Biology subjects

Castro, B.

Publications and source records attributed to Castro, B..

6 recordsLinked to original sources

bioRxiv2026

Physiological and anatomical leaf acclimation of understory trees subjected to a through-fall precipitation exclusion in a temperate rain forest in southern South America.

Water input is a key component of the ecosystems. Water defines the functionality, composition, and structure of biomes; therefore, any change in its availability would have an impact on ecosystem features. Moreover, a change in the water balance of an ecosystem affects its persistence as well as biochemical cycles, such as the carbon and nitrogen. Forests are ecosystems structured using high amounts of water. Thus, trees, the oldest living plants, are the prime species in these ecosystems and are the main managers of this abiotic element. Trees uptake water from the soil, store it in their biomass, and exchange it with the environment through leaf stomata. They also intercepted rainfall and fog with their canopies. All of this water is also transmitted to the entire biological diversity that inhabits these ecosystems. Any change in water input affects the web described above. The ability of trees to modify their anatomy or processes, that is, to acclimate to novel climates, is of great advantage in maintaining the characteristics of ecosystems. In this study, we took advantage of a precipitation exclusion experiment to reveal the acclimation of shade-tolerant understory trees, which will be the main component of a cold temperate rainforest in the future. We evaluated different anatomical and physiological leaf traits involved in the use of water by these species. We hypothesized that, as observed in similar experiments, species would adopt more conservative water-use strategies by adjusting their functional traits accordingly. Contrary to our hypotheses, we found that understory tree species inhabiting this temperate ecosystem will not become more conservative when using water. In minimal, but significant differences, most of the studied species displayed traits, in the precipitation exclusion treatment, that were demonstrated to be water spender, rather than conservative. We attributed these contrasting changes to root metabolism alleviation due to the flooded soils of Chiloe inhabited by these forests.

ecology↗

bioRxiv2025

Genomic and Transcriptomic Insights into the Evolution and Parasitic Strategy of the Woody-Plant Nematode Pratylenchus vulnus

The root-lesion nematode Pratylenchus vulnus parasitizes a wide range of hosts including woody perennials such as walnut (Juglans regia) and grapevine (Vitis vinifera), significantly damaging roots and reducing yields. Here, we present a high-quality, chromosome-level genome assembly of P. vulnus (61.7 Mb across six chromosomes). Comparative genomic analysis revealed high collinearity in protein-coding genes between P. vulnus and the root-knot nematode Meloidogyne graminicola, indicating a closer evolutionary relationship with this sedentary endoparasite. Large chromosomal regions in P. vulnus lack synteny with other nematode genomes, have comparatively low GC content (<30%), and are enriched in genes with unique or lineage-specific functions. Transcriptome analysis highlighted dynamic, stage-specific expressions of genes involved in parasitism, development, and metabolism. Additionally, we identified an extensive repertoire of putative effector genes and characterized lineage-specific expansions of cell wall-degrading enzyme families. Overall, these findings provide insight into the genome organization, chromosome evolution, and parasitism-related gene repertoire in a woody-plant parasitizing nematode.

plant biology↗

bioRxiv2024

Gene editing of the E3 ligase PIRE1 fine-tunes ROS production for enhanced bacterial disease resistance in tomato

Reactive oxygen species (ROS) accumulation is required for effective plant defense. Accumulation of the Arabidopsis NADPH oxidase RBOHD is regulated by phosphorylation of a conserved C-terminal residue (T912) leading to ubiquitination by the RING E3 ligase PIRE. Arabidopsis PIRE knockouts exhibit enhanced ROS production and resistance to the foliar pathogen Pseudomonas syringae. Here, we identified 170 PIRE homologs, which emerged in Tracheophytes and expanded in Angiosperms. We investigated the role of Solanum lycopersicum (tomato) PIRE homologs in regulating ROS production, RBOH stability, and disease resistance. Mutational analyses of residues corresponding to T912 in the tomato RBOHD ortholog, SlRBOHB, affected protein accumulation and ROS production in a PIRE-dependent manner. Using CRISPR-cas9, we generated mutants in two S. lycopersicum PIRE homologs (SlPIRE). SlPIRE1 edited lines (Slpire1) in the tomato cultivar M82 displayed enhanced ROS production upon treatment with flg22, an immunogenic epitope of flagellin. Furthermore, Slpire1 exhibited decreased disease symptoms and bacterial accumulation when inoculated with foliar bacterial pathogens Pseudomonas syringae and Xanthomonas campestris. However, Slpire1 exhibited similar levels of colonization as wild type upon inoculation with diverse soilborne pathogens. These results indicate that phosphorylation and ubiquitination crosstalk regulate RBOHs in multiple plant species, and PIRE is a promising target for foliar disease control. This study also highlights the pathogen-specific role of PIRE, indicating its potential for targeted manipulation to enhance foliar disease resistance without affecting root-associated interactions, positioning PIRE as a promising target for improving overall plant health.

plant biology↗

bioRxiv2024

The widely used cymoxanil fungicide impairs respiration in Saccharomyces cerevisiae via cytochrome c oxidase inhibition

Cymoxanil (CYM) is a synthetic acetamide fungicide that has been widely used to combat downy mildew diseases in grapevine cultures and late blight diseases in tomato and potato caused by the oomycetes Plasmopara viticola and Phytophthora infestans, respectively. Despite its extensive application, the biochemical mode of action of CYM remains elusive. Previous reports indicate that CYM affects growth, DNA and RNA synthesis in Phytophthora and inhibits cell growth, biomass production and respiration rate in the well-characterized fungal model Saccharomyces cerevisiae. We therefore used this model to further characterize the effect of CYM on mitochondria. We found that CYM inhibits oxygen consumption in whole cells after 3 h of exposure, which persists over time. Using isolated mitochondria, we demonstrated that CYM specifically inhibits cytochrome c oxidase (CcO) activity during oxidative phosphorylation. Based on molecular docking algorithms, we propose that CYM acts by blocking the interaction of cytochrome c (cyt c) with CcO, hampering electron transfer and inhibiting CcO catalytic activity. Although other targets cannot be excluded, our data offer valuable insights into the mode of action of CYM that can be instrumental to drive informed management of the use of this fungicide.

biochemistry↗

bioRxiv2024

The antifungal activity of cymoxanil is associated with proton pump inhibition and disruption of plasma membrane potential

Worldwide use of agrochemicals, particularly pesticides, is necessary to increase agricultural production to feed the ever-growing population. However, despite widespread use, the biochemical mode of action of many agrochemicals and their potential deleterious effects on the environment are poorly characterized. Cymoxanil (CYM) is a fungicide used to combat downy mildew diseases in grapevine cultures and late blight diseases in tomato and potato cultures caused by the oomycetes Plasmopara viticola and Phytophthora infestans, respectively. Previous reports indicate that CYM affects growth, DNA and RNA synthesis in Phytophthora and inhibits cell growth, biomass production and respiration rate in the well-characterized fungal model Saccharomyces cerevisiae. We therefore used this model to further dissect mechanisms underlying the toxicological effects of CYM. We found that CYM induced genome-wide alterations, particularly in membrane transporter systems. These alterations were associated with perturbations in lipid-raft organization and inhibition of Pma1p, leading to a decrease in plasma membrane potential and intracellular acidification. Altogether, these findings identify the plasma membrane as one of the targets of CYM and proposes a mode of action underlying its antifungal activity.

cell biology↗

bioRxiv2019

CRISPR-Cas immunity repressed by a biofilm-activating pathway in Pseudomonas aeruginosa

CRISPR-Cas systems are adaptive immune systems that protect bacteria from bacteriophage (phage) infection. To provide immunity, RNA-guided protein surveillance complexes recognize foreign nucleic acids, triggering their destruction by Cas nucleases. While the essential requirements for immune activity are well understood, the physiological cues that regulate CRISPR-Cas expression are not. Here, a forward genetic screen identifies a two-component system (KinB/AlgB), previously characterized in regulating Pseudomonas aeruginosa virulence and biofilm establishment, as a regulator of the biogenesis and activity of the Type I-F CRISPR-Cas system. Downstream of the KinB/AlgB system, activators of biofilm production AlgU (a {sigma}E orthologue) and AlgR, act as repressors of CRISPR-Cas activity during planktonic and surface-associated growth. AmrZ, another biofilm activator, functions as a surface-specific repressor of CRISPR-Cas immunity. Pseudomonas phages and plasmids have taken advantage of this regulatory scheme, and carry hijacked homologs of AmrZ, which are functional CRISPR-Cas repressors. This suggests that while CRISPR-Cas regulation may be important to limit self-toxicity, endogenous repressive pathways represent a vulnerability for parasite manipulation.

microbiology↗