Biology subjects

Azevedo, C.

Publications and source records attributed to Azevedo, C..

7 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↗

bioRxiv2024

Probabilistic Brain MR Image Transformation Using Generative Models

Brain MR image transformation, which is the process of transforming one type of MR image into another, is a critical neuroimaging task that is needed when the target image type is missing or corrupted. Accordingly, several methods have been developed to tackle this problem, with a recent focus on deep learning-based models. In this paper, we investigate the performance of the conditional version of three such probabilistic generative models, including conditional Generative Adversarial Networks (cGAN), Noise Conditioned Score Networks (NCSN), and De-noising Diffusion Probabilistic Models (DDPM). We also compare their performance against a more traditional deterministic U-Net based model. We train and test these models using MR images from publicly available datasets IXI and OASIS. For images from the IXI dataset, we conduct experiments on combinations of transformations between T1-weighted (T1), T2-weighted (T2), and proton density (PD) images, whereas for the OASIS dataset, we consider combinations of T1, T2, and Fluid Attenuated Inversion Recovery (FLAIR) images. In evaluating these models, we measure the similarity between the transformed image and the target image using metrics like PSNR and SSIM. In addition, for the three probabilistic generative models, we evaluate the utility of generating an ensemble of predictions by computing a metric that measures the variance in their predictions and demonstrate that it can be used to identify out-of-distribution (OOD) input images. We conclude that the NCSN model yields the most accurate transformations, while the DDPM model yields variance results that most clearly detect OOD inputs. We also note that while the results for the two diffusion models (NCSN and DDPM) are more accurate than those for the cGAN, the latter was significantly more efficient in generating multiple samples. Overall, our work demonstrates the utility of probabilistic conditional generative models for MR image transformation and highlights the role of generating an ensemble of outputs in identifying OOD input images.

bioengineering↗

bioRxiv2024

Inhibition of Atrial Natriuretic Peptide Clearance Reduces Myocardial Fibrosis and Improves Cardiac Function in Diabetic Rats

BackgroundNatriuretic peptides (NP) exert pleotropic effects through the recruitment of cGMP-signaling pathways depending on their bioavailability which is regulated by clearance receptors and peptidases. Here, we tested the hypothesis that increasing myocardial bioavailability of NP has a beneficial effect on heart failure. We studied the effects of a mutated NP, MANP, resistant to neprilysin in a model of diabetic cardiomyopathy characterized by a marked myocardial fibrosis. MethodsNatriuretic peptides as well as sacubritril were delivered via osmotic mini-pumps to high-fat/streptozotocin-induced type-2 diabetic (T2D) rats. Cardiac function was evaluated by echocardiography. Myocardial remodeling was studied by histological approaches, collagen phenotype and measurement of cGMP tissue concentration. Live-cell cGMP biosensing was conducted on cultured rat cardiac fibroblasts to investigate biological effects of NPs. cGMP signaling pathway was studied using various antibody arrays and biochemicals assays in cardiac tissue and cultured fibroblasts. ResultsMANP exhibits superior efficacy than ANP in reducing left ventricular dysfunction and to reduce myocardial fibrosis with less extracellular matrix deposition. In vitro, MANP and ANP similarly generated cGMP and activated PKG signaling pathway in cardiac fibroblasts, attenuating SMAD activation, collagen secretion and cell proliferation. Nevertheless, in vivo, MANP enhanced cardiac cGMP accumulation and was more potent than ANP in activating myocardial cGMP/PKG signaling and inhibiting the profibrotic SMAD pathway. Endopeptidase inhibition using sacubitril also led to cardiac cGMP accumulation and reduced myocardial fibrosis ConclusionsMyocardial bioavailability of ANP is a major determinant of peptide efficacy in reducing cardiac fibrosis and improving pump function during diabetic cardiomyopathy. Clinical PerspectiveO_ST_ABSWhat Is New?C_ST_ABSO_LIMutated atrial natriuretic peptide (MANP) resistant to neprilysin degradation outperforms wild-type ANP in reducing myocardial fibrosis and improving cardiac function in type-2 diabetes (T2D) C_LIO_LIWhile the antifibrotic effect of the two ANP isoforms involves similarly cGMP-dependent PKG signaling and inhibition of fibroblast activation, MANP enhanced cGMP myocardial concentration more importantly than ANP. C_LIO_LISacubitril that inhibits ANP degradation also reduces cardiac fibrosis through myocardial accumulation of cGMP and activation of cGMP-dependent PKG signaling pathway. C_LIO_LICardiac bioavailability of natriuretic peptides is a major determinant of their effects on myocardial fibrosis and cardiac function. C_LI What Are the Clinical Implications?O_LIMyocardial bioavailability of natriuretic peptides is crucial for mitigating cardiac fibrosis and improving cardiac function in diabetic cardiomyopathy and heart failure in general. C_LIO_LIMANP holds the potential as a new treatment modality in the management of heart failure. C_LI

physiology↗

bioRxiv2024

Genotypic variation in blueberry flower morphology and nectar reward content affects pollinator attraction in a diverse breeding population

Pollination is crucial to obtain optimal blueberry yield and fruit quality. Despite substantial investments in seasonal beekeeping services, blueberry producers consistently report suboptimal pollinator visitation and fruit set in some cultivars. Flower morphology and floral rewards are among the key factors that have shown to contribute to pollinator attraction, however little is known about their relative importance for improving yield in the context of plant breeding. Clarifying the relationships between flower morphology, nectar reward content, pollinator recruitment, and pollination outcomes, as well as their genetic components, can inform breeding priorities for enhancing yield. In the present study, we measured ten flower and nectar traits and indices of successful pollination, including fruit set, seed count, and fruit weight in 38 southern highbush blueberry genotypes. Additionally, we assessed pollinator visitation frequency and foraging behavior over two growing seasons. Several statistical models were tested to optimize the prediction of pollinator visitation and pollination success, including partial least squares, BayesB, ridge-regression, and random forest. Random forest models obtained high predictive abilities for pollinator visitation frequency, with values of 0.54, 0.52, and 0.66 for honey bee, bumble bee, and total pollinator visits, respectively. The BayesB model provided the most consistent prediction of fruit set, fruit weight, and seed set, with predictive abilities of 0.07, -0.08, and 0.42, respectively. Variable importance analysis revealed that genotypic differences in nectar volume had the greatest impact on honey bee and bumble bee recruitment, although preferences for flower morphological traits varied depending on the foraging task. Flower density was a major driving factor attracting nectar-foraging honey bees and bumble bees, while pollen-foraging bumble bees were most influenced by flower accessibility, specifically corolla length and the length-to-width ratio. Corolla length and the length-to-width ratio were also identified as the main predictors of fruit set, fruit weight, and seed count, suggesting that bumble bees and their foraging preferences may play a pivotal role in fruit production. Moderate to high narrow-sense heritability values (ranging from 0.30 to 0.77) were obtained for all floral traits, indicating that selective breeding efforts may enhance cultivar attractiveness to pollinators.

plant biology↗

bioRxiv2020

The smORF-containing gene mille-pattes is required for moulting and Trypanosoma cruzi metacyclogenesis in the Chagas disease vector Rhodnius prolixus

Chagas disease is estimated to affect 8 million people worldwide and is responsible for circa 10,000 deaths in Latin America every year. Vector control has been developed as the main strategy to control disease spreading. The identification of new targets is essential, and genes containing small open reading frames (smORFs - < 100 amino acids) are present as hundreds of putative new candidate targets in insect genomes. Here, we show that the prototypic smORF containing gene mille-pattes/polished-rice/tarsalless (mlpt/pri/tal) is essential for post-embryonic development of the kissing bug Rhodnius prolixus and for the metacyclogenesis of the Trypanosoma cruzi parasite during nymphal stages. Injection of double-stranded RNA against mlpt (Rp-dsmlpt) during nymphal stages leads to a plethora of phenotypes which impairs post-embryonic development. First, nymphs of fourth or fifth stage injected with Rp-dsmlpt do not moult. Second, vector digestive physiology is largely modified, and haemozoin is significantly increased in the posterior midgut of Rp-dsmlpt nymphs. Third, Rp-mlpt knockdown inhibits the metacyclogenesis of Trypanosoma cruzi, the etiologic agent of Chagas disease. Thus, our study provides the first evidence of a smORF-containing gene regulating vector physiology, parasitic cycle and disease transmission.

molecular biology↗

bioRxiv2019

Implanted Nerve Electrical Stimulation allows to Selectively Restore Hand and Forearm Movements in Patients with a Complete Tetraplegia

BackgroundFunctional Electrical Stimulation (FES) is used for decades in rehabilitation centers. For patients with a spinal cord injury (SCI), FES can prevent muscular atrophy, reduce spasticity and/or restore limb movements. To this last aim, FES external devices can be used, but elicit imprecise movements. FES implanted devices used neuromuscular stimulation and required implantation of one electrode for each site (muscle) to stimulate, an heavy surgical procedure and 10 times more electrical charges than nerve stimulation. Moreover, complications related to the numerous implanted components could appear over time. The purpose of this work is to evaluate whether a multi-contact nerve cuff electrode can selectively activate forearm and hand muscles and restore functional movements in patient with a complete tetraplegia. MethodsA 12-contacts cuff electrode was designed to selectively activate, without damage it, multi fascicular peripheral nerve (1). Six subjects rwith at least one extensor or one flexor muscle stimulable by surface electrical stimulation, have been enrolled into the study. During the surgical procedure, radial or median nerve was stimulated through up to 35 different configurations of stimulation at an intensity up to 2.1 mA (25 Hz, pulse width 250 {micro}s, inter-pulse 100 {micro}s). Surface electrodes were positioned upon the forearm to record compound muscle action potentials elicited by nerve electrical stimulation. Recruitments curves and videos were recorded. ResultsThe multicontact cuff electrode allowed us to selectively activate group of muscles to produce multiple, independent and functional hand and forearm movements in persons with tetraplegia. A surface electrical stimulation did not allow all those movements.

clinical trials↗