Biology subjects

Govers, F.

Publications and source records attributed to Govers, F..

6 recordsLinked to original sources

bioRxiv2025

Microtubules in the coenocyte Phytophthora function in nuclear positioning and sustaining tip growth

The microtubule cytoskeleton consists of dynamic intracellular filaments and is involved in numerous processes, ranging from nuclear division to intracellular transport. Some of these microtubule-mediated processes are conserved in all eukaryotic lineages while others are specific for certain groups of organisms. Here, we focus on the microtubule cytoskeleton of oomycetes in the genus Phytophthora, a group of harmful plant pathogens. For visualizing microtubule organization and dynamics, we generated transgenic Phytophthora palmivora lines expressing GFP-tagged -tubulin. Besides a conserved localization in the mitotic spindle, we observed cytoplasmic microtubules originating from microtubule-organizing centers associated with nuclei in the coenocytic hyphae. These dynamic microtubules initiated long-lasting, antiparallel connections with microtubules originating from adjacent nuclei. After mitosis, these microtubules rapidly increased in length while maintaining their antiparallel interaction. Frequent buckling events suggest that microtubule-based force generation plays a role in nuclear spacing. This idea was strengthened by erratic nuclear motility and positioning in hyphae exposed to the microtubule depolymerizing drug oryzalin. Besides aberrant nuclear positioning we also observed defects in hyphal growth; in oryzalin-treated hyphae lacking microtubules, tip growth was less sustained than in non-treated hyphae. This suggests that microtubules radiating into the hyphal tip from the apical nucleus have a function in sustaining tip growth. Altogether, this study provides novel insights in the localization, dynamics and functions of the microtubule cytoskeleton in the coenocytic Phytophthora hyphae.

cell biology↗

bioRxiv2021

Phytophthora capsici sterol reductase PcDHCR7 has a role in mycelium development and pathogenicity

The de novo biosynthesis of sterols is critical for eukaryotes, however, some organisms lack this pathway including most oomycetes. Phytophthora spp. are sterol auxotroph but remarkably, have retained a few genes encoding enzymes in the sterol biosynthesis pathway. Here we investigated the function of PcDHCR7, a gene in Phytophthora capsici predicted to encode the {bigtriangleup}7-sterol reductase. When expressed in Saccharomyces cerevisiae, PcDHCR7 showed a {bigtriangleup}7-sterol reductase activity. Knocking out PcDHCR7 in P. capsici resulted in loss of the capacity to transform ergosterol into brassicasterol, which means PcDHCR7 has a {bigtriangleup}7-sterol reductase activity in P. capsici itself. This enables P. capsici to transform sterols recruited from the environment for better use. Biological characteristics were compared between wild-type isolate and PcDHCR7 knock-out transformants. The results indicated that PcDHCR7 plays a key role in mycelium development and pathogenicity of zoospores in P. capsici.

microbiology↗

bioRxiv2020

Oomycete metabolism is highly dynamic and reflects lifestyle adaptations

Pathogen-host symbiosis drives metabolic adaptations. Animal and plant pathogenic oomycetes are thought to adapt their metabolism to facilitate interactions with their hosts. Here, we performed a large-scale comparison of oomycete metabolism and uncovered considerable variation in oomycete metabolism that could be linked to differences in lifestyle. Pathway comparisons revealed that plant pathogenic oomycetes can be divided in two parts; a conserved part and an accessory part. The accessory part could be associated with the degradation of plant compounds produced during defence responses. Obligate biotrophic oomycetes have smaller metabolic networks, and this group displays converged evolution by repeated gene losses affecting the same metabolic pathways. A comparison of the metabolic networks of obligate biotrophic oomycetes with those of plant pathogenic oomycetes as a whole revealed that the losses of metabolic enzymes in biotrophs are not random and that the network of biotrophs contracts from the periphery inwards. Our analyses represent the first metabolism-focused comparison of oomycetes at this scale and will contribute to a better understanding of the evolution and relationship between metabolism and lifestyle adaptation. ORIGINALITY & SIGNFICANCE STATEMENTThe intimate interaction between pathogens and their hosts exerts strong selection pressure leading to rapid adaptation. How this shapes the metabolism of pathogens is largely unknown. Here, we used comparative genomics to systematically characterize the metabolisms of animal and plant pathogenic oomycetes, a group of eukaryotes comprising many important animal and plant pathogens with significant economic and ecological impact. Core- and pan-genome as well as metabolic network analyses of distantly related oomycetes and their non-pathogenic relatives revealed considerable lifestyle- and lineage-specific adaptations. Extreme lifestyle adaptation could be observed in the metabolism of obligate biotrophic oomycetes - a group of pathogens that require a living host for proliferation. The metabolic networks of obligate biotrophic oomycetes reflect profound patterns of reductive evolution, converging to a loss the same metabolic enzymes during acquisition of an obligate parasitic lifestyle. These findings contribute to a be better understanding of oomycete evolution and the relationship between metabolism and lifestyle adaptation.

evolutionary biology↗

bioRxiv2019

The genome of Peronospora belbahrii reveals high heterozygosity, a low number of canonical effectors and CT-rich promoters

Along with Plasmopara destructor, Peronosopora belbahrii has arguably been the economically most important newly emerging downy mildew pathogen of the past two decades. Originating from Africa, it has started devastating basil production throughout the world, most likely due to the distribution of infested seed material. Here we present the genome of this pathogen and results from comparisons of its genomic features to other oomycetes. The assembly of the nuclear genome was ca. 35.4 Mbp in length, with an N50 scaffold length of ca. 248 kbp and an L50 scaffold count of 46. The circular mitochondrial genome consisted of ca. 40.1 kbp. From the repeat-masked genome 9049 protein-coding genes were predicted, out of which 335 were predicted to have extracellular functions, representing the smallest secretome so far found in peronosporalean oomycetes. About 16 % of the genome consists of repetitive sequences, and based on simple sequence repeat regions, we provide a set of microsatellites that could be used for population genetic studies of Pe. belbahrii. Peronospora belbahrii has undergone a high degree of convergent evolution, reflecting its obligate biotrophic lifestyle. Features of its secretome, signalling networks, and promoters are presented, and some patterns are hypothesised to reflect the high degree of host specificity in Peronospora species. In addition, we suggest the presence of additional virulence factors apart from classical effector classes that are promising candidates for future functional studies.

genomics↗

bioRxiv2018

Attempts to implement CRISPR/Cas9 for genome editing in the oomycete Phytophthora infestans

Few techniques have revolutionized the molecular biology field as much as genome editing using CRISPR/Cas9. Recently, a CRISPR/Cas9 system has been developed for the oomycete Phytophthora sojae, and since then it has been employed in two other Phytophthora spp. Here, we report our progress on efforts to establish the system in the potato late blight pathogen Phytophthora infestans. Using the original constructs as developed for P. sojae, we did not obtain any transformants displaying a mutagenized target gene. We made several modifications to the CRISPR/Cas9 system to pinpoint the reason for failure and also explored the delivery of pre-assembled ribonucleoprotein complexes. With this report we summarize an extensive experimental effort pursuing the application of a CRISPR/Cas9 system for targeted mutagenesis in P. infestans and we conclude with suggestions for future directions.

molecular biology↗

bioRxiv2017

Genome-wide characterization of Phytophthora infestansmetabolism: a systems biology approach

Genome-scale metabolic models (GEMs) provide a functional view of the complex network of biochemical reactions in the living cell. Initially mainly applied to reconstruct the metabolism of model organisms, the availability of increasingly sophisticated reconstruction methods and more extensive biochemical databases now make it possible to reconstruct GEMs for less characterized organisms as well, and have the potential to unravel the metabolism in pathogen-host systems. Here we present a GEM for the oomycete plant pathogen Phytophthora infestans as a first step towards an integrative model with its host. We predict the biochemical reactions in different cellular compartments and investigate the gene-protein-reaction associations in this model to get an impression of the biochemical capabilities of P. infestans. Furthermore, we generate life stage-specific models to place the transcriptomic changes of genes encoding metabolic enzymes into a functional context. In sporangia and zoospores there is an overall downregulation, most strikingly reflected in the fatty acid biosynthesis pathway. To investigate the robustness of the GEM, we simulate gene deletions to predict which enzymes are essential for in vitro growth. While there is room for improvement, this first model is an essential step towards an understanding of P. infestans and its interactions with plants as a system, which will help to formulate new hypotheses on infection mechanisms and disease prevention.

systems biology↗