Biology subjects

Tresguerres, M.

Publications and source records attributed to Tresguerres, M..

14 recordsLinked to original sources

bioRxiv2026

Elevated environmental CO2 stimulates photosynthesis and induces differential oxidative responses in two Caribbean reef-building coral species

Reef-building corals maintain intracellular photosymbiosis with dinoflagellate algae, allowing them to use photosynthetic products as metabolic fuel. Carbon dioxide (CO2) is a key substrate for photosynthesis, but its rapid increase in the global ocean due to anthropogenic emissions (known as ocean acidification) may disrupt coral symbiosis. We examined the effects of elevated CO2 on photosynthetic O2 production, oxidative damage, and antioxidant systems in the Caribbean reef-building corals Porites astreoides and Orbicella franksi. Coral colonies collected at 3m depth in Bocas del Toro (Panama) were exposed to control (390 {micro}atm CO2, pH ~8.00) or elevated CO2 ({approx}1,060 {micro}atm CO2, pH {approx}7.70) conditions in outdoor flow-through aquaria for 10 days. Flowing seawater had higher O2O2 concentrations in elevated CO2 tanks, with the largest differences at higher irradiance. Microsensor measurements confirmed that acute and chronic exposure to elevated CO2 significantly stimulated photosynthetic O2 production in both species. Despite increased O2 production. neither species showed significant changes in lipid peroxidation, reduced glutathione, or superoxide dismutase, catalase, and glutathione-S-transferase activities. Protein oxidation was unchanged in O. franksi but significantly decreased in P. astreoides. These results are consistent with partial relief of carbon limitation in P. astreoides symbionts under elevated CO2, potentially improving photosynthetic efficiency and decreasing reactive oxygen species production. These findings support the resilience of P. astreoides to OA and suggest that elevated CO2 may increase daytime O2 levels on future reefs, with implications for the aerobic metabolism of reef organisms.

physiology↗

bioRxiv2026

Integrating single-cell and bulk transcriptomes identifies neuronal heat-stress-associated candidate genes in a reef-building coral

Cell-type-specific molecular responses are obscured in bulk RNA sequencing, whereas generating matched single-cell datasets across environmental conditions remains costly and technically challenging, particularly in non-model organisms. Here, we present a workflow that integrates existing bulk and single-cell RNA-seq resources to prioritize cell-type-associated environmental-response genes. We demonstrate the workflow by examining heat-stress-associated neuronal genes in the reef-building coral Stylophora pistillata. Neuronal genes were first identified based on cell type-specific expression in single-cell transcriptomic data and then intersected with differentially expressed genes from bulk RNA-seq datasets under heat-stress. In parallel, we applied a deconvolution approach to infer cell type-specific expression changes directly from bulk data, independently capturing neuronal transcriptional responses. This integrated pipeline reduced thousands of heat-responsive genes previously identified in bulk RNA-seq studies to nine heat-associated, neuron-enriched candidates. Eight of the nine candidates showed their highest mean expression in the same neuronal subcluster. Targeted sequence-based characterization supported the identification of a TRPA-family ion channel, two calmodulin/centrin-family Ca2+-binding proteins, and a Class A/rhodopsin-like GPCR of unresolved ligand specificity. Two additional candidates were predicted secreted proteins belonging to conserved coral protein families, while the molecular functions of the remaining candidates remained unresolved. Their coordinated regulation suggests heat-associated remodeling of neuronal sensory and intracellular signaling processes. Our workflow provides a scalable framework for extracting cell type-associated molecular responses from existing transcriptomic resources and prioritizing candidates for further investigation. More broadly, it offers a generalizable strategy for investigating cell type-specific gene expression responses across organisms, cell types, and environmental conditions without requiring new single-cell datasets.

molecular biology↗

bioRxiv2026

Co-option of Lysosomal Machinery for Biomineralization

Biomineralization evolved repeatedly across animals, resulting in novel strategies for buoyancy, locomotion, and defense. Sponges are the only metazoans that build a silica-based skeleton and the mechanisms underlying their biosilicification are relatively understudied compared to other major silicifiers. Here, we show that in freshwater sponges, cells specialized for biosilicification, termed sclerocytes, highly express lysosomal-associated genes, including the V-H+-ATPase (VHA) proton pump, oculocutaneous albinism type 2 (OCA2) anion channels, cathepsins, silicateins, TMEM55A/B, TMEM192, TMEM199, and other proteins involved in lysosomal maintenance and degradation. We demonstrate that VHA protein localizes to the sclerocyte silica deposition vesicle (SDV) and that VHA-dependent SDV acidification is essential for silica spicule formation. This function mirrors the role of VHA in diatom biosilicification and in biocalcification across a broad sweep of taxa. We also found that genes homologous to the plant silicon efflux transporter Lsi2 are highly upregulated in sclerocytes and confirmed their localization using Hybridization Chain Reaction Fluorescence In Situ Hybridization (HCR-FISH). These results corroborate phylogenetic and transcriptomic evidence that Lsi2 homologs are involved in sponge silicic acid transport. Data mining of previous studies revealed many of the sponge sclerocyte lysosomal-associated genes have been correlated with biomineralization across eukaryotes, including coccolithophores, bryozoans, crustaceans, mollusks, and mammals. As detoxification was a likely driver for the evolution of biomineralization, we propose that lysosomal machinery aided in detoxification by allowing sponges to sequester Si in acidified compartments to prevent its catastrophic intracellular precipitation. This lysosomal toolkit was likely independently co-opted for the formation of biomineralized structures in multiple species.

cell biology↗

bioRxiv2024

Bacteria-powered living materials enable coral larval settlement

The global decline of coral reefs calls for new strategies to rapidly restock coral populations and maintain ecosystem functions and services. Low recruitment success on degraded reefs hampers coral sexual propagation and contributes to limited genetic diversity and reef resilience. Here, we introduce a living bacteria-powered reef ink (Brink) for assisted coral recruitment. Brink can be rapidly applied to restoration substrates via photopolymerization, and it has been formulated to cultivate two settlement-inducing bacterial strains (Cellulophaga lytica and Thalassotalea euphylliae). Settlement assays performed with broadcast spawning (Montipora capitata) and brooding (Pocillopora acuta) Indo-Pacific corals showed that Brink-coated substrates increased settlement >5-fold compared to uncoated control substrates. Brink can be applied as a coating or 3D bioprinted, leading to various potential applications for integration with reef engineering. Our approach underscores the potential of using functional living materials for augmented ecosystem engineering and reef rehabilitation. SynopsisThis study introduces a functional and sustainable bacteria-powered living material that enhances coral settlement, promoting coral reef rehabilitation and ecosystem resilience.

bioengineering↗

bioRxiv2024

Advancing coral micropropagation for coral restoration and reef engineering

In the face of escalating threats posed by human-induced climate change, urgent attention to coral reef restoration is imperative due to ongoing reef degradation. Here, we explored the potential of generating coral micropropagates as a tool to rapidly generate coral tissue for reef restoration and reef engineering. We developed a hypersalinity-induced polyp bailout protocol and a simple attachment device to support the growth of micropropagates on commonly used restoration substrates. We found that hypersalinity induction, at a rate of < 1 ppt hr-1, produced healthy micropropagates of the coral Stylophora pistillata. The highest attachment success ([~]74%) was achieved in CaCO3 substrate devices, which outperformed PVC ([~]5%) and Portland cement ([~]48%). Settled micropropagates displayed rapid growth rates on both CaCO3 (0.037 mm2/day {+/-} 0.002 SE) and PVC (0.057 mm2/day {+/-} 0.008 SE) substrates, while Portland cement induced tissue degradation. Our study provides a detailed methodology for reliably generating, attaching, and growing coral micropropagates and underscores the potential of polyp bailout as a viable technique supporting coral restoration and reef engineering efforts.

physiology↗

bioRxiv2024

Gill ionocyte remodeling mediates blood pH regulation in rockfish (Sebastes diploproa) exposed to environmentally relevant hypercapnia

Marine fishes excrete excess H+ using basolateral Na+/K+-ATPase (NKA) and apical Na+/H+-exchanger 3 (NHE3) in gill ionocytes. However, the mechanisms that regulate H+ excretion during exposure to environmentally relevant hypercapnia (ERH) remain poorly understood. Here, we explored transcriptomic, proteomic, and cellular responses in gills of juvenile splitnose rockfish (Sebastes diploproa) exposed to three days of ERH conditions (pH [~]7.5; [~]1,600 atm pCO2). Blood pH was fully regulated at [~]7.75 despite a lack of significant changes in gill (1) mRNAs coding for proteins involved in blood acid-base regulation, (2) total NKA and NHE3 protein abundance, and (3) ionocyte density. However, ERH-exposed rockfish demonstrated increased NKA and NHE3 abundance on the ionocyte plasma membrane coupled with wider apical membranes and greater extension of apical microvilli. The observed gill ionocyte remodeling is consistent with enhanced H+ excretion that maintains blood pH homeostasis during exposure to ERH and does not necessitate changes at the expression or translation levels. These mechanisms of phenotypic plasticity may allow fishes to regulate blood pH during environmentally relevant acid-base challenges, and thus have important implications for both understanding how organisms respond to climate change and for selecting appropriate metrics to evaluate its impact on marine ecosystems.

physiology↗

bioRxiv2023

Immunohistochemical and ultrastructural characterization of the inner ear epithelial cells of splitnose rockfish (Sebastes diploproa)

The inner ear of teleost fish regulates the ionic and acid-base chemistry and secretes the protein matrix of the endolymph to facilitate otolith biomineralization, which are used to maintain vestibular and auditory functions. The otolith is biomineralized in a concentric ring pattern corresponding to seasonal growth, and this CaCO3 polycrystal has become a vital aging and life-history tool for fishery managers, ecologists, and conservation biologists. Moreover, biomineralization patterns are sensitive to environmental variability including climate change, thereby threatening the accuracy and relevance of otolith-reliant toolkits. However, the cellular biology of the inner ear is poorly characterized, which is a hurdle for a mechanistic understanding of the underlying processes. This study provides a systematic characterization of the cell types in the inner ear of splitnose rockfish (Sebastes diploproa). Scanning electron microscopy revealed the apical morphologies of the six inner ear cell types. Additionally, immunostaining and confocal microscopy characterized the expression and subcellular localization of the proteins Na+/K+-ATPase, carbonic anhydrase, V-type H+-ATPase, Na+-K+-2Cl--Co-Transporter, Otolith Matrix Protein 1, and Otolin-1 in six inner ear cell types bordering the endolymph. This fundamental cytological characterization of the rockfish inner ear epithelium illustrates the intricate physiological processes involved in otolith biomineralization, and highlights how greater mechanistic understanding is necessary to predict their multi-stressor responses to future climate change.

physiology↗

bioRxiv2022

The hologenome of Osedax frankpressi reveals the genetic interplay for the symbiotic digestion of vertebrate bone

The marine annelid Osedax has evolved a unique heterotrophic symbiosis that allows it to feed exclusively on sunken bones. Yet, the genetic and physiological principles sustaining this symbiosis are poorly understood. Here we show that Osedax frankpressi has a small, AT-rich genome shaped by extensive gene loss. While the Oceanospirillales endosymbiont of Osedax is enriched in genes for carbohydrate and nitrogen metabolism, O. frankpressi has undergone genetic changes to accommodate bone digestion, including the expansion of matrix metalloproteases, and a loss of pathways to synthesize amino acids that are abundant in collagen. Unlike other symbioses, however, innate immunity genes required to acquire and control the endosymbionts are reduced in O. frankpressi. These findings reveal Osedax has evolved an alternative genomic toolkit to bacterial symbiosis where host-symbiont co-dependence has favoured genome simplicity in the host to exploit the nutritionally unbalanced diet of bones. TeaserGenome reduction and adaptations for collagen digestion underpin the symbiosis of Osedax worms to exploit decaying bones.

genomics↗

bioRxiv2022

Optimizing immunostaining of archival fish samples to enhance museum collection potential

Immunohistochemistry (IHC) is a powerful biochemical technique that uses antibodies to specifically label and visualize proteins of interests within biological samples. However, fluid-preserved specimens within natural history collection often use fixatives and protocols that induce high background signal (autofluorescence), which hampers IHC as it produces low signal-to-noise ratio. Here, we explored techniques to reduce autofluorescence using sodium borohydride (SBH), citrate buffer, and their combination on fish tissue preserved with paraformaldehyde, formalin, ethanol, and glutaraldehyde. We found SBH was the most effective quenching technique, and applied this pretreatment to the gill or skin of 10 different archival fishes - including specimens that had been preserved in formalin or ethanol for up to 65 and 37 years, respectively. The enzyme Na+/K+-ATPase (NKA) was successfully immunostained and imaged using confocal fluorescence microscopy, allowing for the identification and characterization of NKA-rich ionocytes essential for fish ionic and acid-base homeostasis. Altogether, our SBH-based method facilitates the use of IHC on archival samples, and unlocks the historical record on fish biological responses to environmental factors (such as climate change) using specimens from natural history collections that were preserved decades to centuries ago. HighlightsO_LISodium borohydride pretreatment reduced aldehyde-induced autofluorescence C_LIO_LISuccessfully immunostained archival samples of various fixative and fixation time C_LIO_LILarval fish that was formalin-fixed for 63-65 years was successfully immunostained C_LI

biochemistry↗

bioRxiv2022

A proton pump enhancing photosynthesis links phagocytosis to marine phytoplankton symbiogenesis

Diatoms, dinoflagellates, and coccolithophorids are the dominant groups of marine eukaryotic phytoplankton collectively responsible for the majority of primary production in the ocean1. These phytoplankton contain additional intracellular membranes around their chloroplasts derived from ancestral engulfment of red microalgae by unicellular heterotrophic eukaryotes that led to secondary endosymbiosis2. This symbiogenesis hypothesis for the origin of modern secondary endosymbiotic phytoplankton is supported by a wealth of palaeontologic, morphologic, and genomic evidence3-6. However, the selectable evolutionary advantage of these membranes and the physiological significance for extant phytoplankton are unknown. We report that the proton-pumping enzyme V-type H+-ATPase (VHA), ubiquitously used in eukaryotic intercellular digestion, is localized around the chloroplasts of centric diatoms and that VHA-activity significantly enhances photosynthesis over a wide range of oceanic irradiances. Similar results in pennate diatoms, dinoflagellates, and coccolithophorids, but not green or red microalgae, imply a mechanism resulting from the co-option of phagocytic VHA activity into a carbon concentrating mechanism that is common to secondary endosymbiotic phytoplankton. Furthermore, analogous VHA-dependent mechanisms in extant photosymbiotic marine invertebrates7-9 provide functional evidence for an adaptive advantage throughout the transition from endosymbiosis to symbiogenesis. Our results suggest that VHA-dependent enhancement of photosynthesis contributes at least 7% of primary production in the ocean, providing an example of a symbiosis-derived evolutionary innovation with global environmental implications.

evolutionary biology↗

bioRxiv2021

Elucidating the acid-base mechanisms underlying otolith overgrowth in fish exposed to ocean acidification

Over a decade ago, ocean acidification (OA) exposure was reported to induce otolith overgrowth in teleost fish. This phenomenon was subsequently confirmed in multiple species; however, the underlying physiological causes remain unknown. Here, we report that splitnose rockfish (Sebastes diploproa) exposed to ~1,600 atm pCO2 (pH ~7.5) were able to fully regulated the pH of both blood and endolymph (the fluid that surrounds the otolith within the inner ear). However, while blood was regulated around pH 7.80, the endolymph was regulated around pH ~8.30. These different pH setpoints result in increased pCO2 diffusion into the endolymph, which in turn leads to proportional increases in endolymph [HCO3-] and [CO32-]. Endolymph pH regulation despite the increased pCO2 suggests enhanced H+ removal. However, a lack of differences in inner ear bulk and cell-specific Na+/K+-ATPase and vacuolar type H+-ATPase protein abundance localization pointed out to activation of preexisting ATPases, non-bicarbonate pH buffering, or both, as the mechanism for endolymph pH-regulation. These results provide the first direct evidence showcasing the acid-base chemistry of the endolymph of OA-exposed fish favors otolith overgrowth, and suggests that this phenomenon will be more pronounced in species that count with more robust blood and endolymph pH regulatory mechanisms.

physiology↗

bioRxiv2021

Red blood cells protect oxygen transport with adrenergic sodium-proton exchangers in hypoxic and hypercapnic white seabass

White seabass (Atractoscion nobilis) are increasingly experiencing periods of low oxygen (O2; hypoxia) and high carbon dioxide (CO2, hypercapnia) due to climate change and eutrophication of the coastal waters of California. Hemoglobin (Hb) is the principal O2 carrier in the blood and in many teleost fishes Hb-O2 binding is compromised at low pH; however, the red blood cells (RBC) of some species regulate intracellular pH with adrenergically-stimulated sodium-proton-exchangers ({beta}-NHE). We hypothesized that RBC {beta}-NHEs in white seabass are an important mechanism that can protect the blood O2-carrying capacity during hypoxia and hypercapnia. We determined the O2-binding characteristics of white seabass blood, the response of RBCs to adrenergic stimulation, and quantified the protective effect of {beta}-NHE activity on Hb-O2 saturation. White seabass had typical teleost Hb characteristics, with a moderate O2 affinity (PO2 at half-saturation; P50 2.9 kPa) that was highly pH-sensitive (Bohr coefficient -0.92; Root effect 52%). The presence of RBC {beta}-NHEs was confirmed by functional, molecular and bioinformatic data and super-resolution imaging revealed, for the first time, the subcellular location of {beta}-NHE protein in vesicle-like structures and on the RBC membrane, and its translocation after adrenergic stimulation. The activation of RBC {beta}-NHEs increased Hb-O2 saturation by [~]8% in normoxia at 1 kPa PCO2, and by up to 20% in hypoxia. Our results confirm that RBC {beta}-NHE activity in white seabass has great potential to protect arterial O2 transport in environmentally relevant conditions of hypoxia and hypercapnia, but also reveal a potential vulnerability of fish to combinations of these stressors.

physiology↗

bioRxiv2021

Rapid blood acid-base regulation by European sea bass (Dicentrarchus labrax) in response to sudden exposure to high environmental CO2

Fish in coastal ecosystems can be exposed to acute variations in CO2 that can approach 1 kPa CO2 (10,000 atm). Coping with this environmental challenge will depend on the ability to rapidly compensate the internal acid-base disturbance caused by sudden exposure to high environmental CO2 (blood and tissue acidosis); however, studies about the speed of acid-base regulatory responses in marine fish are scarce. We observed that upon exposure to ~1 kPa CO2, European sea bass (Dicentrarchus labrax) completely regulate erythrocyte intracellular pH within ~40 minutes, thus restoring haemoglobin-O2 affinity to pre-exposure levels. Moreover, blood pH returned to normal levels within ~2 hours, which is one of the fastest acid-base recoveries documented in any fish. This was achieved via a large upregulation of net acid excretion and accumulation of HCO3- in blood, which increased from ~4 to ~22 mM. While the abundance and intracellular localisation of gill Na+/K+-ATPase (NKA) and Na+/H+ exchanger 3 (NHE3) remained unchanged, the apical surface area of acid-excreting gill ionocytes doubled. This constitutes a novel mechanism for rapidly increasing acid excretion during sudden blood acidosis. Rapid acid-base regulation was completely prevented when the same high CO2 exposure occurred in seawater with experimentally reduced HCO3- and pH, likely because reduced environmental pH inhibited gill H+ excretion via NHE3. The rapid and robust acid-base regulatory responses identified will enable European sea bass to maintain physiological performance during large and sudden CO2 fluctuations that naturally occur in coastal environments. Summary statementEuropean sea bass exposed to 1 kPa (10,000 atm) CO2 regulate blood and red cell pH within 2 hours and 40 minutes, respectively, protecting O2 transport capacity, via enhanced gill acid excretion.

physiology↗

bioRxiv2021

A novel nitrogen concentrating mechanism in the coral-algae symbiosome

Coral algal symbionts are hosted inside the symbiosome of gastrodermal cells, an intracellular compartment that isolates algae from the external environment and allows host cells to control the delivery of metabolites to their symbionts. However, the underlying molecular mechanisms are largely unknown. Here, we report the diel trafficking of NH3-transporting Rhesus (Rh) channels between the cytoplasm and the symbiosome membrane in the coral Acropora yongei, which matches established patterns of nitrogen delivery to endosymbionts. Heterologous expression in Xenopus oocytes established that A. yongei Rh (ayRhp1) is a channel that facilitates NH3 diffusion across membranes following its partial pressure gradient. Immunostaining revealed ayRhp1 is widely distributed throughout coral tissues and most abundantly present in oral ectodermal cells, desmocytes, and gastrodermal cells. In the latter, ayRhp1 was observed in the symbiosome membrane of alga-containing cells. Together with V-type H+-ATPases that make the symbiosome highly acidic (pH~4), ayRhp1 constitutes an NH4+-trapping mechanism analogous to that in mammalian renal tubule. Remarkably, ayRhp1 presence in the symbiosome membrane was higher during the day than the night. This indicates a regulatory mechanism that facilitates NH4+ delivery to alga during the day, likely to sustain high turnover rates of photosynthetic proteins, while restricting NH4+ delivery at night to maintain the endosymbiotic algae in a nitrogen-limited stage that stagnates their growth. The dynamic trafficking of proteins to and away from the symbiosome membrane is a previously unknown mechanism that contributes to metabolic regulation between symbiotic partners. Significance StatementThe endosymbiotic relationship between corals and algae relies on the coordinated exchange of metabolites. Disruption of these metabolic exchanges can result in interruption of the symbiosis; however, the underlying molecular mechanisms are poorly understood. Here we report that Acropora yongei coral host cells express ammonia-transporting channel proteins (ayRhp1), which traffic to and away from the symbiosome membrane surrounding the endosymbiotic algae. In conjunction with the acidic symbiosome microenvironment, this mechanism allows host cells to regulate nitrogen delivery to endosymbionts sustaining essential functions while restricting growth. This work provides novel mechanistic information about metabolic regulation of animal-algae symbioses, and advances our understanding of physiological mechanisms that might determine coral local adaptation, resilience, and vulnerability to environmental stress including climate change.

physiology↗