Cell Division Research Articles

Identification of Novel CDK 4/6 Inhibitors by High-throughput Virtual Screening

Background: CDK4/6 plays a crucial role in regulating cell proliferation, and inhibiting this kinase can effectively prevent the initiation of cell growth and division. However, current FDAapproved CDK4/6 inhibitors have limitations such as poor bioavailability, adverse effects, high cost, and limited accessibility. Thus, this research aimed to discover novel CDK4/6 inhibitors to overcome the challenges associated with FDA-approved inhibitors. Methods: To identify potential CDK4/6 inhibitors, we have performed structure-based virtual screening. Chem-space and Mcule databases have been screened, followed by a series of filtering steps. These steps included assessing drug-likeness, PAINS alert, synthetic accessibility scores, ADMET properties, consensus molecular docking, and performing molecular dynamics simulations. Results: Four new compounds (CSC089414133, CSC091186116, CSC096023304, CSC101755872) have been identified as potential CDK4/6 inhibitors. These compounds exhibited strong binding affinity with CDK4/6, possessed drug-like features, showed no PAINS alert, had a low synthetic accessibility score, demonstrated effective ADMET properties, were non-toxic, and exhibited high stability. Conclusion: Inhibiting CDK4/6 with the identified compounds may lead to reduced cell proliferation and the promotion of cancer cell death.

Time-Lapse Imaging of Asymmetric Spindle Positioning During Endothelial Tip Cell Division in Angiogenesis In Vivo.

The branching of new blood vessels by angiogenesis is critical to the development, growth, and repair of most vertebrate tissues and is frequently dysregulated in disease. At its core, angiogenesis is driven by the collective migration of leading "tip" and follower "stalk" endothelial cells. Recent work reveals that this collective movement is coordinated by asymmetric tip cell divisions that generate daughters of distinct size, signaling capacity and tip-stalk behaviors. Polarized mitotic spindle positioning is critical to generating such asymmetries in daughter cell size. However, the spatiotemporal dynamics of vertebrate spindle movement are often difficult to explore using in vivo systems. Here we describe a method for the sample preparation, live-imaging and data analysis of endothelial cell mitotic spindle positioning in developing zebrafish embryos. This method enables single-cell and population-level spindle dynamics to be monitored and quantified, both in wild-type or genetically/pharmacologically perturbed embryos. Moreover, this approach can be easily adapted for live imaging of spindle dynamics in other zebrafish embryonic tissues that experience similar asymmetric divisions, such as the trunk neural crest.

The Primary Cell Model: Linking Prenatal Development and Intracellular Biology to Psychology and Consciousness

In this paper, we introduce an entirely new model of psychobiology. Unexpected discoveries are often made by combining different fields of knowledge. Here, prenatal psychology was combined with developmental and cell biology to yield a surprisingly simple yet profoundly important intracellular (subcellular) psychobiology theory. Like many discoveries, this one took us completely by surprise. It explained many puzzling observations in psychology and medicine and has led to effective therapeutic applications. Our breakthrough was realizing that the sensations, feelings, and perceptions inside a single, unique totipotent cell are superimposed on our everyday bodily experience. We have called this unique cell the primary cell. It forms at the fourth cell division after conception and remains with us our entire life. Thus, this cell links psychology to intracellular biology, and its existence has profound implications in both evolutionary biology and understanding the intracellular biology of consciousness itself. This paper presents part one of a three-part series, sharing real-life experiences that ultimately resulted in the development of the primary cell model. By utilizing various viewpoints and techniques from different fields, some of which are not widely known, we aim to provide insight into the key moments that shaped our decade-long journey of discovery. These stories will help you understand how we made our observations and conclusions. Keywords: Prenatal developmental psychology, subcellular psychobiology, primary cell, intracellular biology, epigenetic, RNA trauma

Renshen (Radix Ginseng) polysaccharide promotes repair of the mice intestinal mucosa through regulatory mechanisms based on polyamine and human antigen R.

To investigate the mechanism and effect of Renshen (Radix Ginseng) polysaccharide on the migration of intestinal epithelial cell line 6 (IEC-6), as well as the repair mechanism of Renshen (Radix Ginseng) polysaccharide on colonic injury induced by dextran sulfate sodium (DSS) in mice. Mice were fed 3% (w/v) DSS for 6 d to create colonic lesions. A cell-migration model was created using cell scratching. mRNA expression, protein expression, translation efficiency of mRNA, and nucleoplasmic distribution of human antigen R (HuR) were determined by real-time reverse transcription-quantitative polymerase chain reaction, western blotting, a dual luciferase reporter system, and immunofluorescence staining, respectively. Renshen (Radix Ginseng) polysaccharide promoted the migration of IEC-6 cells and affected expression of stromal interaction molecule 1 (STIM1) and cell division cycle 42 (Cdc42) at transcriptional and post-transcriptional levels. Renshen (Radix Ginseng) polysaccharide-induced repair of intestinal mucosal injury may be mediated by increased cell migration via polyamine-based regulatory mechanisms. In vitro and in vivo experiments suggest that Renshen (Radix Ginseng) polysaccharide-induced post-transcriptional regulation of STIM1 and Cdc42 may be related to differences in the regulation of different target genes by HuR. Taken together, these data provide a reference for further exploration of the protective effect of Renshen (Radix Ginseng) on the intestinal mucosa.

Isolation of Mitotic Centrosomes from Cultured Human Cells.

The centrosome plays a crucial role in facilitating mitotic spindle assembly through its microtubule organizing capacities. Analyzing the composition, structure, and functions of mitotic centrosomes is essential for understanding the mechanisms underlying cell division and centrosome-associated diseases. Isolating centrosomes is an effective method to gain comprehensive information about them while minimizing interference from other cellular components. In this chapter, we describe a protocol for isolating mitotic centrosomes from cultured human cells. This protocol includes cell synchronization and centrosome isolation through ultracentrifugation with a sucrose gradient. We also describe a method for conducting a microtubule nucleation assay to assess the functionality of isolated centrosomes.

Nucleic acid-binding KH domain proteins influence a spectrum of biological pathways including as part of membrane-localized complexes

K-Homology domain (KH domain) proteins bind single-stranded nucleic acids, influence protein–protein interactions of proteins that harbor them, and are found in all kingdoms of life. In concert with other functional protein domains KH-domains contribute to a variety of critical biological activities, often within higher order machineries including membrane-localized protein complexes. Eukaryotic KH domain proteins are linked to developmental processes, morphogenesis, and regulation, and their aberrant expression is often associated with cancer. Prokaryotic KH domain proteins are involved in integral cellular activities including cell division and protein translocation. Eukaryotic and prokaryotic KH domains share structural features, but are differentiated based on their structural organizations. In this review, we explore the structure/function relationships of known examples of KH domain proteins, and highlight cases in which they function within or at membrane surfaces. We also summarize examples of KH domain proteins that influence bacterial virulence and pathogenesis. We conclude the article by discussing prospective research avenues that could be pursued to better investigate this largely understudied protein category.

53BP1-the ‘Pandora’s box’ of genome integrity

53BP1 has several functions in the maintenance of genome integrity. It functions as a key mediator involved in double-strand break (DSB) repair, which functions to maintain a balance in the repair pathway choices and in preserving genomic stability. While its DSB repair functions are relatively well-characterized, its role in DNA replication and replication fork protection is less understood. In response to replication stress, 53BP1 contributes to fork protection by regulating fork reversal and restart. It helps maintain replication fork stability and speed, with 53BP1 loss leading to defective fork progression and increased sensitivity to replication stress agents. However, 53BP1's precise role in fork protection remains debated, as some studies have not observed protective effects. Therefore, it is critical to determine the role of 53BP1 in replication to better understand when it promotes replication fork protection, and the underlying mechanisms involved. Moreover, 53BP1's function in replication stress extends beyond its activity at active replication forks; it also forms specialized nuclear bodies (NBs) which protect stretches of under-replicated DNA (UR-DNA) transmitted from a previous cell cycle to daughter cells through mitosis. The mechanism of 53BP1 NBs in the coordination of replication and repair events at UR-DNA loci is not fully understood and warrants further investigation. The present review article focuses on elucidating 53BP1’s functions in replication stress (RS), its role in replication fork protection, and the significance of 53BP1 NBs in this context to provide a more comprehensive understanding of its less well-established role in DNA replication.

Overexpression of GFP Fusions of Regulators of the SAC from Arabidopsis thaliana.

Cell division is a fundamental biological process, essential for sustaining life on Earth. Accurate replication followed by uniform segregation of the genome is required to ensure cell division is sustainable and reduces the likelihood of aneuploidy. The cell cycle has various checkpoints to safeguard proper replication, for example, the spindle assembly checkpoint (SAC) which ensures that all chromosomes are correctly aligned and attached to the spindle, before the transition to anaphase. The precise function of the SAC and SAC components in plants is so far unclear. First, the high level of polyploidy in plants raises concerns about the efficacy of the SAC. Second, many plant SAC components are implicated in other cellular processes, such as MAD1, which has been implicated in the reproductive transition of Arabidopsis thaliana. Overexpression of GFP fusions of core SAC components provides a key route to establish the functions of the different SAC components in plants. Here we describe two methods for agrobacterium-mediated transformation of plants.

Roles of Cep215/Cdk5rap2 in establishing testicular architecture for mouse male germ cell development.

Cep215/Cdk5rap2 is a centrosome protein crucial for directing microtubule organization during cell division and morphology. Cep215 is a causal gene of autosomal recessive primary microcephaly type 3, characterized by a small brain size and a thin cerebral cortex. Despite previous attempts with Cep215 knockout (KO) mice to elucidate its developmental roles, interpreting their phenotypes remained challenging due to potential interference from alternative variants. Here, we generated KO mice completely lacking the Cep215 gene and investigated its specific contributions to male germ cell development. In the absence of Cep215, testis size decreased significantly, accompanied by a reduction in male germ cell numbers. Histological analyses unveiled the arrested development of male germ cells around the zygotene stage of meiosis. Concurrently, the formation of the blood-testis barrier (BTB) was impaired in Cep215 KO testes. These findings suggest that BTB failure contributes, at least partially, to male germ cell defects observed in Cep215 KO mice. We propose that the deletion of Cep215 may disrupt microtubule organization in Sertoli cells with a delay in spermatogonial stem cell mitosis, thereby impeding proper BTB formation.

Minimizing Radiation Exposure in Neonatal Intensive Care Unit: A Quality Improvement Approach on X-Ray Practices

Purpose: Radiographic examinations are frequently performed for diagnostic and therapeutic purposes in neonatal intensive care units (NICUs). However, concerns are emerging regarding the safety of radiation exposure, especially in vulnerable preterm infants in periods of rapid cellular division. This quality improvement (QI) project aimed to reduce radiation hazards in level-IV NICU.Methods: We established an "X-ray prescription protocol" and educated the physicians to ensure that only essential radiographs were obtained. Additionally, we discouraged full-body infantograms and emphasized the prescription of targeted radiographs, such as chest or abdominal radiographs. Furthermore, to reduce the dose-area product (DAP, Gy·cm<sup>2</sup>) values, which act as a surrogate for radiation exposure, we provided training to radiologic technologists on meticulous collimation for each radiography session. We aimed to achieve a 30% reduction in the average monthly cumulative DAP per patient, which was calculated by dividing the total monthly DAP from radiographs in the NICU by the monthly average of patient admissions. Retrospective baseline data were collected 8 months pre-intervention and prospectively for 4 months post-interventions.Results: The average monthly X-ray count per patient was 28.3 in the pre-intervention period (October 2022 to May 2023), which decreased to 25.4 in the post-intervention period (June 2023 to September 2023), reflecting a 10.2% reduction (<i>p</i>=0.109). The average monthly infantogram count per patient showed an 18.0% reduction (25.9% to 21.2%, <i>p</i>=0.016), and the proportion of infantograms in the total X-ray counts decreased from 91.5% to 83.3% (<i>p</i>=0.017). The DAP value per X-ray decreased by 42.6%, from an average of 0.25 to 0.14 (<i>p</i>=0.011). The primary outcome, the average monthly cumulative DAP value per patient, showed a substantial reduction of 48.6%, dropping from 7.00 to 3.60 (<i>p</i>=0.004). The baseline characteristics and short-term morbidities of the patients did not differ significantly between the pre- and post-intervention period.Conclusion: Our QI approach, which included discouraging excessive prescriptions of infantograms and promoting optimal collimation, significantly reduced the average monthly radiation exposure in the NICU, benefiting both patients and healthcare workers.

ChromEMT: visualizing and reconstructing chromatin ultrastructure and 3D organization in situ.

Structure determines function. The discovery of the DNA double-helix structure revealed how genetic information is stored and copied. In the mammalian cell nucleus, up to two meters of DNA is compacted by histones to form nucleosome/DNA particle chains that form euchromatin and heterochromatin domains, chromosome territories and mitotic chromosomes upon cell division. A critical question is what are the structures, interactions and 3D organization of DNA as chromatin in the nucleus and how do they determine DNA replication timing, gene expression and ultimately cell fate. To visualize genomic DNA across these different length scales in the nucleus, we developed ChromEMT, a method that selectively enhances the electron density and contrast of DNA and interacting nucleosome particles, which enables nucleosome chains, chromatin domains, chromatin ultrastructure and 3D organization to be imaged and reconstructed by using multi-tilt electron microscopy tomography (EMT). ChromEMT exploits a membrane-permeable, fluorescent DNA-binding dye, DRAQ5, which upon excitation drives the photo-oxidation and precipitation of diaminobenzidine polymers on the surface of DNA/nucleosome particles that are visible in the electron microscope when stained with osmium. Here, we describe a detailed protocol for ChromEMT, including DRAQ5 staining, photo-oxidation, sample preparation and multi-tilt EMT that can be applied broadly to reconstruct genomic DNA structure and 3D interactions in cells and tissues and different kingdoms of life. The entire procedure takes ~9 days and requires expertise in electron microscopy sample sectioning and acquisition of multi-tilt EMT data sets.

Broadly conserved FlgV controls flagellar assembly and Borrelia burgdorferi dissemination in mice

Flagella propel pathogens through their environments, yet are expensive to synthesize and are immunogenic. Thus, complex hierarchical regulatory networks control flagellar gene expression. Spirochetes are highly motile bacteria, but peculiarly, the archetypal flagellar regulator σ28 is absent in the Lyme spirochete Borrelia burgdorferi. Here, we show that gene bb0268 (flgV) in B. burgdorferi, previously and incorrectly annotated to encode the RNA-binding protein Hfq, is instead a structural flagellar component that modulates flagellar assembly. The flgV gene is broadly conserved in the flagellar superoperon alongside σ28 in many Spirochaetae, Firmicutes and other phyla, with distant homologs in Epsilonproteobacteria. We find that B. burgdorferi FlgV is localized within flagellar basal bodies, and strains lacking flgV produce fewer and shorter flagellar filaments and are defective in cell division and motility. During the enzootic cycle, flgV-deficient B. burgdorferi survive and replicate in Ixodes ticks but are attenuated for infection and dissemination in mice. Our work defines infection timepoints when spirochete motility is most crucial and implicates FlgV as a broadly distributed structural flagellar component that modulates flagellar assembly.

Theory of epigenetic switching due to stochastic histone mark loss during DNA replication

How much information does a cell inherit from its ancestors beyond its genetic sequence? What are the epigenetic mechanisms that allow this? Despite the rise in available epigenetic data, how such information is inherited through the cell cycle is still not fully understood. Often, epigenetic marks can display bistable behaviour and their bistable state is transmitted to daughter cells through the cell cycle, providing the cell with a form of memory. However, loss-of-memory events also take place, where a daughter cell switches epigenetic state (with respect to the mother cell). Here, we develop a framework to compute these epigenetic switching rates, for the case when they are driven by DNA replication, i.e. the frequency of loss-of-memory events due to replication. We consider the dynamics of histone modifications during the cell cycle deterministically, except at DNA replication, where nucleosomes are randomly distributed between the two daughter DNA strands, which is therefore implemented stochastically. This hybrid stochastic-deterministic approach enables an analytic derivation of the replication-driven switching rate. While retaining great simplicity, this framework can explain experimental switching rate data, establishing its biological importance as a framework to quantitatively study epigenetic inheritance.

The dynamin-related protein PfDyn2 is essential for both apicoplast and mitochondrial fission in Plasmodium falciparum.

Dynamins, or dynamin-related proteins (DRPs), are large mechano-sensitive GTPases that mediate membrane dynamics or organellar fission/fusion events. Plasmodium falciparum encodes three dynamin-like proteins whose functions are poorly understood. Here, we demonstrate that one of these dynamin-related proteins, PfDyn2, is required to divide both the apicoplast and the mitochondrion, a striking divergence from the biology of related parasites. Using super-resolution and ultrastructure expansion microscopy (U-ExM), we show that PfDyn2 is expressed in dividing schizonts, and that it localizes to both the apicoplast and the mitochondrion. Our use of long-term, live-cell microscopy allows for the visualization of apicoplast and mitochondrial division in live parasites at super resolution for the first time, and demonstrates that in PfDyn2-deficient parasites, while the apicoplast and mitochondrion increase in size and complexity, they do not undergo fission. We also show that these organellar fission defects prevent successful individualization of the schizont mass and the formation of new daughter cells, or merozoites because the basal complex, the cytokinetic ring of Plasmodium, cannot fully contract in PfDyn2-deficient parasites, a phenotype secondary to physical blockage by undivided organelles occluding the ring. PfDyn2's singular role in mediating both apicoplast and mitochondrial fission has not been observed in other organisms possessing two endosymbiotic organelles, including other Apicomplexans, thus reflecting a unique, potentially exploitable method of organellar division in P. falciparum.IMPORTANCEPlasmodium falciparum remains a significant global pathogen, causing over 200 million infections and over 600,000 deaths per year. One significant obstacle to the control of malaria is increasing resistance to first-line artemisinin-based antimalarials. Another is a lack of basic knowledge about the cell biology of the parasite. Along with the mitochondrion, Plasmodium contains a second organelle descended from an endosymbiotic event, the apicoplast. Both organelles are common targets for antimalarials, but because many proteins involved in organellar fission are not conserved in Plasmodium, until now, the mechanisms underlying apicoplast and mitochondrial division have been unknown. In this study, we demonstrate that PfDyn2, a dynamin-related protein (DRP), is required for the division of both organelles. We also show that defects in organellar division hinder segmentation of the schizont and formation of invasive merozoites by preventing full contraction of the basal complex. By demonstrating its necessity for the proper division of both the apicoplast and the mitochondria, this study highlights PfDyn2 as a potential target for new antimalarials.

Anti-cancer effect of sodium pentaborate in combination with cisplatin on lung cancer cell lines.

Despite the development of novel therapeutic modalities, lung cancer persists as the leading cause of cancer-related mortality. Platinum-based treatments represent the most prominent treatment option, with cisplatin being the most frequently utilized chemotherapeutic agent. However, cisplatin has several serious side effects. A substantial body of evidence has emerged in recent years indicating that boron compounds exhibit anti-cancer properties when administered as monotherapy or in combination with chemotherapy agents. The objective of this study is to examine the anti-cancer effects of Cisplatin (Cis) and sodium pentaborate pentahydrate (NaB), both individually and in combination, on non-small cell lung cancer (NSCLC) cell line A-549 cells and small cell lung cancer (SCLC) cell line DMS-114 cells under in vitro conditions. The effects of cisplatin and NAB on cell survival, apoptosis, the cell cycle, and the expression levels of apoptotic, anti-apoptotic, and tumor suppressor genes were determined by an MTS assay, an Annexin-V assay, a cell cycle analysis, and real-time PCR (qPCR). It was found that the IC-50 value of cisplatin, which was 10 µM when used alone, decreased to 2.5 µM when combined with a non-toxic dose of NaB on the A-549 cell line. BAX and TP53 gene expression levels were elevated by the Nab-Cisplatin combination in the A-549 cell line. The combination was observed to result in an approximately 19-fold increase in CDK2 gene expression in the A-549 cell line and an approximately 6-fold increase in the DMS-114 line, which resulted in S phase and/or G2 phase arrest on the cell cycle. Gene expression levels of Survivin and Ki-67 were decreased by the combination on both cell lines when compared with cisplatin alone. The findings demonstrate that NaB exerts an anti-cancer effect on the A-549 and DMS-114 cell lines. Moreover, when combined with cisplatin, it produces a synergistic anti-cancer effect on the A-549 cell line, whereby apoptosis is activated and cell proliferation is inhibited. The combination of NaB and cisplatin represents a novel approach to the treatment of NSCLC. This is due to the fact that it reduces the IC-50 value of cisplatin and also results in a greater inhibition of cell division and a stronger induction of cell death when used in the context of a combined treatment. Further insight into the effects of the NaB-cisplatin combination will be gained from in vivo experiments and clinical studies.

Effects of Pterostilbene on the Cell Division Cycle of a Neuroblastoma Cell Line

Background. The “Cell Cycle Hypothesis” suggests that the abnormal re-entry of neurons into the cell division cycle leads to neurodegeneration, a mechanism supported by in vitro studies on neuronal-like cells treated with the hyperphosphorylating agent forskolin. Pterostilbene, a bioavailable compound found in foods such as blueberries and grapes, may exert neuroprotective effects and could serve as a potential adjunct therapy for neurodegenerative diseases. Methods. In this study, we investigated the effects of pterostilbene on neuronal-like cells derived from the human neuroblastoma SK-N-BE cell line, where cell cycle reactivation was induced by forskolin treatment. We analyzed molecular endpoints associated with differentiated versus replicative cell states, specifically the following: (a) the expression of cyclin CCND1, (b) the Ki67 cell proliferation marker, (c) the AT8 nuclear tau epitope, and (d) genome-wide DNA methylation changes. Results. Our findings indicate that pterostilbene exerts distinct effects on the cell division cycle depending on the cellular state, with neuroprotective benefits observed in differentiated neuronal-like cells, but not in cells undergoing induced division. Additionally, pterostilbene alters DNA methylation patterns. Conclusion. These results suggest that pterostilbene may offer neuroprotective advantages for differentiated neuronal-like cells. However, further studies are required to confirm these effects in vivo by examining specific biomarkers in human populations consuming pterostilbene-containing foods.

Self-organized spatial targeting of contractile actomyosin rings for synthetic cell division

A key challenge for bottom-up synthetic biology is engineering a minimal module for self-division of synthetic cells. Actin-based cytokinetic rings are considered a promising structure to produce the forces required for the controlled excision of cell-like compartments such as giant unilamellar vesicles (GUVs). Despite prior demonstrations of actin ring targeting to GUV membranes and myosin-induced constriction, large-scale vesicle deformation has been precluded due to the lacking spatial control of these contractile structures. Here we show the combined reconstitution of actomyosin rings and the bacterial MinDE protein system within GUVs. Incorporating this spatial positioning tool, able to induce active transport of membrane-attached diffusible molecules, yields self-organized equatorial assembly of actomyosin rings in vesicles. Remarkably, the synergistic effect of Min oscillations and the contractility of actomyosin bundles induces mid-vesicle deformations and vesicle blebbing. Our system showcases how functional machineries from various organisms may be combined in vitro, leading to the emergence of functionalities towards a synthetic division system.

Impact of gibberellic acid GA3, quantum dot biochar, and rhizosphere bacteria on fenugreek plant growth and stress responses under lead stress

Lead (Pb) is a stress that can cause problems with several aspects of a plant’s metabolism, potentially impeding the plant’s ability to grow and develop. The use of gibberellic acid (GA3), quantum dot biochar (QDBC), and rhizobacteria (RB) can be effective methods to overcome this problem. Gibberellic acid is a crucial plant hormone that regulates plant growth, cell division, tissue differentiation, flowering, photosynthesis, and transpiration rate. It also significantly impacts crop resilience to stress, affecting plant morphology, enzymatic activity, and physiology. Biochar, a soil supplement, enhances plant development soil health, and reduces stress effects. Due to its large surface area and porosity, it increases soil water-holding capacity, nutrient retention, and microbial activity. Quantum dots, semiconductor nanoparticles, have been proposed as a potential method to alleviate plant stress by acting as antioxidants, reducing oxidative stress, and controlling nutrient and growth regulators. Rhizobacteria, soil bacteria in plant roots, stimulate plant growth, nutrient absorption, and harvesting capacity. They produce phytohormones, increase mineral and nitrogen accessibility, and can induce systemic resistance (ISR), affecting plant defense. This study investigates the effects of combining GA3, QDBC, and RB as amendments to fenugreek, both with 500 Pb stress and without Pb stress. Treatments (control, 0.25 GA3mg/L-QDBC, 0.5 GA3mg/L-QDBC, 0.25 GA3mg/L-QDBC + RB, and 0.5 GA3mg/L-QDBC + RB) were applied in six replications using a completely randomized design. Results demonstrate that the combination of 0.5 GA3mg/L-QDBC + RB with 500 Pb stress led to significant enhancements in fenugreek shoot fresh weight (15.62%), root fresh weight (73.53%), shoot dry weight (24.00%), and root dry weight (36.53%) compared to the control. Additionally, there were notable improvements in chlorophyll a (57.23%), chlorophyll b (19.21%), and total chlorophyll (36.23%) compared to the control under Pb stress, also showing the potential of 0.5 GA3mg/L-QDBC + RB with 500 Pb stress. The study suggests that combining 0.5 GA3mg/L-QDBC + RB with 500 Pb stress can effectively mitigate Pb stress in fenugreek.

Distinct interspecies thermal resistance strategies exhibited by euplanktonic, tychoplanktonic and benthic diatoms under marine heatwaves

Extreme climate events, such as marine heatwaves (MHWs), are expected to occur more frequently and intensely in the future, resulting in a substantial impact on marine life. The way that diatoms respond to MHWs may have crucial effects on global primary production and biogeochemical cycles. Euplanktonic diatoms appear to benefit from MHWs directly, but this phenomenon needs an explanation. As concerns tychoplanktonic and benthic diatoms, no studies have been addressed on their thermal response strategies. To address this, we investigated the responses and underlying mechanisms of three typical growth forms of diatoms, Pseudo-nitzschia multiseries (euplanktonic), Paralia guyana (tychoplanktonic) and Navicula avium (benthic), under heat stress by combining a growth experiment with transcriptomic analysis. Our results showed that the physiological responses of diatoms to MHWs and underlying molecular mechanisms are largely related to their growth forms. The euplanktonic diatom was first depressed, but then had a distinct increase in the growth rate accompanied by inducing zeatin and unsaturated fatty acid biosynthesis and repressing substance assimilation and energy metabolism. Contrarily, the benthic diatom showed elevated substance and energy demands for macromolecules accumulation by reducing cell division and increasing photosynthesis and nitrogen assimilation. The tychoplanktonic diatom exhibited higher physiological plasticity to maintain growth and cellular homeostasis. Our results indicate the increased rate of cell division in euplanktonic diatoms under heat stress is likely an emergency response strategy promoting diatom dispersal for survival, but at the cost of disturbances of metabolic balance.

Integrative studies shed light on the pseudocryptic genus Crassohymena n. gen. (Protozoa, Ciliophora)

The morphology, morphogenesis, molecular phylogeny, and the resting cyst morphology of the freshwater ciliate, Crassohymena primicirrata (Berger and Foissner, 1987) n. gen., n. comb., found in samples collected from South Korea, were investigated. The Korean two populations observed are identical to each other and are highly similar to the type population showing only few and minor differences in the size and arrangement of cortical granules and the length of dorsal kinety 4. The new genus Crassohymena n. gen. is established and characterized by a number of morphological and ontogenetic features: the thick undulating membranes comprising three or four rows of kinetosomes and in Cyrtohymena pattern; the anteriorly distinctly displaced transverse cirri; the posteriorly set-off cirrus V/3; the opisthe's anlagen IV–VI originate from cirri IV/2, V/4, and V/3, respectively; the proter's anlagen IV–VI originate from cirrus IV/3; and the enormous anlage I in each daughter cell. Phylogenetic analyses based on 18S rRNA gene sequences show that Crassohymena primicirrata n. gen., n. comb. is separated from all other morphologically most similar taxa and forms an adelphotaxon to the clade containing sequences of the families Neokeronopsidae and Spirofilidae, and the two oxytrichid genera Australocirrus and Notohymena.