Oxidation resistance 1 (OXR1) participates in silkworm defense against bacterial infection through the JNK pathway

Catalase promotes whitefly adaptation to high temperature by eliminating reactive oxygen species

Thermal stress usually leads to excessive production of reactive oxygen species (ROS) in all aerobic organisms. Catalases (CAT) are the key antioxidant enzymes, which act as the first line of defense against ROS in the antioxidant pathway. The highly invasive and widely distributed whitefly Bemisia tabaci MED damages plants by feeding as well as by transmitting many plant viruses. Previous studies have shown that strong adaptability to high temperature helps explain the spread of MED around the world. However, the mechanism underlying high temperature adaptation of this pest is not well understood. In this study, 6 CAT genes were identified from the MED genome and transcriptome dataset, among which BtCAT1, BtCAT2, and BtCAT3 were found to be highly expressed in adults. The expression of BtCAT1, BtCAT2, or BtCAT3 increased with induction temperature and induction time. The MED was exposed with mean high temperature (30 °C or 35 °C) and a short-term extremely high temperature (39 °C or 41 °C) after the silencing of BtCAT1, BtCAT2, or BtCAT3 to significantly increased ROS levels by at least 0.5 times and significantly decreased survival rate and fecundity of MED adults. The ROS level in the treated specimens gradually returned to a normal level after 24 h at 25 °C, but the survival rate still declined significantly. Taken together, our results demonstrate that CAT could help B. tabaci adapt to long-term mean high temperatures and short-term extremely high temperatures by eliminating excessive ROS.

A loss-of-function mutation in human Oxidation Resistance 1 disrupts the spatial-temporal regulation of histone arginine methylation in neurodevelopment

BACKGROUND

Oxidation Resistance 1 (OXR1) gene is a highly conserved gene of the TLDc domain-containing family. OXR1 is involved in fundamental biological and cellular processes, including DNA damage response, antioxidant pathways, cell cycle, neuronal protection, and arginine methylation. In 2019, five patients from three families carrying four biallelic loss-of-function variants in OXR1 were reported to be associated with cerebellar atrophy. However, the impact of OXR1 on cellular functions and molecular mechanisms in the human brain is largely unknown. Notably, no human disease models are available to explore the pathological impact of OXR1 deficiency.

RESULTS

We report a novel loss-of-function mutation in the TLDc domain of the human OXR1 gene, resulting in early-onset epilepsy, developmental delay, cognitive disabilities, and cerebellar atrophy. Patient lymphoblasts show impaired cell survival, proliferation, and hypersensitivity to oxidative stress. These phenotypes are rescued by TLDc domain replacement. We generate patient-derived induced pluripotent stem cells (iPSCs) revealing impaired neural differentiation along with dysregulation of genes essential for neurodevelopment. We identify that OXR1 influences histone arginine methylation by activating protein arginine methyltransferases (PRMTs), suggesting OXR1-dependent mechanisms regulating gene expression during neurodevelopment. We model the function of OXR1 in early human brain development using patient-derived brain organoids revealing that OXR1 contributes to the spatial-temporal regulation of histone arginine methylation in specific brain regions.

CONCLUSIONS

This study provides new insights into pathological features and molecular underpinnings associated with OXR1 deficiency in patients.

Putative C2H2 Transcription Factor AflZKS3 Regulates Aflatoxin and Pathogenicity in Aspergillus flavus

Aflatoxin is a carcinogenic secondary metabolite that poses a serious threat to human and animal health. Some C₂H₂ transcription factors are associated with fungal growth and secondary metabolic regulation. In this study, we characterized the role of AflZKS3, a putative C₂H₂ transcription factor based on genome annotation, in the growth and aflatoxin biosynthesis of A. flavus and explored its possible mechanisms of action. Surprisingly, the protein was found to be located in the cytoplasm, and gene deletion in A. flavus resulted in defective growth and conidia formation, as well as increased sensitivity to the fluorescent brightener Calcofluor white, Congo red, NaCl, and sorbitol stress. Notably, the biosynthesis of aflatoxin B₁ was completely inhibited in the ΔAflZKS3 deletion strain, and its ability to infect peanut and corn seeds was also reduced. RNA sequencing showed that differentially expressed genes in the ΔAflZKS3 strain compared with the control and complementation strains were mainly associated with growth, aflatoxin biosynthesis, and oxidative stress. Thus, AflZKS3 likely contributes to growth, cell development, and aflatoxin synthesis in A. flavus. These findings lay the foundation for a deeper understanding of the roles of C₂H₂ transcription factors in A. flavus and provide a potential biocontrol target for preventing aflatoxin contamination.

Molecular mechanism and potential application of bacterial infection in the silkworm, Bombyx mori

As a representative species of Lepidoptera, Bombyx mori has been widely studied and applied. However, bacterial infection has always been an important pathogen threatening the growth of silkworms. Bombyx mori can resist various pathogenic bacteria through their own physical barrier and innate immune system. However, compared with other insects, such as Drosophila melanogaster, research on the antibacterial mechanism of silkworms is still in its infancy. This review systematically summarized the routes of bacterial infection in silkworms, the antibacterial mechanism of silkworms after ingestion or wounding infection, and the intestinal bacteria and infection of silkworms. Finally, we will discuss silkworms as a model animal for studying bacterial infectious diseases and screening antibacterial drugs.

The OxrA Protein of Aspergillus fumigatus Is Required for the Oxidative Stress Response and Fungal Pathogenesis

An efficient reactive oxygen species (ROS) detoxification system is vital for the survival of the pathogenic fungus Aspergillus fumigatus within the host high-ROS environment of the host. Therefore, identifying and targeting factors essential for oxidative stress response is one approach to developing novel treatments for fungal infections. The oxidation resistance 1 (Oxr1) protein is essential for protection against oxidative stress in mammals, but its functions in pathogenic fungi remain unknown. The present study aimed to characterize the role of an Oxr1 homolog in A. fumigatus. The results indicated that the OxrA protein plays an important role in oxidative stress resistance by regulating the catalase function in A. fumigatus, and overexpression of catalase can rescue the phenotype associated with OxrA deficiency. Importantly, the deficiency of oxrA decreased the virulence of A. fumigatus and altered the host immune response. Using the Aspergillus-induced lung infection model, we demonstrated that the ΔoxrA mutant strain induced less tissue damage along with decreased levels of lactate dehydrogenase (LDH) and albumin release. Additionally, the ΔoxrA mutant caused inflammation at a lower degree, along with a markedly reduced influx of neutrophils to the lungs and a decreased secretion of cytokine usually associated with recruitment of neutrophils in mice. These results characterize the role of OxrA in A. fumigatus as a core regulator of oxidative stress resistance and fungal pathogenesis. IMPORTANCE Knowledge of ROS detoxification in fungal pathogens is useful in the design of new antifungal drugs and could aid in the study of oxidative stress resistance mechanisms. In this study, we demonstrate that OxrA protein localizes to the mitochondria and functions to protect against oxidative damage. We demonstrate that OxrA contributes to oxidative stress resistance by regulating catalase function, and overexpression of catalase (CatA or CatB) can rescue the phenotype that is associated with OxrA deficiency. Remarkably, a loss of OxrA attenuated the fungal virulence in a mouse model of invasive pulmonary aspergillosis and altered the host immune response. Therefore, our finding indicates that inhibition of OxrA might be an effective approach for alleviating A. fumigatus infection. The present study is, to the best of our knowledge, a pioneer in reporting the vital role of Oxr1 protein in pathogenic fungi.

Base excision repair causes age-dependent accumulation of single-stranded DNA breaks that contribute to Parkinson disease pathology

Aging, genomic stress, and mitochondrial dysfunction are risk factors for neurodegenerative pathologies, such as Parkinson disease (PD). Although genomic instability is associated with aging and mitochondrial impairment, the underlying mechanisms are poorly understood. Here, we show that base excision repair generates genomic stress, promoting age-related neurodegeneration in a Caenorhabditis elegans PD model. A physiological level of NTH-1 DNA glycosylase mediates mitochondrial and nuclear genomic instability, which promote degeneration of dopaminergic neurons in older nematodes. Conversely, NTH-1 deficiency protects against α-synuclein-induced neurotoxicity, maintaining neuronal function with age. This apparent paradox is caused by modulation of mitochondrial transcription in NTH-1-deficient cells, and this modulation activates LMD-3, JNK-1, and SKN-1 and induces mitohormesis. The dependance of neuroprotection on mitochondrial transcription highlights the integration of BER and transcription regulation during physiological aging. Finally, whole-exome sequencing of genomic DNA from patients with idiopathic PD suggests that base excision repair might modulate susceptibility to PD in humans.

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Incomplete base excision repair is a source of genomic stress during aging

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The NTH-1 DNA glycosylase is a key mediator of age-dependent genomic instability

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Compromised NTH-1 activity promotes neuroprotection in PD nematodes

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NTH-1 deficiency triggers LMD-3/JNK-1/SKN-1-dependent mitohormetic response

Preventing Neurodegeneration by Controlling Oxidative Stress: The Role of OXR1

Parkinson’s disease, diabetic retinopathy, hyperoxia induced retinopathy, and neuronal damage resulting from ischemia are among the notable neurodegenerative diseases in which oxidative stress occurs shortly before the onset of neurodegeneration. A shared feature of these diseases is the depletion of OXR1 (oxidation resistance 1) gene products shortly before the onset of neurodegeneration. In animal models of these diseases, restoration of OXR1 has been shown to reduce or eliminate the deleterious effects of oxidative stress induced cell death, delay the onset of symptoms, and reduce overall severity. Moreover, increasing OXR1 expression in cells further increases oxidative stress resistance and delays onset of disease while showing no detectable side effects. Thus, restoring or increasing OXR1 function shows promise as a therapeutic for multiple neurodegenerative diseases. This review examines the role of OXR1 in oxidative stress resistance and its impact on neurodegenerative diseases. We describe the potential of OXR1 as a therapeutic in light of our current understanding of its function at the cellular and molecular level and propose a possible cascade of molecular events linked to OXR1’s regulatory functions.

The sunflower TLDc-containing protein HaOXR2 confers tolerance to oxidative stress and waterlogging when expressed in maize plants

The sunflower (Helianthus annuus L.) genome encodes six proteins containing a TLDc domain, typical of the eukaryotic OXidation Resistance (OXR) protein family. Expression of sunflower HaOXR2 in Arabidopsis generated plants with increased rosette diameter, higher number of leaves and increased seed production. Maize inbred lines expressing HaOXR2 also showed increased total leaf area per plant. In addition, heterologous expression of HaOXR2 induced an increase in the oxidative stress tolerance in Arabidopsis and maize. Maize transgenic plants expressing HaOXR2 experienced less oxidative damage and exhibited increased photosynthetic performance and efficiency than non-transgenic segregant plants after treatment of leaves with the reactive oxygen species generating compound Paraquat. Expression of HaOXR2 in maize also improved tolerance to waterlogging. The number of expanded leaves, aerial biomass, and stem height and cross-section area were less affected by waterlogging in HaOXR2 expressing plants, which also displayed less aerial tissue damage under these conditions. Transgenic plants also showed an increased production of roots, a typical adaptive stress response. The results show the existence of functional conservation of OXR proteins in dicot and monocot plants and indicate that HaOXR2 could be useful to improve plant performance under conditions that increase oxidative stress.

Zebrafish Oxr1a Knockout Reveals Its Role in Regulating Antioxidant Defenses and Aging

Oxidation resistance gene 1 (OXR1) is essential for protection against oxidative stress in mammals, but its functions in non-mammalian vertebrates, especially in fish, remain uncertain. Here, we created a homozygous oxr1a-knockout zebrafish via the CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR associated protein 9) system. Compared with wild-type (WT) zebrafish, oxr1a^−/− mutants exhibited higher mortality and more apoptotic cells under oxidative stress, and multiple antioxidant genes (i.e., gpx1b, gpx4a, gpx7 and sod3a) involved in detoxifying cellular reactive oxygen species were downregulated significantly. Based on these observations, we conducted a comparative transcriptome analysis of early oxidative stress response. The results show that oxr1a mutation caused more extensive changes in transcriptional networks compared to WT zebrafish, and several stress response and pro-inflammatory pathways in oxr1a^−/− mutant zebrafish were strongly induced. More importantly, we only observed the activation of the p53 signaling and apoptosis pathway in oxr1a^−/− mutant zebrafish, revealing an important role of oxr1a in regulating apoptosis via the p53 signaling pathway. Additionally, we found that oxr1a mutation displayed a shortened lifespan and premature ovarian failure in prolonged observation, which may be caused by the loss of oxr1a impaired antioxidant defenses, thereby increasing pro-apoptotic events. Altogether, our findings demonstrate that oxr1a is vital for antioxidant defenses and anti-aging in zebrafish.

JNK pathway plays a key role in the immune system of the pea aphid and is regulated by microRNA-184

Different from holometabolous insects, the hemipteran species such as pea aphid Acyrthosiphon pisum exhibit reduced immune responses with the absence of the genes coding for antimicrobial peptide (AMP), immune deficiency (IMD), peptidoglycan recognition proteins (PGRPs), and other immune-related molecules. Prior studies have proved that phenoloxidase (PO)-mediated melanization, hemocyte-mediated phagocytosis, and reactive oxygen species (ROS) participate in pea aphid defense against bacterial infection. Also, the conserved signaling, Jun N-terminal kinase (JNK) pathway, has been suggested to be involved in pea aphid immune defense. However, the precise role of the JNK signaling, its interplay with other immune responses and its regulation in pea aphid are largely unknown. In this study, using in vitro biochemical assays and in vivo bioassays, we demonstrated that the JNK pathway regulated hemolymph PO activity, hydrogen peroxide concentration and hemocyte phagocytosis in bacteria infected pea aphids, suggesting that the JNK pathway plays a central role in regulating immune responses in pea aphid. We further revealed the JNK pathway is regulated by microRNA-184 in response to bacterial infection. It is possible that in common the JNK pathway plays a key role in immune system of hemipteran insects and microRNA-184 regulates the JNK pathway in animals.

Loss of Oxidation Resistance 1, OXR1, Is Associated with an Autosomal-Recessive Neurological Disease with Cerebellar Atrophy and Lysosomal Dysfunction

We report an early-onset autosomal-recessive neurological disease with cerebellar atrophy and lysosomal dysfunction. We identified bi-allelic loss-of-function (LoF) variants in Oxidative Resistance 1 (OXR1) in five individuals from three families; these individuals presented with a history of severe global developmental delay, current intellectual disability, language delay, cerebellar atrophy, and seizures. While OXR1 is known to play a role in oxidative stress resistance, its molecular functions are not well established. OXR1 contains three conserved domains: LysM, GRAM, and TLDc. The gene encodes at least six transcripts, including some that only consist of the C-terminal TLDc domain. We utilized Drosophila to assess the phenotypes associated with loss of mustard (mtd), the fly homolog of OXR1. Strong LoF mutants exhibit late pupal lethality or pupal eclosion defects. Interestingly, although mtd encodes 26 transcripts, severe LoF and null mutations can be rescued by a single short human OXR1 cDNA that only contains the TLDc domain. Similar rescue is observed with the TLDc domain of NCOA7, another human homolog of mtd. Loss of mtd in neurons leads to massive cell loss, early death, and an accumulation of aberrant lysosomal structures, similar to what we observe in fibroblasts of affected individuals. Our data indicate that mtd and OXR1 are required for proper lysosomal function; this is consistent with observations that NCOA7 is required for lysosomal acidification.

Characterization of immune-related PGRP gene expression and phenoloxidase activity in Cry1Ac-susceptible and -resistant Plutella xylostella (L.)

Peptidoglycan recognition proteins (PGRPs) are important recognition receptors which play a critical role in signal identification and transmission in Toll or immune deficiency (IMD) pathways, particularly when pathogens evade and circumvent reactive oxygen species. Antimicrobial peptides (AMPs) synthesis can be activated by these signals to further eliminate pathogens. In this study, we cloned and characterized three different PGRP genes in Plutella xylostella strains, DBM1Ac-S, DBM1Ac-R and a field strain (DBMF). The results showed that PGRP1 belongs to the PGRP-SA family, PGRP2 to PGRP-LB, and PGRP3 to PGRP-LF. Moreover, PGRP1 expressed the highest transcript level, followed by PGRP3 and PGRP2, in two tissues including the gut and the larval carcass tissues of the DBM1Ac-S strain. Furthermore, altered expression levels of PGRP1-3 genes were detected in both gut and carcass tissues. Moreover, the DBM1Ac-R strain had the highest phenol oxidase (PO) activity among these three strains. The characterization of PGRP gene expression and PO activity in DBM1Ac-S, DBM1Ac-R and DBM-F provides insights into their important physiological roles in the immune system of P. xylostella exposed to Bt Cry1Ac toxin.

The mitochondrial oxidation resistance protein AtOXR2 increases plant biomass and tolerance to oxidative stress

This study demonstrates the existence of the oxidation resistance (OXR) protein family in plants. There are six OXR members in Arabidopsis that contain the highly conserved TLDc domain that is characteristic of this eukaryotic protein family. AtOXR2 is a mitochondrial protein able to alleviate the stress sensitivity of a yeast oxr1 mutant. It was induced by oxidative stress and its overexpression in Arabidopsis (oeOXR2) increased leaf ascorbate, photosynthesis, biomass, and seed production, as well as conferring tolerance to methyl viologen, antimycin A, and high light intensities. The oeOXR2 plants also showed higher ABA content, changes in ABA sensitivity, and modified expression of ABA- and stress-regulated genes. While the oxr2 mutants had a similar shoot phenotype to the wild-type, they exhibited increased sensitivity to stress. We propose that by influencing the levels of reactive oxygen species (ROS), AtOXR2 improves the efficiency of photosynthesis and elicits basal tolerance to environmental challenges that increase oxidative stress, allowing improved plant growth and biomass production.

MicroRNA-373 promotes the development of esophageal squamous cell carcinoma by targeting LATS2 and OXR1

INTRODUCTION

MicroRNA373 was highly expressed in many tumors including esophageal cancer. However, its molecular mechanism is still unclear, especially epigenetic modification, in esophageal squamous cell carcinoma (ESCC).

METHODS

In this study, we investigated serum levels of the miR-371-373 cluster in ESCC patients before and after surgical removal, and further focused on the expression level of miR-373-3p in tumor tissues of ESCC patients and its target genes. In addition, the epigenetic alterations of miR-373-3p promoter was analyzed.

RESULTS

The expression levels of miR-371-5p and miR-373-3p were significantly increased in preoperative serum of ESCC patients compared with that of healthy volunteers (P<0.01); however, they dropped significantly after surgical removal (P<0.01). Compared with adjacent normal tissues, miR-373-3p also showed significant up-regulation in cancer tissues (P<0.05). The methylation levels of miR-373-3p promoter were 42.86% in ESCC cancer tissue and 66.67% in adjacent normal tissues. The low methylation of the miR-373-3p promoter may promote the expression of miR-373-3p. Large tumor suppressor 2 (LATS2) and oxidation resistance 1(OXR1) are predicted to be targets of miR-373-3p by the bioinformatics method. They are the genes in the Hippo and the p53 signaling pathway, respectively. Their respective upstream genes, neurofibromatosis type 2 (NF2) and Jun Kinase, and the downstream genes, transcriptional co-activator with PDZ-binding motif (TAZ) and caspase 9, were also detected. The expression of all these genes were significantly decreased in ESCC cancer tissues compared with adjacent normal tissues.

CONCLUSIONS

This study shows that DNA epigenetic modification in the miR-373-3p promoter region and the Hippo and p53 signaling pathways play important roles during the miR-373-3p mediating ESCC development process.

Immune responses to bacterial and fungal infections in the silkworm, Bombyx mori

The silkworm Bombyx mori, an economically important insect that is usually reared indoors, is susceptible to various pathogens, including bacteria, fungi, viruses, and microsporidia. As with other insects, the silkworm lacks an adaptive immune system and relies solely on innate immunity to defend itself against infection. Compared to other intensively studied insects, such as the fruit fly and tobacco hornworm, the principal immune pathways in the silkworm remain unclear. In this article, we review the literature concerning silkworm immune responses to bacteria and fungi and present our perspectives on future research into silkworm immunity.

Bacterial Community Structure in the Asian Rice Gall Midge Reveals a Varied Microbiome Rich in Proteobacteria

The Asian rice gall midge (ARGM) has emerged as a model gall forming pest of rice. The ARGM infestation of rice results in failure of panicle formation and economic loss. Understanding the molecular basis of ARGM-rice interactions is very crucial in order to control this devastating pest of rice. The current investigation was devised to identify bacterial communities present in the ARGM and in addition the bacterial diversity in the maggots during their interaction with susceptible or resistant rice varieties. Sequencing of 16S rRNA bacterial gene (V3-V4 region) revealed differences in the microflora of the ARGM maggots feeding on susceptible or resistant rice hosts. Results revealed that Wolbachia was the predominant bacterium in pupae and adults while Pseudomonas was predominant in maggots. Further, we observed that members of proteobacteria were predominant across all the samples. There was high species diversity in maggots isolated from susceptible rice and a high representation of unclassified bacteria in maggots isolated from resistant rice. This is the first study that reports variation of microbiome of the ARGM, based on host phenotype from which it was isolated, and results suggest that these variations could have an important role in host's susceptibility.

TLDc proteins: new players in the oxidative stress response and neurological disease

Oxidative stress (OS) arises from an imbalance in the cellular redox state, which can lead to intracellular damage and ultimately cell death. OS occurs as a result of normal ageing, but it is also implicated as a common etiological factor in neurological disease; thus identifying novel proteins that modulate the OS response may facilitate the design of new therapeutic approaches applicable to many disorders. In this review, we describe the recent progress that has been made using a range of genetic approaches to understand a family of proteins that share the highly conserved TLDc domain. We highlight their shared ability to prevent OS-related cell death and their unique functional characteristics, as well as discussing their potential application as new neuroprotective factors. Furthermore, with an increasing number of pathogenic mutations leading to epilepsy and hearing loss being discovered in the TLDc protein TBC1D24, understanding the function of this family has important implications for a range of inherited neurological diseases.

A Pseudomonas T6SS effector recruits PQS-containing outer membrane vesicles for iron acquisition

Iron sequestration by host proteins contributes to the defence against bacterial pathogens, which need iron for their metabolism and virulence. A Pseudomonas aeruginosa mutant lacking all three known iron acquisition systems retains the ability to grow in media containing iron chelators, suggesting the presence of additional pathways involved in iron uptake. Here we screen P. aeruginosa mutants defective in growth in iron-depleted media and find that gene PA2374, proximal to the type VI secretion system H3 (H3-T6SS), functions synergistically with known iron acquisition systems. PA2374 (which we have renamed TseF) appears to be secreted by H3-T6SS and is incorporated into outer membrane vesicles (OMVs) by directly interacting with the iron-binding Pseudomonas quinolone signal (PQS), a cell–cell signalling compound. TseF facilitates the delivery of OMV-associated iron to bacterial cells by engaging the Fe(III)-pyochelin receptor FptA and the porin OprF. Our results reveal links between type VI secretion, cell–cell signalling and classic siderophore receptors for iron acquisition in P. aeruginosa.

Pathogens require iron for their metabolism and virulence. Here the authors identify an iron acquisition system in Pseudomonas aeruginosa involving a protein secreted by a type VI secretion system, the PQS signalling compound and siderophore receptors.