I03-Macromolecular Crystallography
I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[18565, 13467]
Open Access
Abstract: Accelerated gene evolution is a hallmark of pathogen adaptation and specialization following host-jumps. However, the molecular processes associated with adaptive evolution between host-specific lineages of a multihost plant pathogen remain poorly understood. In the blast fungus Magnaporthe oryzae (Syn. Pyricularia oryzae), host specialization on different grass hosts is generally associated with dynamic patterns of gain and loss of virulence effector genes that tend to define the distinct genetic lineages of this pathogen. Here, we unravelled the biochemical and structural basis of adaptive evolution of APikL2, an exceptionally conserved paralog of the well-studied rice-lineage specific effector AVR-Pik. Whereas AVR-Pik and other members of the six-gene AVR-Pik family show specific patterns of presence/absence polymorphisms between grass-specific lineages of M. oryzae, APikL2 stands out by being ubiquitously present in all blast fungus lineages from 13 different host species. Using biochemical, biophysical and structural biology methods, we show that a single aspartate to asparagine polymorphism expands the binding spectrum of APikL2 to host proteins of the heavy-metal associated (HMA) domain family. This mutation maps to one of the APikL2-HMA binding interfaces and contributes to an altered hydrogen-bonding network. By combining phylogenetic ancestral reconstruction with an analysis of the structural consequences of allelic diversification, we revealed a common mechanism of effector specialization in the AVR-Pik/APikL2 family that involves two major HMA-binding interfaces. Together, our findings provide a detailed molecular evolution and structural biology framework for diversification and adaptation of a fungal pathogen effector family following host-jumps.
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Nov 2021
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I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[14493]
Open Access
Abstract: SUGARWINs are PR-4 proteins associated with sugarcane defense against phytopathogens. Their expression is induced in response to damage by Diatraea saccharalis larvae. These proteins play an important role in plant defense, in particular against fungal pathogens, such as Colletothricum falcatum (Went) and Fusarium verticillioides. The pathogenesis-related protein-4 (PR-4) family is a group of proteins equipped with a BARWIN domain, which may be associated with a chitin-binding domain also known as the hevein-like domain. Several PR-4 proteins exhibit both chitinase and RNase activity, with the latter being associated with the presence of two histidine residues H11 and H113 (BARWIN) [H44 and H146, SUGARWINs] in the BARWIN-like domain. In sugarcane, similar to other PR-4 proteins, SUGARWIN1 exhibits ribonuclease, chitosanase and chitinase activities, whereas SUGARWIN2 only exhibits chitosanase activity. In order to decipher the structural determinants involved in this diverse range of enzyme specificities, we determined the 3-D structure of SUGARWIN2, at 1.55Å by X-ray diffraction. This is the first structure of a PR-4 protein where the first histidine has been replaced by asparagine and was subsequently used to build a homology model for SUGARWIN1. Molecular dynamics simulations of both proteins revealed the presence of a flexible loop only in SUGARWIN1 and we postulate that this, together with the presence of the catalytic histidine at position 42, renders it competent as a ribonuclease. The more electropositive surface potential of SUGARWIN1 would also be expected to favor complex formation with RNA. A phylogenetic analysis of PR-4 proteins obtained from 106 Embryophyta genomes showed that both catalytic histidines are widespread among them with few replacements in these amino acid positions during the gene family evolutionary history. We observe that the H11 replacement by N11 is also present in two other sugarcane PR-4 proteins: SUGARWIN3 and SUGARWIN4. We propose that RNase activity was present in the first Embryophyta PR-4 proteins but was recently lost in members of this family during the course of evolution.
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Sep 2021
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[21817]
Abstract: Teleost fishes comprise one-half of all vertebrate species and possess a duplicated genome. This whole-genome duplication (WGD) occurred on the teleost stem lineage in an ancient common ancestor of all living teleosts and is hypothesized as a trigger of their exceptional evolutionary radiation. Genomic and phylogenetic data indicate that WGD occurred in the Mesozoic after the divergence of teleosts from their closest living relatives but before the origin of the extant teleost groups. However, these approaches cannot pinpoint WGD among the many extinct groups that populate this 50- to 100-million-y lineage, preventing tests of the evolutionary effects of WGD. We infer patterns of genome size evolution in fossil stem-group teleosts using high-resolution synchrotron X-ray tomography to measure the bone cell volumes, which correlate with genome size in living species. Our findings indicate that WGD occurred very early on the teleost stem lineage and that all extinct stem-group teleosts known so far possessed duplicated genomes. WGD therefore predates both the origin of proposed key innovations of the teleost skeleton and the onset of substantial morphological diversification in the clade. Moreover, the early occurrence of WGD allowed considerable time for postduplication reorganization prior to the origin of the teleost crown group. This suggests at most an indirect link between WGD and evolutionary success, with broad implications for the relationship between genomic architecture and large-scale evolutionary patterns in the vertebrate Tree of Life.
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Jul 2021
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I03-Macromolecular Crystallography
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Aleksandra
Bialas
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Thorsten
Langner
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Adeline
Harant
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Mauricio P.
Contreras
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Clare E. M.
Stevenson
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David M.
Lawson
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Jan
Sklenar
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Ronny
Kellner
,
Matthew J
Moscou
,
Ryohei
Terauchi
,
Mark J.
Banfield
,
Sophien
Kamoun
Diamond Proposal Number(s):
[18565]
Open Access
Abstract: A subset of plant NLR immune receptors carry unconventional integrated domains in addition to their canonical domain architecture. One example is rice Pik-1 that comprises an integrated heavy metal-associated (HMA) domain. Here, we reconstructed the evolutionary history of Pik-1 and its NLR partner, Pik-2, and tested hypotheses about adaptive evolution of the HMA domain. Phylogenetic analyses revealed that the HMA domain integrated into Pik-1 before Oryzinae speciation over 15 million years ago and has been under diversifying selection. Ancestral sequence reconstruction coupled with functional studies showed that two Pik-1 allelic variants independently evolved from a weakly binding ancestral state to high-affinity binding of the blast fungus effector AVR-PikD. We conclude that for most of its evolutionary history the Pik-1 HMA domain did not sense AVR-PikD, and that different Pik-1 receptors have recently evolved through distinct biochemical paths to produce similar phenotypic outcomes. These findings highlight the dynamic nature of the evolutionary mechanisms underpinning NLR adaptation to plant pathogens.
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Jul 2021
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I12-JEEP: Joint Engineering, Environmental and Processing
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Diamond Proposal Number(s):
[21334]
Open Access
Abstract: Numerous aspects of early hominin biology remain debated or simply unknown. However, recent developments in high-resolution imaging techniques have opened new avenues in the field of paleoanthropology. More specifically, X-ray synchrotron-based analytical imaging techniques have the potential to provide crucial details on the ontogeny, physiology, biomechanics, and biological identity of fossil specimens. Here we present preliminary results of our X-ray synchrotron-based investigation of the skull of the 3.67-million-year-old Australopithecus specimen StW 573 (‘Little Foot’) at the I12 beamline of the Diamond Light Source (United Kingdom). Besides showing fine details of the enamel (i.e., hypoplasias) and cementum (i.e., incremental lines), as well as of the cranial bone microarchitecture (e.g., diploic channels), our synchrotron-based investigation reveals for the first time the 3D spatial organization of the Haversian systems in the mandibular symphysis of an early hominin.
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Mar 2021
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B21-High Throughput SAXS
I04-1-Macromolecular Crystallography (fixed wavelength)
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Diamond Proposal Number(s):
[20229]
Open Access
Abstract: Thioredoxin reductases control the redox state of thioredoxins (Trxs)—ubiquitous proteins that regulate a spectrum of enzymes by dithiol-disulfide exchange reactions. In most organisms, Trx is reduced by NADPH via a thioredoxin reductase flavoenzyme (NTR), but in oxygenic photosynthetic organisms, this function can also be performed by an iron-sulfur ferredoxin (Fdx)-dependent thioredoxin reductase (FTR) that links light to metabolic regulation. We have recently found that some cyanobacteria, such as the thylakoid-less Gloeobacter and the ocean-dwelling green oxyphotobacterium Prochlorococcus, lack NTR and FTR but contain a thioredoxin reductase flavoenzyme (formerly tentatively called deeply-rooted thioredoxin reductase or DTR), whose electron donor remained undefined. Here we demonstrate that Fdx functions in this capacity and report the crystallographic structure of the transient complex between the plant-type Fdx1 and the thioredoxin reductase flavoenzyme from Gloeobacter violaceus. Thereby, our data demonstrate that this cyanobacterial enzyme belongs to the Fdx flavin-thioredoxin reductase (FFTR) family, originally described in the anaerobic bacterium Clostridium pasteurianum. Accordingly, the enzyme hitherto termed DTR is renamed FFTR. Our experiments further show that the redox sensitive peptide CP12 is modulated in vitro by the FFTR/Trx system, demonstrating that FFTR functionally substitutes for FTR in light-linked enzyme regulation in Gloeobacter. Altogether, we demonstrate the FFTR is spread within the cyanobacteria phylum and propose that, by substituting for FTR, it connects the reduction of target proteins to photosynthesis. Besides, the results indicate that FFTR acquisition constitutes a mechanism of evolutionary adaptation in marine phytoplankton such as Prochlorococcus that live in low-iron environments.
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Feb 2021
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[23722]
Open Access
Abstract: Terrestrial life appeared on our planet within a time window of [4.4–3.5] billion years ago. During that time, it is suggested that the first proto-cellular forms developed in the surrounding of deep-sea hydrothermal vents, oceanic crust fractures that are still present nowadays. However, these environments are characterized by extreme temperature and pressure conditions that question the early membrane compartment’s capability to endure a stable structural state. Recent studies proposed an adaptive strategy employed by present-day extremophiles: the use of apolar molecules as structural membrane components in order to tune the bilayer dynamic response when needed. Here we extend this hypothesis on early life protomembrane models, using linear and branched alkanes as apolar stabilizing molecules of prebiotic relevance. The structural ordering and chain dynamics of these systems have been investigated as a function of temperature and pressure. We found that both types of alkanes studied, even the simplest linear ones, impact highly the multilamellar vesicle ordering and chain dynamics. Our data show that alkane-enriched membranes have a lower multilamellar vesicle swelling induced by the temperature increase and are significantly less affected by pressure variation as compared to alkane-free samples, suggesting a possible survival strategy for the first living forms.
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Feb 2021
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I13-2-Diamond Manchester Imaging
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Diamond Proposal Number(s):
[23250]
Abstract: The compound eyes of insects exhibit striking variation in size, reflecting adaptation to different lifestyles and habitats. However, the genetic and developmental bases of variation in insect eye size is poorly understood, which limits our understanding of how these important morphological differences evolve. To address this, we further explored natural variation in eye size within and between four species of the Drosophila melanogaster species subgroup. We found extensive variation in eye size among these species, and flies with larger eyes generally had a shorter inter-ocular distance and vice versa. We then carried out quantitative trait loci (QTL) mapping of intra-specific variation in eye size and inter-ocular distance in both D. melanogaster and D. simulans. This revealed that different genomic regions underlie variation in eye size and inter-ocular distance in both species, which we corroborated by introgression mapping in D. simulans. This suggests that although there is a trade-off between eye size and inter-ocular distance, variation in these two traits is likely to be caused by different genes and so can be genetically decoupled. Finally, although we detected QTL for intra-specific variation in eye size at similar positions in D. melanogaster and D. simulans, we observed differences in eye fate commitment between strains of these two species. This indicates that different developmental mechanisms and therefore, most likely, different genes contribute to eye size variation in these species. Taken together with the results of previous studies, our findings suggest that the gene regulatory network that specifies eye size has evolved at multiple genetic nodes to give rise to natural variation in this trait within and among species.
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Jan 2020
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I22-Small angle scattering & Diffraction
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Open Access
Abstract: A variety of photonic mechanisms give rise to iridescence and other structural colors in insects. In weevils (Coleoptera: Curculionoidea), iridescence is created by the most complex of these mechanisms, the three-dimensional photonic crystal. These self-assembling crystals take the form of triply periodic networks with single diamond or single gyroid symmetries and have been the subject of many descriptive studies based on individual species (often on a single specimen). To determine how these extraordinary nanostructures have evolved, we conduct the first comparative study of photonic crystals and setal nanostructure across Curculionoidea. By integrating structural data with newly available phylogenetic information, we demonstrate that — despite their widespread geographical and taxonomic distribution — three-dimensional photonic crystals appear to have evolved only once in weevils, in the common ancestor of a clade comprising the current subfamilies Entiminae and Cyclominae. Flattened, hollow setae with an unordered, spongy network in the lumen appear to be a necessary precursor to three-dimensional photonic crystals; we propose an evolutionary pathway by which this transformation has occurred.
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May 2019
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B23-Circular Dichroism
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Abstract: The nucleobase cation symporter-1 (NCS1) family of secondary active transport proteins comprises over 2500 sequenced members from bacteria, archaea, fungi and plants. NCS1 proteins use a proton or sodium gradient to drive inward cellular transport of purine and pyrimidine nucleobases and nucleosides, hydantoins and related compounds. The structural organization, substrate binding residues and molecular mechanism of NCS1 proteins are defined by crystal structures of sodium-coupled hydantoin transporter, Mhp1. Plant proteins are most closely related to bacterial/archaeal proteins and the distinct Fur-type and Fcy-type fungal proteins and plant proteins originated through independent horizontal transfers from prokaryotes. Analyses of 25 experimentally characterized proteins reveal high substrate specificity in bacterial proteins, distinct non-overlapping specificities in Fur-type and Fcy-type fungal proteins and broad specificity in plant proteins. Possible structural explanations are identified for differences in substrate specificity between bacterial proteins, whilst specificities of other proteins cannot be predicted by simple sequence comparisons. Specificity appears to be species specific and determined by combinations of effects dictated by multiple residues in the major substrate binding site and gating domains. This is an exploratory research review of evolutionary relationships, function and structural organization, molecular mechanism and origins of substrate specificity in NCS1 proteins and avenues of future direction.
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Jul 2018
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