Biology subjects

Rosa, P.

Publications and source records attributed to Rosa, P..

8 recordsLinked to original sources

bioRxiv2026

Pathogen-dependent biocontrol activity of Chlorella sorokoniana aqueous extracts against fungal and oomycete plant pathogens

Fungal and oomycete plant pathogens are major drivers of yield losses worldwide and are spurring the search for sustainable alternatives to synthetic pesticides. Algae, in general, and microalgae, in particular, represent a promising source of bioactive compounds for crop protection. Despite this, their efficacy across different host-pathogen systems remains poorly characterised. This study evaluated the biocontrol potential of the aqueous extract of Chlorella sorokoniana against three economically important phytopathogens using complementary in vitro, ex vivo, and in planta assays. The strongest activity was observed against Magnaporthe oryzae, with the extract reducing fungal growth by approximately 70% in vitro, inhibiting appressorium formation by 55%, suppressing lesion development on detached rice leaves by more than 75%, and reducing rice blast severity by 64.5% as a preventive foliar treatment. In contrast, the extract showed little or no direct in vitro antifungal activity against Pythium ultimum and Rhizoctonia solani, yet it significantly reduced disease severity in planta by 13-37% and 48-55%, respectively. The contrasting responses among pathosystems suggest that C. sorokoniana aqueous extracts act through different mechanisms depending on the pathogen and the crop, combining direct antifungal activity against M. oryzae with plant-associated protective effects against soil-borne pathogens. These findings highlight the importance of evaluating candidate biocontrol products using complementary in vitro and in planta approaches, as laboratory antimicrobial assays alone may substantially underestimate their agricultural potential. The broad-spectrum protection achieved with an unrefined aqueous extract further supports C. sorokoniana as a promising source of sustainable crop protection products and provides a strong foundation for future mechanistic studies, formulation development, and field validation. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/742703v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@428ebaorg.highwire.dtl.DTLVardef@1a85992org.highwire.dtl.DTLVardef@190a605org.highwire.dtl.DTLVardef@183b905_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2026

High Quality Complete Genomes of Two Virulent Field Isolates of Pyricularia oryzae from Portugal

The fungal pathogen Pyricularia oryzae is notorious for causing blast disease in various important cereal crops, including wheat, rice, millet, and oat. Whole-genome-informed data on this pathogen are necessary to better understand the host adaptability of the fungus, including identifying key determinants of infection to enable more precise disease control. Here, we report highly contiguous genome sequences (using long-read PacBio technology) of two isolates from rice paddies in Portugal, M22.7 and T22.2, which exhibit distinctly aggressive symptoms in rice. Both mitochondrial and nuclear sequences were characterised in this study. The resulting nuclear genomes have assembly lengths of 46.4 Mb for M22.7 (198x coverage) and 46.3 Mb for T22.2 (163x coverage), with near-complete BUSCO completeness (98.8%) and a 0% contamination score (EukCC). Phenotypic analysis showed M22.7 to be more virulent than T22.2, which may be explained by the lower number of predicted effector genes and higher transposable element content in M22.7 relative to T22.2. This announcement represents the first genome resource for natural isolates of P. oryzae from Portugal in over 20 years, filling an important data gap from a major European rice-producing country that produces locally adapted rice varieties under specific agro-environmental conditions (near the Atlantic coast).

genomics↗

bioRxiv2026

The peculiar photobiology of a giant motile diatom inhabiting the subtidal sediments of the bay of Brest.

Microphytobenthos (MPB) contributes significantly to the marine primary production in estuarine ecosystems. MPB is mainly composed of benthic motile diatoms inhabiting intertidal and shallow subtidal sediments. Unlike intertidal small-sized diatom models, subtidal ([≥] 10 m depth) MPB and large-sized (>100 {micro}m) species, have comparatively received much less attention, especially as regards to their photosynthetic productivity. Yet, the subtidal light environment shows unusual (very) low intensities and a green-blue light spectrum at high tide. The present study investigates the light-dependent green-blue responses of the subtidal giant diatom Pleurosigma strigosum, combining in situ monitoring with laboratory experiments. In both MPB and P. strigosum, we documented a strong photophysiological plasticity, and a striking alignment with the photophysiology of (very) low light-adapted polar diatoms. Altogether, our results highlight the nature of subtidal photoadaptation: a very low green-blue light sensitive response, which explains the early blooming of P. strigosum at the very beginning of spring and underpins the ecological success of MPB in colonizing coastal subtidal sediments. The general coherence between subtidal P. strigosum and MPB light-responses offers a unique model species and growth form to further decipher the specific light-driven metabolism of subtidal MPB under precisely controlled environmental conditions.

ecology↗

bioRxiv2024

Hypoxic stress dysregulates functions of glioma-associated myeloid cells through epigenomic and transcriptional programs

Hypoxia rapidly alters gene expression to allow cellular adaptation to challenging conditions and support tumour growth. Hypoxia also affects the chromatin structure by modifications of histones and DNA methylation. Glioblastoma (GBM) is an aggressive, deadly primary brain tumour for which there is no effective treatment. The tumour microenvironment of GBM is highly heterogeneous, with infiltration of glioma-associated microglia and macrophages (GAMs) and the presence of necrotic, hypoxic regions which significantly impair effectiveness of therapies. The mechanisms through which hypoxia alters the tumour microenvironment and regulates functions of infiltrating immune cells remain poorly understood. Here, we show that hypoxia modulates the expression of myeloid markers in distinct ways: upregulates the expression of monocytic marker Lgals3 and downregulates the microglial markers P2ry12 and Tmem119 in microglial and monocytic GAMs in vitro and in vivo. Underlying genome-wide hypoxia-dependent transcriptomic changes in microglial cells were identified using microglia-glioma co-cultures and validated in human and mouse GBM single- cell transcriptomics datasets. Numerous GAM subtype markers are dysregulated in response to hypoxic stress due to associated changes in chromatin accessibility, as determined using ATACseq. While hypoxia alone drives a decrease of the overall chromatin accessibility at gene promoters, the exposure to glioma cells under hypoxic conditions leads to both increases and decreases of chromatin accessibility at promoter regions in microglial cells. Hypoxia downregulates the chromatin accessibility at the regions enriched in motifs for transcription factors known as master regulators of microglial cell identity and function, including SPI1 or IRF8. Overall, our results highlight the importance of hypoxic stress as a strong intratumoral regulator of myeloid cell functions, which adds a new dimension to the characterisation of particular GAM subpopulations.

cancer biology↗

bioRxiv2024

Tracking changes in functionality and morphology of repopulated microglia in young and old mice

Microglia (MG) are myeloid cells of the central nervous system supporting its homeostasis and instigating neuroinflammation in pathologies. Single-cell RNA sequencing (scRNA-seq) revealed the functional heterogeneity of MG in mice brains. Inhibition of colony-stimulating factor 1 receptor (CSF1R) signaling with inhibitors deplete microglia which rapidly repopulate. Functionalities of repopulated microglia are poorly known. We combined scRNA-seq, bulk RNA-seq, immunofluorescence and confocal imaging to study functionalities and morphology of repopulated microglia. CSRF1R inhibitor (BLZ-945) depleted MG in 21 days and their numbers were restored 7 days later as evidenced by TMEM119 staining and flow cytometry. ScRNA-seq and computational analyses demonstrate that repopulated MG originate from preexisting MG progenitors and reconstitute functional clusters but upregulate inflammatory genes. Percentages of proliferating, immature MG displaying inflammatory gene expression increase in aging mice. Morphometric analysis of MG cell body and branching shows distinct morphology of repopulated MG, particularly in old mouse brains. We demonstrate that with aging some repopulated MG fail to reach the homeostatic phenotype. These differences microglia may contribute to the deterioration of microglia protective functions with age.

neuroscience↗

bioRxiv2022

Identification of microbial exopolymer producers in sandy and muddy intertidal sediments by compound-specific isotope analysis

Extracellular polymeric substances (EPS) refer to a wide variety of high molecular weight molecules secreted outside the cell membrane by biofilm microorganisms. In the present study, EPS from marine microphytobenthic biofilms were extracted and their isotope ratios were analysed. A comparison of these ratios with the carbon isotope ratios of fatty acid biomarkers allowed the identification of the main EPS producers of two contrasting types of intertidal marine sediments. Our study reveals that EPS sources are more diverse in sandy sediments than in muddy sediments. We also found distinct patterns in the production and breakdown of EPS in sandy and muddy environments. The main difference observed was in how epipelic and epipsammic diatoms affected the chemistry of EPS, which had significant implications for the growth of bacteria specialized in utilizing EPS. These differences were likely linked to variations in the functioning of epipelic and epipsammic communities, specifically in how EPS was used either for motility or for cell attachment.

ecology↗

bioRxiv2022

Remote adipose tissue-derived stromal cells of patients with lung adenocarcinoma generate a similar malignant microenvironment of the lung stromal counterpart

Cancer alters both local and distant tissue by influencing the microenvironment. In this regard, the interplay with the stromal fraction is considered critical as this latter can either foster or hamper the progression of the disease. Accordingly, the modality by which tumor may alter distant niches of stromal cells is still unclear, expecially at early stages. In this short report we attempt to better understand the biology of this cross talk. In our "autologous stromal experimental setting", we found that remote adipose tissue-derived mesenchymal stem cells (mediastinal AMSC) obtained from patients with lung adenocarcinoma sustain proliferation and clonogenic ability of A549 and human primary lung adenocarcinoma cells similarly to the autologous stromal lung counterpart (LMSC). This effect is not observed in lung benign diseases as the hamartochondroma. This finding was validated by conditioning benign AMSC with supernatants from LAC up to 21 days. The new reconditioned media of the stromal fraction so obtained, was able to increase cell proliferation of A549 cells at 14 and 21 days similarly to that derived from AMSC of patients with lung adenocarcinoma. The secretome generated by remote AMSC revealed overlapping to the corresponding malignant microenvironment of the autologous local LMSC. Among the plethora of 80 soluble factors analysed by arrays, a small pool of 5 upregulated molecules including IL1-{beta}, IL-3, MCP-1, TNF- and EGF, was commonly shared by both malignant-like autologous A- and LMSC derived microenvironments vs those benign. The bioinformatic analysis both revealed that these proteins were strictly and functionally interconnected to the lung fibrosis and proinflammation and that miR-126, 101, 486 and let-7-g were their main targets. Accordingly, we found that in lung cancer tissues and blood samples from the same set of patients here employed, miR-126 and miR-486 displayed the highest expression levels in tissue and blood, respectively.

cell biology↗

bioRxiv2017

Constrained Instruments and their Application to Mendelian Randomization with Pleiotropy

In Mendelian randomization (MR), genetic variants are used to construct instrumental variables, which enable inference about the causal relationship between a phenotype of interest and a response or disease outcome. However, standard MR inference requires several assumptions, including the assumption that the genetic variants only influence the response through the phenotype of interest. Pleiotropy occurs when a genetic variant has an effect on more than one phenotype; therefore, a pleiotropic genetic variant may be an invalid instrumental variable. Hence, a naive method for constructing instrumental variables may lead to biased estimation of the causality between the phenotype and the response. Here, we present a set of intuitive methods (Constrained Instrumental Variable methods [CIV]) to construct valid instrumental variables and perform adjusted causal effect estimation when pleiotropy exists, focusing particularly on the situation where pleiotropic phenotypes have been measured. Our approach includes an automatic and valid selection of genetic variants when building the instrumental variables. We also provide details of the features of many existing methods, together with a comparison of their performance in a large series of simulations. CIV methods performed consistently better than many comparators across four different pleiotropic violations of the MR assumptions. We analyzed data from the Alzheimers Disease Neuroimaging Initiative (ADNI) Mueller et al. (2005) to disentangle causal relationships of several biomarkers with AD progression. The results showed that CIV methods can provide causal effect estimates, as well as selection of valid instruments while accounting for pleiotropy.

genetics↗