Last Common Ancestor Research Articles

Evolutionary history of Chinese karst loaches (Nemacheilidae, Karstsinnectes): new insights from mitochondrial-based genomes and description of a new species from Guangxi, China

The genus Karstsinnectes of blind fishes known as karst loaches from China was established in 2023 during a revision of the genus Oreonectes (Nemacheilidae). Six species are recorded in this study and some taxonomic progress has been made; however, the lack of genetic data for some species (e.g., K. anophthalmus) may have weakened our current understanding of Karstsinnectes. This study reassessed the phylogeny and evolutionary history of Karstsinnectes by integrating a combination of previously published and newly sequenced mitochondrial genomic data. A phylogenetic tree was developed that was able to divide Karstsinnectes into two clades corresponding to drainages and clarify the phylogenetic position of K. anophthalmus. Divergence times show that Karstsinnectes originated at the Oligocene/Miocene boundary (~22.37 Mya), with the most recent common ancestor occurring in the early Miocene (~18.87 Mya) and interspecific divergence occurring in the late Miocene. Ancestral area reconstruction suggests that the most recent common ancestor of Karstsinnectes most likely inhabited the Hongshui River basin and dispersed into the Zuojiang-Yujiang, Beipanjiang, and Youjiang river basins during the early Miocene (~18.87 Mya), middle Miocene (~12.78 Mya), and late Miocene (~6.71 Mya), respectively. The dispersal under the influence of orogenesis and a monsoon climate drove the speciation and diverse distribution of Karstsinnectes. Such findings are important for conservation considering that Karstsinnectes strictly inhabits deep caves. Additionally, the taxonomic status of the distributed Karstsinnectes population in Leiping Town, Daxin County, Guangxi, China was revised by combining genetic and morphological differences to describe this population as a new species, Karstsinnectes daxinensis Luo, Zhou & Zhou, sp. nov. The definition of the phylogenetic position of K. anophthalmus emphasizes the importance of using type locality material for the identification of cryptic species.

Rapid Evolution of Host Repertoire and Geographic Range in a Young and Diverse Genus of Montane Butterflies.

Evolutionary changes in geographic distribution and larval host plants may promote the rapid diversification of montane insects, but this scenario has been rarely investigated. We studied rapid radiation of the butterfly genus Colias, which has diversified in mountain ecosystems in Eurasia, Africa, and the Americas. Based on a dataset of 150 nuclear protein-coding genetic loci and mitochondrial genomes, we constructed a time-calibrated phylogenetic tree of Colias species with broad taxon sampling. We then inferred their ancestral geographic ranges, historical diversification rates, and the evolution of host use. We found that the most recent common ancestor of Colias was likely geographically widespread and originated ~3.5 Ma. The group subsequently diversified in different regions across the world, often in tandem with geographic expansion events. No aspect of elevation was found to have a direct effect on diversification. The genus underwent a burst of diversification soon after the divergence of the Neotropical lineage, followed by an exponential decline in diversification rate toward the present. The ancestral host repertoire included the legume genera Astragalus and Trifolium but later expanded to include a wide range of Fabaceae genera and plants in more distantly related families, punctuated with periods of host range expansion and contraction. We suggest that the widespread distribution of the ancestor of all extant Colias lineages set the stage for diversification by isolation of populations that locally adapted to the various different environments they encountered, including different host plants. In this scenario, elevation is not the main driver but might have accelerated diversification by isolating populations.

DNA sequencing of topotypes helps delineate species distributions in the Ischnocnema verrucosa complex (Anura, Brachycephalidae)

As many new evolutionary lineages are being discovered and formally named, sequencing topotypes when holotypes are not available becomes essential for taxonomy. This study uses a DNA-taxonomy approach to sequence new populations of the Ischnocnema verrucosa species complex (Brazilian Wart Frogs) from different locations, including, for the first time, individuals from the type localities. Phylogenetic analysis of the mitochondrial 16S gene recovered a monophyletic Ischnocnema verrucosa species series composed of three main clades. The most recent common ancestor was estimated to be 33.76 million years ago, and diversification within the three main clades occurred primarily during the Miocene. We delimited eight species-level lineages with high levels of sequence divergence (7% to 16%). Our study highlights the importance of DNA taxonomy and the necessity of protecting and sequencing topotypes in taxonomic studies. Our study also contributes to the conservation and understanding of the genus Ischnocnema and the biodiversity of the Brazilian Atlantic Forest region.

Genomic characterization of a clonal emergent Salmonella Minnesota lineage in Brazil reveals the presence of a novel megaplasmid of resistance and virulence.

Salmonella Minnesota has emerged in Brazil as the predominant serovar in poultry and poultry products, along with Salmonella Heidelberg. To understand the emergence of Salmonella Minnesota over the last few years in Brazil, we performed a comparative analysis between 69 selected S. Minnesota genomes from Pathogen Detection database and 65 clonal emergent genomes isolated from Brazil. We demonstrate the presence of multidrug resistance genes against tetracycline [tet(A)], sulfonamide (sul2), and AmpC beta-lactamase (blaCMY-2) in emergent genomes, along with the carriage of a megaplasmid of resistance and virulence (~210 kb), designated pESM (plasmid for emergent Salmonella Minnesota). pESM is an IncC/A2 plasmid predicted to increase S. Minnesota environmental tolerance to mercury (mer operon) and provide resistance to tetracycline and ampicillin due to the presence of tet(A) and blaCMY-2, respectively. Moreover, pESM carries the yersiniabactin siderophore (high-pathogenicity island of Yersinia) related to the iron uptake. The temporal inference demonstrated that the most recent common ancestor dated from ~1978 and that the clonal emergent genomes carrying the pESM belong to a completely different lineage of S. Minnesota. Our results indicate that the presence of pESM likely contributes to the emergence of S. Minnesota and is precisely related to the successful spread of this particular clonal lineage in Brazil.IMPORTANCESalmonella Minnesota has emerged in Brazil as one of the leading serovars related to human and animal infection, presenting high virulence and antibiotic resistance to drugs classified as the highest priority for clinical treatment in humans. This study performed whole-genome sequencing, temporal analysis, and phylogenetics to understand the genetic insights related to the emergence of Salmonella Minnesota in Brazil. Long-read sequencing has led to the identification and characterization of a unique megaplasmid carrying virulence, antibiotic resistance, and heavy-metal tolerance genes, which may play a central role in S. Minnesota's successful emergence in Brazil and possibly worldwide. The potentially high transmissibility of this plasmid between clones and serovars represents a risk to public health since its acquisition may increase Salmonella's fitness, virulence, resistance, and persistence. Understanding the genetic aspects related to the emergence of serovars can help devise measures to mitigate the spread of hazardous multidrug-resistant strains.

Ancient large-scale gene duplications and diversification in bryophytes illuminate the plant terrestrialization.

Large-scale gene duplications (LSGDs) are crucial for evolutionary adaptation and recurrent in vascular plants. However, the role of ancient LSGDs in the terrestrialization and diversification of bryophytes, the second most species-rich group of land plants, remains largely elusive due to limited sampling in bryophytes. Employing the most extensive nuclear gene dataset in bryophytes to date, we reconstructed a time-calibrated phylogenetic tree from 209 species, covering virtually all key bryophyte lineages, for phylogenomic analyses of LSGDs and diversification. We newly identified two ancient LSGDs: one in the most recent common ancestor (MRCA) of extant bryophytes and another in the MRCA of the majority of Jungermanniales s.lato.Duplicated genes from these two LSGDs show significant enrichment in photosynthesis-related processes and structures. Rhizoid-responsive ROOTHAIR DEFECTIVE SIX-LIKE (RSL) genes from ancient LSGDs are present in rhizoidless bryophytes, challenging assumptions about rhizoid absence mechanisms. We highlighted four major diversification rate upshifts, two of which slightly postdated LSGDs, potentially linked to the flourishing of gymnosperms and angiosperms and explaining over 80% of bryophyte diversity. Our findings, supported by extensive bryophyte sampling, highlight the significance of LSGDs in the early terrestrialization and diversification of bryophytes, offering new insights into land plant evolution.

Linking intercontinental biogeographic events to decipher how European vineyards escaped Pierce's disease.

Global change is believed to be a major driver of the emergence of invasive pathogens. Yet, there are few documented examples that illustrate the processes that hinder or trigger their geographic spread. Here, we present phylogenetic, epidemiological and historical evidence to explain how European vineyards escaped Xylella fastidiosa (Xf), the vector-borne bacterium responsible for Pierce's disease (PD). Using Bayesian temporal reconstruction, we show that the export of American grapevines to France as rootstocks to combat phylloxera (~1872-1895) preceded the spread of the Xf grapevine lineage in the USA. We found that the time of the most recent common ancestor in California dates to around 1875, which agrees with the emergence of the first PD outbreak and the expansion into the southeastern US around 1895. We also show that between 1870 and 1990, climatic conditions in continental Europe were mostly below the threshold for the development of PD epidemics. However, our model indicates an inadvertent expansion of risk in southern Europe since the 1990s, which is accelerating with global warming. Our temporal approach identifies the biogeographical conditions that have so far prevented PD in southern European wine-producing areas and predicts that disease risk will increase substantially with increasing temperatures.

Molecular Epidemiology and Phyloevolutionary Analysis of Porcine Parvoviruses (PPV1 through PPV7) Detected in Replacement Gilts from Colombia.

Eight porcine parvovirus (PPV) species, designated as PPV1 through PPV8, have been identified in swine. Despite their similarities, knowledge about their distribution and genetic differences remains limited, resulting in a gap in the genetic classification of these viruses. In this study, we conducted a comprehensive analysis using PPV1 to PPV7 genome sequences from Colombia and others available in the GenBank database to propose a classification scheme for all PPVs. Sera from 234 gilts aged 180 to 200 days were collected from 40 herds in Colombia. Individual detection of each PPV (PPV1 through PPV7) was performed using end-point PCR. Complete nucleotide (nt) sequencing was performed on the PPV1 viral protein (VP), and near-complete genome (NCG) sequencing was carried out for novel porcine parvoviruses (nPPVs) (PPV2 through PPV7). Phylogenetic analyses were conducted by comparing PPV1-VP sequences to 94 available sequences and nPPVs with 565 NCG, 846 nPPV-VP, and 667 nPPV-nonstructural protein (NS) sequences. Bayesian phylogenetic analysis was used to estimate substitution rates and the time to the most recent common ancestor for each PPV. The highest prevalence was detected for PPV3 (40.1%), followed by PPV5 (20.5%), PPV6 (17%), PPV1 (14.5%), PPV2 (9.8%), PPV4 (4.2%), and PPV7 (1.3%). Notably, all tested sera were negative for PPV8 genomes. An analysis of the PPV1-VP sequences revealed two main clades (PPV1-I and PPV1-II), with the sequences recovered in this study grouped in the PPV1-II clade. Comparative analysis showed significant genetic distances for PPV2 to PPV7 at the NCG (>6.5%), NS (>6.3%), and VP (>7.5%) regions, particularly when compared to equivalent regions of PPV genomes recovered worldwide. This study highlights the endemic circulation of nPPVs in Colombian pig herds, specifically among gilts. Additionally, it contributes to the phylogenetic classification and evolutionary studies of these viruses. The proposed method aims to categorize and divide subtypes based on current knowledge and the genomes available in databanks.

The TMRCA of general genealogies in populations of variable size.

We study the time to the most recent common ancestor of a sample of finite size in a wide class of genealogical models for populations with variable size. This is made possible by recently developed results on inhomogeneous phase-type random variables, allowing us to obtain the density and the moments of the TMRCA of time-dependent coalescent processes in terms of matrix formulas. We also provide matrix simplifications permitting a more straightforward calculation. With these results, the TMRCA provides an explicative variable to distinguish different evolutionary scenarios.

Case Study: Contribution of Extended Sequencing and Phylogeographic Analysis in the Investigation of Measles Outbreaks in Tunisia in 2019.

Despite the availability of an effective vaccine for several decades, the measles virus continues to spread worldwide. From 2018 to 2019, several countries experienced large measles outbreaks with genotype B3, including Tunisia. We analyzed 66 samples collected from serologically confirmed measles cases during this outbreak. Fifty-five percent were aged less than 12 months and had not received a measles vaccine. Phylogenetic analysis using the 450 nucleoprotein (N450) window revealed that all strains belonged to genotype B3, with five different variants identified. The N450 sequence of the predominant one, which circulated all through the epidemic period, was identical to the named strain MVs/Kabul.AFG/20.14/3. For better molecular discrimination, the amplification and sequencing of 1018 nucleotides in the non-coding region between the M and F genes (MF-NCRs) revealed higher variability with at least nine clusters. A phylogeographic study using Bayesian methods suggested the Governorate of Kasserine (on the borders of Algeria) as the introduction point with a TMRCA (Time to Most Recent Common Ancestor) for the 2019 sequences estimated around October 2018. These findings emphasize the crucial role of advanced molecular investigations in tracing measles transmission pathways which, together with good vaccine coverage, will help the final success of the global measles elimination program.

Introduction to the Special Issue on Early Evolution and the Last Common Ancestor.

The early evolution of life spans an extensive period preceding the emergence of the first eukaryotic cell. This epoch, which transpired from 4.5 to 2.5 billion years ago, marked the advent of many fundamental cellular attributes and witnessed the existence of the Last Common Ancestor (LCA) of all life forms. Uncovering and reconstructing this elusive LCA's characteristics and genetic makeup represents a formidable challenge and a pivotal pursuit in early evolution. While most scientific accounts concur that the LCA resembles contemporary prokaryotes, its precise definition, genome composition, metabolic capabilities, and ecological niche remain subjects of contentious debate.

The Discovery of a Citrus Yellow Vein Clearing Virus Hacienda Heights Isolate Diversifies the Geological Origins of the Virus in California, United States.

The citrus yellow vein clearing virus (CYVCV) is an emerging threat to the U.S. citrus industry. Reports from China shows it cause significant reductions in fruit yield and growth, particularly in lemon trees. In 2022, CYVCV was detected in a wide range of citrus cultivars in localized urban properties in Tulare, California. In 2024, a CYVCV-infected lemon tree was detected in Hacienda Heights in Los Angeles County, California, geographically separated from the Tulare foci. Through long-read sequencing technology, the whole-genome sequence of a CYVCV isolate from Hacienda Heights (designated as CYVCV-CA-HH1, Accession number PP840891.1) was obtained. Sequence alignments and neighbornet analysis strongly suggested that the CYVCV-CA-HH1 isolate has a different origin than the Tulare CYVCV (CYVCV CA-TL) isolates. The CYVCV CA-TL isolates were grouped with those from South Asia (India and Pakistan) and the Middle East (Türkiye), while the CYVCV-CA-HH1 isolate was grouped with isolates from East Asia (China and South Korea). Maximum likelihood phylogenetic analysis further supports this finding, showing that the CYVCV-CA-HH1 isolate shares the most recent common ancestor with a South Korean lineage, which derives from Chinese isolates. Together, our data suggest a diverse geological origin of CYVCV isolates in California.

Genomic surveillance reveals low-level circulation of two subtypes of genogroup C coxsackievirus A10 in Nanchang, Jiangxi Province, China, 2015-2023.

In recent years, coxsackievirus (CV) A10 has been associated with increasing sporadic hand, foot, and mouth disease (HFMD) cases and outbreaks globally. In addition to mild symptoms such as pharyngitis and herpangina, CVA10-related complications or even fatality can occur. Currently, systematic phylogenetic studies of CVA10 are limited. In this study, we first explored the epidemiological and genetic characteristics of CVA10 in Nanchang, an inland southeastern city of China, based on the HFMD surveillance network from 2015-2023. Among 3429 enterovirus-positive cases, 110 (3.04%) were associated with CVA10, with a male-to-female ratio of 1.62. The median age of the CVA10 patients was 2.3 years (interquartile range, IQR 1.0-4.0), with 94.55% (104/110) of the patients aged less than 5 years. Phylogenetic analyses using the full-length VP1, 5'UTR, P1, P2, P3 sequences and near full-length genomes indicated that CVA10 strains (n = 57) isolated in Nanchang belonged to genogroup C; two strains identified in 2017 belonged to C1 subtypes clustered with strains from Vietnam, Madagascar, France and Spain; and the others belonged to C2 subtypes interdigitating with CVA10 isolates from mainland China, the United States and Australia. Through extensive analysis, we identified a rare F168Y mutation in epitope 4 of VP1 in a Madagascar strain of genogroup F and a Chinese strain of genogroup C. Based on Bayesian evolutionary analyses, the average nucleotide substitution rate for the VP1 gene of CV10 strains was 3.07×10-3 substitutions/site/year. The most recent common ancestor (tMRCA) of genogroup C was dated 1990.84, and the tMRCA of CVA10 strains from Nanchang was dated approximately 2003.16, similar to strains circulating in other regions of China, suggesting that the viruses were likely introduced and cryptically circulated in China before the establishment of the HFMD surveillance network. Recombination analysis indicated intertypic recombination of the Nanchang strain with the genogroup G strain in the 3D region. Given the shifting dominance of viral genotypes and frequent recombination events, the existing surveillance system needs to be regulated to enhance genomic surveillance efforts on a more diverse spectrum of genotypes in the future.

Region‐specific diversification dynamics and biogeographic history of one of the most diverse families of insects

AbstractA long‐standing question in evolutionary biology is how historical biogeographic processes have shaped the current diversity of organisms, especially for highly diverse groups. We study the diversification dynamics and biogeographic processes of one of the most diverse families of Lepidoptera, Geometridae, with over 24,000 described species and a worldwide distribution. Despite the cosmopolitan distribution of the family, most species of Geometridae have limited distribution ranges. We present the largest historical biogeography and diversification study on the current diversity patterns and distribution ranges of Geometridae. We use a multi‐locus dataset of 1200 taxa to estimate the historical biogeography of Geometridae, implementing a Bayesian approach of the Dispersal‐Extinction‐Cladogenesis (DEC) model that incorporates palaeographic‐based dispersal graphs with uncertainty in geological ages in RevBayes. We also implement a Bayesian time‐variable, episodic birth–death model and a model that allows branch‐specific speciation rates to estimate the diversification dynamics in the family. Our results suggest that the most recent common ancestor of Geometridae was distributed in the New World, with the Neotropics being the most likely ancestral area. An increase in diversification rates occurred circa 30–40 million years ago (Mya), coinciding with a time of a major global climate cooling in the Eocene. Clade‐specific shifts in speciation rates also occurred around 10–15 Mya, coincident with another period of major climate change in the Oligocene. Our results point to different biogeographical and evolutionary histories per area to show the differences of the diversification rates in different biogeographical regions through time, showing the relative importance of each region in the diversification history of Geometridae.

Molecular cluster, transmission characteristics, origin and dynamics analysis of HIV-1 CRF59_01B in China: A molecular epidemiology study

PurposeThis study investigated for the HIV-1 CRF59_01B epidemic's spatiotemporal dynamics and its transmission networks in China. MethodsBetween 2007 and 2020, a total of 250 partial pol gene sequences of HIV-1 CRF59_01B were collected from four regions (10 Chinese provinces). Phylogenetic tree construction and cluster identification were then performed. The Bayesian skyline and birth–death susceptible–infected–removed models were employed for the phylodynamic analyses of subtypes and large clusters, respectively. Phylogenetic analyses and trait diffusion of these sequences were performed using Bayesian phylogenetic methods (beast-classic package). Distance-based molecular network analyses were performed to identify putative relationships. ResultsUsing a genetic distance threshold of 1.3 %, We identified 45 clusters that included 62.40 % (156/250) of the sequences. Three clusters (6.67 %, 3/45) had 10 or more sequences, and were considered "large clusters". Six clusters (13.33 %) included sequences from different regions (Southeast, Northeast, Southeast, and Central China). Thirteen clusters (28.89 %) included sequences of men who had sex with men only, three clusters (6.67 %) included sequences of heterosexuals only, and 12 clusters (26.67 %) included sequences of both groups. The substitution rate of CRF59_01B was 1.91 × 10–3 substitutions per site per year [95 % highest posterior density (HPD) interval: 1.39 × 10−3–2.49 × 10−3)], the time to the most recent common ancestor of CRF59_01B was to be 1992.83 (95 % HPD: 1977.97–2002.81). A Bayesian skyline plot revealed that the effective population size of CRF59_01B increased from 2000 to 2015 and remained stable after 2015. The large clusters showed continuous growth from 2013 to 2020. Phylogeographic analysis showed that CRF59_01B B most likely originated in Southeast China, with a posterior probability of 97.44 %, and then spread to other regions. ConclusionsOur study revealed the temporal and geographical origins of HIV-1 CRF59_01B as well as the process of transmission among various regions and risk groups in China, which can help develop targeted HIV prevention strategies.

Phylogenomics resolves a 100-year-old debate regarding the evolutionary history of caddisflies (Insecta: Trichoptera)

Trichoptera (caddisfly) phylogeny provides an interesting example of aquatic insect evolution, with rich ecological diversification, especially for underwater architecture. Trichoptera provide numerous critical ecosystem services and are also one of the most important groups of aquatic insects for assessing water quality. The phylogenetic relationships of Trichoptera have been debated for nearly a century. In particular, the phylogenetic position of the “cocoon-makers” within Trichoptera has long been contested. Here, we designed a universal single-copy orthologue and sets of ultraconserved element markers specific for Trichoptera for the first time. Simultaneously, we reconstructed the phylogenetic relationship of Trichoptera based on genome data from 111 species, representing 29 families and 71 genera. Our phylogenetic inference clarifies the probable phylogenetic relationships of “cocoon-makers” within Integripalpia. Hydroptilidae is considered as the basal lineage within Integripalpia, and the families Glossosomatidae, Hydrobiosidae, and Rhyacophilidae formed a monophyletic clade, sister to the integripalpian subterorder Phryganides. The resulting divergence time and ancestral state reconstruction suggest that the most recent common ancestor of Trichoptera appeared in the early Permian and that diversification was strongly correlated with habitat change.

On the Nature of the Last Common Ancestor: A Story from its Translation Machinery.

The Last Common Ancestor (LCA) is understood as a hypothetical population of organisms from which all extant living creatures are thought to have descended. Its biology and environment have been and continue to be the subject of discussions within the scientific community. Since the first bacterial genomes were obtained, multiple attempts to reconstruct the genetic content of the LCA have been made. In this review, we compare 10 of the most extensive reconstructions of the gene content possessed by the LCA as they relate to aspects of the translation machinery. Although each reconstruction has its own methodological biases and many disagree in the metabolic nature of the LCA all, to some extent, indicate that several components of the translation machinery are among the most conserved genetic elements. The datasets from each reconstruction clearly show that the LCA already had a largely complete translational system with a genetic code already in place and therefore was not a progenote. Among these features several ribosomal proteins, transcription factors like IF2, EF-G, and EF-Tu and both class I and class II aminoacyl tRNA synthetases were found in essentially all reconstructions. Due to the limitations of the various methodologies, some features such as the occurrence of rRNA posttranscriptional modified bases are not fully addressed. However, conserved as it is, non-universal ribosomal features found in various reconstructions indicate that LCA's translation machinery was still evolving, thereby acquiring the domain specific features in the process. Although progenotes from the pre-LCA likely no longer exist recent results obtained by unraveling the early history of the ribosome and other genetic processes can provide insight to the nature of the pre-LCA world.

Bayesian phylogeographic inference of wheat yellow mosaic virus in China and Japan suggests that the virus migration history coincided with historical events

Wheat yellow mosaic virus (WYMV) is one of the most serious viral pathogens causing reductions in wheat yield in East Asia. We investigated the phylodynamics of WYMV by analysing the CP, VPg and P1 genes to understand the origin and dispersal of the virus. A Bayesian phylogenetic analysis revealed that the most recent common WYMV ancestor occurred in approximately 1742 (95% credibility interval, 1439–1916) CE (Common Era), and the evolutionary rates of the VPg, CP and P1 genes were 6.669 × 10−4 (95% credibility interval: 4.575 × 10−4–8.927 × 10−4), 2.468 × 10−4 (95% credibility interval: 1.667 × 10−4–3.338 × 10−4) and 5.765 × 10−5 (95% credibility interval: 3.285 × 10−6–1.252 × 10−4), respectively. Our phylogeographic analysis indicated that the WYMV population may have originated in Henan Province, China, first spreading to Japan in the mid-19th century and stopping after the Japanese surrender in World War II. The second wave spread to Japan from Shandong Province, China, in approximately 1977, a few years after the establishment of diplomatic relations between China and Japan. Before the founding of the People's Republic of China, Henan Province was the emigration centre of WYMV in East Asia, and after the late 20th century, Jiangsu and Shandong Provinces were also the virus emigration centres in East Asia. In addition, there were two migration pathways from Japan to Jiangsu and Shandong Provinces, China, in approximately 1918 and approximately 1999 respectively. Our results suggest that the wide spread of WYMV in East Asia is strongly related to human factors.

Evolution of chitin-synthase in molluscs and their response to ocean acidification

Chitin-synthase (CHS) is found in most eukaryotes and has a complex evolutionary history. Research into CHS has mainly been in the context of biomineralization of mollusc shells an area of high interest due to the consequences of ocean acidification. Exploration of CHS at the genomic level in molluscs, the evolution of isoforms, their tissue distribution, and response to environmental challenges are largely unknown. Exploiting the extensive molecular resources for mollusc species it is revealed that bivalves possess the largest number of CHS genes (12–22) reported to date in eukaryotes. The evolutionary tree constructed at the class level of molluscs indicates four CHS Type II isoforms (A-D) probably existed in the most recent common ancestor, and Type II-A (Type II-A-1/Type II-A-2) and Type II-C (Type II-C-1/Type II-C-2) underwent further differentiation. Non-specific loss of CHS isoforms occurred at the class level, and in some Type II (B-D groups) isoforms the myosin head domain, which is associated with shell formation, was not preserved and highly species-specific tissue expression of CHS isoforms occurred. These observations strongly support the idea of CHS functional diversification with shell biomineralization being one of several important functions. Analysis of transcriptome data uncovered the species-specific potential of CHS isoforms in shell formation and a species-specific response to ocean acidification (OA). The impact of OA was not CHS isoform-dependent although in Mytilus, Type I-B and Type II-D gene expression was down-regulated in both M. galloprovincialis and M. coruscus. In summary, during CHS evolution the gene family expanded in bivalves generating a large diversity of isoforms with different structures and with a ubiquitous tissue distribution suggesting that chitin is involved in many biological functions. These findings provide insight into CHS evolution in molluscs and lay the foundation for research into their function and response to environmental changes.

Long-term persistence of diverse clones shapes the transmission landscape of invasive Listeria monocytogenes

BackgroundThe foodborne bacterium Listeria monocytogenes (Lm) causes a range of diseases, from mild gastroenteritis to invasive infections that have high fatality rate in vulnerable individuals. Understanding the population genomic structure of invasive Lm is critical to informing public health interventions and infection control policies that will be most effective especially in local and regional communities.MethodsWe sequenced the whole draft genomes of 936 Lm isolates from human clinical samples obtained in a two-decade active surveillance program across 58 counties in New York State, USA. Samples came mostly from blood and cerebrospinal fluid. We characterized the phylogenetic relationships, population structure, antimicrobial resistance genes, virulence genes, and mobile genetic elements.ResultsThe population is genetically heterogenous, consisting of lineages I–IV, 89 clonal complexes, 200 sequence types, and six known serogroups. In addition to intrinsic antimicrobial resistance genes (fosX, lin, norB, and sul), other resistance genes tetM, tetS, ermG, msrD, and mefA were sparsely distributed in the population. Within each lineage, we identified clusters of isolates with ≤ 20 single nucleotide polymorphisms in the core genome alignment. These clusters may represent isolates that share a most recent common ancestor, e.g., they are derived from the same contamination source or demonstrate evidence of transmission or outbreak. We identified 38 epidemiologically linked clusters of isolates, confirming eight previously reported disease outbreaks and the discovery of cryptic outbreaks and undetected chains of transmission, even in the rarely reported Lm lineage III (ST3171). The presence of animal-associated lineages III and IV may suggest a possible spillover of animal-restricted strains to humans. Many transmissible clones persisted over several years and traversed distant sites across the state.ConclusionsOur findings revealed the bacterial determinants of invasive listeriosis, driven mainly by the diversity of locally circulating lineages, intrinsic and mobile antimicrobial resistance and virulence genes, and persistence across geographical and temporal scales. Our findings will inform public health efforts to reduce the burden of invasive listeriosis, including the design of food safety measures, source traceback, and outbreak detection.

A Spanish saltasauroid titanosaur reveals Europe as a melting pot of endemic and immigrant sauropods in the Late Cretaceous

A new lithostrotian titanosaur, Qunkasaura pintiquiniestra gen. et sp. nov., is described based on a single partial skeleton from the late Campanian-early Maastrichtian fossil-site of Lo Hueco (Cuenca, Spain). This new taxon is supported by an exclusive combination of characters that highlights strong convergences with members of the South American Aeolosaurini. Qunkasaura allows to reorganise the complex phylogenetic relationships of the increasingly diverse finicretaceous sauropods of Europe. Phylogenetic analyses places Qunkasaura within Saltasauridae and possibly Opisthocoelicaudiinae, together with Abditosaurus. A new clade is established, Lohuecosauria, including Saltasaurus, Lohuecotitan, their most recent common ancestor and all its descendants. Two distinct Ibero-Armorican Campanian-Maastrichtian saltasauroid lineages are recognised: (i) Lirainosaurinae that is exclusive from Europe, and (ii) a saltasaurid lineage with possible opisthocoelicaudiine affinities, with a Laurasian distribution. Lirainosaurinae was a relict lineage including possible dwarf forms that evolved in isolation after reaching Europe before the Late Cretaceous through the Apulian route. The occurrence of opisthocoelicaudiines in Europe may be the result of a Late Cretaceous interchange between Europe and Asia. No evidence of insular dwarfism is found in the Ibero-Armorican opisthocoelicaudiines suggesting that they may have been newcomers to the area that arrived before the ‘Maastrichtian Dinosaur Turnover’ in southwestern Europe.