Biology subjects

Lopez-Llorca, L. V.

Publications and source records attributed to Lopez-Llorca, L. V..

7 recordsLinked to original sources

bioRxiv2026

Species-dependent antifungal profiles reveal stronger yeast inhibition by chitosan than by a sulfate-containing polysaccharide-rich extract from Jania adhaerens

Yeast infections are becoming an increasing public health concern, mainly due to the spread of opportunistic species and the emergence of strains resistant to commonly used antifungal drugs. Marine resources are a promising source of bioactive compounds, including polysaccharides and other biopolymers with potential antifungal applications. In this study, a sulfate-containing polysaccharide-rich extract was obtained from the red alga Jania adhaerens and chemically characterized. Its antifungal activity was compared with that of a commercial chitosan formulation against clinically relevant yeasts, including species of Candida, Cryptococcus, 'Clavispora, Naganishia and Trichosporon. Growth kinetics were monitored in liquid medium over 24 h, and antifungal activity was evaluated through growth rate analysis, growth inhibition at 20 h and susceptibility clustering. The polysaccharide extract showed moderate but consistent growth inhibition, with the strongest effects observed at 5 mg mL-1. Maximum growth inhibition reached 60.9% in Cryptococcus deuterogattii and 59.8% in Candida albicans, although no complete inhibition was observed within the tested concentration range. In contrast, chitosan showed a stronger antifungal effect, with minimal inhibitory concentration (MIC) values between 10 and 20 {micro}g mL-1 in several species and maximum inhibition values above 80% in the most susceptible yeasts. However, C. albicans showed marked resistance to chitosan, with inhibition below 12%. K-means clustering confirmed distinct susceptibility profiles between treatments, supporting a species-dependent response. Overall, these results highlight marine-derived biopolymers as promising antifungal candidates and show that chitosan and algal sulphated polysaccharides produce distinct, species-dependent antifungal profiles.

microbiology↗

bioRxiv2024

Chitosan reduces naturally occurring plant pathogenic fungi and increases nematophagous fungus Purpureocillium in field soil

Chitosan reduced soil pH, conductivity (CE) and cation exchange capacity (CEC) in pots when applied at field capacity. However, chitosan did not affect these soil physicochemical properties, when applied monthly to agricultural fields. Chitosan did not affect field respiration. Increases in field soil respiration found in chitosan plots, especially in spring-midsummer, were not significant. Although, no differences in soil mineral nitrogen were found, chitosan influenced field soil microbiota. Metabarcoding showed chitosan significantly modifies fungal genera composition of ecologically managed field soil. On the contrary, chitosan caused no significant differences in bacterial taxa composition of field soil. Chitosan coacervates increase naturally occurring nematophagous fungus Purpureocillium in soil respect to chitosan solution treated soil and untreated controls. Besides chitosan reduces inoculum of plant pathogenic fungi Alternaria and Fusarium in field soil. Soil microbial co-occurrence network analysis clustering coefficient (CC) for ITS+V1-V2 regions show that the nematophagous fungus Pochonia promoted network clustering into modules. In addition, CC in ITS+V3-V4 regions show that the nematode trapping-fungus Orbilia and bacteria belonging to Acidimicrobiales and Cytophagales also significantly contributed to microbial network clustering in field soil. Our results show that chitosan coacervates increase soil nematophagous microbiota and that both nematode egg-parasites and trapping-fungi help to structure soil microbiota.

ecology↗

bioRxiv2024

Chitosan induces salicylic acid local and systemically in banana plants and reduces colonization by the pathogen Fusarium oxysporum f. sp. cubense TR4

Banana (Musa spp.) is essential for food security. For its clonality is highly susceptible to pests and diseases. The wilt fungus Fusarium oxysporum f. sp. cubense Tropical Race 4 (FocTR4) threatens banana production worldwide. We notice that chitosan protects banana from biotic stress. Chitosan, a plant defence elicitor with antimicrobial activity, triggers salicylic acid (SA) and methyl salicylate biosynthesis and induces systemic acquired resistance (SAR) genes, mainly flavin-dependent monooxygenase 1 (FMO1), in banana. Chitosan promotes root exudation of SA and emission of methyl salicylate (MeSA). Banana germplasm, Petit Naine, Gros Michel, Enzirabahima, Yangambi Km5 and Foconah banana differ in their response to chitosan. Chitosan induces, in Foc resistant Yangambi Km5, ca. 7-fold FMO1. Preventive chitosan treatments together with the endophytic biocontrol fungus Pochonia chlamydosporia strain 123 reduce (ca. 4-fold) colonization of banana roots by FocTR4. Therefore, chitosan and beneficial endophytes can help to manage sustainably FocTR4 in banana.

plant biology↗

bioRxiv2020

Volatile organic compounds from entomopathogenic and nematophagous fungi, repel banana black weevil (Cosmopolites sordidus)

Fungal Volatile Organic Compounds (VOCs) repel banana black weevil (BW), Cosmopolites sordidus (Germar, 1824), the key-pest of banana (Musa spp.). The entomopathogens Beauveria bassiana (Bb1TS11) and Metarhizium robertsii (Mr4TS04) were isolated from banana plantation soils using an insect bait. Bb1TS11 and Mr4TS04 were pathogenic to BW adults. Bb1TS11, Bb203 (from infected palm weevils), Mr4TS04 and the nematophagous fungus Pochonia clamydosporia (Pc123), were tested for VOCs production. VOCs were identified by Gas Chromatography/Mass Spectrometry - Solid-Phase Micro Extraction (GC/MS-SPME). GC/MS-SPME identified a total of 97 VOCs in all strains tested. Seven VOCs (C1 - C7) were selected for their abundance or previous record as insect repellents. BW starved adults in the dark showed the highest mobility to banana corm in olfactometry bioassays. C7, produced by all fungal strains, is the best BW repellent (p<0.05), followed by C5. The rest of VOCs have a milder repellency to BW. C1 and C2 (known to repel palm weevil) block the attraction of banana corm and BW pheromone to BW adults in bioassays. Therefore, VOCs from biocontrol fungi can be used in future studies for biomanagement of BW in the field.

microbiology↗

bioRxiv2020

Worldwide strains of the nematophagous fungus Pochonia chlamydosporia are endophytic in banana roots and promote plant growth

The biocontrol fungus, Pochonia chlamydosporia, colonizes endophytically banana roots. Root hairs and root surface were found colonize by the fungus using a stable GFP transformant. Hyphal penetration of root cells was also observed. Spores of P. chlamydosporia 123, significantly increase root and leaf length and weight in banana plantlets (Musa acuminata cv. Dwarf Cavendish) in growth chamber experiments 30 days post-inoculation (dpi). In greenhouse 8L pot experiments, P. chlamydosporia 123 spore inoculation significantly increases leaf and root length and leaf weight in banana plants (75 dpi). Spore inoculation of P. chlamydosporia strains from worldwide origin (Pc21 Italy, Pc123 Spain, Pc399 China, and Pccat Cuba), significantly increases root, corm and leaf length and weight in banana plantlets. Pc21 was the best colonizer of banana roots. Consequently, this strain significantly increases most banana root and leaf length. Root colonization by P. chlamydosporia was also detected using cultural techniques and qPCR.

plant biology↗

bioRxiv2020

Chitosan induces plant hormones and defences in tomato root exudates

In this work, we use electrophysiological and metabolomic tools to determine the role of chitosan as plant defence elicitor in soil for preventing or manage root pests and diseases sustainably. Root exudates include a wide variety of molecules that plants and root microbiota use to communicate in the rhizosphere. Tomato plants were treated with chitosan. Root exudates from plants were analysed at 3, 10, 20 and 30 days after planting (dap). We found, using High Performance Liquid Chromatography (HPLC) and Excitation Emission Matrix (EEM) fluorescence, that chitosan induces plant hormones, lipid signalling and defence compounds in tomato root exudates, including phenolics. High doses of chitosan induce membrane depolarization and affect membrane integrity. 1H-NMR showed the dynamic of exudation, detecting the largest number of signals in 20 dap root exudates. Root exudates from plants irrigated with chitosan inhibit ca. 2-fold growth kinetics of the tomato root parasitic fungus Fusarium oxysporum f. sp. radicis-lycopersici. and reduced ca. 1.5-fold egg hatching of the root-knot nematode Meloidogyne javanica. One-sentence summaryChitosan depolarizes plasma membrane of root cells, causing the secretion of hormones, lipid signalling and plant defence compounds, including phenolics. These root exudates inhibit soil-borne pathogens.

plant biology↗

bioRxiv2020

Chitosan inhibits septin-mediated plant infection by the rice blast fungus Magnaporthe oryzae in a Protein Kinase C and Nox1 NADPH oxidase-dependent manner

O_LIChitosan is a partially deacetylated linear polysaccharide composed of {beta}-1,4-linked units of D-glucosamine and N-acetyl glucosamine. As well as acting as a structural component of fungal cell walls, chitosan can be applied as a potent antifungal agent. However, the mode-of-action of chitosan in fungal pathogens is poorly understood. C_LIO_LIHere, we report that chitosan is effective for control of rice blast disease. Chitosan application impairs growth of the blast fungus Magnaporthe oryzae and has a pronounced effect on appressorium-mediated plant infection. Chitosan inhibits septin-mediated F-actin re-modelling at the appressorium pore, thereby preventing re-polarisation of the infection cell and rice leaf cuticle penetration. C_LIO_LIWe found that chitosan causes plasma membrane permeabilization of M. oryzae and affects NADPH oxidase-dependent synthesis of reactive oxygen species, essential for septin ring formation and fungal pathogenicity. Our data further show that the toxicity of chitosan to M. oryzae requires the protein kinase C-dependent cell wall integrity pathway and the Nox1 NADPH oxidase. A conditionally lethal, analogue (PP1)-sensitive mutant of Pkc1 is partially remediated for growth in the presence of chitosan and PP1, while {Delta}nox1 mutants increase their glucan/chitin cell wall ratio, rendering them resistant to chitosan. C_LIO_LITaken together, our data show that chitosan is a potent fungicide for control of the rice blast fungus which involves the cell wall integrity pathway, disrupts plasma membrane and inhibits septin-mediated plant infection. C_LI

plant biology↗