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InstructThe latest webinar in the Instruct-ERIC Structure Meets Function series this month includes speakers from Latin America, who have attended Instruct-ERIC Training courses with funding and support from the EU-CELAC Working Group. The work is also linked with Instruct's work with the EU-LAC ResInfra Plus project.
The webinar series offers an insight into the very cutting edge of structural biology research, utilising the latest techniques available through Instruct-ERIC facilities and centres.
This month we have two speakers from Latin America, with which Instruct has had a long collaboration. The first speaker will be María Eugenia Flores Giubi of Universidad Nacional de Asunción, Paraguay, who visited colleagues in IBS Grenoble, Instruct-FR2. Second, we will hear from Julio César Gonzalez Olvera of Universidad Tecnológica de Querétaro, Mexico, outlining their research and connection with CEITEC, part of Instruct-CZ.
Moderator: Lionel Imbert, IBS Grenoble
Speaker: Kathrin Megerle, DLR
Talk Title: EU-LAC ResInfra Plus Project
Speaker: María Eugenia Flores Giubi, Universidad Nacional de Asunción, Paraguay
Talk Title: The Role of Secondary Metabolites and Proteins in Macrophomina phaseolina Pathogenesis
Abstract: Macrophomina phaseolina is a necrotrophic soil-borne fungus that infects a wide range of economically important crops, including soybean, sesame, jute, sorghum, maize, and sunflower. Despite its significant impact on agriculture, the molecular mechanisms driving its pathogenicity remain poorly understood.
A key aspect of M. phaseolina virulence is the secretion of toxic secondary metabolites such as phaseolinone, botriodiplodin, phaseocyclopentanones A and B, and guignardone A. While some of these metabolites exhibit phytotoxic or antimicrobial properties, their precise biosynthetic pathways and roles in infection remain unclear. Additionally, certain fungal metabolites can influence plant development and crop yield in a hormone-like manner, further complicating their pathogenic interactions.
To colonize host plants, M. phaseolina must breach the plant cell wall, which consists mainly of cellulose, hemicellulose, and pectin. The fungus achieves this by secreting cell wall-degrading enzymes (CWDEs), which are classified as carbohydrate-active enzymes (CAZymes). While CAZymes facilitate host invasion, some also help the fungus evade plant immune responses by modifying or sequestering chitin, a key microbe-associated molecular pattern (MAMP) recognized by plants.
Gene expression studies suggest that several protein-coding genes are induced during infection, highlighting their potential role in fungal virulence. Additionally, in vitro studies have identified differentially secreted metabolites, such as (R)-mellein, (3R,4R)-hydroximellein, and (-)-botryodiplodin, but further research is needed under conditions that mimic natural infection.
Understanding the mechanisms of metabolite toxicity and host cell wall degradation by M. phaseolina is crucial for developing effective biocontrol strategies and improving crop resistance to this devastating pathogen.
Speaker: Julio César Gonzalez Olvera, Universidad Tecnológica de Querétaro, Mexico
Talk Title: Studies on the protonation of 5-methylcytosine groups in double-stranded DNA polynucleotides
Abstract: Recent investigations (González-Olvera et al., 2018, 2022), conducted in collaboration with CEITEC, revealed a pH-dependent transition in double-stranded model oligodeoxyribonucleotides containing centrally located guanine:5-methylcytosine (G:MeC) base pairs, which was interpreted in terms of a protonation of the O2-position of the 5-methylcytosine (MeC) group, without breaking the G:MeC pair. This transition, observed by UV-absorption spectroscopy as well as by NMR spectroscopy, occurred at around neutral pH, under near-physiological conditions, raising the possibility that double-stranded DNA in its natural state may have a significant proportion of its Me C residues protonated at O2. 5-Methylcytosines bases are involved in various control regions in DNA, silencing and repression of gene expression, cell differentiation processes, RNA postprocessing and splicing, regulation of non-coding RNA, etc. Therefore, the issue of an O2-protonation of these bases in biological DNA is of importance for our understanding of DNA function at the molecular level. In order to examine the postulated O2-protonation of these bases in biological DNA, we propose to investigate, with the use of model oligonucleotides, the dependence of the O2-protonation at Me C on the chain length of the model duplexes, the temperature, and the type and concentration of the salt in the solution. Additionally, the effect of different nearest-neighbour bases and the type of nucleic acid on the O2-protonation on Me C, will be examined. For this purpose, several techniques will be used, namely UV absorption and NMR spectroscopies, differential scanning calorimetry (DSC), isothermal titration calorimetry (ITC), polyacrylamide gel electrophoresis (PAGE), as well as theoretical calculations.
