Effector Proteins Research Articles

Purpurin suppresses Salmonella invasion of host cells by reducing the secretion of T3SS-1 effector proteins

Salmonella Typhimurium (S. Typhimurium, ST) is a food-borne pathogen that can be transmitted from animals to humans and causes symptoms such as diarrhea, fever, and vomiting. While antibiotics are commonly used to treat clinical infections, the increase in drug resistance has limited their effectiveness. Antivirulence drugs offer a new approach to treating bacterial infections by targeting specific virulence factors without affecting bacterial growth, thus helping to combat infection without exerting selective pressure on bacteria or inducing resistance. Salmonella pathogenicity island 1 (SPI-1), encoding type three secretion system 1 (T3SS-1), serves as a crucial virulence factor for the invasion of ST into host cells, making it an ideal target for screening anti-Salmonella virulence drugs. This project involved screening of ST invasion inhibitors through a gentamicin protection assay and identified purpurin (PPR) as capable of inhibiting the ST invasion of HeLa cells. Subsequent studies revealed that PPR had no effect on the natural growth of bacteria and was not cytotoxic to host cells. A mechanistic study revealed that PPR effectively inhibits the secretion of T3SS-1 in ST. The results from animal experiments indicated that PPR exhibited significant efficacy in a mouse enteritis model caused by ST infection, increasing the survival rate of mice infected with a lethal dose by 50%, reducing spleen colonization in infected mice, and alleviating tissue damage resulting from ST infection. Therefore, PPR represents a promising antivirulence drug that targets the T3SS of ST and may serve as a hit compound for the development of novel antivirulence drugs for the treatment of ST.

A bacterial membrane-disrupting protein stimulates animal metamorphosis.

This research describes a mechanism wherein a bacterium prompts the metamorphic development of an animal from larva to juvenile form by injecting a protein that disrupts membranes in the larval cilia. Specifically, results show that a bacterial contractile injection system and the protein effector it injects form pores in larval cilia, influencing critical signaling pathways like mitogen-activated protein kinase and calcium flux, ultimately driving animal metamorphosis. This discovery sheds light on how a bacterial protein effector exerts its activity through membrane disruption, a phenomenon observed in various bacterial toxins affecting cellular functions, and elicits a developmental response. This work reveals a potential strategy used by marine organisms to respond to microbial cues, which could inform efforts in coral reef restoration and biofouling prevention. The study's insights into metamorphosis-associated contractile structures' delivery of protein effectors to specific anatomical locations highlight prospects for future biomedical and environmental applications.

The Protein Kinase aPKC as Well as the Small GTPases RhoA and Cdc42 Regulates Neutrophil Chemotaxis Partly by Recruiting the ROCK Kinase to the Leading Edge.

The small GTPases RhoA and Cdc42 and their effector proteins play crucial roles in neutrophil chemotaxis. However, endogenous localization and regulation of these proteins have remained largely unknown. Here, we show, using a trichloroacetic acid fixation method, that endogenous RhoA and Cdc42 are preferentially accumulated at the F-actin-rich leading edge (pseudopod) during chemotaxis of human neutrophil-like PLB-985 cells in response to the chemoattractant C5a. Interestingly, the enrichment of RhoA is impaired by knockdown of Cdc42, indicating a positive regulation by Cdc42. Depletion of Cdc42 or RhoA each induces the formation of multiple pseudopods, confirming their significance in cell polarization with an organized actin network at the front. The Rho-associated kinase ROCK is also recruited to the leading edge during chemotaxis in a manner dependent on not only RhoA and Cdc42 but also aPKC, a Cdc42-interacting kinase that can also bind to ROCK. ROCK promotes phosphorylation of the myosin light chain at the front, possibly regulating pseudopod contractility. Knockdown of aPKC suppresses neutrophil chemotaxis by disturbing pseudopod orientation without forming multiple protrusions. An incorrectly oriented pseudopod is also observed in ROCK-depleted cells. Thus, aPKC, as well as RhoA and Cdc42, likely regulates neutrophil chemotaxis partly by recruiting ROCK to the leading edge for correct directionality.

Melampsora larici-populina homologous effectors Mlp72983 and Mlp52166 display cell-type specific accumulation in Arabidopsis and Populus

Plants interact with microorganisms that can cause diseases and reduce crop productivity. The fungal pathogen Melampsora larici-populina (Mlp) causes the leaf rust disease of poplar trees by secreting proteins, termed effectors, into host tissues to promote pathogenesis. In this study, we functionally characterized two homologous Mlp candidate secreted effector proteins (CSEPs), Mlp72983 and Mlp52166. Confocal microscopy experiments revealed that Mlp72983 has cell type-specific differential localization. It accumulates in the guard cells’ chloroplast of the epidermis and in the nucleus of the spongy mesophyll of Arabidopsis thaliana and Populus alba x Populus tremula. Mlp52166 has a nucleocytosolic accumulation in the epidermal layer and has nuclear localization in the mesophyll layer of the two species. Transcriptomic experiments showed that Mlp72983 and Mlp52166 deregulate plant genes, when constitutively expressed in either Arabidopsis or poplar. The two CSEPs deregulate genes that encode histones, hydroxysteroid dehydrogenases and multidrug and toxic compound extrusion proteins, with roles in DNA repair, methylation, and xenobiotic detoxification. Inoculation assays showed that CSEPs overexpression in poplar transgenics did not enhance susceptibility to rust infection. Despite being closely related in sequence identity, Mlp72983 and Mlp52166 have cell-type specific subcellular localization and deregulate mostly unique sets of plant genes.

Not just passengers: effectors contribute to the assembly of the type VI secretion system as structural building blocks.

Protein secretion systems are critical macromolecular machines employed by bacteria to interact with diverse environments and hosts during their life cycle. Cytosolically produced protein effectors are translocated across at least one membrane to the outside of the cells or directly into target cells. In most secretion systems, these effectors are mere passengers in unfolded or folded states. However, the type VI secretion system (T6SS) stands out as a powerful contractile device that requires some of its effectors as structural components. This review aims to provide an updated view of the diverse functions of effectors, especially focusing on their roles in T6SS assembly, the implications for T6SS engineering, and the potential of recently developed T6SS models to study effector-T6SS association.

A Puccinia striiformis f. sp. tritici Effector with DPBB Domain Suppresses Wheat Defense

Wheat (Triticum aestivum L.) is a primary crop globally. Among the numerous pathogens affecting wheat production, Puccinia striiformis f. sp. tritici (Pst) is a significant biotic stress agent and poses a major threat to world food security by causing stripe rust or yellow rust disease. Understanding the molecular basis of plant–pathogen interactions is crucial for developing new means of disease management. It is well established that the effector proteins play a pivotal role in pathogenesis. Therefore, studying effector proteins has become an important area of research in plant biology. Our previous work identified differentially expressed candidate secretory effector proteins of stripe rust based on transcriptome sequencing data from susceptible wheat (Avocet S) and resistant wheat (Avocet YR10) infected with Pst. Among the secreted effector proteins, PSTG_14090 contained an ancient double-psi beta-barrel (DPBB) fold, which is conserved in the rare lipoprotein A (RlpA) superfamily. This study investigated the role of PSTG_14090 in plant immune responses, which encodes a protein, here referred to as Pst-DPBB, having 131 amino acids with a predicted signal peptide (SP) of 19 amino acids at the N-terminal end, and the DNA sequence of this effector is highly conserved among different stripe rust races. qRT-PCR analysis indicated that expression levels are upregulated during the early stages of infection. Subcellular localization studies in Nicotiana benthamiana leaves and wheat protoplasts revealed that it is distributed in the cytoplasm, nucleus, and apoplast. We demonstrated that Pst-DPBB negatively regulates the immune response by functioning in various compartments of the plant cells. Based on Co-IP and structural predictions and putative interaction analyses by AlphaFold 3, we propose the probable biological function(s). Pst-DPBB behaves as a papain inhibitor of wheat cysteine protease; Pst-DPBB has high structural homology to kiwellin, which is known to interact with chorismate mutase, suggesting that Pst-DPBB inhibits the native function of the host chorismate mutase involved in salicylic acid synthesis. The DPBB fold is also known to interact with DNA and RNA, which may suggest its possible role in regulating the host gene expression.

Receptor-independent regulation of Gα13 by alpha-1-antitrypsin C-terminal peptides.

Alpha-1-antitrypsin (AAT), a circulating serine protease inhibitor, is an acute inflammatory response protein with anti-inflammatory functions. The C-terminal peptides of AAT are found in various tissues and have been proposed as putative bioactive peptides with multiple functions, but its mechanism of action remains unclear. We previously reported that a mouse AAT C-terminal peptide of 35 amino acids (mAAT-C1-35) penetrates plasma membrane and associates guanine nucleotide-binding protein subunit alpha 13 (Gα13). Here, we show that mAAT-C1-35 binds directly to the guanosine diphosphate (GDP)-bound form of Gα13 through the N-terminal region (mAAT-C1-17), thereby facilitating the interaction of Gα13・GDP with its effector proteins. The minimal sequence (mAAT-C3-16) and essential amino acid residue (Phe11) of mAAT-C1-17 were identified as being necessary forthis effect. A molecular dynamics simulation for the Gα13・GDP-mAAT-C1-17 complex model showed that binding of mAAT-C1-17 to the region surrounded by switch regions of Gα13 stabilizes the flexible switch II and III regions, thereby maintaining their active conformation. In addition, mAAT-C1-35 activates the Gα13 signaling pathway in cells where Phe11 is required. Our study reveals the structure-based mechanism of action of AAT-C peptides in the regulation of Gα13 and demonstrates that AAT-C peptides represent a biological peptide capable of activating G protein signals in a manner that is independent of G-protein-coupled receptors.

Upregulation of haematopoetic cell kinase (Hck) activity by a secreted parasite effector protein (Ta9) drives proliferation of Theileria annulata-transformed leukocytes.

Reversible transformation of bovine leukocytes by the intracellular parasites Theileria annulata and Theileria parva is central to pathogenesis of the diseases they cause, tropical theileriosis and East Coast Fever, respectively. Parasite-dependent constitutive activation of major host transcription factors such as AP-1 (Activating Protein 1) and NF-κB (Nuclear Factor-Kappa B) sustains the transformed state. Although parasite interaction with host cell signaling pathways upstream of AP-1 have been studied, the precise contribution of Theileria encoded factors capable of modulating AP-1 transcriptional activity, and other infection-altered signaling pathways is not fully understood. We previously showed that the Ta9 protein from T. annulata (TA15705) is secreted into the host cell cytoplasm and contributes to infection-induced AP-1 transcriptional activity. The current study employed RNA-seq to investigate the ability of ectopically expressed Ta9 to modulate the gene transcription profile of a bovine macrophage cell line, BoMac. RNA-seq identified 560 (400 upregulated and 160 downregulated) differentially expressed genes. KEGG analysis predicted a high number of upregulated genes associated with carcinogenesis such as CCND1, CDKN1A, ETV4, ETV5, FLI1, FRA1, GLI2, GRO1, HCK, IL7R, MYBL1, MYCN, PIM1 and TAL1. Ta9 introduction also affected genes associated with proinflammatory processes such as cytokines, chemokines, growth factors and metalloproteinases. Enrichment analysis of differentially expressed genes revealed that Ta9 is potentially involved in activating other host cell signaling pathways in addition to those that lead to induction of AP-1. Comparing our data with data on differentially expressed BoMac genes modulated by the secreted TashAT2 factor of T. annulata identified the gene encoding the tyrosine protein kinase hematopoietic cell kinase (HCK) as common to both data sets. HCK is essential for the proliferation of T. parva-transformed B cells and herein, we demonstrate that enzymatic activity of HCK is also essential for T. annulata- and T. lestoquardi-transformed macrophage proliferation.

Structure-activity relationship studies and design of a PTPN22 inhibitor with enhanced isozyme selectivity and cellular efficacy.

Protein tyrosine phosphatase non-receptor type 22 (PTPN22) lies downstream of the T cell receptor (TCR) and attenuates T cell signaling by dephosphorylating key effector proteins such as LCK, Zap70, and the intracellular region of the TCR. Recent evidence implicates PTPN22 as an exciting target for enabling immunotherapeutic efficacy against cancer. We carried out structural optimization of a benzofuran salicylic acid-based orthosteric PTPN22 inhibitor 8b, using a combination of crystal structure analysis, synthesis, matched molecular pairs analysis, and biochemical and cell-based assays. Herein, we report structure-activity relationship studies, lead optimization based on the 8b-PTPN22 co-crystal structure, and cellular evaluation of the top analog. Notably, our efforts yielded compound 8b-19, an essentially equipotent scaffold with superior isozyme selectivity, improved aqueous solubility, and significantly enhanced cellular efficacy compared to the parent 8b. This compound may serve as a lead for further optimization of PTPN22-targeting immunotherapies or as a chemical probe for interrogation for additional links between PTPN22 and immunomodulation in cells.

The Wheat NLR Protein PM3b Localises to Endoplasmic Reticulum-Plasma Membrane Contact Sites and Interacts With AVRPM3b2/c2 Through Its LRR Domain.

Plant nucleotide-binding leucine-rich repeat (NLR) proteins are intracellular immune receptors that directly or indirectly perceive pathogen-derived effector proteins to induce an immune response. NLRs display diverse subcellular localisations, which are associated with the capacity of the immune receptor to confer disease resistance and recognise its corresponding avirulence effector. In wheat, the NLR PM3b recognises the wheat powdery mildew effector AVRPM3b2/c2 and we examined the molecular mechanism underlying this recognition. We show that PM3b and other PM3 variants localise to endoplasmic reticulum (ER)-plasma membrane (PM) contact sites (EPCS), while AVRPM3b2/c2 localises to the nucleocytoplasmic space. Additionally, we found that PM3b interacts in planta with AVRPM3b2/c2 through its LRR domain. We further demonstrate that full-length PM3b interaction with AVRPM3b2/c2 is considerably weaker than for the isolated PM3b LRR domain or the susceptible PM3 variant PM3CS, indicating that activation of PM3b leads to dissociation of the complex. In line with this, we observed a strong interaction between PM3b and AVRPM3b2/c2 in a P-loop mutant of PM3b that was unable to initiate a cell death response, or when an inactive variant of AVRPM3b2/c2 was used. We propose that PM3b transiently interacts with AVRPM3b2/c2 through residues in the LRR that are conserved among PM3 variants, while the amino acids necessary for full activation and cell death signalling are unique to PM3b. Our data suggests that PM3b localisation and interaction with AVRPM3b2/c2 differ from other well-studied NLRs and further highlights the mechanistic diversity in NLR-mediated responses against pathogens in plants.

The Xanthomonas fragariae effector XopK suppresses stomatal immunity by perturbing abscisic acid accumulation and ABA-transciptional responses in strawberry.

Xanthomonas fragariae (Xaf) is the cause of strawberry crown dry cavity rot and strawberry leaf angular spots. Despite having a long evolutionary history with strawberries, the plant-pathogen interaction is poorly understood. Pathogenicity for most plant pathogens is mostly dependent on the type-III secretion system, which introduces virulence type III effectors (T3Es) into eukaryotic host cells. Understanding how effector proteins escape from plant surveillance is important for plant breeding and resistance deployment. In this study, a core conserved secreted effector called Xanthomonas Outer Protein K (XopK) was identified in Xaf strain YL19. Transgenic strawberries expressing XopK exhibit increased susceptibility to Xaf YL19, and this was associated with weakened stomatal immunity. Additionally, abscisic acid (ABA) accumulation and signaling were significantly suppressed in XopK-OX strawberry plants. Overexpression of XopK also inhibited ABA- and methyl jasmonate (MeJA)-induced stomatal closure in strawberry leaves. Moreover, endogenous ABA is critical for Xaf-induced stomatal closure. These results suggested that Xaf YL19 uses XopK to suppress ABA signaling to disrupt stomatal closure allowing bacterial colonization for disease development.

Temozolomide-Promoted MGMT Transcription Contributes to Chemoresistance by Activating the ERK Signalling Pathway in Malignant Melanoma.

Tumour cells possess a multitude of chemoresistance mechanisms, which could plausibly contribute to the ineffectiveness of chemotherapy. O6-methylguanine-DNA methyltransferase (MGMT) is an important effector protein associated with Temozolomide (TMZ) resistance in various tumours. To some extent, the expression level of MGMT determines the sensitivity of cells to TMZ, but the mechanism of its expression regulation has not been fully elucidated. Cultured malignant melanoma cell lines A375 and Sk-MEL28 were employed. A luciferase assay was used to detect the transcriptional activity of the MGMT promoter. Western blotting was used to compare the expression levels of phosphorylated ERK1/2 (P-ERK1/2) after TMZ treatment. Immunofluorescent staining was used to detect TMZ-induced DNA damage protein levels. The sensitivity of melanoma cells to TMZ was detected by MTT assay and animal experiments. The expression of MGMT mRNA was tested by Quantitative real-time PCR (RT-qPCR). Flow cytometry was used to measure the apoptosis of TMZ-treated cells. TMZ enhanced the transcription of MGMT through activating the ERK pathway. ERK inhibitors U0126 and vemurafenib (vMF) inhibited the TMZ induced transcription of MGMT. The expression of MGMT and p-ERK1/2 was closely related in human MM tissues. vMF increased the sensitivity of melanoma (MM) to TMZ invitro and invivo through downregulating MGMT and promoting the TMZ induced DNA damage in MM. TMZ-promoted MGMT transcription contributed to instinctive chemoresistance by activating the ERK signalling pathway in malignant melanoma. Our study indicates that the use of the ERK inhibitor in combination with TMZ could potentially enhance the effectiveness of clinical treatment for malignant melanoma.

A phytoplasma effector suppresses insect melanization immune response to promote pathogen persistent transmission.

Insect melanization triggered by the conversion of prophenoloxidase to active phenoloxidase via serine proteases (SPs) is an important immediate immune response. However, how phytoplasmas evade this immune response to promote their propagation in insect vectors remains unknown. Here, we demonstrate that infection of leafhopper vectors with rice orange leaf phytoplasma (ROLP) activates the mild melanization response in hemolymph. ROLP-encoded effector protein SRP1 is highly expressed in leafhopper hemolymph, where it competitively binds to SP2, thereby inhibiting SP2-mediated cleavage of prophenoloxidase into active phenoloxidase. Consequently, microinjection of SRP1 effectively suppresses the melanization response and enhances ROLP propagation. The histidine residue at position 23 of SRP1 is essential for SRP1-SP2 interaction, and the mutation of this position abolishes its ability to inhibit such SP2-meidated cleavage, ultimately promoting melanization response and inhibiting ROLP propagation. Our findings provide insights into how phytoplasmas antagonize insect melanization response to facilitate their persistent transmission.

Two homologous Zn2Cys6 transcription factors play crucial roles in host specificity of Colletotrichum orbiculare by controlling the expression of cucurbit-specific virulence effectors.

Fungal plant pathogens preferentially express a set of effector genes at specific infection stages to successfully colonize the host. However, it remains unclear how effector gene expression is regulated during host infection. This study identified a Zn2Cys6 transcription factor, TFV1 (Transcription Factor for Virulence 1), whose deletion weakened virulence of Colletotrichum orbiculare on its cucurbit hosts. The additional deletion of a TFV1 paralog gene, TVL1 (TFV1-like 1), resulted in a further reduction in virulence on the cucurbits. Notably, TFV1 TVL1 double mutants retained wild-type virulence on the Solanaceae host Nicotiana benthamiana. Expression of putative effector genes, including four cucurbit host-specific virulence effectors (effector protein for cucurbit infection, EPC1-4), was commonly downregulated in the TFV1 knockout mutants. Yeast one-hybrid assays suggested that TFV1 binds to the putative promoter regions of EPC2, EPC3, and EPC4, indicating the importance of TFV1 for the induced expression of key effector genes in cucurbit infection. Among the effector-like genes whose expression was affected by TVL1 deletion, a novel LysM effector gene, EPC5, was identified as being specifically required for virulence on cucurbit hosts. Our study extends the knowledge of the regulatory mechanisms governing host- and stage-specific effectors in C. orbiculare.

VopX, a novel Vibrio cholerae T3SS effector, modulates host actin dynamics.

Despite different infection strategies, enteric pathogens commonly employ a T3SS to colonize the human host and cause disease. Effector proteins are unique to each T3SS-encoding bacterial species and generally lack conserved amino acid sequences. However, T3SS effectors from diverse pathogens target and manipulate common host cell structures and signaling proteins, such as the actin cytoskeleton and MAPK pathway components. T3SS-encoding Vibrio cholerae strains and effectors have been relatively recently identified, and the mechanisms used to mediate colonization and secretory diarrhea are poorly understood. Two V. cholerae effectors that modify the host actin cytoskeleton were shown to be important for colonization. We therefore sought to determine the target(s) and mechanism of a third actin-reorganizing effector, VopX, based on results obtained from a yeast model system. We recapitulated actin-based phenotypes in multiple mammalian model systems, leading us to identify the molecular function of the V. cholerae VopX effector protein.

The Fusarium graminearum Effector Protease FgTPP1 Suppresses Immune Responses and Facilitates Fusarium Head Blight Disease.

Most plant pathogens secrete effector proteins to circumvent host immune responses, thereby promoting pathogen virulence. One such pathogen is the fungus Fusarium graminearum, which causes Fusarium Head Blight (FHB) disease on wheat and barley. Transcriptomic analyses revealed that F. graminearum expresses many candidate effector proteins during early phases of the infection process, some of which are annotated as proteases. However, the contributions of these proteases to virulence remains poorly defined. Here, we characterize a F. graminearum endopeptidase, FgTPP1 (FGSG_11164), that is highly upregulated during wheat spikelet infection and is secreted from fungal cells. To elucidate the potential role of FgTPP1 in F. graminearum virulence, we generated FgTPP1 deletion mutants (ΔFgtpp1) and performed FHB infection assays. Deletion of FgTPP1 reduced the virulence of F. graminearium as assessed by spikelet bleaching. Infection with wild-type F. graminearum induced full bleaching in about 50% of the spikes at 10-11 days post infection, while this fraction was reduced to between 18 and 27% when using ΔFgtpp1 mutants. Transient expression of green fluorescent protein (GFP)-tagged FgTPP1 revealed that FgTPP1 localizes, in part, to chloroplasts and attenuates chitin-mediated activation of mitogen-activated protein kinase (MAPK) signaling, reactive oxygen species production, and cell death induced by an autoactive disease resistance protein when expressed in planta. Notably, the FgTPP1 protein is conserved across the Ascomycota phylum, suggesting it may be a core effector among ascomycete plant pathogens. These properties make FgTPP1 an ideal candidate for decoy substrate engineering, with the goal of engineering resistance to FHB.

Exploring effector protein dynamics and natural fungicidal potential in rice blast pathogen Magnaporthe oryzae.

Rice blast, caused by Magnaporthe oryzae, is one of the most destructive fungal diseases in rice, resulting in major economic losses worldwide. Genetic and genomic studies have identified key genes and proteins, such as AvrPik variants and MAX proteins, that are crucial for the pathogen's virulence. These effector proteins interact with specific alleles of the Pik gene family on rice chromosome 11, modulating the host's immune response. In this study, we investigated 35 plant-derived metabolites known for their antifungal properties as potential fungicides against M. oryzae. Using molecular docking, we identified Hecogenin and Cucurbitacin E as strong binders to MAX40 and APIKL2A proteins, which are essential for the fungus's immune evasion and pathogenicity. Molecular dynamics simulations further confirmed that these compounds form stable, strong interactions with the target proteins, validating their potential as therapeutic agents. Additionally, the compounds were evaluated based on Lipinski's rule of five and toxicity predictions, indicating their suitability for agricultural use. These results suggest that Hecogenin and Cucurbitacin E could serve as promising lead candidates in the development of novel fungicides for rice blast, offering new strategies for crop protection and sustainable agricultural practices.

The roles of STAT1, CASP8, and MYD88 in the care of ischemic stroke.

Ischemic stroke is caused by blockage of blood vessels in brain, affecting normal function. The roles of Signal Transformer and Activator of Transcription 1 (STAT1), CASP8, and MYD88 in ischemic stroke and its care are unclear. The ischemic stroke datasets GSE16561 and GSE180470 were found from the Gene Expression Omnibus database. Batch effect removal, finding differentially expressed genes (DEGs), weighted gene co-expression network analysis, protein-protein interaction analysis, functional enrichment analysis, immune infiltration analysis, comparative toxicogenomics database analysis were carried out. Gene expression heat maps were drawn, and miRNAs were found that regulate core DEGs. A total of 1183 DEGs were obtained, which were mainly concentrated in immune effector processes, cell activation, and protein serine/threonine kinase activity, the NOD-like receptor signaling pathway, NF-kappa B signaling pathway, C-type lectin receptor signaling pathway, and P53 signaling pathway. Four core genes were identified. Heatmap revealed high expression of (CASP8, MYD88, and STAT1) in whole blood samples of ischemic stroke. Comparative toxicogenomics database analysis demonstrated (CASP8, MYD88, and STAT1) are related to cerebral hemorrhage, reperfusion injury, hypertension, and inflammation. In ischemic stroke, expression of STAT1, CASP8, and MYD88 is higher and leads to poorer prognosis.

Penicillium psychrofluorescens sp. nov., a naturally autofluorescent Antarctic fungus

ABSTRACT A new fungal species, Penicillium psychrofluorescens sp. nov. is described as a member of section Torulomyces. The new species is sister to P. catalonicum, and was isolated from soil collected from Robinson Ridge, East Antarctica, following enrichment cultivation under oligotrophic conditions supplemented with excess hydrogen gas. Penicillium psychrofluorescens is named for its intense autofluorescence derived from a combination of compounds that may include NADPH, porphyrins, and secondary metabolites, such as polyketides. Comparative genomics with both Antarctic and mesophilic Penicillium spp. shows that Penicillium psychrofluorescens has a wide repertoire of glycoside hydrolases, but almost no polysaccharide lyases, has comparably large effector proteins, lacks the machinery to use nitrate as an N-source, but has the genes for the assimilation of phosphorus from phosphonates via oxidative pathway. The strain was found to have 30 biosynthetic gene clusters (BGCs), the majority of which were unrelated to known compound BGCs. Given the remarkable diversity of natural products already characterised from Penicillium spp. and the presence of >30 BGCs with low similarity to known genes, there is biotechnological potential within this novel species that is yet to be explored.

The Asgard archaeal origins of Arf family GTPases involved in eukaryotic organelle dynamics.

The evolution of eukaryotes is a fundamental event in the history of life. The closest prokaryotic lineage to eukaryotes, the Asgardarchaeota, encode proteins previously found only in eukaryotes, providing insight into their archaeal ancestor. Eukaryotic cells are characterized by endomembrane organelles, and the Arf family GTPases regulate organelle dynamics by recruiting effector proteins to membranes upon activation. The Arf family is ubiquitous among eukaryotes, but its origins remain elusive. Here we report a group of prokaryotic GTPases, the ArfRs, which are widely present in Asgardarchaeota. Phylogenetic analyses reveal that eukaryotic Arf family proteins arose from the ArfR group. Expression of representative Asgardarchaeota ArfR proteins in yeast and X-ray crystallographic studies show that ArfR GTPases possess the mechanism of membrane binding and structural features unique to Arf family proteins. Our results indicate that Arf family GTPases originated in the archaeal ancestor of eukaryotes, consistent with aspects of the endomembrane system evolving early in eukaryogenesis.