Example Of Convergent Evolution Research Articles

The function of secondary metabolites in plant carnivory.

Carnivorous plants are an ideal model system for evaluating the role of secondary metabolites in plant ecology and evolution. Carnivory is a striking example of convergent evolution to attract, capture and digest prey for nutrients to enhance growth and reproduction and has evolved independently at least ten times. Though the roles of many traits in plant carnivory have been well studied, the role of secondary metabolites in the carnivorous habit is considerably less understood. This review provides the first synthesis of research in which secondary plant metabolites have been demonstrated to have a functional role in plant carnivory. From these studies we identify key metabolites for plant carnivory and their functional role, and highlight biochemical similarities across taxa. From this synthesis we provide new research directions for integrating secondary metabolites into understanding of the ecology and evolution of plant carnivory. Carnivorous plants use secondary metabolites to facilitate prey attraction, capture, digestion and assimilation. We found ~170 metabolites for which a functional role in carnivory has been demonstrated. Of these, 26 compounds are present across genera that independently evolved a carnivorous habit, suggesting convergent evolution. Some secondary metabolites have been co-opted from other processes, such as defence or pollinator attraction. Secondary metabolites in carnivorous plants provide a potentially powerful model system for exploring the role of metabolites in plant evolution. They also show promise for elucidating how the generation of novel compounds, as well as the co-option of pre-existing metabolites, provides a strategy for plants to occupy different environments.

How to build distylous flowers: comparative floral development and evolution of distylous species across the angiosperms.

Distyly, a plant breeding system characterized by two floral morphs that have reciprocal positioning of anthers and stigmas, is known from at least 27 angiosperm families, making it an excellent example of convergent evolution. The various manners in which patterns of floral development produce the distinct anther and stigma heights in each morph remain largely unexplored from developmental and evolutionary perspectives. In 15 species representing at least 12 origins of distyly, heights and lengths of floral organs in each morph throughout development were examined using light microscopy. Patterns of floral organ development were determined and compared among species. Family-level phylogenies of distylous species and relatives were reconstructed, and patterns of ancestral herkogamy were resolved. Differences in floral development between morphs resulted in 12 patterns leading to the anther and stigma positions characterizing distyly. Distylous species evolved from ancestors with different types of herkogamy, with approach herkogamy and lack of herkogamy resolved most frequently. Seven of the 12 patterns of floral development are known from only one species, with three other patterns described among pairs of close relatives. The most common pattern of floral development, described from at least seven genera, involves for anther heights, distinct intermorph growth rates and for stigma heights, growth rates that differ between morphs only during later development. This pattern is common among subclass Lamiidae, suggesting canalized development within the taxon. Among distylous species, the same type of ancestral herkogamy can give rise to different patterns of floral development.

Widespread cis-regulatory convergence between the extinct Tasmanian tiger and gray wolf.

The extinct marsupial Tasmanian tiger, or thylacine, and the eutherian gray wolf are among the most widely recognized examples of convergent evolution in mammals. Despite being distantly related, these large predators independently evolved extremely similar craniofacial morphologies, and evidence suggests that they filled similar ecological niches. Previous analyses revealed little evidence of adaptive convergence between their protein-coding genes. Thus, the genetic basis of their convergence is still unclear. Here, we identified candidate craniofacial cis-regulatory elements across vertebrates and compared their evolutionary rates in the thylacine and wolf, revealing abundant signatures of convergent positive selection. Craniofacial thylacine–wolf accelerated regions were enriched near genes involved in TGF beta (TGFB) and BMP signaling, both of which are key morphological signaling pathways with critical roles in establishing the identities and boundaries between craniofacial tissues. Similarly, enhancers of genes involved in craniofacial nerve development showed convergent selection and involvement in these pathways. Taken together, these results suggest that adaptation in cis-regulators of TGF beta and BMP signaling may provide a mechanism to explain the coevolution of developmentally and functionally integrated craniofacial structures in these species. We also found that despite major structural differences in marsupial and eutherian brains, accelerated regions in both species were common near genes with roles in brain development. Our findings support the hypothesis that, relative to protein-coding genes, positive selection on cis-regulatory elements is likely to be an essential driver of adaptive convergent evolution and may underpin thylacine–wolf phenotypic similarities.

Third upper molar enlargement in sigmodontine rodents (Cricetidae): morphological disparity and evolutionary convergence

Abstract We studied the enlargement of the upper third molar (M3), with respect to the upper second molar in sigmodontine rodents, the largest subfamily of living cricetids. M3 is enlarged in extant and extinct members of at least six tribes (Andinomyini, Euneomyini, Oryzomyini, Phyllotini, Reithrodontini and Sigmodontini), all of them also sharing hypsodonty, planate crowns and overall dental simplification in the context of Sigmodontinae. Enlargement is expressed in four ways, including simplification or modest complication of occlusal design on a single plane. M3 enlargement in sigmodontines is primarily associated with increasing herbivory rather than strictly with phylogeny, and thus presents a classic example of evolutionary convergence.

The pre-Pleistocene fossil thylacinids (Dasyuromorphia: Thylacinidae) and the evolutionary context of the modern thylacine.

The thylacine is popularly used as a classic example of convergent evolution between placental and marsupial mammals. Despite having a fossil history spanning over 20 million years and known since the 1960s, the thylacine is often presented in both scientific literature and popular culture as an evolutionary singleton unique in its morphological and ecological adaptations within the Australian ecosystem. Here, we synthesise and critically evaluate the current state of published knowledge regarding the known fossil record of Thylacinidae prior to the appearance of the modern species. We also present phylogenetic analyses and body mass estimates of the thylacinids to reveal trends in the evolution of hypercarnivory and ecological shifts within the family. We find support that Mutpuracinus archibaldi occupies an uncertain position outside of Thylacinidae, and consider Nimbacinus richi to likely be synonymous with N. dicksoni. The Thylacinidae were small-bodied (< ~8 kg) unspecialised faunivores until after the ~15–14 Ma middle Miocene climatic transition (MMCT). After the MMCT they dramatically increase in size and develop adaptations to a hypercarnivorous diet, potentially in response to the aridification of the Australian environment and the concomitant radiation of dasyurids. This fossil history of the thylacinids provides a foundation for understanding the ecology of the modern thylacine. It provides a framework for future studies of the evolution of hypercarnivory, cursoriality, morphological and ecological disparity, and convergence within mammalian carnivores.

Recurrent convergent evolution at amino acid residue 261 in fish rhodopsin

The evolutionary process that occurs when a species colonizes a new environment provides an opportunity to explore the mechanisms underlying genetic adaptation, which is essential knowledge for understanding evolution and the maintenance of biodiversity. Atlantic herring has an estimated total breeding stock of about 1 trillion (1012) and has colonized the brackish Baltic Sea within the last 10,000 y. Minute genetic differentiation between Atlantic and Baltic herring populations at selectively neutral loci combined with this rapid adaptation to a new environment facilitated the identification of hundreds of loci underlying ecological adaptation. A major question in the field of evolutionary biology is to what extent such an adaptive process involves selection of novel mutations with large effects or genetic changes at many loci, each with a small effect on phenotype (i.e., selection on standing genetic variation). Here we show that a missense mutation in rhodopsin (Phe261Tyr) is an adaptation to the red-shifted Baltic Sea light environment. The transition from phenylalanine to tyrosine differs only by the presence of a hydroxyl moiety in the latter, but this results in an up to 10-nm red-shifted light absorbance of the receptor. Remarkably, an examination of the rhodopsin sequences from 2,056 species of fish revealed that the same missense mutation has occurred independently and been selected for during at least 20 transitions between light environments across all fish. Our results provide a spectacular example of convergent evolution and how a single amino acid change can have a major effect on ecological adaptation.

A Cell-Penetrating Scorpion Toxin Enables Mode-Specific Modulation of TRPA1 and Pain.

TRPA1 is a chemosensory ion channel that functions as a sentinel for structurally diverse electrophilic irritants. Channel activation occurs through an unusual mechanism involving covalent modification of cysteine residues clustered within an amino-terminal cytoplasmic domain. Here, we describe a peptidergic scorpion toxin (WaTx) that activates TRPA1 by penetrating the plasma membrane to accessthe same intracellular site modified by reactiveelectrophiles. WaTx stabilizes TRPA1 in a biophysically distinct active state characterized by prolonged channel openings and low Ca2+ permeability. Consequently, WaTx elicits acute pain and pain hypersensitivity but fails to trigger efferent release of neuropeptides and neurogenic inflammation typically produced by noxious electrophiles. These findings provide a striking example of convergent evolution whereby chemically disparate animal- and plant-derived irritants target the same key allosteric regulatory site to differentially modulate channel activity. WaTx is a unique pharmacological probe for dissecting TRPA1 function and its contribution to acute and persistent pain.

Comparative Transcriptome Analyses Reveal the Role of Conserved Function in Electric Organ Convergence Across Electric Fishes.

The independent origins of multiple electric organs (EOs) of fish are fascinating examples of convergent evolution. However, comparative transcriptomics of different electric fish lineages are scarce. In this study, we found that the gene expression of EOs and skeletal muscles from three lineages (Mormyroidea, Siluriformes, and Gymnotiformes) tended to cluster together based on the species of origin, irrespective of the organ from which they are derived. A pairwise comparison of differentially expressed genes (DEGs) revealed that no less than half of shared DEGs exhibited parallel expression differentiation, indicating conserved directionality of differential expression either in or between lineages, but only a few shared DEGs were identified across all focal species. Nevertheless, the functional enrichment analysis of DEGs indicated that there were more parallel gene expression changes at the level of pathways and biological functions. Therefore, we may conclude that there is no parallel evolution of the entire transcriptomes of EOs among different lineages. Further, our results support the hypothesis that it is not different genes but conserved biological functions that play a crucial role in the convergence of complex phenotypes. This study provides insight into the genetic basis underlying the EO convergent evolution; however, more studies in different cases will be needed to demonstrate whether this pattern can be extended to other cases to derive a general rule for convergent evolution.

EPAS1 Gain-of-Function Mutation Contributes to High-Altitude Adaptation in Tibetan Horses.

High altitude represents some of the most extreme environments worldwide. The genetic changes underlying adaptation to such environments have been recently identified in multiple animals but remain unknown in horses. Here, we sequence the complete genome of 138 domestic horses encompassing a whole altitudinal range across China to uncover the genetic basis for adaptation to high-altitude hypoxia. Our genome data set includes 65 lowland animals across ten Chinese native breeds, 61 horses living at least 3,300 m above sea level across seven locations along Qinghai-Tibetan Plateau, as well as 7 Thoroughbred and 5 Przewalski’s horses added for comparison. We find that Tibetan horses do not descend from Przewalski’s horses but were most likely introduced from a distinct horse lineage, following the emergence of pastoral nomadism in Northwestern China ∼3,700 years ago. We identify that the endothelial PAS domain protein 1 gene (EPAS1, also HIF2A) shows the strongest signature for positive selection in the Tibetan horse genome. Two missense mutations at this locus appear strongly associated with blood physiological parameters facilitating blood circulation as well as oxygen transportation and consumption in hypoxic conditions. Functional validation through protein mutagenesis shows that these mutations increase EPAS1 stability and its hetero dimerization affinity to ARNT (HIF1B). Our study demonstrates that missense mutations in the EPAS1 gene provided key evolutionary molecular adaptation to Tibetan horses living in high-altitude hypoxic environments. It reveals possible targets for genomic selection programs aimed at increasing hypoxia tolerance in livestock and provides a textbook example of evolutionary convergence across independent mammal lineages.

The Ptr1 Locus of Solanum lycopersicoides Confers Resistance to Race 1 Strains of Pseudomonas syringae pv. tomato and to Ralstonia pseudosolanacearum by Recognizing the Type III Effectors AvrRpt2 and RipBN.

Race 1 strains of Pseudomonas syringae pv. tomato, which cause bacterial speck disease of tomato, are becoming increasingly common and no simply inherited genetic resistance to such strains is known. We discovered that a locus in Solanum lycopersicoides, termed Pseudomonas tomato race 1 (Ptr1), confers resistance to race 1 P. syringae pv. tomato strains by detecting the activity of type III effector AvrRpt2. In Arabidopsis, AvrRpt2 degrades the RIN4 protein, thereby activating RPS2-mediated immunity. Using site-directed mutagenesis of AvrRpt2, we found that, like RPS2, activation of Ptr1 requires AvrRpt2 proteolytic activity. Ptr1 also detected the activity of AvrRpt2 homologs from diverse bacteria, including one in Ralstonia pseudosolanacearum. The genome sequence of S. lycopersicoides revealed no RPS2 homolog in the Ptr1 region. Ptr1 could play an important role in controlling bacterial speck disease and its future cloning may shed light on an example of convergent evolution for recognition of a widespread type III effector.

Structures of two ArsR As(III)-responsive transcriptional repressors: Implications for the mechanism of derepression

ArsR As(III)-responsive transcriptional repressors, members of the ArsR/SmtB family of metalloregulatory proteins, have been characterized biochemically but, to date, no As(III)-bound structure has been solved. Here we report two crystal structures of ArsR repressors from Acidithiobacillus ferrooxidans (AfArsR) and Corynebacterium glutamicum (CgArsR) in the As(III)-bound form. AfArsR crystallized in P21 space group and diffracted up to 1.86 Å. CgArsR crystallized in P212121 and diffracted up to 1.6 Å. AfArsR showed one As(III) bound in one subunit of the homodimer, while the CgArsR structure showed two As(III) bound with S3 coordination, one in each monomer. Previous studies indicated that in AfArsR As(III) binds to Cys95, Cys96 and Cys102 from the same monomer, while, in CgArsR, to Cys15, Cys16 from one monomer and Cys55 from the other monomer. The dimer interfaces of these structures showed distinct differences from other members of the ArsR/SmtB family of proteins, which potentially renders multiple options for evolving metal(loid) binding sites in this family of proteins. Also, CgArsR presents a new α2-N binding site, not the previously predicted α3-N site. Despite differences in the location of the binding cysteines in the primary sequences of these proteins, the two metal binding sites are almost congruent on their structures, an example of convergent evolution. Analyses of the electrostatic surface of the proteins at the DNA binding domain indicate that there two different modes of derepression in the ArsR/SmtB family of metalloregulatory proteins.

A revision of Dolichogenidea (Hymenoptera, Braconidae, Microgastrinae) with the second mediotergite broadly rectangular from Area de Conservación Guanacaste, Costa Rica.

The first species of Dolichogenidea (Hymenoptera: Braconidae, Microgastrinae) with the second mediotergite broadly quadrate to rectangular are revised, and eight new species from Area de Conservación Guanacaste (ACG), Costa Rica are described, all authored by Fernandez-Triana & Boudreault: alejandromasisi, angelagonzalezae, carlosmanuelrodriguezi, genuarnunezi, josealfredohernandezi, melaniamunozae, rogerblancoi, and yeimycedenoae. A new species group (carlosmanuelrodriguezi) within the genus is proposed to accommodate those species, as well as additional undescribed species from the Neotropical region found in collections. All new species are found in rainforests (120–900 m) and all are parasitoids of Depressariidae (except for one species parasitizing Choreutidae). The unique shape of the second mediotergite and long ovipositor are features shared with the alejandromorai species group in the genus Apanteles, an example of convergent evolution; both wasp groups also parasitize similar hosts in ACG.

Comparing Plasticity of Response to Perceived Risk in the Textbook Example of Convergent Evolution of Desert Rodents and Their Predators; a Manipulative Study Employing the Landscape of Fear.

Foragers process information they gain from their surroundings to assess the risk from predators and balance it with the resources in their environment. Measuring these perceived risks from the perspective of the forager can produce a heatmap or their “fear” in the environments, a so-called “landscape of fear” (LOF). In an intercontinental comparison of rodents from the Mojave and Negev Deserts, we set to compare families that are used regularly as examples of convergent evolution, heteromyid and gerbilline respectively. Using a LOF spatial-analysis on data collected from common garden experiments in a semi-natural arena we asked: (1) do all four species understand the risk similarly in the exact same physical environment; (2) does relative relation between species affect the way species draw their LOFs, or does the evolutionary niche of a species have a greater impact on its LOF?; and (3) does predator facilitation between vipers and barn owls cause similar changes to the shape of the measured LOFs. For stronger comparative power we mapped the LOF of the rodents under two levels of risk: low risk (snakes only) and high risk (snakes and barn owls). We found concordance in the way all four species assessed risk in the arena. However, the patterns observed in the LOFs of each rodent family were different, and the way the topographic shape of the LOF changed when owls were introduced varied by species. Specifically, gerbils were more sensitive to owl-related risk than snakes and at the opposite correct for heteromyids. Our findings suggest that the community and environment in which a species evolved has a strong impact on the strategies said animals employ. We also conclude, that given the homogenous landscape we provide in our arena and the non- homogenous patterns of LOF maps, risk assessment can be independent of the physical conditions under which the animals find themselves.

The genetics of convergent evolution: insights from plant photosynthesis.

The tree of life is resplendent with examples of convergent evolution, whereby distinct species evolve the same trait independently. Many highly convergent adaptations are also complex, which makes their repeated emergence surprising. In plants, the evolutionary history of two carbon concentrating mechanisms (CCMs) - C4 and crassulacean acid metabolism (CAM) photosynthesis - presents such a paradox. Both of these modifications of ancestral C3 photosynthesis require the integration of multiple anatomical and biochemical components, yet together they have evolved more than one hundred times. The presence of CCM enzymes in all plants suggests that a rudimentary CCM might emerge via relatively few genetic changes in potentiated lineages. Here, we propose that many of the complexities often associated with C4 and CAM photosynthesis may have evolved during a post-emergence optimization phase. The ongoing development of new model clades for young, emerging CCMs is enabling the comparative studies needed to test these ideas.

Apd1 and Aim32 Are Prototypes of Bishistidinyl-Coordinated Non-Rieske [2Fe-2S] Proteins.

Apd1, a cytosolic yeast protein, and Aim32, its counterpart in the mitochondrial matrix, have a C-terminal thioredoxin-like ferredoxin (TLF) domain and a widely divergent N-terminal domain. These proteins are found in bacteria, plants, fungi, and unicellular pathogenic eukaryotes but not in Metazoa. Our chemogenetic experiments demonstrate that the highly conserved cysteine and histidine residues within the C-X8-C-X24-75-H-X-G-G-H motif of the TLF domain of Apd1 and Aim32 proteins are essential for viability of yeast cells upon treatment with the redox mediators gallobenzophenone or pyrogallol, respectively. UV-vis, EPR, and Mössbauer spectroscopy of purified wild-type Apd1 and three His to Cys variants demonstrated that Cys207 and Cys216 are the ligands of the ferric ion, and His255 and His259 are the ligands of the reducible iron ion of the [2Fe-2S]2+/1+ cluster. The [2Fe-2S] center of Apd1 ( Em,7 = -164 ± 5 mV, p Kox1,2 = 7.9 ± 0.1 and 9.7 ± 0.1) differs from both dioxygenase ( Em,7 ≈ -150 mV, p Kox1,2 = 9.8 and 11.5) and cytochrome bc1/ b6 f Rieske clusters ( Em,7 ≈ +300 mV, p Kox1,2= 7.7 and 9.8). Apd1 and its engineered variants represent an unprecedented flexible system for which a stable [2Fe-2S] cluster with two histidine ligands, (two different) single histidine ligands, or only cysteinyl ligands is possible in the same protein fold. Our results define a remarkable example of convergent evolution of the [2Fe-2S] cluster containing proteins with bishistidinyl coordination.

Phylogenetic Studies on the Prodigiosin Biosynthetic Operon.

Prodigiosin and undecylprodigiosin are tripyrrolic red pigmented antibiotics produced by certain bacteria. Many strains of Serratia and certain other Gammaproteobacteria produce prodigiosin and undecylprodigiosin is produced by certain strains of Streptomyces. This is a multistage process which involves the synthesis of a bipyrrolic compound from L-proline and its subsequent condensation with a mono pyrrole synthesized from 2-octenal in the case of prodigiosin and malonyl-CoA in the case of undecylprodigiosin respectively. We have carried out sequence analysis of the genes involved in the pathway and identified the distribution of the prodigiosin producing genes amongst the various bacteria which have been fully sequenced. The presence of the operon was clearly seen in certain clustered branches suggesting inheritance from a common ancestor. This was further confirmed by the absence of traits observed in horizontally acquired genes like, GC content variation, codon bias or the presence of mobile elements. Multiple sequence alignment of the promoter of the prodigiosin operon in seven fully sequenced Serratia marcescens strains showed excellent homology. Putative regulatory elements in this region were identified by sequence analysis studies and many of them have been found to influence pigment production. The undecylprodigiosin gene cluster on the other hand, shows homology to other gene clusters involved in the production of other pyrrole-containing antibiotics of the genus Streptomyces. This coupled with the presence of ORFs with three different promoters could indicate lateral gene transfer. Hence the evolution of undecylprodigiosin operon could be an example of convergent evolution.

Tail Weaponry in Ankylosaurs and Glyptodonts: An Example of a Rare but Strongly Convergent Phenotype.

The unusual clubbed tails of glyptodonts among mammals and ankylosaurines among dinosaurs most likely functioned as weapons of intraspecific combat or interspecific defense and are characterized by stiffening of the distal tail and, in some taxa, expansion of the distal tail tip. Although similarities in tail weaponry have been noted as a potential example of convergent evolution, this hypothesis has not been tested quantitatively, particularly with metrics that can distinguish convergence from long-term stasis, assess the relative strength of convergence, and identify potential constraints in the appearance of traits during the stepwise, independent evolution of these structures. Using recently developed metrics of convergence within a phylomorphospace framework, we document that convergence accounts for over 80% of the morphological evolution in traits associated with tail weaponry in ankylosaurs and glyptodonts. In addition, we find that ankylosaurs and glyptodonts shared an independently derived, yet constrained progression of traits correlated with the presence of a tail club, including stiffening of the distal tail as a precedent to expansion of the tail tip in both clades. Despite differences in the anatomical construction of the tail club linked to lineage-specific historical contingency, these lineages experienced pronounced, quantifiable convergent evolution, supporting hypotheses of functional constraints and shared selective pressures on the evolution of these distinctive weapons. Anat Rec, 303:988-998, 2020. © 2019 Wiley Periodicals, Inc.

Re-Discovering the Squid Brain

Cephalopods have the most complicated central nervous system (CNS) of all invertebrates at both anatomical and functional levels as demonstrated by the pioneering neuroanatomical work of Cajal and Young decades or indeed a century ago. An octopus brain with over 200 million neurons is equivalent, numerically at least, to that of a rat. Brain complexity, their rich behavioral repertoire and most famously the eye, highlight cephalopods and vertebrates as an example of convergent evolution. Perhaps due to its size and complexity, our knowledge of the cephalopod brain still relies mostly on old histological approaches and a few attempts at dye-labelled projections. Here using the new technique of diffusion magnetic resonance imagery (dMRI) tempered with highly conservative tract-acceptance thresholds and cross-validated with traditional histology and neural tracers, we reveal 153 previously undescribed lobe interconnections and novel within-lobe morphologies in the brain of the reef squid, Sepioteuthis lessoniana. Almost all established connections are re-confirmed and the beginnings of a new brain-wide neural connection “atlas” is erected. As with vertebrate examples, using the complementary techniques of MRI, traditional histology and dye-based tractography, such a ‘circuit diagram’ for cephalopod neural architecture leads to a better understanding of their complex behaviors. It also supports emerging hypotheses around anatomical and functional convergence with parts of the vertebrate central nervous system, including projections of overall body axes. Notably it provides a firm base upon which to place the currently fashionable but contentious cephalopod cognitive capabilities.

Evolutionary Tinkering of the Mandibular Canal Linked to Convergent Regression of Teeth in Placental Mammals

Loss or reduction of teeth has occurred independently in all major clades of mammals [1]. This process is associated with specialized diets, such as myrmecophagy and filter feeding [2, 3], and led to an extensive rearrangement of the mandibular anatomy. Themandibular canal enables lower jaw innervation through the passage of the inferior alveolar nerve (IAN) [4, 5]. In order to innervate teeth, the IAN projects ascending branches directly through tooth roots [5, 6], bone trabeculae [6], or bone canaliculi (i.e., dorsal canaliculi) [7]. Here, we used micro-computed tomography (μ-CT) scans of mandibles, from eight myrmecophagous species with reduced dentition and 21 non-myrmecophages, to investigate the evolutionary fate of dental innervation structures following convergent tooth regression in mammals. Our observations provide strong evidence for a link between the presence of tooth loci and the development of dorsal canaliculi. Interestingly, toothless anteaters present dorsal canaliculi and preserve intact tooth innervation, while equally toothless pangolins do not. We show that the internal mandibular morphology of anteaters has a closer resemblance to that of baleen whales [7] than to pangolins. This is despite masticatory apparatus resemblances that have made anteaters and pangolins a textbook example of convergent evolution. Our results suggest that early tooth loci innervation [8] is required for maintaining the dorsal innervation of the mandible and underlines the dorsal canaliculi sensorial role inthe context of mediolateral mandibular movements. This study presents a unique example of convergent redeployment of the tooth developmental pathway toa strictly sensorial function following tooth regression in anteaters and baleen whales.

Capacity To Utilize Raffinose Dictates Pneumococcal Disease Phenotype.

Streptococcus pneumoniae is commonly carried asymptomatically in the human nasopharynx, but it also causes serious and invasive diseases such as pneumonia, bacteremia, and meningitis, as well as less serious but highly prevalent infections such as otitis media. We have previously shown that closely related pneumococci (of the same capsular serotype and multilocus sequence type [ST]) can display distinct pathogenic profiles in mice that correlate with clinical isolation site (e.g., blood versus ear), suggesting stable niche adaptation within a clonal lineage. This has provided an opportunity to identify determinants of disease tropism. Genomic analysis identified 17 and 27 single nucleotide polymorphisms (SNPs) or insertions/deletions in protein coding sequences between blood and ear isolates of serotype 14 ST15 and serotype 3 ST180, respectively. SNPs in raffinose uptake and utilization genes (rafR or rafK) were detected in both serotypes/lineages. Ear isolates were consistently defective in growth in media containing raffinose as the sole carbon source, as well as in expression of raffinose pathway genes aga, rafG, and rafK, relative to their serotype/ST-matched blood isolates. Similar differences were also seen between serotype 23F ST81 blood and ear isolates. Analysis of rafR allelic exchange mutants of the serotype 14 ST15 blood and ear isolates demonstrated that the SNP in rafR was entirely responsible for their distinct in vitro phenotypes and was also the determinant of differential tropism for the lungs versus ear and brain in a mouse intranasal challenge model. These data suggest that the ability of pneumococci to utilize raffinose determines the nature of disease.IMPORTANCES. pneumoniae is a component of the commensal nasopharyngeal microflora of humans, but from this reservoir, it can progress to localized or invasive disease with a frequency that translates into massive global morbidity and mortality. However, the factors that govern the switch from commensal to pathogen, as well as those that determine disease tropism, are poorly understood. Here we show that capacity to utilize raffinose can determine the nature of the disease caused by a given pneumococcal strain. Moreover, our findings provide an interesting example of convergent evolution, whereby pneumococci belonging to two unrelated serotypes/lineages exhibit SNPs in separate genes affecting raffinose uptake and utilization that correlate with distinct pathogenic profiles in vivo This further underscores the critical role of differential carbohydrate metabolism in the pathogenesis of localized versus invasive pneumococcal disease.