Biology subjects

Francisco, C. S.

Publications and source records attributed to Francisco, C. S..

5 recordsLinked to original sources

bioRxiv2023

The apoplastic space of two wheat genotypes provide highly different environment for pathogen colonization: Insights from proteome and microbiome profiling

The intercellular space comprising the plant apoplast harbors a diverse range of microorganisms. The apoplastic interface represents the main compartment for interactions between proteins produced and secreted by the plant and the microbial endophytes. The outcomes of these interactions can play a role in plant cell wall metabolism, stress tolerance, and plant-pathogen resistance. So far the underlying factors that determine microbiota composition in the apoplast are not fully understood. However, it is considered that cell wall composition, nutrient availability, and the plant immune system are main determinants of microbiota composition. The plant immune system is considered to play a crucial role in modulating microbiota composition through the recognition of specific microbe-associated molecular patterns and the activation of defense responses. Hereby the plant may restrict non-beneficial microbial members and facilitate the propagation of beneficial ones. In this study, we investigated changes in the apoplastic environment during pathogen invasion using wheat as a model system. Infection of wheat with Zymoseptoria tritici, a fungal pathogen, resulted in notable alterations in the apoplast composition, reduced microbial diversity, and the accumulation of antimicrobial defense metabolites. Intriguingly, certain core microbial members persisted even in the presence of pathogen-induced immune responses, indicating their ability to evade or tolerate host immune defenses. To further explore these dynamics, we developed a protocol for extracting apoplastic fluids from wheat leaves and conducted proteome analyses to characterize the dynamic environment of the wheat leaves. Our findings uncovered a highly variable apoplastic environment that selects for microbes with specific adaptations. Notably, a core microbial community enriched in the resistant wheat cultivar exhibited antagonistic activity against Z. tritici, suggesting a potential role in conferring pathogen defense. This study advances our understanding of the dynamic interactions and adaptations of the wheat apoplastic microbiota during pathogen invasion, emphasizing the pivotal role of microbial interactions in pathogen defenses.

microbiology↗

bioRxiv2022

A transcription factor and a phosphatase regulate temperature-dependent morphogenesis in a fungal plant pathogen

Naturally fluctuating temperatures provide a constant environmental stress that requires adaptation. Some fungal pathogens respond to heat stress by producing new morphotypes that maximize their overall fitness. The fungal wheat pathogen Z. tritici responds to heat stress by switching from its yeast-like blastospore form to hyphae or chlamydospores. The regulatory mechanisms underlying this switch are unknown. Here, we demonstrate that a differential heat stress response is ubiquitous in Z. tritici populations around the world. We used QTL mapping to identify a single locus associated with the temperature-dependent morphogenesis and we found two genes, the transcription factor ZtMsr1 and the protein phosphatase ZtYvh1, regulating this mechanism. We find that ZtMsr1 regulates repression of hyphal growth and induces chlamydospore formation whereas ZtYvh1 is required for hyphal growth. We next pinpointed that chlamydospore formation is a response to the intracellular osmotic stress generated by the heat stress. This intracellular stress stimulates the CWI and HOG MAPK pathways resulting in hyphal growth. If cell wall integrity is however compromised, ZtMsr1 represses the hyphal development program and might induce the chlamydospore-inducing genes as a stress-response survival strategy. Taken together, these results suggest a novel mechanism through which morphological transitions are orchestrated in Z. tritici - a mechanism possibly also present in other pleomorphic fungi. IMPORTANCETemperature is an environmental signal constantly monitored by pleomorphic fungi. Our experiments showed that yeast-to-hyphal or yeast-to-chlamydospore transitions are ubiquitous heat stress responses in Z. tritici. QTL mapping allowed us to identify a transcription factor and a protein phosphatase contributing to temperature-dependent morphogenesis. We showed that intracellular osmolarity is the pivotal signal inducing these transitions. We propose a regulatory network controlling Z. tritici morphogenesis, which may have broad implications for temperature sensing of fungal pathogens.

molecular biology↗

bioRxiv2020

Mapping the adaptive landscape of a major agricultural pathogen reveals evolutionary constraints across heterogeneous environments

The adaptive potential of pathogens in novel or heterogeneous environments underpins the risk of disease epidemics. Antagonistic pleiotropy or differential resource allocation among life-history traits can constrain pathogen adaptation. However, we lack understanding how the genetic architecture of individual traits can generate trade-offs. Here, we report a large-scale study based on 145 global strains of the fungal wheat pathogen Zymoseptoria tritici from four continents. We measured 50 life-history traits, including virulence and reproduction on 12 different wheat hosts and growth responses to several abiotic stressors. To elucidate the genetic basis of adaptation, we used multi-trait genome-wide association mapping. We show that most traits are governed by polygenic architectures and are highly heritable suggesting that adaptation proceeds mainly through allele frequency shifts at many loci. We identified numerous pleiotropic SNPs with conflicting effects on host colonization and survival in stressful environments. Such genetic constraints are likely limiting the pathogens ability to cause host damage and could be exploited for pathogen control. In contrast, adaptation to abiotic stress factors was likely facilitated by synergistic pleiotropy. Our study illustrates how comprehensive mapping of life-history trait architectures across diverse environments allows to predict evolutionary trajectories of pathogens confronted with environmental perturbations.

evolutionary biology↗

bioRxiv2020

The role of vegetative cell fusions in the lifestyle of the wheat fungal pathogen Zymoseptoria tritici

The ability of fungal cells to undergo cell fusion allows them to maximize their overall fitness. In this study, we characterized the role of the so gene orthologous in Zymoseptoria tritici and the biological contribution of vegetative cell fusions in the lifestyle of this latent necrotrophic fungus. Firstly, we show that Z. tritici undergoes self-fusion between distinct cellular structures and its mechanism is dependent on the initial cell density. Next, the deletion of ZtSo resulted in the loss of cell-to-cell communication affecting both hyphal and germlings fusion. We show that Z. tritici mutants for MAP kinase-encoding ZtSlt2 (orthologous MAK-1) and ZtFus3 (orthologous MAK-2) genes also fail to undergo self-stimulation and self-fusion, demonstrating the functional conservation of this signaling mechanism across species. Additionally, the{Delta} ZtSo mutant was severely impaired in melanization, which leads us to identify a trade-off between fungal growth and melanization. Though it has been proposed that So is a scaffold protein for MAP kinase genes from the CWI pathway, its deletion did not affect the cell wall integrity of the fungus. Finally, we demonstrated that anastomose is dispensable for pathogenicity, but essential for the fruiting body development and its absence abolish the asexual reproduction of Z. tritici. Taken together, our data show that ZtSo is required for fungal development, while vegetative cell fusions are essential for fungal fitness.

cell biology↗

bioRxiv2018

Differential morphological changes in response to environmental stimuli in a fungal plant pathogen

During their life cycles, pathogens have to adapt to many biotic and abiotic environmental stresses to maximize their overall fitness. Morphological transitions are one of the least understood of the many strategies employed by fungal plant pathogens to adapt to constantly changing environments, even though different morphotypes may play important biological roles. We characterized the responses of the wheat pathogen Zymoseptoria tritici to a series of environmental stresses in order to understand the effects of changing environments on fungal morphology and adaptation. We found that all tested stresses induced morphological changes, but different responses were found among four different strains. A transcription analysis showed that morphogenesis and virulence factors are co-regulated. We discovered that Z. tritici forms chlamydospores and demonstrated that these structures are better able to survive extreme cold, heat and drought than other cell types. We also show that blastospores (the \"yeast-like\" form of the pathogen typically found only in laboratory conditions) can form from germinated pycnidiospores on the surface of wheat leaves, suggesting that this morphotype can play an important role in the natural history of Z. tritici. Our findings illustrate how changing environmental conditions can affect cellular morphology and lead to the formation of new morphotypes, with each morphotype having a potential impact on both pathogen survival and disease epidemiology.

microbiology↗