Biology subjects

Johnson, J.

Publications and source records attributed to Johnson, J..

At least 73 records · Page 4Linked to original sources

bioRxiv2022

A greenhouse-based high-throughput phenotyping platform for identification and genetic dissection of resistance to Aphanomyces root rot in field pea

Aphanomyces root rot (ARR) is a devastating disease in field pea (Pisum sativum L.) that can cause up to 100% crop failure. Assessment of ARR resistance can be a rigorous, costly, time-demanding activity that is relatively low-throughput and prone to human errors. These limits the ability to effectively and efficiently phenotype the disease symptoms arising from ARR infection, which remains a perennial bottleneck to the successful evaluation and incorporation of disease resistance into new cultivars. In this study, we developed a greenhouse-based high throughput phenotyping (HTP) platform that moves along the rails above the greenhouse benches and captures the visual symptoms caused by Aphanomyces euteiches in field pea. We pilot tested this platform alongside with conventional visual scoring in five experimental trials under greenhouse conditions, assaying over 12,600 single plants. Precision estimated through broad-sense heritability (H2) was consistently higher for the HTP-indices (H2 Exg =0.86) than the traditional visual scores (H2 DSI=0.59), potentially increasing the power of genetic mapping. We genetically dissected variation for ARR resistance using the HTP-indices, and identified a total of 260 associated single nucleotide polymorphism (SNP) through genome-wide association (GWA) mapping. The number of associated SNP for HTP-indices was consistently higher with some SNP overlapped to the associated SNP identified using the visual scores. We identified numerous small-effect QTLs, with the most significant SNP explaining about 5 to 9% of the phenotypic variance per index, and identified previously mapped genes known to be involved in the biological pathways that trigger immunity against ARR, including Psat5g280480, Psat5g282800, Psat5g282880, and Psat2g167800. We also identified a few novel QTLs with small-effect sizes that may be worthy of validation in the future. The newly identified QTLs and underlying genes, along with genotypes with promising resistance identified in this study, can be useful for improving a long-term, durable resistance to ARR.

pathology↗

bioRxiv2022

Dysfunction of the Polycomb protein RYBP and of 5-methylcytosine oxidases leads to widespread CpG island hypermethylation and cell transformation

DNA hypermethylation is a hallmark of cancer and predominantly affects CpG island regions. Although this phenomenon was first described more than three decades ago, its mechanisms have remained unknown. Since CpG island hypermethylation is strongly biased towards Polycomb target genes, we reasoned that dysfunction of Polycomb repression complexes (PRCs) may underlie CpG island hypermethylation. We observed that a few genes coding for components of the PRC1 complex are downregulated in many cancer types. We focused on RYBP, a key activator of variant PRC1 complexes responsible for H2AK119 monoubiquitylation. We inactivated RYBP in nontumorigenic bronchial epithelial cells and observed a limited extent of DNA hypermethylation. Considering that tumors are deficient in 5-methylcytosine oxidase (TET protein) function as documented by substantially reduced levels of 5-hydroxymethylcytosine in all solid tumors, we then inactivated TET1, TET2, and TET3 in bronchial cells, individually and in combination. Using quadruple knockouts of RYBP and all three TET proteins, we observed widespread hypermethylation of H2AK119Ub1-marked CpG islands affecting almost 4,000 target genes. This hypermethylation closely mirrored the DNA hypermethylation landscape observed in human lung tumors. These cells showed aberrant methylation and dysregulation of several cancer-relevant pathways including cell cycle control genes, defects in the Hippo pathway and overexpression of AP-1 transcription factor genes. As a result, the quadruple knockout bronchial cells acquired properties of a transformed phenotype, including efficient growth in soft agar and formation of squamous cell carcinomas in immune-compromised mice. Our data provide a long- sought mechanism for DNA hypermethylation in cancer and explain how such hypermethylation leads to cell transformation. Cancer formation, therefore, is achievable by misregulation of two epigenetic pathways without introduction of cancer driver mutations.

cancer biology↗

bioRxiv2022

Recapitulating Human Ovarian Aging Using Random Walks

Mechanism(s) that control whether individual human primordial ovarian follicles (PFs) remain dormant, or begin to grow, are all but unknown. One of our groups has recently shown that activation of the Integrated Stress Response (ISR) pathway can slow follicular granulosa cell proliferation by activating cell cycle checkpoints. Those data suggest that the ISR is active and fluctuates according to local conditions in dormant PFs. Because cell cycle entry of (pre)granulosa cells is required for PF growth activation (PFGA), we propose that rare ISR checkpoint resolution allows individual PFs to begin to grow. Fluctuating ISR activity within individual PFs can be described by a random process. In this paper, we model ISR activity of individual PFs by one-dimensional random walks (RWs) and monitor the rate at which simulated checkpoint resolution and thus PFGA threshold crossing occurs. We show that that the simultaneous recapitulation of i) the loss of PFs over time within simulated subjects, and ii) the timing of PF depletion in populations of simulated subjects equivalent to the distribution of the human age of natural menopause can be produced using this approach. In the RW model, the probability that individual PFs grow is influenced by regionally fluctuating conditions, that over time manifests in the known pattern of PFGA. Considered at the level of the ovary, randomness appears to be a key, purposeful feature of human ovarian aging.

physiology↗

bioRxiv2022

Temporal and spatial patterns of vertebrate extinctions during the Anthropocene

The human-induced annihilation of modern biodiversity is dragging the planet into a mass extinction that has already altered patterns of life globally. Among vertebrates, over 500 species have become extinct or possibly extinct in the last five centuries - an extinction rate that would have taken several millennia without human intervention. Vertebrate extinctions have often been quantified as cumulative counts that reveal sharp increases in losses over time. Here, we quantify global tetrapod extinctions since the 1400s using numbers of species losses across successive and independent time periods until present. Our results reveal that extinctions were low and fundamentally restricted to islands in pre-industrial times, experiencing a significant increase and spread over continental mainland following the onset of the industrial revolution. Recent amphibian extinctions alarmingly exceed the extinctions of all tetrapods, while extinctions of island birds account for a third of all extinctions. Finally, we quantified the relationship between human population growth (HPG, as a proxy for aggregate human effects on the environment) and extinctions between 1800-2000, to then predict that an estimated 838 tetrapod species will go extinct between 2030-2100 based on United Nations HPG projections. These findings further warn humanity about the need to sustainably control HPG and the destructive impacts of rapid environmental change on ecosystems worldwide.

ecology↗

bioRxiv2022

Multi-trait genomic prediction improves selection accuracy for enhancing seed mineral concentrations in pea (Pisum sativum L.)

The superiority of multi-trait genomic selection (MT-GS) over univariate genomic selection (UNI-GS) can be improved by redesigning the phenotyping strategy. In this study, we used about 300 advanced breeding lines from North Dakota State University (NDSU) pulse breeding program and about 200 USDA accessions evaluated for ten nutritional traits to assess the efficiency of sparse testing in MT-GS. Our results showed that sparse phenotyping using MT-GS consistently outperformed UNI-GS when compared to partially balanced phenotyping using MT-GS. This strategy can be further extended to multi-environment multi-trait GS to improve prediction performance and reduce the cost of phenotyping and time-consuming data collection process. Given that MT-GS relies on borrowing information from genetically correlated traits and relatives, consideration should be given to trait combinations in the training and prediction sets to improve model parameters estimate and ultimately prediction performance. Our results point to heritability and genetic correlation between traits as possible parameters to achieve this objective.

genetics↗

bioRxiv2022

A phospholipase assay screen identifies synergistic inhibitors of the P. aeruginosa toxin ExoU

The opportunistic pathogen Pseudomonas aeruginosa is a leading cause of disability and mortality worldwide and the World Health Organisation has listed it with the highest priority for the need of new therapies. P. aeruginosa strains that express ExoU are implicated in the worst clinical outcomes. ExoU is phospholipase that is secreted by P. aeruginosa directly into the cytoplasm of target host cells, where its catalytic activity, directed towards plasma membranes, causes rapid cell lysis. Inhibition of ExoU may be a novel strategy to combat acutely cytotoxic ExoU expressing P. aeruginosa infections. Using an in vitro phospholipase assay, we performed a high throughput screen to identify compounds that might be repurposed as therapeutic ExoU inhibitors. We discovered a panel of compounds that appeared to inhibit ExoU through distinct mechanisms. Compound C prevented ExoU membrane localisation in HEK293T cells and caused colocalization with lysosomes, whereas compound D prevented PIP2 dependent oligomerisation of ExoU in vitro suggestive of synergistic action. Indeed, the concentrations required by compounds C and D to inhibit in vitro ExoU catalytic activity, when used in combination, was in the nanomolar region. In corneal scratch and infection assays, these compounds reduced ExoU mediated cytotoxicity, as assessed by fluorescence microscopy and lactate dehydrogenase release assays.

biochemistry↗

bioRxiv2022

MaxQuant and MSstats in Galaxy enable reproducible cloud-based analysis of quantitative proteomics experiments for everyone

Quantitative mass spectrometry-based proteomics has become a high-throughput technology for the identification and quantification of thousands of proteins in complex biological samples. Two de facto standard tools, MaxQuant and MSstats, allow for the analysis of raw data and finding proteins with differential abundance between conditions of interest. To enable accessible and reproducible quantitative proteomics analyses in a cloud environment, we have integrated MaxQuant (including TMTpro 16/18plex), Proteomics Quality Control (PTXQC), MSstats and MSstatsTMT into the open-source Galaxy framework. This enables the web-based analysis of label-free and isobaric labeling proteomics experiments via Galaxys graphical user interface on public clouds. MaxQuant and MSstats in Galaxy can be applied in conjunction with thousands of existing Galaxy tools and integrated into standardized, sharable workflows. Galaxy tracks all metadata and intermediate results in analysis histories, which can be shared privately for collaborations or publicly, allowing full reproducibility and transparency of published analysis. To further increase accessibility, we provide detailed hands-on training materials. The integration of MaxQuant and MSstats into the Galaxy framework enables their usage in a reproducible way on accessible large computational infrastructures, hence realizing the foundation for high throughput proteomics data science for everyone.

biochemistry↗

bioRxiv2021

Decoding the absolute stoichiometric composition and structural plasticity of α-carboxysomes

Carboxysomes are anabolic bacterial microcompartments that play an essential role in carbon fixation in cyanobacteria and some chemoautotrophs. This self-assembling organelle encapsulates the key CO2-fixing enzymes, Rubisco, and carbonic anhydrase using a polyhedral protein shell that is constructed by hundreds of shell protein paralogs. The -carboxysome from the chemoautotroph Halothiobacillus neapolitanus serves as a model system in fundamental studies and synthetic engineering of carboxysomes. Here we adopt a QconCAT-based quantitative mass spectrometry to determine the absolute stoichiometric composition of native -carboxysomes from H. neapolitanus. We further performed an in-depth comparison of the protein stoichiometry of native and recombinant -carboxysomes heterologously generated in Escherichia coli to evaluate the structural variability and remodeling of -carboxysomes. Our results provide insight into the molecular principles that mediate carboxysome assembly, which may aid in rational design and reprogramming of carboxysomes in new contexts for biotechnological applications.

biochemistry↗

bioRxiv2021

Transcriptional expression changes during compensatory plasticity in the prothoracic ganglion of the adult cricket Gryllus bimaculatus

Most adult organisms are limited in their capacity to recover from neurological damage. The auditory system of the Mediterranean field cricket, Gryllus bimaculatus, presents a compelling model for investigating neuroplasticity due to its unusual capabilities for structural reorganization into adulthood. Specifically, the dendrites of the central auditory neurons of the prothoracic ganglion sprout in response to the loss of auditory afferents. Deafferented auditory dendrites grow across the midline, a boundary they normally respect, and form functional synapses with the contralateral auditory afferents, restoring tuning-curve specificity. The molecular pathways underlying these changes are entirely unknown. Here, we used a multiple k-mer approach to re-assemble a previously reported prothoracic ganglion transcriptome that included ganglia collected one, three, and seven days after unilateral deafferentation in adult, male animals. We used EdgeR and DESeq2 to perform differential expression analysis and we examined Gene Ontologies to further understand the potential molecular basis of this compensatory anatomical plasticity. Enriched GO terms included those related to protein translation and degradation, enzymatic activity, and Toll signaling. Extracellular space GO terms were also enriched and included the upregulation of several protein yellow family members one day after deafferentation. Investigation of these regulated GO terms help to provide a broader understanding of the types of pathways that might be involved in this compensatory growth and can be used to design hypotheses around identified molecular mechanisms that may be involved in this unique example of adult structural plasticity.

neuroscience↗

bioRxiv2021

The 4D Nucleome Data Portal: a resource for searching and visualizing curated nucleomics data

The 4D Nucleome (4DN) Network aims to elucidate the complex structure and organization of chromosomes in the nucleus and the impact of their disruption in disease biology. We present the 4DN Data Portal (https://data.4dnucleome.org/), a repository for datasets generated in the 4DN network and relevant external datasets. Datasets were generated with a wide range of experiments, including chromosome conformation capture assays such as Hi-C and other innovative sequencing and microscopy-based assays probing chromosome architecture. All together, the 4DN data portal hosts more than 1800 experiment sets and 34000 files. Results of sequencing-based assays from different laboratories are uniformly processed and quality-controlled. The portal interface allows easy browsing, filtering, and bulk downloads, and the integrated HiGlass genome browser allows interactive visualization and comparison of multiple datasets. The 4DN data portal represents a primary resource for chromosome contact and other nuclear architecture data for the scientific community.

genomics↗

bioRxiv2021

Proton export drives the Warburg Effect

Aggressive cancers commonly ferment glucose to lactic acid at high rates, even in the presence of oxygen. This is known as aerobic glycolysis, or the "Warburg Effect". It is widely assumed that this is a consequence of the upregulation of glycolytic enzymes. Oncogenic drivers can increase the expression of most proteins in the glycolytic pathway, including the terminal step of exporting H+ equivalents from the cytoplasm. Proton exporters maintain an alkaline cytoplasmic pH, which can enhance all glycolytic enzyme activities, even in the absence of oncogene-related expression changes. Based on this observation, we hypothesized that increased uptake and fermentative metabolism of glucose could be driven by the expulsion of H+ equivalents from the cell. To test this hypothesis, we stably transfected lowly-glycolytic MCF-7, U2-OS, and glycolytic HEK293 cells to express proton exporting systems: either PMA1 (yeast H+-ATPase) or CAIX (carbonic anhydrase 9). The expression of either exporter in vitro enhanced aerobic glycolysis as measured by glucose consumption, lactate production, and extracellular acidification rate. This resulted in an increased intracellular pH, and metabolomic analyses indicated that this was associated with an increased flux of all glycolytic enzymes upstream of pyruvate kinase. These cells also demonstrated increased migratory and invasive phenotypes in vitro, and these were recapitulated in vivo by more aggressive behavior, whereby the acid-producing cells formed higher grade tumors with higher rates of metastases. Neutralizing tumor acidity with oral buffers reduced the metastatic burden. Therefore, cancer cells with increased H+ export increase intracellular alkalization, even without oncogenic driver mutations, and this is sufficient to alter cancer metabolism towards a Warburg phenotype.

cancer biology↗

bioRxiv2021

Evolutionary innovations through gain and loss of genes in the ectomycorrhizal Boletales

O_LIIn this study, we aim to identify genomic traits of the transitions to the ectomycorrhizal ecology within the Boletales, one of the most diverse lineages of symbiotrophic fungi. C_LIO_LIWe sequenced the genomes and compared the gene repertoires of symbiotrophic Boletales species to their saprotrophic brown-rot relatives. We also reconstructed gene duplication/loss histories along a time-calibrated phylogeny. C_LIO_LIWe showed that the rate of gene duplication is constant along the backbone of Boletales phylogeny with large loss events in lineages leading to several families. The rate of gene family expansion sharply increased in the late Miocene and mostly took place in Boletaceae. C_LIO_LIMost of the ectomycorrhizal Boletales are characterized by a large genome size due to transposable element (TE) expansions and a reduction in the diversity of plant cell wall degrading enzymes (PCWDEs) compared to their brown-rot relatives. However, several species in the Boletaceae, Paxillaceae and Boletinellaceae have kept a substantial set of endoglucanases and LPMOs acting on cellulose/hemicellulose and fungal polysaccharides suggesting that they may partly decompose organic matter by a combined activity of oxidative and hydrolytic enzymes. C_LIO_LIThe present study provides novel insights on our understanding of the mechanisms that influence the evolutionary diversification of boletes and symbiosis evolution. C_LI

genomics↗

bioRxiv2021

NBI-921352, a First-in-Class, Na V 1.6 Selective, Sodium Channel Inhibitor That Prevents Seizures in Scn8a Gain-of- Function Mice, and Wild-Type Mice and Rats

NBI-921352 (formerly XEN901) is a novel sodium channel inhibitor designed to specifically target NaV1.6 channels. Such a molecule provides a precision-medicine approach to target SCN8A-related epilepsy syndromes (SCN8A-RES), where gain-of-function (GoF) mutations lead to excess NaV1.6 sodium current, or other indications where NaV1.6 mediated hyper-excitability contributes to disease (Gardella and Moller, 2019; Johannesen et al., 2019; Veeramah et al., 2012). NBI-921352 is a potent inhibitor of NaV1.6 (IC50 0.051 {micro}M), with exquisite selectivity over other sodium channel isoforms (selectivity ratios of 756X for NaV1.1, 134X for NaV1.2, 276X for NaV1.7, and >583X for NaV1.3, NaV1.4, and NaV1.5). NBI-921352 is a state-dependent inhibitor, preferentially inhibiting activated (inactivated or open) channels. The state dependence leads to potent stabilization of inactivation, inhibiting NaV1.6 currents, including resurgent and persistent NaV1.6 currents, while sparing the closed/rested channels. The isoform-selective profile of NBI-921352 led to a robust inhibition of action-potential firing in glutamatergic excitatory pyramidal neurons, while sparing fast-spiking inhibitory interneurons, where NaV1.1 predominates. Oral administration of NBI-921352 prevented electrically induced seizures in a Scn8a GoF mouse, as well as in wild-type mouse and rat seizure models. NBI-921352 was effective in preventing seizures at lower brain and plasma concentrations than commonly prescribed sodium channel inhibitor antiseizure medicines (ASMs) carbamazepine, phenytoin, and lacosamide. NBI-921352 was well tolerated at higher multiples of the effective plasma and brain concentrations than those ASMs. NBI-921352 is entering phase II proof-of-concept trials for the treatment of SCN8A-developmental epileptic encephalopathy (SCN8A-DEE) and adult focal-onset seizures.

pharmacology and toxicology↗

bioRxiv2021

Balancing growth amidst salinity stress-lifestyle perspectives from the extremophyte model Schrenkiella parvula

Schrenkiella parvula, a leading extremophyte model in Brassicaceae, can grow and complete its life cycle under multiple environmental stresses, including high salinity. While foundational genomic resources have been created for S. parvula, a comprehensive physiological or structural characterization of its salt stress responses is absent. We aimed to identify the influential traits that lead to stress-resilient growth of this species. We examined salt-induced changes in the physiology and anatomy of S. parvula throughout its lifecycle across multiple tissues. We found that S. parvula maintains or even exhibits enhanced growth during various developmental stages at salt stress levels known to inhibit growth in Arabidopsis and most crops. The resilient growth of S. parvula was associated with key traits that synergistically allow continued primary root growth, expansion of xylem vessels across the root-shoot continuum, and a high capacity to maintain tissue water levels by developing larger and thicker leaves while facilitating continued photosynthesis during salt stress. These traits at the vegetative phase were followed by a successful transition to the reproductive phase via early flowering, development of larger siliques, and production of viable seeds during salt stress. Additionally, the success of self-fertilization during early flowering stages was dependent on salt-induced filament elongation in flowers that aborted in the absence of salt. Our results suggest that the maintenance of leaf water status and enhancement of selfing in early flowers to ensure reproductive success, are among the most influential traits that contribute to the extremophyte lifestyle of S. parvula in its natural habitat. One sentence summarySchrenkiella parvula salt-resilient growth is facilitated by uncompromised primary root growth, expansion of xylem vessels, maintenance of leaf water status and photosynthesis, and early flowering.

plant biology↗

bioRxiv2021

Mangrove forests mitigate coral bleaching under thermal stress from climate change

Anthropogenic marine heatwaves are progressively degrading coral reef ecosystems worldwide via the process of coral bleaching (the expulsion of photosynthetic endosymbionts which reveals the coral skeleton). Corals from mangrove lagoons are hypothesised to increase resistance and resilience to coral bleaching, highlighting these areas as potential natural refuges for corals. Our study, the first conducted at a global-scale, reveals that coral reefs associated with mangrove forests are less likely to bleach under thermal stress, and thus, under scenarios of climate warming. The onset of severe bleaching occurred after 3.6 Degree Heating Weeks (DHW) in mangrove-associated reefs, compared to 2.23 DHW for non-mangrove associated reefs. These findings highlight the critical role of mangrove forests for coral reef persistence under climate change. Accordingly, conservation actions targeting the protection of mangroves are expected to contribute to the resilience and resistance of reef corals from bleaching as marine heatwaves continue to become more common.

ecology↗

bioRxiv2021

SARS-COV-2 Recombinant Receptor-Binding-Domain (RBD) Induces Neutralising Antibodies Against Variant Strains of SARS-CoV-2 and SARS-CoV-1

SARS-CoV-2 is the etiological agent of COVID19. There are currently several licensed vaccines approved for human use and most of them are targeting the spike protein (or virion) in the virion envelope to induce protective immunity. Recently, variants that spread more quickly have emerged. There is evidence that some of these variants are less sensitive to neutralization in vitro, but it is not clear whether they can evade vaccine induced protection. In this study, we tested the utility of SARS-CoV-2 spike RBD as a vaccine antigen and explore the effect of formulation with Alum/MPLA or AddaS03 adjuvants. Our results indicate RBD induces high titers of neutralizing antibodies and activates strong cellular immune responses. There is also significant cross-neutralisation of variants B1.1.7 and B.1.351 and to a lesser extent, SARS-CoV-1. These results indicate that recombinant RBD can be a viable candidate as a stand-alone vaccine or as a booster shot to diversify our strategy for COVID19 protection.

microbiology↗

bioRxiv2021

Effects of BCG vaccination on donor unrestricted T cells in humans

Antigen classes other than proteins can be presented to T cells by near-monomorphic antigen-presenting molecules such as CD1, MR1, and butyrophilin 3A1. We sought to define the roles of donor unrestricted T (DURT) cells, including MR1-reactive MAIT cells, CD1b-reactive glucose monomycolate (GMM)-specific T cells, CD1d-reactive NKT cells, and {gamma}{delta} T cells, in vaccination against Mycobacterium tuberculosis. We characterized DURT cells following primary bacille Calmette-Guerin (BCG) vaccination in infants or BCG-revaccination in adults. BCG (re)vaccination did not modulate peripheral blood frequencies, T cell activation or memory profiles of MAIT cells, CD1b-restricted GMM-specific and germline-encoded mycolyl-reactive (GEM) cells or CD1d- restricted NKT cells. By contrast, BCG vaccination was associated with increased frequencies of {gamma}{delta} T cells as well as a novel subset of IFN-{gamma}-expressing CD4+ T cells with a CD26+CD161+TRAV1-2- phenotype in infants. More studies are required to understand the full potential of DURT cells in new TB vaccine strategies.

immunology↗

bioRxiv2021

Evolutionary priming and transition to the ectomycorrhizal habit in an iconic lineage of mushroom-forming fungi: is preadaptation a requirement?

The ectomycorrhizal symbiosis is an essential guild of many forested ecosystems and has a dynamic evolutionary history across kingdom Fungi, having independently evolved from diverse types of saprotrophic ancestors. In this study, we seek to identify genomic features of the transition to the ectomycorrhizal habit within the Russulaceae, one of the most diverse lineages of ectomycorrhizal fungi. We present comparative analyses of the pangenome and gene repertoires of 21 species across the order Russulales, including a closely related saprotrophic member of Russulaceae. The ectomycorrhizal Russulaceae is inferred to have originated around the Cretaceous-Paleogene extinction event (73.6-60.1 million years ago (MY)). The genomes of the ectomycorrhizal Russulaceae are characterized by a loss of genes for plant cell-wall degrading enzymes (PCWDEs), an expansion of genome size through increased transposable element (TE) content, a reduction in secondary metabolism clusters, and an association of genes coding for certain secreted proteins with TE "nests". The saprotrophic sister group of the ectomycorrhizal Russulaceae, Gloeopeniophorella convolvens, possesses some of these aspects (e.g., loss of some PCWDE and protease orthologs, TE expansion, reduction in secondary metabolism clusters), resulting from an accelerated rate of gene evolution in the shared ancestor of Russulaceae that predates the evolution of the ectomycorrhizal habit. Genomes of Russulaceae possess a high degree of synteny, including a conserved set of terpene secondary metabolite gene clusters. We hypothesize that the evolution of the ectomycorrhizal habit requires premodification of the genome for plant root association followed by an accelerated rate of gene evolution within the secretome for host-defense circumvention and symbiosis establishment.

evolutionary biology↗