The incidence of arbuscular mycorrhiza in two submerged Isoëtes species

We investigated the occurrence of arbuscular mycorrhizal fungi in the roots of Isoëtes lacustris and I. echinospora. These submerged lycopsids are the only macrophyte species inhabiting the bottom of two acidified glacial lakes in the Czech Republic. Arbuscular mycorrhizal (AM) fungi were detected in the roots of both species but the percentage of root colonization was both low and variable. Nevertheless, planting Littorella uniflora in the sediments from Isoëtes rhizosphere revealed high levels of viable AM propagules in both lakes. While AM colonization of Isoëtes roots did not exceed 25%, the average colonization of Littorella roots amounted to more than 80%. Although colonization of quillwort roots by AM fungi is evident, the taxonomic identity and role of these AM fungi in plant growth remain unclear. In addition to AM fungi, root-colonizing dark septate endophytic fungi were observed in both Isoëtes species.     

CO2 starvation experiments provide support for the carbon-limited hypothesis on the evolution of CAM-like behaviour in Isoëtes

Background and AimsCrassulacean acid metabolism (CAM) is an adaptation to increase water use efficiency in dry environments. Similar biochemical patterns occur in the aquatic lycophyte genus Isoëtes. It has long been assumed and accepted that CAM-like behaviour in these aquatic plants is an adaptation to low daytime carbon levels in aquatic ecosystems, but this has never been directly tested.MethodsTo test this hypothesis, populations of Isoëtes engelmannii and I. tuckermanii were grown in climate-controlled chambers and starved of atmospheric CO₂ during the day while pH was measured for 24 h.Key ResultsWe demonstrate that terrestrial plants exposed to low atmospheric CO₂ display diel acidity cycles similar to those in both xerophytic CAM plants and submerged Isoëtes.ConclusionsDaytime CO₂ starvation induces CAM-like nocturnal acid accumulation in terrestrial Isoëtes, substantiating the hypothesis that carbon starvation is a selective pressure for this physiological behaviour.     

Typha for paludiculture—Suitable water table and nutrient conditions for potential biomass utilization explored in mesocosm gradient experiments

Drainage has turned 650,000 km² of peatlands worldwide into greenhouse gas sources. To counteract climate change, large‐scale rewetting is necessary while agricultural use of rewetted areas, termed paludiculture, is still possible. However, more information is required on the performance of suitable species, such as cattail, in the range of environmental conditions after rewetting. We investigated productivity and biomass quality (morphological traits and tissue chemical composition) of Typha angustifolia and Typha latifolia along gradients of water table depth (−45 to +40 cm) and nutrient addition (3.6–400 kg N ha⁻¹ a⁻¹) in a six‐month mesocosm experiment with an emphasis on their high‐value utilization, e.g., as building material, paper, or biodegradable packaging. Over a wide range of investigated conditions, T. latifolia was more productive than T. angustifolia. Productivity was remarkably tolerant of low nutrient addition, suggesting that long‐term productive paludiculture is possible. Low water tables were beneficial for T. latifolia productivity and high water tables for T. angustifolia biomass quality. Rewetting will likely create a mosaic of different water table depths. Our findings that the yield of T. angustifolia and tissue chemical composition of T. latifolia were largely unaffected by water table depth are therefore promising. Depending on intended utilization, optimal cultivation conditions and preferable species differ. Considering yield or diameter, e.g., for building materials, T. latifolia is generally preferable over T. angustifolia. A low N, P, K content, high Si content and high C/N‐ratio can be beneficial for processing into disposable tableware, charcoal, or building material. For these utilizations, T. angustifolia is preferable at high water tables, and both species should be cultivated at a low nutrient supply. When cellulose and lignin contents are relevant, e.g., for paper and biodegradable packaging, T. angustifolia is preferable at high water tables and both species should be cultivated at nutrient additions of about 20 kg N ha⁻¹ a⁻¹.     

Intercolony variation in reproductive skipping in the African penguin

In long‐lived species, reproductive skipping is a common strategy whereby sexually mature animals skip a breeding season, potentially reducing population growth. This may be an adaptive decision to protect survival, or a non‐adaptive decision driven by individual‐specific constraints. Understanding the presence and drivers of reproductive skipping behavior can be important for effective population management, yet in many species such as the endangered African penguin (Spheniscus demersus), these factors remain unknown. This study uses multistate mark‐recapture methods to estimate African penguin survival and breeding probabilities at two colonies between 2013 and 2020. Overall, survival (mean ± SE) was higher at Stony Point (0.82 ± 0.01) than at Robben Island (0.77 ± 0.02). Inter‐colony differences were linked to food availability; under decreasing sardine (Sardinops sagax) abundance, survival decreased at Robben Island and increased at Stony Point. Additionally, reproductive skipping was evident across both colonies; at Robben Island the probability of a breeder becoming a nonbreeder was ~0.22, versus ~0.1 at Stony Point. Penguins skipping reproduction had a lower probability of future breeding than breeding individuals; this lack of adaptive benefit suggests reproductive skipping is driven by individual‐specific constraints. Lower survival and breeding propensity at Robben Island places this colony in greater need of conservation action. However, further research on the drivers of inter‐colony differences is needed.     

Clinical characteristics and outcomes of newly diagnosed patients with HIV‐associated aggressive B‐cell NHL in China

Little is known about the incidence, clinical characteristics and prognostic factors in HIV associated lymphoma as these are less common than HIV‐negative lymphoma in China. Currently, there are no standard guidelines for treatment of these patients. Therefore, we performed a study to analyse the clinical characteristics and outcomes of newly diagnosed HIV‐associated aggressive B‐cell non‐Hodgkin''s lymphoma (NHL) patients in Chongqing University Cancer Hospital (CUCH). Totally 86 newly diagnosed HIV‐associated aggressive B‐cell NHL patients in CUCH, southwest China, from July 2008 to August 2021, were analysed. In the entire cohort, median age was 48 years (range, 23–87 years), and more patients were male (87.2%). Most patients had elevated lactate dehydrogenase (LDH) (82.6%), advanced ann arbor stage (80.2%) and high IPI score (IPI score, 3–5) (62.7%) at diagnosis. Median CD4+ T‐cell count at diagnosis was 191/μl (range, 4–1022), 84 patients (97.7%) were on combination antiretroviral therapy (cART) at lymphoma diagnosis. In DLBCL patients, cox multivariate analysis showed that age ≥ 60 (HR = 2.251, 95%CI 1.122–4.516; p = 0.012), elevated LDH (HR = 4.452, 95%CI 1.027–19.297; p = 0.041) and received less than two cycles of chemotherapy (HR = 0.629, 95%CI 0.589–1.071; p = 0.012) were independent risk factors for adverse prognosis based on PFS. Age ≥ 60 (HR = 3.162, 95%CI 1.500–6.665; p = 0.002) and received less than two cycles of chemotherapy (HR = 0.524, 95%CI 0.347–0.791; p = 0.002) were also independent risk factor for adverse prognosis based on OS. In BL patients, cox multivariate analysis showed that elevated LDH and received less than two cycles of chemotherapy were independent risk factors for adverse prognosis. In the DLBCL group, median PFS times in the received rituximab and no received rituximab groups were not reached and 12 months, respectively (p = 0.006). Median OS times were not reached and 36 months, respectively (p = 0.021). In the BL group, median PFS times in the received rituximab and no received rituximab groups were not reached and 4.8 months, respectively (p = 0.046). Median OS times were not reached and 10.1 months, respectively (p = 0.035). Overall, these data indicated that standardized anti‐lymphoma therapy and rituximab administration were significantly associated with improved outcomes in patients with HIV‐associated DLBCL and BL.     

Microtubules are not required to generate a nascent axon in embryonic spinal neurons in vivo

Our understanding of the cell behaviours and cytoskeletal requirements of axon formation is largely derived from in vitro models but how these relate to axon formation in vivo is not clear. In vitro, neurons progress through a well‐defined multineurite stage to form an axon and both actin and microtubules cooperate to drive the first steps in neurite and axon morphogenesis. However, these steps are not recapitulated in vivo, and it is not clear whether the underlying cell biological mechanisms may differ also. Here, we investigate the mechanisms that regulate axon formation in embryonic zebrafish spinal neurons in vivo. We find microtubule organising centres are located distant from the site of axon initiation, and microtubule plus‐ends are not enriched in the axon during axon initiation. Focal F‐actin accumulation precedes axon formation, and we find that nocodazole‐treated neurons with no detectable microtubules are still able to form nascent axonal protrusions that are approximately 10‐μm long, dilated and relatively long‐lived. We suggest spinal axon formation in vivo is fundamentally different from axon formation in in vitro models.     

Trade‐off between flight capability and reproduction in Acridoidea (Insecta: Orthoptera)

In many insect taxa, there is a well‐established trade‐off between flight capability and reproduction. The wing types of Acridoidea exhibit extremely variability from full length to complete loss in many groups, thus, provide a good model for studying the trade‐off between flight and reproduction. In this study, we completed the sampling of 63 Acridoidea species, measured the body length, wing length, body weight, flight muscle weight, testis and ovary weight, and the relative wing length (RWL), relative flight muscle weight (RFW), and gonadosomatic index (GSI) of different species were statistically analyzed. The results showed that there were significant differences in RWL, RFW, and GSI among Acridoidea species with different wing types. RFW of long‐winged species was significantly higher than that of short‐winged and wingless species (p < .01), while GSI of wingless species was higher than that of long‐winged and short‐winged species. The RWL and RFW had a strong positive correlation in species with different wing types (correlation coefficient r = .8344 for male and .7269 for female, and p < .05), while RFW was strong negatively correlated with GSI (r = −.2649 for male and −.5024 for female, and p < .05). For Acridoidea species with wing dimorphism, males with relatively long wings had higher RFW than that of females with relatively short wings, while females had higher GSI. Phylogenetic comparative analysis showed that RWL, RFW, and GSI all had phylogenetic signals and phylogenetic dependence. These results revealed that long‐winged individuals are flight capable at the expense of reproduction, while short‐winged and wingless individuals cannot fly, but has greater reproductive output. The results support the trade‐off between flight and reproduction in Acridoidea.     

Long‐term changes in occurrence,relative abundance,and reproductive fitness of bat species in relation to arrival of White‐nose Syndrome in West Virginia,USA

White‐nose syndrome (WNS) is a disease caused by the fungus Pseudogymnoascus destructans which has resulted in the deaths of millions of bats across eastern North America. To date, hibernacula counts have been the predominant means of tracking the spread and impact of this disease on bat populations. However, an understanding of the impacts of WNS on demographic parameters outside the winter season is critical to conservation and recovery of bat populations impacted by this disease. We used long‐term monitoring data to examine WNS‐related impacts to summer populations in West Virginia, where WNS has been documented since 2009. Using capture data from 290 mist‐net sites surveyed from 2003 to 2019 on the Monongahela National Forest, we estimated temporal patterns in presence and relative abundance for each bat species. For species that exhibited a population‐level response to WNS, we investigated post‐WNS changes in adult female reproductive state and body mass. Myotis lucifugus (little brown bat), M. septentrionalis (northern long‐eared bat), and Perimyotis subflavus (tri‐colored bat) all showed significant decreases in presence and relative abundance during and following the introduction of WNS, while Eptesicus fuscus (big brown bat) and Lasiurus borealis (eastern red bat) responded positively during the WNS invasion. Probability of being reproductively active was not significantly different for any species, though a shift to earlier reproduction was estimated for E. fuscus and M. septentrionalis. For some species, body mass appeared to be influenced by the WNS invasion, but the response differed by species and reproductive state. Results suggest that continued long‐term monitoring studies, additional research into impacts of this disease on the fitness of WNS survivors, and a focus on providing optimal nonwintering habitat may be valuable strategies for assessing and promoting recovery of WNS‐affected bat populations.     

An alternative miRISC targets a cancer‐associated coding sequence mutation in FOXL2

The authors note that P values presented in the original Fig 1A and Appendix Fig S1A were not assessed using a proper statistical analysis method. In contrast to the initially employed two‐group t‐test, a one‐sample one‐tailed t‐test is appropriate here, as the basic null hypothesis is that the proportion of MT FOXL2 mRNA in each AGCT patient is lower than WT {H ₀: WT(%) > MT(%) }. New p values are presented in the corrected Fig 1A and Appendix Fig S1A, which are P < 0.00001 and P < 0.05, respectively. These revised P values did not affect the conclusion drawn.     

Phospholipase D1 promotes cervical cancer progression by activating the RAS pathway

This study aimed to further investigate the effect of PLD1 on the biological characteristics of human cervical cancer (CC) cell line, CASKI and the potential related molecular mechanism. CRISPR/Cas9 genome editing technology was used to knock out the PLD1 gene in CASKI cells. Cell function assays were performed to evaluate the effect of PLD1 on the biological function of CASKI cells in vivo and in vitro. A PLD1‐overexpression rescue experiment in these knockout cells was performed to further confirm its function. Two PLD1‐knockout CASKI cell lines (named PC‐11 and PC‐40, which carried the ins1/del4 mutation and del1/del2/ins1 mutation, respectively), were constructed by CRISPR/Cas9. PLD1 was overexpressed in these knockout cells (named PC11‐PLD1 and PC40‐PLD1 cells), which rescued the expression of PLD1 by approximately 71.33% and 74.54%, respectively. In vivo, the cell function assay results revealed that compared with wild‐type (WT)‐CASKI cells, the ability of PC‐11 and PC‐40 cells to proliferate, invade and migrate was significantly inhibited. The expression of H‐Ras and phosphorylation of Erk1/2 (p‐Erk1/2) was decreased in PC‐11 and PC‐40 cells compared with WT‐CASKI cells. PC‐11 and PC‐40 cells could sensitize CASKI cells to cisplatin. More importantly, the proliferation, migration and invasion of PC11‐PLD1 and PC40‐PLD1 cells with PLD1 overexpression were significantly improved compared with those of the two types of PLD1 knockout cells. The sensitivity to cisplatin was decreased in PC11‐PLD1 and PC40‐PLD1 cells compared with PC‐11 and PC‐40 cells. In vivo, in the PC‐11 and PC‐40 tumour groups, tumour growth was significantly inhibited and tumour weight (0.95 ± 0.27 g and 0.66 ± 0.43 g vs. 1.59 ± 0.67 g, p = 0.0313 and 0.0108) and volume (1069.41 ± 393.84 and 1077.72 mm³ ± 815.07 vs. 2142.94 ± 577.37 mm³, p = 0.0153 and 0.0128) were significantly reduced compared to those in the WT‐CASKI group. Tumour differentiation of the PC‐11 and PC40 cells was significantly better than that of the WT‐CASKI cells. The immunohistochemistry results confirmed that the expression of H‐Ras and p‐Erk1/2 was decreased in PC‐11 and PC‐40 tumour tissues compared with WT‐CASKI tumour tissues. PLD1 promotes CC progression by activating the RAS pathway. Inhibition of PLD1 may serve as an attractive therapeutic modality for CC.     

Heterologous expression of Arabidopsis pattern recognition receptor RLP23 increases broad‐spectrum resistance in poplar to fungal pathogens

The pattern recognition receptor AtRLP23 from Arabidopsis thaliana recognizes the epitopes (nlp24s) of necrosis and ethylene‐inducing peptide 1‐like proteins (NLPs) and triggers pattern‐triggered immunity (PTI). Here, we established methods for studying the early events of PTI in the hybrid poplar cultivar Shanxin (Populus davidiana × Populus bolleana) in response to the flagellin epitope. We confirmed that wild‐type Shanxin cannot generate PTI responses on nlp24 treatment. Four NLP homologues were characterized from two common fungal pathogens of Shanxin, namely Marssonina brunnea f. sp. monogermtubi (MbMo) and Elsinoë australis (Ea), which cause black leaf spot and anthracnose disease, respectively, and the nlp24s of three of them could be responded to by Nicotiana benthamiana leaves expressing AtRLP23. We then created AtRLP23 transgenic Shanxin lines and confirmed that the heterologous expression of AtRLP23 conferred on transgenic Shanxin the ability to respond to one nlp24 of each fungal pathogen. Consistently, infection assays with MbMo or Ea showed obviously lower levels of disease symptoms and significantly inhibited the growth of fungi on the transgenic poplar compared with that in wild‐type poplar. Overall, our results indicated that the heterologous expression of AtRLP23 allowed transgenic Shanxin to generate a PTI response to nlp24s, resulting in increased broad‐spectrum fungal disease resistance.     

AmiP from hyperthermophilic Thermus parvatiensis prophage is a thermoactive and ultrathermostable peptidoglycan lytic amidase

Bacteriophages encode a wide variety of cell wall disrupting enzymes that aid the viral escape in the final stages of infection. These lytic enzymes have accumulated notable interest due to their potential as novel antibacterials for infection treatment caused by multiple‐drug resistant bacteria. Here, the detailed functional and structural characterization of Thermus parvatiensis prophage peptidoglycan lytic amidase AmiP, a globular Amidase_3 type lytic enzyme adapted to high temperatures is presented. The sequence and structure comparison with homologous lytic amidases reveals the key adaptation traits that ensure the activity and stability of AmiP at high temperatures. The crystal structure determined at a resolution of 1.8 Å displays a compact α/β‐fold with multiple secondary structure elements omitted or shortened compared with protein structures of similar proteins. The functional characterization of AmiP demonstrates high efficiency of catalytic activity and broad substrate specificity toward thermophilic and mesophilic bacteria strains containing Orn‐type or DAP‐type peptidoglycan. The here presented AmiP constitutes the most thermoactive and ultrathermostable Amidase_3 type lytic enzyme biochemically characterized with a temperature optimum at 85°C. The extraordinary high melting temperature T _m 102.6°C confirms fold stability up to approximately 100°C. Furthermore, AmiP is shown to be more active over the alkaline pH range with pH optimum at pH 8.5 and tolerates NaCl up to 300 mM with the activity optimum at 25 mM NaCl. This set of beneficial characteristics suggests that AmiP can be further exploited in biotechnology.     

PAPPA2 mutation as a novel indicator stratifying beneficiaries of immune checkpoint inhibitors in skin cutaneous melanoma and non‐small cell lung cancer

BackgroundPappalysin 2 (PAPPA2) mutation, occurring most frequently in skin cutaneous melanoma (SKCM) and non‐small cell lung cancer (NSCLC), is found to be related to anti‐tumour immune response. However, the association between PAPPA2 and the efficacy of immune checkpoint inhibitors (ICIs) therapy remains unknown.MethodsTo analyse the performance of PAPPA2 mutation as an indicator stratifying beneficiaries of ICIs, seven public cohorts with whole‐exome sequencing (WES) data were divided into the NSCLC set (n = 165) and the SKCM set (n = 210). For further validation, 41 NSCLC patients receiving anti‐PD‐(L)1 treatment were enrolled in China cohort (n = 41). The mechanism was explored based on The Cancer Genome Atlas database (n = 1467).ResultsIn the NSCLC set, patients with PAPPA2 mutation (PAPPA2‐Mut) demonstrated a significantly superior progress free survival (PFS, hazard ratio [HR], 0.28 [95% CI, 0.14–0.53]; p < 0.001) and objective response rate (ORR, 77.8% vs. 23.2%; p < 0.001) compared to those with wide‐type PAPPA2 (PAPPA2‐WT), consistent in the SKCM set (overall survival, HR, 0.49 [95% CI: 0.31–0.78], p < 0.001; ORR, 34.1% vs. 16.9%, p = 0.039) and China cohort. Similar results were observed in multivariable models. Accordingly, PAPPA2 mutation exhibited superior performance in predicting ICIs efficacy compared with other published ICIs‐related gene mutations, such as EPHA family, MUC16, LRP1B and TTN, etc. In addition, combined utilization of PAPPA2 mutation and tumour mutational burden (TMB) could expand the identification of potential responders to ICIs therapy in both NSCLC set (HR, 0.36 [95% CI: 0.23–0.57], p < 0.001) and SKCM set (HR, 0.51 [95% CI: 0.34–0.76], p < 0.001). Moreover, PAPPA2 mutation was correlated with enhanced anti‐tumour immunity including higher activated CD4 memory T cells level, lower Treg cells level, and upregulated DNA damage repair pathways.ConclusionsOur findings indicated that PAPPA2 mutation could serve as a novel indicator to stratify beneficiaries from ICIs therapy in NSCLC and SKCM, warranting further prospective studies.

Flow diagram of the study. (A) Preliminary analysis. PAPPA2 mutated most frequently in skin cutaneous melanoma (SKCM) and non‐small cell lung cancer (NSCLC) in the The Cancer Genome Atlas (TCGA) database. PAPPA2 mutational rates in patients with objective response (CR + PR) versus without (SD + PD) were compared with other immune checkpoint inhibitors‐related gene mutations in the NSCLC and SKCM sets. (B) Biomarker development. Association between PAPPA2 mutation and clinical outcomes has been analysed in the NSCLC set, the SKCM set and China cohort. (C) Mechanism exploring. Based on the TCGA database, the correlation of PAPPA2 mutation with tumour mutation burden, infiltrating immune cells and DNA damage repair was explored for further immunogenicity and anti‐tumour activity mechanisms.     

Demographic effects of a megafire on a declining prairie grouse in the mixed‐grass prairie

Recent studies have documented benefits of small, prescribed fire and wildfire for grassland‐dependent wildlife, such as lesser prairie‐chickens (Tympanuchus pallidicintus), but wildlife demographic response to the scale and intensity of megafire (wildfire >40,000 ha) in modern, fragmented grasslands remains unknown. Limited available grassland habitat makes it imperative to understand if increasing frequency of megafires could further reduce already declining lesser prairie‐chicken populations, or if historical evolutionary interactions with fire make lesser prairie‐chickens resilient. To evaluate lesser prairie‐chicken demographic response to megafires, we compared lek counts, nest density, and survival rates of adults, nests, and chicks before (2014–2016) and after (2018–2020) a 2017 megafire in the mixed‐grass prairie of Kansas, USA (Starbuck fire ~254,000 ha). There was a 67% decline in attending males on leks post‐fire and a 57% decline in occupied leks post‐fire. Despite population declines as indicated by lek counts, adult female breeding season survival (S^) was similar pre‐ (S^ = 0.65 ± 0.08 [SE]) and post‐fire (0.61 ± 0.08), as was chick survival (pre‐fire: 0.23 ± 0.07; post‐fire: 0.27 ± 0.11). Nest survival appeared lower post‐fire (pre‐fire: 0.38 ± 0.06; post‐fire: 0.20 ± 0.06), but did not differ at the 95% confidence interval. Nest density of marked females declined 73% in areas burned by megafire. Although lesser prairie‐chickens persisted in the study area and we documented minimal effects on most demographic rates, reduced lesser prairie‐chicken abundance and reproductive output suggests full recovery may take >3 years. Increased propensity for megafire resulting from suppression of smaller fires, compounded by climate change and woody encroachment, may impose a short‐term (3–5 year) threat to already declining lesser prairie‐chicken populations.     

Hepatoprotective effect of nanoniosome loaded Myristica fragrans phenolic compounds in mice‐induced hepatotoxicity

In this study, nanoniosome‐loaded Myristica fragrans'' (MF) phenolic compounds (NLMP) were synthesized and characterized for their physical properties, and hepatoprotective effects on mice with liver toxicity induced by L‐asparaginase (LA) injection. According to the results, NLMP has a spherical shape with a 263 nm diameter, a zeta potential of −26.55 mV and a polydispersity index (PDI) of 0.192. The weight and feed intake of mice induced with hepatotoxicity were significantly (p ≤ 0.05) increased after they were treated with NLMP (2.5 mg/kg body weight of mice). In addition, the blood levels of triglyceride (TG), cholesterol (Chol), liver enzymes (aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP)) and total bilirubin were significantly (p ≤ 0.05) decreased. A significant increase (p ≤ 0.05) in the blood levels of the antioxidant defence system (glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT)) were also reported after NLMP treatment. NLMP was also led to a significant decrease (p ≤ 0.05) in inflammatory‐related gene expression of inducible nitric oxide synthase (iNOS) and Interferon‐gamma (IFN‐γ) in the liver, as well as a meaningful (p ≤ 0.05) increase in the expression of SOD as an antioxidant status biomarker. Consequently, the NLMP is recommended as a potential dietary supplement to alleviate the symptoms of LA‐induced hepatotoxicity.     

Transition metal cation inhibition of Mycobacterium tuberculosis esterase RV0045C

Mycobacterium tuberculosis virulence is highly metal‐dependent with metal availability modulating the shift from the dormant to active states of M. tuberculosis infection. Rv0045c from M. tuberculosis is a proposed metabolic serine hydrolase whose folded stability is dependent on divalent metal concentration. Herein, we measured the divalent metal inhibition profile of the enzymatic activity of Rv0045c and found specific divalent transition metal cations (Cu²⁺ ≥ Zn²⁺ > Ni²⁺ > Co²⁺) strongly inhibited its enzymatic activity. The metal cations bind allosterically, largely affecting values for k _cat rather than K _M. Removal of the artificial N‐terminal 6xHis‐tag did not change the metal‐dependent inhibition, indicating that the allosteric inhibition site is native to Rv0045c. To isolate the site of this allosteric regulation in Rv0045c, the structures of Rv0045c were determined at 1.8 Å and 2.0 Å resolution in the presence and absence of Zn²⁺ with each structure containing a previously unresolved dynamic loop spanning the binding pocket. Through the combination of structural analysis with and without zinc and targeted mutagenesis, this metal‐dependent inhibition was traced to multiple chelating residues (H202A/E204A) on a flexible loop, suggesting dynamic allosteric regulation of Rv0045c by divalent metals. Although serine hydrolases like Rv0045c are a large and diverse enzyme superfamily, this is the first structural confirmation of allosteric regulation of their enzymatic activity by divalent metals.     

Taphonomic experiments imply a possible link between the evolution of multicellularity and the fossilization potential of soft‐bodied organisms

The reliability of evolutionary reconstructions based on the fossil record critically depends on our knowledge of the factors affecting the fossilization of soft‐bodied organisms. Despite considerable research effort, these factors are still poorly understood. In order to elucidate the main prerequisites for the preservation of soft‐bodied organisms, we conducted long‐term (1–5 years) taphonomic experiments with the model crustacean Artemia salina buried in five different sediments. The subsequent analysis of the carcasses and sediments revealed that, in our experimental settings, better preservation was associated with the fast deposition of aluminum and silicon on organic tissues. Other elements such as calcium, magnesium, and iron, which can also accumulate quickly on the carcasses, appear to be much less efficient in preventing decay. Next, we asked if the carcasses of uni‐ and multicellular organisms differ in their ability to accumulate aluminum ions on their surface. The experiments with the flagellate Euglena gracilis and the sponge Spongilla lacustris showed that aluminum ions are more readily deposited onto a multicellular body. This was further confirmed by the experiments with uni‐ and multicellular stages of the social ameba Dictyostelium discoideum. The results lead us to speculate that the evolution of cell adhesion molecules, which provide efficient cell–cell and cell–substrate binding, probably can explain the rich fossil record of soft‐bodied animals, the comparatively poor fossil record of nonskeletal unicellular eukaryotes, and the explosive emergence of the Cambrian diversity of soft‐bodied fossils.     

Population dynamics of the glacial relict amphipods in a subarctic lake: role of density‐dependent and density‐independent factors

Relative role of intrinsic density‐dependent factors (such as inter‐ and intraspecific competition, predation) and extrinsic density‐independent factors (environmental changes) in population dynamics is a key issue in ecology. Density‐dependent mechanisms are considered as important drivers of population dynamics in many vertebrate and insect species; however, their influence on the population dynamics of freshwater invertebrates is not clearly understood. In this study, I examined interannual variations in the abundance of the glacial relict amphipod Monoporeia affinis in a small subarctic lake based on long‐term (2002–2019) monitoring data. The results suggest that the population dynamics of amphipods in the lake is influenced by the combined effects of both intrinsic and extrinsic factors. The reproductive success of amphipod cohorts was inversely related to its initial abundance, indicating it is influenced by density‐dependent factors. M. affinis recruitment was negatively correlated with population density and near‐bottom temperature but positively correlated with food availability, which is defined as the concentration of chlorophyll a. Multiple regression with chlorophyll, temperature, and abundance of parent cohort as independent factors explained about 80% of the variation in the reproductive success of amphipods. The negative correlation between amphipod recruitment and water temperature indicates that the current climate conditions adversely affect the populations of glacial relict amphipods even in cold‐water lakes of the subarctic zone. Results of this study can be useful in environmental assessments to separate population oscillations connected with density‐dependent mechanisms from human‐mediated changes.