Biology subjects

Mattila, H.

Publications and source records attributed to Mattila, H..

9 recordsLinked to original sources

bioRxiv2026

Acute scalp EEG signatures of anterior thalamic DBS in epilepsy:reproducible gamma power enhancement within an aperiodic spectral-state shift

Background: Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is an established treatment for drug-resistant epilepsy, but acute scalp-EEG signatures of stimulation remain incompletely characterized. Objective: To identify acute scalp-EEG signatures of ANT-DBS and assess their cross-year reproducibility in a proof-of-concept repeated-session cohort. Methods: Scalp EEG from five patients recorded one year apart (10 sessions) was analyzed during nominal cyclic DBS (1 s ON, ~5 s OFF). DBS ON was compared with the within-cycle OFFmean and consecutive post-offset OFF windows using power spectral density (PSD), spatiotemporal-frequency (STF) analysis, and spectral parameterization. Results: DBS ON showed higher 30-70 Hz gamma power than OFFmean in all sessions (median +0.94 dB), with significant PSD clusters overlapping gamma in 10/10 sessions. STF identified gamma increases as the most reproducible spatiotemporal effect. Exploratory frontal 34-44 Hz and central 56-70 Hz components showed cross-year support, and the broader pattern persisted when 48-52 or 45-55 Hz were excluded before clustering. Lower-frequency effects were more heterogeneous and weakened from early to late OFF windows. Aperiodic parameterization showed lower ON exponent and offset in all sessions (Delta chi = -0.20; Delta b = -0.25). After correction, theta suppression was not preserved, whereas a smaller low-gamma residual remained. Conclusions: ANT-DBS was associated with consistent acute scalp-EEG state signatures comprising raw gamma enhancement, lower aperiodic exponent and offset, and a modest residual low-gamma effect. These hypothesis-generating findings show that scalp EEG can capture acute ANT-DBS state changes, while larger prospective studies are needed to establish clinical relevance.

neuroscience↗

bioRxiv2026

Chloroplast movements in siphonous macroalgae in response to high light and grazing

Fast cytoplasmic streaming enables extensive chloroplast movements in the giant cells of unicellular, siphonous macroalgae. Here, we studied chloroplast movements in two such algae: the Dasycladalean Acetabularia acetabulum and the Bryopsidales Bryopsis sp.. We hypothesised that chloroplast movements function as a protective avoidance mechanism under excess light, particularly in Bryopsis sp., which lacks capacity for fast induction of photoprotective non-photochemical quenching (NPQ) and state transitions. In addition, we also investigated whether chloroplast movements are involved in responses to wounding and herbivory. The movements were studied by light microscopy, photography and pulse modulated chlorophyll a fluorescence quenching analysis. Chemical inhibitors of actin polymerization and microtubules assembly were used to confirm that the observed effects were active responses controlled by the cytoskeleton. A. acetabulum responded to high light by reversible chloroplast aggregation, probed by macro-imaging; and chemical inhibition of chloroplast movements led to an enhancement of Photosystem II photoinhibition, as probed by the fluorescence parameter FV/FM. No chloroplast movements were observed in Bryopsis sp. in response to high light. In A. acetabulum, wounding caused either by cutting or due to feeding by the sap-sucking sea slug Elysia timida triggered aggregation of chloroplasts within minutes of incurring the damage. Interestingly, the aggregation also occurred in intact cells away from the cutting site. Furthermore, the addition of media collected from the vicinity of cut algae was sufficient to induce chloroplast aggregation in intact algae, suggesting that water-borne cues or signals triggered the aggregation response in A. acetabulum. Bryopsis sp., however, responded to cutting by only local chloroplast aggregation. The relevance of chloroplast movements in protection against both abiotic and biotic stressors in A. acetabulum, and the potential reasons behind the different defence strategies of the algae, are discussed.

cell biology↗

bioRxiv2026

Protease suppression by native I9 inhibitor improves recombinant protein production in Trichoderma reesei

Microbes are powerful cell factories for making molecules that are difficult or impossible to produce by other means. Filamentous fungi such as Trichoderma reesei are superior hosts for recombinant protein production, yet secreted proteases often degrade target proteins, reducing yields and limiting process robustness. Preventing proteolysis without relying on expensive commercial inhibitors or compromising strain fitness has been a longstanding challenge in fungal biotechnology, particularly for scaling up production to industrially relevant levels. Here, we report the identification of a native inhibitory protein from T. reesei, TrI9, and show that directing its secretion into the culture medium markedly reduces extracellular protease activity and enables production of the highly protease-sensitive spider silk-like protein CBM-AQ12-CBM, which could be used in high-performance biomaterials. Computational and in vitro analyses provide mechanistic insight, showing that TrI9 functions as a multi-target inhibitor of subtilisin-like proteases (SLPs), including SLP2, a protease that cannot be eliminated by gene deletion due to its crucial role in normal growth and development. This TrI9-based strategy for protease mitigation presents a novel approach for strain improvement, protecting a wide range of protease-labile products beyond silk proteins during large-scale fermentation. Protecting sensitive proteins without added inhibitors offers a cost-effective alternative for scaling up protein production across multiple applications, from protein-based materials manufacturing to pharmaceuticals, as well as enzyme and food applications. SignificanceThe discovery and characterization of an independently encoded I9 inhibitor (TrI9) in the filamentous fungus Trichoderma reesei reveals a new layer of biological regulation of subtilisin-like protease activity in fungi. We show that overexpressing and secreting TrI9 into the culture supernatant can suppress extracellular proteolysis, including activity from the essential SLP2 protease thereby overcoming a major barrier to production of protease-sensitive recombinant proteins without compromising strain fitness. For industrial biomanufacturing, this translates into higher effective titers, more consistent product integrity and reduced reliance on costly commercial protease inhibitors, hence, improving process robustness and economics. As a broadly applicable strain-and-process strategy, TrI9-enabled protease control strengthens T. reesei as a scalable platform for precision fermentation of diverse, otherwise hard-to-produce proteins.

bioengineering↗

bioRxiv2025

Provision of phosphates by the host supports kleptoplast functionality in photosynthetic sea slugs

Phosphorus and nitrogen are two fundamental macronutrients needed for photosynthesis, and their balance in photosymbiotic relationships, like those between corals and their zooxanthellae, is known to be highly important for maintaining a healthy partnership between the host and the symbiont. Kleptoplasty is a special case of algae-herbivore interaction, where the host animal or protist sequesters the chloroplasts from their prey algae as kleptoplasts inside their own cells. In some kleptoplastic sea slugs, the kleptoplasts can remain functional for months without the help from the algal nucleus, and the fundamental mechanisms in place to achieve this are still largely unsolved. Unlike in purely symbiotic systems like corals, the importance of nutrient balance to kleptoplast longevity has not been addressed in kleptoplastic sea slugs. We studied the phosphate and nitrogen exchange between the sea slug Elysia timida and its Acetabularia acetabulum derived kleptoplasts in various nutrient depletion and replenishment experiments. Our results show that sea slugs consumed phosphate from their surrounding medium and were able to recover electron transfer rates of kleptoplasts originating from phosphate depleted algae, suggesting that the sea slug provided the acquired organelles with phosphate to the extent that they increased the photosynthetic capacity remarkably well. Additional available phosphate in the water also increased the overall longevity of the kleptoplasts. The sea slugs were not able to recover the photosynthesis of nitrogen-depleted kleptoplasts, and additional dissolved nitrate and ammonium were not beneficial for kleptoplast longevity. Our results suggest that the phosphate-nitrogen balance inside the sea slug cells is mainly limited by phosphate, the addition of which can help the kleptoplasts maintain photosynthesis, perhaps by allowing the use of the glutamine synthetase (GS) and glutamate synthase (GOGAT) nitrogen assimilation pathway to function as an efficient alternative electron sink.

plant biology↗

bioRxiv2025

Siphonous green macroalgae with contrasting capacities for the energy-dependent quenching, qE, rely on different photoprotective mechanisms

To combat light-induced damage, photosynthetic organisms have evolved several photoprotective mechanisms, including non-photochemical quenching (NPQ) of excess light energy. Bryopsidales green macroalgae lack the energy-dependent quenching (qE) and can therefore induce NPQ only slowly. We illuminated a Bryopsidales macroalga (Bryopsis sp.) and a morphologically similar Dasycladales alga (Acetabularia acetabulum), capable of qE, with high light. No differences in the rate of Photosystem II (PSII) damage, probed by the chlorophyll a fluorescence parameter FV/FM in the absence and presence of lincomycin, were observed between constant and fluctuating light in Bryopsis sp., nor between the two algae. In Bryopsis sp., however, photoinhibition lead to decreased rates of electron transfer (estimated by fluorescence and oxygen evolution), while a stimulation was observed in A. acetabulum. Compared to A. acetabulum, Bryopsis sp. showed slow PSII repair, but as the rate of repair increased with increasing rates of the damage, the slow repair may not indicate increased oxidative stress but be a regulatory response. We observed, in A. acetabulum, a post-illumination dip in PSII activity and a concurring bump in NPQ, which were removed by an inhibitor of the NDA2-dependent cyclic electron transfer route and enhanced in the presence of inhibitor of mitochondrial respiration, suggesting that these pathways reduce and oxidise, respectively, the plastoquinone pool in the dark in this alga. Nigericin, which prevents the formation of proton gradient and thus qE, increased photoinhibition in A. acetabulum but not in Bryopsis sp.. Anoxia and inhibitors of the plastid terminal oxidase and mitochondrial respiration, on the other hand, enhanced photoinhibition only in Bryopsis sp., suggesting that oxygen-dependent pathways (including flavodiiron proteins) are important for photoprotection in the qE-deficient Bryopsidales algae.

plant biology↗

bioRxiv2024

Evolution and theft: loss of state transitions in Bryopsidales macroalgae and photosynthetic sea slugs

Green macroalgae within the order Bryopsidales lack the fundamental photoprotective mechanisms of green algae, the xanthophyll cycle and energy-dependent dissipation of excess light. Here, by measuring chlorophyll fluorescence at 77K after specific light treatments, we show that Bryopsidales algae also lack state transitions, another ubiquitous photoprotection mechanism present in other green algae. Certain Sacoglossa sea slugs can feed on Ulvophyceae algae, including some Bryopsidales, and steal chloroplasts -kleptoplasts- that remain functional inside the animal cells for months without the support of the algal nucleus. Our data reveal that the state transition capacity is not retained in the kleptoplasts of the sea slugs, and we provide evidence that the loss is caused by structural changes during their incorporation by the animals. This enforced chloroplast sphericity was observed in all studied kleptoplastic associations, and we propose that it is a fundamental property supporting long-term retention of kleptoplasts in photosynthetic sea slugs.

plant biology↗

bioRxiv2021

Ultraviolet screening by slug tissue and tight packing of plastids protect photosynthetic sea slugs from photoinhibition

O_LIOne of the main unsolved questions regarding photosynthetic sea slugs is how the slug plastids handle photoinhibition of Photosystem II. Photoinhibition has not been studied in detail in these animals although resilience against photoinhibition might obviously explain the longevity of plastids inside animal cytosol. C_LIO_LILight response and action spectrum of photoinhibition were measured from the slug Elysia timida and its prey alga Acetabularia acetabulum. Plastid packing in the slugs and algae was compared with spectroscopic and microscopic methods. The importance of plastid concentration was also estimated by measuring photoinhibition from starved slugs. C_LIO_LICompared to A. acetabulum, E. timida is highly resistant against photoinhibition. The resilience of the slugs is even more pronounced in the UV-region, as the slug tissue screens UV radiation. The plastids in the slug tissue are tightly packed, and the outer plastids protect the inner ones from photoinhibition. C_LIO_LIThe sea slug E. timida protects its plastids from photoinhibition by screening UV radiation and packing the plastids tightly in its tissues. Both mechanisms enhance the longevity of the plastids in slug cytosol and ameliorate the need for repair of photoinhibited Photosystem II. C_LI

plant biology↗

bioRxiv2019

Photosystem II does not convert nascent oxygen to the poisonous singlet form

In the light, the Mn4CaO5 complex of Photosystem II (PSII) splits water producing O2 and the triplet state of the primary donor (3P680) of PSII generates reactive singlet oxygen (1O2). We show that nascent O2 is not converted to 1O2, but originates exclusively from ambient O2, indicating that the sensitivity of PSII to oxidative damage is not a consequence of the water-splitting per se, and showing that the suggested oxygen channels function nearly perfectly, conveying nascent O2 out of the reach of 3P680. This may have been crucial during evolution of oxygenic photosynthesis, as 3P680 cannot be quenched by carotenoids that protect non- oxygenic photosystems. In addition, the data indicate that a 1O2-independent mechanism contributes to the light-induced damage of PSII.

plant biology↗

bioRxiv2019

Effects of low temperature and cold-acclimation on photoinhibition and singlet oxygen production in four natural accessions of Arabidopsis

To understand the effects of low temperature and cold-acclimation on reactive oxygen species and photoinhibition of photosystem II (PSII), light-induced inactivation of PSII was measured at 22 and 4 {degrees}C from four Arabidopsis thaliana accessions (Rschew, Tenela, Columbia-0 and Coimbra) grown under optimal conditions. Photoinhibition was also measured at 4 {degrees}C from plants cold-acclimated at 4 {degrees}C for two weeks. Measurements were done in the absence and presence of lincomycin that blocks PSII repair, and PSII activity was assayed with the ratio of variable to maximum chlorophyll a fluorescence (FV/FM) and with light-saturated rate of oxygen evolution using a quinone acceptor. Of the non-acclimated accessions, Rschew was the most tolerant to photoinhibition and Coimbra the least; the rate constants of photoinhibition of the most sensitive accession were 1.3-1.9 times as high as those of the tolerant ones. The damaging reaction of photoinhibition in non-acclimated plants was slower or equal at 4 {degrees}C than at 22 {degrees}C. The rate constants of photoinhibition of cold-acclimated plants, at 4 {degrees}C, were 0.55 to 1.25 times as high as those of non-acclimated plants; the protective effect of cold-acclimation on photoinhibition was consistent in Columbia-0 and Coimbra whereas Rschew and Tenela were either slightly more tolerant or susceptible, depending on the method used to assay photoinhibition. Production of singlet oxygen, measured from thylakoid membranes isolated from non-acclimated and cold-acclimated plants, did not decrease due to cold-acclimation, nor did singlet oxygen production correlate with the rate of photoinhibition or with flavonol contents of the leaves.

plant biology↗