Positive Selection Pressure Research Articles

Modelling the biocontrol of Spodoptera frugiperda: A mechanistic approach considering Bt crops and oviposition behaviour

The fall armyworm (Spodoptera frugiperda Smith & Abbot, 1797, Lepidoptera, Noctuidae) is a widespread agricultural pest native of the Americas. It is a lepidopteran pest with the ability to consume an enormous variety of crops. There are several control strategies, including natural enemies employed to control the pest, particularly egg parasitoids and genetically modified crops with Bacillus thuringiensis Berliner, 1915, Bacillaceae (Bt) toxins. However, the constant use of Bt crops has allowed the emergence of positive selection pressure to create pests increasingly resistant to the toxins. Furthermore, female moths can lay eggs in layers and deposit scales to enhance their defences against egg parasitoids. In the present work, we intend to understand how (i) the attack rate of the parasitoid, (ii) the degree of vulnerability of the eggs to parasitism, and (iii) the mortality caused by Bt toxins affect crop production and the overall dynamics. We developed a tritrophic crop-pest-parasitoid mathematical model to study the fall armyworm dynamics focusing on crop density. Our findings indicate that crop production decreases by approximately 60.03% in the absence of parasitoids. We discuss the results regarding pest resistance to Bt toxins, pest defence against parasitism, and the selection of parasitoids for pest control, and propose potential extensions for future work.

GA20ox Family Genes Mediate Gibberellin and Auxin Crosstalk in Moso bamboo (Phyllostachys edulis).

Moso bamboo (Phyllostachys edulis) is one of the fastest growing plants. Gibberellin (GA) is a key phytohormone regulating growth, but there are few studies on the growth of Moso bamboo regulated by GA. The gibberellin 20 oxidase (GA20ox) gene family was targeted in this study. Chromosomal distribution and collinearity analysis identified 10 GA20ox genes evenly distributed on chromosomes, and the family genes were relatively conservative in evolution. The genetic relationship of GA20ox genes had been confirmed to be closest in different genera of plants in a phylogenetic and selective pressure analysis between Moso bamboo and rice. About 1/3 GA20ox genes experienced positive selective pressure with segmental duplication being the main driver of gene family expansion. Analysis of expression patterns revealed that only six PheGA20ox genes were expressed in different organs of shoot development and flowers, that there was redundancy in gene function. Underground organs were not the main site of GA synthesis in Moso bamboo, and floral organs are involved in the GA biosynthesis process. The auxin signaling factor PheARF47 was located upstream of PheGA20ox3 and PheGA20ox6 genes, where PheARF47 regulated PheGA20ox3 through cis-P box elements and cis-AuxRR elements, based on the result that promoter analysis combined with yeast one-hybrid and dual luciferase detection analysis identified. Overall, we identified the evolutionary pattern of PheGA20ox genes in Moso bamboo and the possible major synthesis sites of GA, screened for key genes in the crosstalk between auxin and GA, and laid the foundation for further exploration of the synergistic regulation of growth by GA and auxin in Moso bamboo.

Serological relationships among strains of grapevine leafroll-associated virus 4 reflect the evolutive behavior of its coat protein gene

This research studied serological relationships and genetic diversity of Argentinean isolates of grapevine leafroll-associated virus-4 (GLRaV-4). Phylogenetic analysis of coat protein (CP) sequences from 19 local isolates revealed clustering with the previously described GLRaV-4 strain 5, strain 6, and strain 9 groups. Evolutionary sequence analysis of the obtained and database-available sequences showed evidence of recombination events. Additionally, both CP N- and C-terminal regions appeared to be under purifying selection, but the N-terminal region presented seven sites under positive selection, with a dN/dS ratio 5-fold greater than that of the C-terminal region. Serological reactivity against monoclonal antibodies supports a higher occurrence probability for linear epitopes in the N-terminal region, as inferred by the sequence analysis. The obtained results reflect an unusual evolutionary behavior of the CP that, together with protein serological reactivity, suggests biological significance of the observed variability. Highlights: The occurrence of GLRaV-4 strains -5, -6 and -9 was recorded in Argentina. The coat protein sequence showed a highly variable N-terminal region among the strains. An evolutionary analysis inferred the occurrence of sites under positive diversifying selection pressure. The most variable region of the coat protein presented the highest probability of occurrence of linear epitopes.

Genetic Analysis of Orf Virus (ORFV) Strains Isolated from Goats in China: Insights into Epidemiological Characteristics and Evolutionary Patterns

Contagious ecthyma (CE) is an acute infectious zoonosis caused by orf virus (ORFV) that mainly infects sheep and goats and causes obvious lesions and low market value of livestock, resulting in huge economic losses for farmers. In this study, two strains of ORFV were isolated from Shaanxi Province and Yunnan Province in China, named FX and LX. The two ORFVs were located in the major clades of domestic strains respectively, and exhibited distinct sequence homology. We analyzed the genetic data of core genes (B2L, F1L, VIR, ORF109) and variable genes (GIF, ORF125 and vIL-10) of ORFV to investigate its epidemiological and evolutionary characteristics. The sequences from 2007 to 2018 constituted the majority of the viral population, predominantly concentrated in India and China. Most genes were clustered into SA00-like type and IA82-like type, and the hotspots in East and South Asia were identified in the ORFV transmission trajectories. For these genes, VIR had the highest substitution rate of 4.85 × 10−4, both VIR and vIL-10 suffered the positive selection pressure during ORFV evolution. Many motifs associated with viral survival were distributed among ORFVs. In addition, some possible viral epitopes have been predicted, which still require validation in vivo and in vitro. This work gives more insight into the prevalence and phylogenetic relationships of existing orf viruses and facilitate better vaccine design.

Molecular characterization, adaptive evolution, and expression analysis of the Toll-like receptor gene family in Fenneropenaeus chinensis

Global warming is a challenge to animal health because of the increased environmental temperature, with subsequent induction of immune suppression and increased susceptibility to disease during summer. The Toll-like receptor (TLR) family is an essential pattern recognition receptor (PRR) that initiates the innate immune response by sensing conserved molecular patterns of pathogens. However, research on the TLR gene family in decapod crustaceans has been conducted sporadically, without systematic naming, and the relationship between pathogen immunity adaptation and adaptive evolution of immune-related genes is unclear. In this study, various TLR gene sequences in decapod crustaceans were collected, and the unified name of Fenneropenaeus chinensis was confirmed using sequence alignment. Structural characteristics and evolutionary analyses of TLR genes in decapod crustaceans were performed, and ten FcTLR genes were identified in F. chinensis. Protein domain analysis revealed that FcTLR proteins contain 4–25 LRR domains used to recognize different pathogens. Selection pressure analysis revealed that TLR1 and TLR9 were subjected to positive selection pressure in decapod crustaceans, which may be related to their resistance to environmental changes. Furthermore, the expression of ten TLR genes was detected in F. chinensis following white spot syndrome virus (WSSV) infection. The results demonstrated that FcTLR1, FcTLR7, and FcTLR9 responded positively, which was also consistent with the results of the protein domain and selection pressure analyses. This study provides new insights into the immune response and adaptive evolution of TLRs in decapod crustaceans to prevent environmental damage, such as pathogens and high temperature.

Characterization of the Attachment of Three New Coliphages onto the Ferrichrome Transporter FhuA.

Receptor-binding proteins (RBPs) allow phages to dock onto their host and initiate infection through the recognition of proteinaceous or saccharidic receptors located on the cell surface. FhuA is the ferrichrome hydroxamate transporter in Escherichia coli and serves as a receptor for the well-characterized phages T1, T5, and phi80. To further characterize how other FhuA-dependent phages attach to FhuA, we isolated and published the genomes of three new FhuA-dependent coliphages: JLBYU37, JLBYU41, and JLBYU60. We identified the egions of FhuA involved in phage attachment by testing the effect of mutant fhuA alleles containing single-loop deletions of extracellular loops (L3, L4, L5, L8, L10, and L11) on phage infectivity. Deletion of loop 8 resulted in complete resistance to SO1-like phages JLBYU37 and JLBYU60 and the previously isolated vB_EcoD_Teewinot phage, but no single-loop deletions significantly altered the infection of T1-like JLBYU41. Additionally, lipopolysaccharide (LPS) truncation coupled with the L5 mutant significantly impaired the infectivity of JLBYU37 and JLBYU60. Moreover, significant reductions in the infectivity of JLBYU41 were observed upon LPS truncation in the L8 mutant strain. Analysis of the evolutionary relationships among FhuA-dependent phage RBPs highlights the conservation of L8 dependence in JLBYU37, JLBYU60, Teewinot, T5, and phi80, but also showcases how positive selective pressure and/or homologous recombination also selected for L4 dependence in T1 and even the lack of complete loop dependence in JLBYU41. IMPORTANCE Phage attachment is the first step of phage infection and plays a role in governing host specificity. Characterizing the interactions taking place between phage tail fibers and bacterial receptors that better equip bacteria to survive within the human body may provide insights to aid the development of phage therapeutics.

The Pioneer platform: A novel approach for selection of selective anti-cancer cytotoxic activity in bacteria through co-culturing with engineered human cells.

Most of the small-molecule drugs approved for the treatment of cancer over the past 40 years are based on natural compounds. Bacteria provide an extensive reservoir for the development of further anti-cancer therapeutics to meet the challenges posed by the diversity of these malignant diseases. While identifying cytotoxic compounds is often easy, achieving selective targeting of cancer cells is challenging. Here we describe a novel experimental approach (the Pioneer platform) for the identification and development of 'pioneering' bacterial variants that either show or are conduced to exhibit selective contact-independent anti-cancer cytotoxic activities. We engineered human cancer cells to secrete Colicin M that repress the growth of the bacterium Escherichia coli, while immortalised non-transformed cells were engineered to express Chloramphenicol Acetyltransferase capable of relieving the bacteriostatic effect of Chloramphenicol. Through co-culturing of E. coli with these two engineered human cell lines, we show bacterial outgrowth of DH5α E. coli is constrained by the combination of negative and positive selection pressures. This result supports the potential for this approach to screen or adaptively evolve 'pioneering' bacterial variants that can selectively eliminate the cancer cell population. Overall, the Pioneer platform demonstrates potential utility for drug discovery through multi-partner experimental evolution.

Genetic characterizations and molecular evolution of human norovirus GII.6 genotype during the past five decades.

The norovirus genotype GII.6 is circulating in the population with a relatively high prevalence, but in-depth molecular characterization studies of GII.6 are needed. In this study, norovirus GII.6 sequences were retrieved and analyzed to demonstrate the molecular characterizations of norovirus GII.6. The results show that GII.6 VP1 gene can be divided into three variants and all variants cocirculated in humans in the past decades. The intragenotypic showed no growth trend over time. Since the overall evolutionary rate was 3.432 × 10-3 substitutions/site/year, the infer most recent common ancestor was estimated as 1913. Only a few amino acid sites were recognized to be under positive selection pressure. The mean effective population size was stable in the recent years. The variant C (especially 87 GII.P7-GII.6 strains) had a higher evolutionary rate and more sites under positive selection pressure compared to other variants. NS4 protein had the higher diversity than other nonstructural proteins, and VP1 and VP2 genes had the same phylogenetic relationships. This study provides a systematic description of genetic characterizations and molecular evolution of GII.6. Research on norovirus molecular epidemiology should be pursued to enrich the genomic data of the diverse genotypes and improve their analysis.

Biological properties, genetic structure and molecular variability of brome mosaic virus population

AbstractBrome mosaic virus (BMV) is a member of the Bromovirus genus in the Bromoviridae family. Due to its genetic and biochemical features, BMV is considered as one of the most important plant viruses in molecular plant pathology. Although BMV is widely used in many laboratories as a convenient model for molecular studies, knowledge regarding its biology, pathogenicity, virulence and genetic differentiation within natural populations is rather limited. In this study, the complete genome sequence of 16 BMV isolates originating from different hosts was obtained. Recombination, selection pressure and phylogenetic analyses were carried out using newly obtained BMV sequences and 10 others described to date. The nucleotide and amino acid sequence identities of the 26 BMV sequences were relatively high and ranged from 96.4% to 99.4% for nucleotide sequences and from 95.7% to 99.6% for amino acid sequences. Further analysis revealed that both selection and recombination are shaping the population structure of BMV. The presence of six possible recombination sites within open reading frames and one within the 3′ untranslated region of RNA2 was identified. Selection pressure analysis indicated that most codons were subjected to purifying selection; however, 14 codons were found to be under positive selection pressure. The results presented here expand the current knowledge regarding BMV diversity and the evolutionary forces shaping BMV population structure.

Genetic Evolution and Variation of Human Adenovirus Serotype 31 Epidemic Strains in Beijing, China, during 2010-2022.

Human adenovirus serotype 31 (HAdV-31) is closely associated with gastroenteritis in children and can cause fatal systemic disseminated diseases in immunocompromised patients. The lack of genomic data for HAdV-31, especially in China, will greatly limit research on its prevention and control. Sequencing and bioinformatics analyses were performed for HAdV-31 strains from diarrheal children in Beijing, China, during 2010-2022. Three capsid protein genes (hexon, penton, and fiber) were obtained in 37 cases, including one in which the whole genome was sequenced. HAdV-31 strains clustered into three distinct clades (I-III) in a phylogenetic tree constructed based on concatenated genes and the whole genome; the endemic strains only gathered into clade II, and most of the reference strains clustered into clade I. Compared with penton and hexon, fiber had a faster evolutionary rate (1.32 × 10-4 substitutions/site/year), an earlier divergence time (1697), lower homology (98.32-100% at the amino acid level), and greater genetic variation (0.0032). Four out of the six predicted positive selection pressure codons were also in the knob of fiber. These results reveal the molecular evolution characteristics and variations of HAdV-31 in Beijing, and fiber may be one of the main evolution driving forces.

Genomic characterization and phylogenetic evolution of the canine parvoviruses in Iranian dogs, a nationwide study: CPV evolutionary analysis in Iran

Canine Parvo Virus 2 (CPV-2) culminated in lots of fatalities in domestic dogs since its emergence in 1978. Mainly, it is responsible for severe hemorrhagic diarrhea, vomiting, and dehydration. CPV-2 has three main variants known as 2a, 2b, and 2c. Due to the necessity of monitoring the evolutionary parameters of the virus, and also the lack of comprehensive study of CPV2 in Iran, this study is done for the first time in this country not only to characterize Iranian CPV genomes but also to study the evolutionary parameters and phylodynamics of CPV. The phylogenetic trees were constructed using the Maximum Likelihood (ML) method. By the use of the Bayesian Monte Carlo Markov Chain (BMCMC) method, evolutionary analysis and phylodynamics of the virus were investigated. Phylogenetic results showed that all Iranian isolates were classified in the CPV-2a variant. The central part of Iran was suggested to be the origin of the virus, especially the Alborz province. Before its prevalence throughout the country, the virus circulated in the central part, in Thran, Karaj, and Qom. Mutational analysis showed a positive selection pressure of CPV-2a. Investigating the evolutionary parameters of the virus proposed 1970 to be the date of birth of the virus, with a 95% credible interval between 1953 and 1987. The effective number of infections increased dramatically from 2012 to 2015, then faced a slightly decreasing trend from 2015 to 2019. A considerable up warding pattern was witnessed from the middle of 2019, which can be taken as a concern about the risk of vaccination failure.

Phyloepidemiology and adaptive evolution of SARS-CoV2 during the first and second wave of COVID-19 in India

Introduction. This study aimed to identify the circulating lineages of SARS-CoV-2, prevalent mutations in these lineages, and the selective pressure on the genome of SARS-CoV-2 during the first and second waves of the COVID-19 pandemic in India. Methods. We downloaded 1,451 sequences from June 2020 to June 2021 from the National Center for Biotechnology Information (NCBI) and the Global Initiative on Sharing All Influenza Database (GISAID). We identified the lineages using the Pangolin COVID-19 lineage assigner. Results. We found 41 circulating lineages in India during the year studied. Thirty-five lineages were circulating during the first wave and twenty during the second wave, including six new lineages. During the first wave in 2020, only one Variant of Concern (Alpha) was found, but during the second wave in 2021, three Variants of Concern (Alpha, Beta, and Delta) were in circulation, as well as one Variant Under Monitoring. The most frequent mutations observed were S: D614G, NSP3: F106F, NSP12b: P314L, ORF3a: Q57H, M: Y71Y, NSP14:C279C, S: D294D, and N: S194L. The ten most mutated samples all belonged to the Delta variant of B.1.617.2 lineage and were found in the second wave. Five mutations in the spike protein (L452R, T478K, E484Q, N501Y, and D614G), responsible for increased transmissibility and reduced neutralization by convalescent sera, were majorly prevalent during the second wave. D614G, L452R, and T478K were present at prevalence rates of 88.25%, 21.04%, and 16.80%, respectively. The major selection was purifying selection, but a few sites in the NSP2, NSP3, NSP13, S protein, ORF3a, and ORF9 evolved under positive selection. Conclusion. We report six novel mutations (three in NSP2 [P129A, V381A, V381F], one in NSP3 [P822S], and one in the S protein [Q23R]) that evolved under positive selection pressure.

The Lesson Learned from the Unique Evolutionary Story of Avirulence Gene AvrPii of Magnaporthe oryzae.

Blast, caused by Magnaporthe oryzae, is one of the most destructive diseases affecting rice production. Understanding population dynamics of the pathogen's avirulence genes is pre-required for breeding and then deploying new cultivars carrying promising resistance genes. The divergence and population structure of AvrPii was dissected in the populations of southern (Guangdong, Hunan, and Guizhou) and northern (Jilin, Liaoning, and Heilongjiang) China, via population genetic and evolutionary approaches. The evolutionary divergence between a known haplotype AvrPii-J and a novel one AvrPii-C was demonstrated by haplotype-specific amplicon-based sequencing and genetic transformation. The different avirulent performances of a set of seven haplotype-chimeric mutants suggested that the integrity of the full-length gene structures is crucial to express functionality of individual haplotypes. All the four combinations of phenotypes/genotypes were detected in the three southern populations, and only two in the northern three, suggesting that genic diversity in the southern region was higher than those in the northern one. The population structure of the AvrPii family was shaped by balancing, purifying, and positive selection pressures in the Chinese populations. The AvrPii-J was recognized as the wild type that emerged before rice domestication. Considering higher frequencies of avirulent isolates were detected in Hunan, Guizhou, and Liaoning, the cognate resistance gene Pii could be continuously used as a basic and critical resistance resource in such regions. The unique population structures of the AvrPii family found in China have significant implications for understanding how the AvrPii family has kept an artful balance and purity among its members (haplotypes) those keenly interact with Pii under gene-for-gene relationships. The lesson learned from case studies on the AvrPii family is that much attention should be paid to haplotype divergence of target gene.

A burst of genomic innovation at the origin of placental mammals mediated embryo implantation

The origin of embryo implantation in mammals ~148 million years ago was a dramatic shift in reproductive strategy, yet the molecular changes that established mammal implantation are largely unknown. Although progesterone receptor signalling predates the origin of mammals and is highly conserved in, and critical for, successful mammal pregnancy, it alone cannot explain the origin and subsequent diversity of implantation strategies throughout the placental mammal radiation. MiRNAs are known to be flexible and dynamic regulators with a well-established role in the pathophysiology of mammal placenta. We propose that a dynamic core microRNA (miRNA) network originated early in placental mammal evolution, responds to conserved mammal pregnancy cues (e.g. progesterone), and facilitates species-specific responses. Here we identify 13 miRNA gene families that arose at the origin of placental mammals and were subsequently retained in all descendent lineages. The expression of these miRNAs in response to early pregnancy molecules is regulated in a species-specific manner in endometrial epithelia of species with extreme implantation strategies (i.e. bovine and human). Furthermore, this set of miRNAs preferentially target proteins under positive selective pressure on the ancestral eutherian lineage. Discovery of this core embryo implantation toolkit and specifically adapted proteins helps explain the origin and evolution of implantation in mammals.

Putative Local Adaptive SNPs in the Genus Avicennia.

The genusAvicennia with eight species grow in intertidal zones of tropical and temperate regions, ranging in distribution from West Asia, to Australia, and Latin America. These mangroves have several medicinal applications for mankind. Many genetic and phylogenetic studies have been carried out on mangroves, but none is concerned with geographical adaptation of SNPs. We therefore, used ITS sequences of about 120 Avicennia taxa growing in different parts of the world and undertook computational analyses to identify discriminating SNPs among these species and to study their association with geographical variables. A combination of multivariate and Bayesian approaches such as CCA, RDA, and LFMM were conducted to identify the SNPs with potential adaptation to geographical and ecological variables. Manhattan plot revealed that many of these SNPs are significantly associated with these variables. The genetic changes accompanied by local and geographical adaptation were illustrated by skyline plot. These genetic changes occurred not under a molecular clock model of evolution and probably under a positive selection pressure imposed in different geographical regions in which these plants grow.

Viral intra-host evolutionary dynamics revealed via serial passage of Japanese encephalitis virus in vitro.

Analyses of viral inter- and intra-host mutations could better guide the prevention and control of infectious diseases. For a long time, studies on viral evolution have focused on viral inter-host variations. Next-generation sequencing has accelerated the investigations of viral intra-host diversity. However, the theoretical basis and dynamic characteristics of viral intra-host mutations remain unknown. Here, using serial passages of the SA14-14-2 vaccine strain of Japanese encephalitis virus (JEV) as the in vitro model, the distribution characteristics of 1,788 detected intra-host single-nucleotide variations (iSNVs) and their mutated frequencies from 477 deep-sequenced samples were analyzed. Our results revealed that in adaptive (baby hamster kidney (BHK)) cells, JEV is under a nearly neutral selection pressure, and both non-synonymous and synonymous mutations represent an S-shaped growth trend over time. A higher positive selection pressure was observed in the nonadaptive (C6/36) cells, and logarithmic growth in non-synonymous iSNVs and linear growth in synonymous iSNVs were observed over time. Moreover, the mutation rates of the NS4B protein and the untranslated region (UTR) of the JEV are significantly different between BHK and C6/36 cells, suggesting that viral selection pressure is regulated by different cellular environments. In addition, no significant difference was detected in the distribution of mutated frequencies of iSNVs between BHK and C6/36 cells.

Positive and Relaxed Selective Pressures Have Both Strongly Influenced the Evolution of Cryonotothenioid Fishes during Their Radiation in the Freezing Southern Ocean.

Evolution in the chronic cold of the Southern Ocean has had a profound influence on the physiology of cryonotothenioid fishes. However, the suite of genetic changes underlying the physiological gains and losses in these fishes is still poorly surveyed. By identifying the genomic signatures of selection, this study aims to identify the functional classes of genes that have been changed following two major physiological transitions: the onset of freezing temperatures and the loss of hemoproteins. Looking at the changes that followed the onset of freezing temperatures, positive selective pressure was found among a set of broadly acting gene regulatory factors, suggesting a route through which cryonotothenioid gene expression has been retooled for life in the cold. Further, genes related to the cell cycle and cellular adhesion were found under positive selection suggesting that both present key challenges to life in freezing waters. By contrast, genes showing signatures of the relaxation of selective pressure showed a narrower biological impact, acting on genes related to mitochondrial function. Finally, although chronic cold-water temperatures appear correlated with substantial genetic change, the loss of hemoproteins resulted in little observable change in protein-coding genes relative to their red-blooded relatives. Combined, the influence of positive and relaxed selection shows that long-term exposure to cold has led to profound changes in cryonotothenioid genomes that may make it challenging for them to adapt to a rapidly changing climate.

Genome-wide identification and expression analysis of diacylglycerol acyltransferase genes in soybean (Glycine max).

Soybean (Glycine max) is a major protein and vegetable oil source. In plants, diacylglycerol acyltransferase (DGAT) can exert strong flux control, which is rate-limiting for triacylglycerol biosynthesis in seed oil formation. Here, we identified soybean DGAT genes via a bioinformatics method, thereby laying a solid foundation for further research on their function. Based on our bioinformatics analyses, including gene structure, protein domain characteristics, and phylogenetic analysis, 26 DGAT putative gene family members unevenly distributed on 12 of the 20 soybean chromosomes were identified and divided into the following four groups: DGAT1, DGAT2, WS/DGAT, and cytoplasmic DGAT. The Ka/Ks ratio of most of these genes indicated a significant positive selection pressure. DGAT genes exhibited characteristic expression patterns in soybean tissues. The differences in the structure and expression of soybean DGAT genes revealed the diversity of their functions and the complexity of soybean fatty acid metabolism. Our findings provide important information for research on the fatty acid metabolism pathway in soybean. Furthermore, our results will help identify candidate genes for potential fatty acid-profile modifications to improve soybean seed oil content. This is the first time that in silico studies have been used to report the genomic and proteomic characteristics of DGAT in soybean and the effect of its specific expression on organs, age, and stages.

Evolution of tetraspanin antigens in the zoonotic Asian blood fluke Schistosoma japonicum

BackgroundDespite successful control efforts in China over the past 60 years, zoonotic schistosomiasis caused by Schistosoma japonicum remains a threat with transmission ongoing and the risk of localised resurgences prompting calls for a novel integrated control strategy, with an anti-schistosome vaccine as a core element. Anti-schistosome vaccine development and immunisation attempts in non-human mammalian host species, intended to interrupt transmission, and utilising various antigen targets, have yielded mixed success, with some studies highlighting variation in schistosome antigen coding genes (ACGs) as possible confounders of vaccine efficacy. Thus, robust selection of target ACGs, including assessment of their genetic diversity and antigenic variability, is paramount. Tetraspanins (TSPs), a family of tegument-surface antigens in schistosomes, interact directly with the host’s immune system and are promising vaccine candidates. Here, for the first time to our knowledge, diversity in S. japonicum TSPs (SjTSPs) and the impact of diversifying selection and sequence variation on immunogenicity in these protiens were evaluated.MethodsSjTSP sequences, representing parasite populations from seven provinces across China, were gathered by baiting published short-read NGS data and were analysed using in silico methods to measure sequence variation and selection pressures and predict the impact of selection on variation in antigen protein structure, function and antigenic propensity.ResultsHere, 27 SjTSPs were identified across three subfamilies, highlighting the diversity of TSPs in S. japonicum. Considerable variation was demonstrated for several SjTSPs between geographical regions/provinces, revealing that episodic, diversifying positive selection pressures promote amino acid variation/variability in the large extracellular loop (LEL) domain of certain SjTSPs. Accumulating polymorphisms in the LEL domain of SjTSP-2, -8 and -23 led to altered structural, functional and antibody binding characteristics, which are predicted to impact antibody recognition and possibly blunt the host’s ability to respond to infection. Such changes, therefore, appear to represent a mechanism utilised by S. japonicum to evade the host’s immune system.ConclusionWhilst the genetic and antigenic geographic variability observed amongst certain SjTSPs could present challenges to vaccine development, here we demonstrate conservation amongst SjTSP-1, -13 and -14, revealing their likely improved utility as efficacious vaccine candidates. Importantly, our data highlight that robust evaluation of vaccine target variability in natural parasite populations should be a prerequisite for anti-schistosome vaccine development.Graphical abstract

Comparative genomics analysis of endangered wild Egyptian Moringa peregrina (Forssk.) Fiori plastome, with implications for the evolution of Brassicales order.

Moringa is a mono-genus belonging to the Moringaceae family, which includes 13 species. Among them, Moringa peregrina is plant species native to the Arabian Peninsula, Southern Sinai in Egypt, and the Horn of Africa, and comprehensive studies on its nutritional, industrial, and medicinal values have been performed. Herein, we sequenced and analyzed the initial complete chloroplast genome of Moringa peregrina. Concurrently, we analyzed the new chloroplast genome along with 25 chloroplast genomes related to species representing eight families in the Brassicales order. The results indicate that the plastome sequence of M. peregrina consists of 131 genes, with an average GC content of 39.23%. There is a disparity in the IR regions of the 26 species ranging from 25,804 to 31,477 bp. Plastome structural variations generated 20 hotspot regions that could be considered prospective DNA barcode locations in the Brassicales order. Tandem repeats and SSR structures are reported as significant evidence of structural variations among the 26 tested specimens. Furthermore, selective pressure analysis was performed to estimate the substitution rate within the Moringaceae family, which revealing that the ndhA and accD genes are under positive selective pressure. The phylogenetic analysis of the Brassicales order produced an accurate monophyletic annotation cluster of the Moringaceae and Capparaceae species, offering unambiguous identification without overlapping groups between M. oleifera and M. peregrina, which are genetically strongly associated. Divergence time estimation suggests that the two Moringa species recently diversified, 0.467Ma. Our findings highlight the first complete plastome of the Egyptian wild-type of M. peregrina, which can be used for determining plastome phylogenetic relationships and systematic evolution history within studies on the Moringaceae family.