Biology subjects

Thies, A.

Publications and source records attributed to Thies, A..

4 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↗

bioRxiv2025

Four Decades of Breeding and Increasing Plant Density Management Reshaped Maize Root System Architecture

Understanding how crop root system architecture (RSA) is influenced by genetics and management is vital for root-based improvement. We examined the impact of four decades of maize breeding on RSA using a panel of maize hybrids planted at different densities across six site-years in the Midwest. Root crowns were shovel-excavated and imaged via X-ray tomography, generating dozens of fine-grained 3D traits. Modern root systems were significantly smaller with fewer, thinner roots at higher density compared to older hybrids. However, the total amount of roots in the topsoil extrapolated across an acre was indistinguishable, revealing an equilibrium between crown size and density. Surprisingly, there was a 20% increase in the soil volume explored by individual modern hybrids, indicating increased overlap of root systems. We estimated modern hybrids share 43-46% of the topsoil with neighbors, compared to 14% in the oldest. Furthermore, when the oldest hybrids were grown at modern densities, their root crowns became more elliptical than modern hybrids, highlighting potential differences in avoidance response. Root systems of modern hybrids may be more intertwined and less competitive, revealing an adaptation to increased density stress in maize agriculture with implications for trait-based approaches to engineer more productive, efficient systems. HIGHLIGHTThis study uses a new panel of maize hybrids to explore how decades of yield-focused breeding and advancements in planting density have indirectly impacted maize root systems.

plant biology↗

bioRxiv2021

Modelling altered signalling of G-protein coupled receptors in inflamed environment to advance drug design

We previously reported the successful design, synthesis and testing of the prototype opioid painkiller NFEPP that does not elicit adverse side effects. Uniquely, this design was based on mathematical modelling of extracellular interactions between G-protein coupled receptors (GPCRs) and ligands, recognizing that GPCRs function differently under pathological versus healthy conditions. We now present a novel stochastic model of GPCR function that includes intracellular dissociation of G-protein subunits and modulation of plasma membrane calcium channels associated with parameters of inflamed and healthy tissue (pH, radicals). The model is validated against in vitro experimental data for NFEPP and fentanyl ligands at different pH values. We found markedly reduced calcium channel inhibition induced by NFEPP at normal pH compared to lower pH, in contrast to the effect of fentanyl, and enhanced constitutive G-protein activation but lower probability of ligand binding with increasing radical concentrations. By means of molecular dynamics simulations, we also assessed qualitative changes of reaction rates due to additional disulfide bridges inside the GPCR binding pocket. The results suggest that, compared to radicals, low pH is a more important determinant of overall GPCR function in an inflamed environment. Future drug design efforts should take this into account.

systems biology↗

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↗