherry provides the distribution of these proteins across the nucleoid to gain insight on how and if Dps interacts with other nucleoid associated proteins. By observing these structural changes over the growth period of E. coli, insight can be gained about how changes in DNA structure can lead to protection via Dps.

Diplosoma simile (Ascidiacea: Didemnidae) distribution and its photosynthetic thermal stress responses from Mauritius: Implications for invasive or opportunistic behavior

Abstract. Fai ALY, Kaullysing D, Jeetun S, Soondur M, Bhagooli R. 2023. Diplosoma simile (Ascidiacea: Didemnidae) distribution and its photosynthetic thermal stress responses from Mauritius: Implications for invasive or opportunistic behavior. Indo Pac J Ocean Life 7: 16-26. This study aimed to investigate the morphological identity of the ascidian Diplosoma, its distribution, experimental thermal stress responses, and its characteristics of being potentially invasive or opportunistic in Mauritian waters. The Diplosoma species were anesthetized in menthol, fixed, and preserved in a formalin-seawater solution. Isolated zooids and embryos were examined under a microscope for distinct morphological characteristics, which revealed their identity as D. simile (Sluiter, 1909). The D. simile percentage cover studied at seven sites in 2019 around Mauritius tended to be high at the near-reef zone, with a high percentage of dead coral cover per 0.5 m2. At Flic en Flac, long-term observations in 2008, 2010, 2016, and 2019 indicated a significant decrease and increased from 61.25±3.31 to 6.15±0.60 % and 0.08±0.05 to 2.50±090% for the percentage covers of live coral and D. simile, respectively. The D. simile was recorded on five coral species, and its percentage occurrence increased from 2008 to 2019 in Acropora muricata, A. cytherea, Pocillopora damicornis, and Montipora aequituberculata with the highest levels occurring in Acropora while Porites lutea was not found to be covered by D. simile during the study. Visual observations from the thermal exposures at 27ºC, 30ºC, and 33ºC during 19 hrs revealed that D. simile was more affected by increasing temperature and exposure time. Using four observed conditions of normal, bleached/paled, tissue sloughing, and mortality, D. simile suffered from only bleaching/paling at 33ºC at 19 hrs exposure. Variable visual responses were noted for corals, with P. lutea appearing normal at all trials while A. cytherea was suffering from mortality both at 30ºC and 33ºC at 19 hrs exposure. The effective quantum yield (?PSII), measured using a Diving-PAM, declined significantly at 33ºC treatments at 6 and 19 hrs of exposure. D. simile generally tended to be more thermally tolerant than corals like P. lutea, P. damicornis, M. aequituberculata, A. muricata, A, cytherea, though the ?PSII thermal responses were variable among the tested corals. When considering the reported behavioral characteristics of D. simile, namely the lack of broad dispersal range and wide environmental tolerance, it is tempting to deduce that the species is potentially invasive. However, in this study, D. simile’s significant distribution on dead corals, its presence in zones of high anthropogenic activities, and its relatively more robust thermal stress responses than corals colonized suggest an opportunistic behavior.

Mutation of the polyadenylation complex subunit CstF77 reveals that mRNA 3' end formation and HSP101 levels are critical for a robust heat stress response.

Heat shock protein 101 (HSP101) in plants, and bacterial and yeast orthologs, is essential for thermotolerance. To investigate thermotolerance mechanisms involving HSP101, we performed a suppressor screen in Arabidopsis thaliana of a missense HSP101 allele (hot1-4). hot1-4 plants are sensitive to acclimation heat treatments that are otherwise permissive for HSP101 null mutants, indicating that the hot1-4 protein is toxic. We report one suppressor (shot2, suppressor of hot1-4 2) has a missense mutation of a conserved residue in CLEAVAGE STIMULATION FACTOR77 (CstF77), a subunit of the polyadenylation complex critical for mRNA 3' end maturation. We performed ribosomal RNA depletion RNA-Seq and captured transcriptional readthrough with a custom bioinformatics pipeline. Acclimation heat treatment caused transcriptional readthrough in hot1-4 shot2, with more readthrough in heat-induced genes, reducing the levels of toxic hot1-4 protein and suppressing hot1-4 heat sensitivity. Although shot2 mutants develop like the wild type in the absence of stress and survive mild heat stress, reduction of heat-induced genes and decreased HSP accumulation makes shot2 in HSP101 null and wild-type backgrounds sensitive to severe heat stress. Our study reveals the critical function of CstF77 for 3' end formation of mRNA and the dominant role of HSP101 in dictating the outcome of severe heat stress.

The Slc25a47 locus is a novel determinant of hepatic mitochondrial function implicated in liver fibrosis.

Transporters of the SLC25 mitochondrial carrier superfamily bridge cytoplasmic and mitochondrial metabolism by channeling metabolites across mitochondrial membranes and are pivotal for metabolic homeostasis. Despite their physiological relevance as gatekeepers of cellular metabolism, most of the SLC25 family members remain uncharacterized. We undertook a comprehensive tissue distribution analysis of all Slc25 family members across metabolic organs and identified SLC25A47 as a liver-specific mitochondrial carrier. We used a murine loss-of-function model to unravel the role of this transporter in mitochondrial and hepatic homeostasis. We performed extensive metabolic phenotyping and molecular characterization of newly generated Slc25a47hep-/- and Slc25a47-Fgf21hep-/- mice. Slc25a47hep-/- mice displayed a wide variety of metabolic abnormalities, as a result of sustained energy deficiency in the liver originating from impaired mitochondrial respiration. This mitochondrial phenotype was associated with an activation of the mitochondrial stress response (MSR) in the liver, and the development of fibrosis, which was exacerbated upon feeding a high-fat high-sucrose diet. The MSR induced the secretion of several mitokines, amongst which FGF21 played a preponderant role on systemic physiology. To dissect the FGF21-dependent and -independent physiological changes induced in Slc25a47hep-/- mice, we generated a double Slc25a47-Fgf21hep-/- mouse model and demonstrated that several aspects of the hypermetabolic state were driven by hepatic secretion of FGF21. On the other hand, the metabolic fuel inflexibility observed in Slc25a47hep-/- mice could not be rescued with the genetic removal of Fgf21. Collectively, our data place the Slc25a47 locus at the center of mitochondrial homeostasis, which upon dysfunction triggers robust liver-specific and systemic adaptive stress responses. The prominent role of the Slc25a47 locus in hepatic fibrosis identifies this carrier, or its transported metabolite, as a potential target for therapeutic intervention. Herein, we report the importance ofa locus containing a liver-specific gene coding for a mitochondrial transport protein called SLC25A47. Mitochondria are the powerhouses of cells. They are crucial for metabolism and energy generation. We show that mice with genetic disruption of the Slc25a47 locus cannot maintain mitochondrial homeostasis (balance), leading to wide-ranging problems in the liver that have far-reaching physiological consequences.

Ecological and genomic responses of soil microbiomes to high-severity wildfire: linking community assembly to functional potential

Increasing wildfire severity, which is common throughout the western United States, can have deleterious effects on plant regeneration and large impacts on carbon (C) and nitrogen (N) cycling rates. Soil microbes are pivotal in facilitating these elemental cycles, so understanding the impact of increasing fire severity on soil microbial communities is critical. Here, we assess the long-term impact of high-severity fires on the soil microbiome. We find that high-severity wildfires result in a multi-decadal (>25 y) recovery of the soil microbiome mediated by concomitant differences in aboveground vegetation, soil chemistry, and microbial assembly processes. Our results depict a distinct taxonomic and functional successional pattern of increasing selection in post-fire soil microbial communities. Changes in microbiome composition corresponded with changes in microbial functional potential, specifically altered C metabolism and enhanced N cycling potential, which related to rates of potential decomposition and inorganic N availability, respectively. Based on metagenome-assembled genomes, we show that bacterial genomes enriched in our earliest site (4 y since fire) harbor distinct traits such as a robust stress response and a high potential to degrade pyrogenic, polyaromatic C that allow them to thrive in post-fire environments. Taken together, these results provide a biological basis for previously reported process rate measurements and explain the temporal dynamics of post-fire biogeochemistry, which ultimately constrains ecosystem recovery.

Combined exposure to non-antibiotic pharmaceutics and antibiotics in the gut synergistically promote the development of multi-drug-resistance in Escherichia coli

ABSTRACT The gut microbiota represents an important reservoir of antibiotic-resistant bacteria (ARB), which poses a significant threat to public health. However, little is known about the emergence of ARB in the gut after the combined exposure to antibiotics and non-antibiotic pharmaceutics. Here, Escherichia coli, a common opportunistic pathogen in the gut microbiota, was exposed to the antidepressant duloxetine (2.5 µg/L–25 mg/L) and/or chloramphenicol (6 µg/L–4 mg/L). The resistant strains were isolated to determine the minimum inhibition concentration (MIC) of 29 antibiotics. Then, genome-wide DNA sequencing, global transcriptomic sequencing, and real-time quantitative polymerase chain reaction were performed to quantify the synergy between duloxetine and chloramphenicol. Combined exposure synergistically increased the mutation frequency of chloramphenicol resistance by 2.45–9.01 fold compared with the independent exposure. A combination index reaching 187.7 indicated strong duloxetine and chloramphenicol synergy. The resultant mutants presented heritable enhanced resistance to 12 antibiotics and became ARB to eight antibiotics. Furthermore, combined exposure significantly increased the transcriptomic expression of acrA, acrB, and marA in E. coli, and generated a more robust oxidative stress response. Together with the occurrence of DNA mutations in marR in the mutants, stronger triggers to the AcrAB-TolC transport system and the MlaFEDB ABC transporter via reactive oxygen species (ROS)-induced mutagenesis, verified by gene knockout, contributed to the synergistic enhancement of antibiotic resistance in the combined exposure group. Regardless of whether their formation was induced by duloxetine, chloramphenicol, or their combination, the E. coli mutants showed 1.1–1.7-fold increases in the expression levels of acrA, acrB, acrZ, mdtE, and mdtF. This pattern indicated that the mutants shared the same resistance mechanisms against chloramphenicol, involving the improved efflux pumps AcrAB-TolC and mdtEF. Our findings demonstrated that antibiotics and non-antibiotic pharmaceutics synergistically accelerate the evolution of ARB and may enhance their spread.

Double stranded DNA breaks and genome editing trigger loss of ribosomal protein RPS27A.

DNA damage activates a robust transcriptional stress response, but much less is known about how DNA damage impacts translation. The advent of genome editing with Cas9 has intensified interest in understanding cellular responses to DNA damage. Here, we find that DNA double‐strand breaks (DSBs), including those induced by Cas9, trigger the loss of ribosomal protein RPS27A from ribosomes via p53‐independent proteasomal degradation. Comparisons of Cas9 and dCas9 ribosome profiling and mRNA‐seq experiments reveal a global translational response to DSBs that precedes changes in transcript abundance. Our results demonstrate that even a single DSB can lead to altered translational output and ribosome remodeling, suggesting caution in interpreting cellular phenotypes measured immediately after genome editing.

Selectivity and molecular stress responses to classical and botanical acaricides in the predatory mite Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae).

Acaricide application remains an integral component of integrated pest management (IPM) for the two-spotted spider mite Tetranychus urticae. Species and strains of phytoseiid predatory mites vary significantly in their response to acaricides. For the success of IPM, it is imperative to identify the determinants of selectivity and molecular stress responses of acaricides in predatory mites. The three classical acaricides bifenazate, cyflumetofen, and fenbutatin oxide did not affect the survival and fecundity of Phytoseiulus persimilis regardless of the route of exposure. Selectivity of the orange oil and terpenoid blend-based botanical acaricides was low via a combination of direct exposure, acaricide-laced diet, and residual exposure but improved when limiting exposure only to diet. To gain insights into the molecular stress responses, the transcriptome of P. persimilis was assembled. Subsequent gene expression analysis of predatory mites orally exposed to fenbutatin oxide and orange oil yielded only a limited xenobiotic stress response. In contrast, P. persimilis exhibited target-site resistance mutations, including I260M in SdhB, I1017M in CHS1, and kdr and super-kdr in VGSC. Extending the screen using available Phytoseiidae sequences uncovered I136T, S141F in cytb, G119S in AChE, and A2083V in ACC, well-known target-sites of acaricides. Selectivity of the tested botanical acaricides to P. persimilis was low but could be enhanced by restricting exposure to a single route. Differential gene expression analysis did not show a robust induced stress response after sublethal exposure. In contrast, this study uncovered target-site mutations that may help to explain the physiological selectivity of several classical acaricides to phytoseiid predators.

Essential role of a Plasmodium berghei heat shock protein (PBANKA_0938300) in gametocyte development

The continued existence of Plasmodium parasites in physiologically distinct environments during their transmission in mosquitoes and vertebrate hosts requires effector proteins encoded by parasite genes to provide adaptability. Parasites utilize their robust stress response system involving heat shock proteins for their survival. Molecular chaperones are involved in maintaining protein homeostasis within a cell during stress, protein biogenesis and the formation of protein complexes. Due to their critical role in parasite virulence, they are considered targets for therapeutic interventions. Our results identified a putative P. berghei heat shock protein (HSP) belonging to the HSP40 family (HspJ62), which is abundantly induced upon heat stress and expressed during all parasite stages. To determine the role HspJ62, a gene-disrupted P. berghei transgenic line was developed (ΔHspJ62), which resulted in disruption of gametocyte formation. Such parasites were unable to form subsequent sexual stages because of disrupted gametogenesis, indicating the essential role of HspJ62 in gametocyte formation. Transcriptomic analysis of the transgenic line showed downregulation of a number of genes, most of which were specific to male or female gametocytes. The transcription factor ApiAP2 was also downregulated in ΔHspJ62 parasites. Our findings suggest that the downregulation of ApiAP2 likely disrupts the transcriptional regulation of sexual stage genes, leading to impaired gametogenesis. This finding also highlights the critical role that HspJ62 indirectly plays in the development of P. berghei sexual stages and in facilitating the conversion from the asexual blood stage to the sexual stage. This study characterizes the HspJ62 protein as a fertility factor because parasites lacking it are unable to transmit to mosquitoes. This study adds an important contribution to ongoing research aimed at understanding gametocyte differentiation and formation in parasites. The molecule adds to the list of potential drug targets that can be targeted to inhibit parasite sexual development and consequently parasite transmission.

Cardiomyocyte-produced miR-339-5p mediates pathology in Duchenne muscular dystrophy cardiomyopathy.

Duchenne muscular dystrophy (DMD) is an X-linked genetic disease characterized by severe, progressive muscle wasting. Cardiomyopathy has emerged as a leading cause of death in patients with DMD. The mechanisms contributing to DMD cardiac disease remain under investigation and specific therapies available are lacking. Our prior work has shown that DMD-iPSC-derived cardiomyocytes (DMD-iCMs) are vulnerable to oxidative stress injury and chronic exposure to DMD-secreted exosomes impaired the cell's ability to protect against stress. In this study, we sought to examine a mechanism by which DMD cardiac exosomes impair cellular response through altering important stress-responsive genes in the recipient cells. Here, we report that DMD-iCMs secrete exosomes containing altered microRNA (miR) profiles in comparison to healthy controls. In particular, miR-339-5p was upregulated in DMD-iCMs, DMD exosomes and mdx mouse cardiac tissue. Restoring dystrophin in DMD-iCMs improved the cellular response to stress and was associated with downregulation of miR-339-5p, suggesting that it is disease-specific. Knockdown of miR-339-5p was associated with increased expression of MDM2, GSK3A and MAP2K3, which are genes involved in important stress-responsive signaling pathways. Finally, knockdown of miR-339-5p led to mitochondrial protection and a reduction in cell death in DMD-iCMs, indicating miR-339-5p is involved in direct modulation of stress-responsiveness. Together, these findings identify a potential mechanism by which exosomal miR-339-5p may be modulating cell signaling pathways that are important for robust stress responses. Additionally, these exosomal miRs may provide important disease-specific targets for future therapeutic advancements for the management and diagnosis of DMD cardiomyopathy.