Reduced Cell Size Research Articles

Drosophila Tropomodulin is required for multiple actin-dependent processes within developing myofibers.

Proper muscle contraction requires the assembly and maintenance of sarcomeres and myofibrils. Although the protein components of myofibrils are generally known, less is known about the mechanisms by which they individually function and together synergize for myofibril assembly and maintenance. For example, it is unclear how the disruption of actin filament (F-actin) regulatory proteins leads to the muscle weakness observed in myopathies. Here, we show that knockdown of Drosophila Tropomodulin (Tmod), results in several myopathy-related phenotypes, including reduction of muscle cell (myofiber) size, increased sarcomere length, disorganization and misorientation of myofibrils, ectopic F-actin accumulation, loss of tension-mediating proteins at the myotendinous junction, and misshaped and internalized nuclei. Our findings support and extend the tension-driven self-organizing myofibrillogenesis model. We show that, like its mammalian counterpart, Drosophila Tmod caps F-actin pointed-ends, and we propose that this activity is crucial for cellular processes in different locations within the myofiber that directly and indirectly contribute to the maintenance of muscle function. Our findings provide significant insights to the role of Tmod in muscle development, maintenance and disease.

A mobility aware handover scheme for 4G LTE system

Reduction in cell size in an ultra-dense network faces the challenge of increase in frequency of handovers and signaling overhead (mobility management) as well as inter-cell interference. Such frequent handovers leads to increased packet loss and blocking rate if the handover latency is very high, which have adverse effect on connectivity and performance. However, most existing schemes have the common characteristics of increasing spectral and energy efficiency due to increase in the number of micro cell on a network, thus decreases the general network performance. In this study, an improved scheme was developed for fixed mobility management pattern (FMP). A comparison module was established and an identifier algorithm that uses the user equipment international mobile equipment identity (IMEI) as a decisive component of its cell selection camping process was designed. Network simulator (NS-3) was used to study the impact of macro cell and inter site distance (ISD) on user throughput and battery life usage using mobility pattern of 3km/h, with A3 event based measurement for ISD 50, 150, 300, 500, and 1000 respectively. The performance evaluation metrics used are; reference signal received power (RSRP), flow monitor and handover time. The FMP results were compared with micro cell performance in an ultra-dense network. The RSRP result from FMP was higher than that of micro cell at ISD 50 and 150 respectively (-71.36, -73.97 and 83.77, 85.13). The handover time for FMP was higher than that of micro cell except for ISD 50 which was 50s and 51s respectively. The flow monitor of FMP showed a packet loss ratio of 0.0001 compare to 0.21 of micro cell. The battery life usage shows that FMP used 5943±8.7mw compare to micro cell which used 1680.2±15.7 mw. These results showed that FMP is efficient in managing the frequency of handover and battery life consumption for better connectivity and performance.

A rapid method for measuring ATP + ADP + AMP in marine sediment.

In this report, I describe a method for rapid measurement of total adenylate (ATP + ADP + AMP) in marine sediment samples for estimating microbial biomass. A simple 'boil and dilute' method is described here, whereby adding boiled MilliQ water to sediments increases the detection limit for ATP + ADP + AMP up to 100-fold. The lowered detection limit of this method enabled the detection ATP + ADP + AMP in relatively low-biomass sub-seafloor sediment cores with 104 16S rRNA gene copies per gram. Concentrations of ATP + ADP + AMP correlated with 16S rRNA gene concentrations from bacteria and archaea across six different sites that range in water depth from 1 to 6000 m indicating that the ATP + ADP + AMP method can be used as an additional biomass proxy. In deep sea microbial communities, the ratio of ATP + ADP + AMP concentrations to 16S rRNA genes >1m below seafloor was significantly lower compared to communities in the upper 30 cm of sediment, which may be due to reduced cell sizes and or lower ATP + ADP + AMP concentrations per cell in the deep sea sub-seafloor biosphere. The boil and dilute method for ATP + ADP + AMP is demonstrated here to have a detection limit sufficient for measuring low biomass communities from deep sea sub-seafloor cores. The method can be applied to frozen samples, enabling measurements of ATP + ADP + AMP from frozen sediment cores stored in core repositories from past and future international drilling campaigns.

Synergistic antifungal interaction of N-(butylcarbamothioyl) benzamide and amphotericin B against Cryptococcus neoformans.

Cryptococcus neoformans is one of the leading causes of invasive fungal infections worldwide. Cryptococcal meningoencephalitis is the main challenge of antifungal therapy due to high morbidity and mortality rates, especially in low- and middle-income countries. This can be partly attributed to the lack of specific diagnosis difficulty accessing treatment, antifungal resistance and antifungal toxicity. In the present study, the effect of the synthetic thiourea derivative N-(butylcarbamothioyl) benzamide (BTU-01), alone and combined with amphotericin B (AmB), was evaluated in planktonic and sessile (biofilm) cells of C. neoformans. BTU-01 alone exhibited a fungistatic activity with minimal inhibitory concentrations (MICs) ranging from 31.25 to 62.5 μg/mL for planktonic cells; and sessile MICs ranging from 125.0 to 1000.0 μg/mL. BTU-01 caused a concentration-dependent inhibitory activity on cryptococcal urease and did not interfere with plasma membrane fluidity. Molecular docking was performed on Canavalia ensiformis urease, and BTU-01 showed relevant interactions with the enzyme. The combination of BTU-01 and AmB exhibited synergistic fungicidal activity against planktonic and sessile cells of C. neoformans. Microscopic analysis of C. neoformans treated with BTU-01, alone or combined with AmB, revealed a reduction in cell and capsule sizes, changes in the morphology of planktonic cells; a significant decrease in the number of cells within the biofilm; and absence of exopolymeric matrix surrounding the sessile cells. Neither hemolytic activity nor cytotoxicity to mammalian cells was detected for BTU-01, alone or combined with AmB, at concentrations that exhibited antifungal activity. BTU-01 also displayed drug-likeness properties. These results indicate the potential of BTU-01, for the development of new strategies for controlling C. neoformans infections.

A novel proteinaceous molecule produced by Lysinibacillus sp. OF-1 depends on the Ami oligopeptide transporter to kill Streptococcus pneumoniae.

Infections caused by antibiotic-resistant Streptococcus pneumoniae are of growing concern for healthcare systems, which need new treatment options. Screening microorganisms in terrestrial environments has proved successful for discovering antibiotics, while production of antimicrobials by marine microorganisms remains underexplored. Here we have screened microorganisms sampled from the Oslo Fjord in Norway for production of molecules that prevent the human pathogen S. pneumoniae from growing. A bacterium belonging to the genus Lysinibacillus was identified. We show that this bacterium produces a molecule that kills a wide range of streptococcal species. Genome mining in BAGEL4 and AntiSmash suggested that it was a new antimicrobial compound, and we therefore named it lysinicin OF. The compound was resistant to heat (100 °C) and polymyxin acylase but susceptible to proteinase K, showing that it is of proteinaceous nature, but most probably not a lipopeptide. S. pneumoniae became resistant to lysinicin OF by obtaining suppressor mutations in the ami locus, which encodes the AmiACDEF oligo peptide transporter. We created ΔamiC and ΔamiEF mutants to show that pneumococci expressing a compromised Ami system were resistant to lysinicin OF. Furthermore, by creating mutants expressing an intact but inactive Ami system (AmiED184A and AmiFD175A) we could conclude that the lysinicin OF activity depended on the active form (ATP-hydrolysing) of the Ami system. Microscopic imaging and fluorescent labelling of DNA showed that S. pneumoniae treated with lysinicin OF had an average reduced cell size with condensed DNA nucleoid, while the integrity of the cell membrane remained intact. The characteristics and possible mode of action of lysinicin OF are discussed.

Phenotypic and transcriptomic acclimation of the green microalga Raphidocelis subcapitata to high environmental levels of the herbicide diflufenican

Herbicide pollution poses a worldwide threat to plants and freshwater ecosystems. However, the understanding of how organisms develop tolerance to these chemicals and the associated trade-off expenses are largely unknown. This study aims to investigate the physiological and transcriptional mechanisms underlying the acclimation of the green microalgal model species Raphidocelis subcapitata (Selenastraceae) towards the herbicide diflufenican, and the fitness costs associated with tolerance development. Algae were exposed for 12 weeks (corresponding to 100 generations) to diflufenican at the two environmental concentrations 10 and 310 ng/L. The monitoring of growth, pigment composition, and photosynthetic performance throughout the experiment revealed an initial dose-dependent stress phase (week 1) with an EC50 of 397 ng/L, followed by a time-dependent recovery phase during weeks 2 to 4. After week 4, R. subcapitata was acclimated to diflufenican exposure with a similar growth rate, content of carotenoids, and photosynthetic performance as the unexposed control algae. This acclimation state of the algae was explored in terms of tolerance acquisition, changes in the fatty acids composition, diflufenican removal rate, cell size, and changes in mRNA gene expression profile, revealing potential fitness costs associated with acclimation, such as up-regulation of genes related to cell division, structure, morphology, and reduction of cell size. Overall, this study demonstrates that R. subcapitata can quickly acclimate to environmental but toxic levels of diflufenican; however, the acclimation is associated with trade-off expenses that result in smaller cell size.

Effect of tellurite on growth of extensively drug resistant (XDR) Mycobacterium tuberculosis and action on mycobacterial drug efflux pump

In the present study genotypic resistance of bacterial strain to first- and second-line anti-tuberculosis drugs was determined by Line probe assay. Toxic effect of tellurite on the growth of Mycobacterium tuberculosis (MTB) was determined by growing cells in different concentrations of tellurite (1 to 5 mM). Morphological effects of tellurite and uptake of metal in bacterial cells were confirmed by Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis. Change in fold expression of the efflux pump gene was measured by RT-PCR. Mycobacterial strain was characterized as XDR-TB based on the genotypic resistance to rifampicin and isoniazid, along with resistance to fluoroquinolones and second line injectable. XDR-TB showed black colonies in tellurite presence and growth was delayed (2–3 weeks) when compared with the control. The reduced cell size, metal accumulation and the characteristic tellurite peaks appeared in metal-treated cells. MTB showed MIC value of 1 mM and had high susceptibility for higher concentrations (2–5 mM). However, no significant metal inhibitory effect on the mmpL7 efflux system was determined. Tellurite shows significant growth reduction potential against XDR-TB strain. However, the exact mechanism of action needs to be elucidated with further research.

The role of cell size in shaping responses to oxygen and temperature in fruit flies

Abstract The body size of an animal is strongly coupled to key ecological traits such as fecundity, mortality and growth. Ectothermic animals mature at smaller body sizes in warmer conditions and under low oxygen availability (hypoxia). Whether these responses result from changes in cell size and cell number (which together determine body size) and how such cellular responses may help ectotherms cope with heat and hypoxia is poorly understood. The theory of optimal cell size postulates that cell size imposes constraints on oxygen delivery: Differences in cell size result in differences in membrane surface‐to‐volume ratio, which impact the capacity of cells to take up oxygen and has consequences for growth rate and hence body size. Here, using inbred lines of fruit flies Drosophila melanogaster, which exhibit differences in cell size, we demonstrate that thermal responses in body size are magnified under hypoxia and in lines of flies that exhibit larger cell size. Furthermore, reductions in body size were partly manifested via reductions in cell size, resulting in a coupling between the body mass and cell size of flies. The coupling between cell size and body size was tighter under conditions where oxygen is expected to become limited, that is, warm or hypoxia, supporting the idea that capacity for oxygen uptake is causally related to organismal growth and the resulting body size. Our data indicate that the benefits of diffusive oxygen uptake due to the higher surface‐to‐volume ratios in smaller cells can help explain the temperature‐size rule in this species. Read the free Plain Language Summary for this article on the Journal blog.

Backscattering Statistics of Indoor Full-Polarization Scatterometric and Synthetic Aperture Radar Measurements of a Rice Field

The backscattering coefficient σ0 of a rice field is closely related to the amplitude, power, and phase of its radar backscattered signals. An investigation of the statistics of indoor full-polarization scatterometric and synthetic aperture radar (SAR) measurements on rice fields in the Laboratory of Target Microwave Properties (LAMP) is implemented in terms of the amplitude, power, and phase difference of backscattered signals. The validity and accuracy of LAMP measured data are studied and confirmed for the first time. The Rayleigh fading model and phase difference statistical model are both validated by the experimental data. Continuous microwave spectrum is obtained after spatial and frequency averaging over N independent scatterometric samples and full-polarization images are generated by applying a focusing algorithm to the SAR data. Comparisons between scatterometric results and SAR images with three resolutions of rice field scene are conducted with respect to amplitude and co-pol phase difference (CPD) statistics, as well as backscattering coefficients. The results show that the measured statistics of a rice field scene are in good agreement with those calculated by theoretical formulas. Spatial and frequency averaging of scatterometric data can increase N and thus improve the estimation accuracy of the backscattering coefficients. SAR images show a shift to the near range due to the intrinsic height of the rice plants and the probable existence of the double bounce scattering between vertical rice stems and the water surface considering the measurement geometry. The measured amplitude statistics of the SAR images approach a Rayleigh distribution with reduction of the resolution cell size while the size has little effect on the CPD statistics. The differences between backscattering coefficients extracted from the scatterometric data and SAR images confirm a 1-dB calibration accuracy in power of the LAMP measurement system.

HypERlnc attenuates angiotensin II-induced cardiomyocyte hypertrophy via promoting SIRT1 SUMOylation-mediated activation of PGC-1α/PPARα pathway in AC16 cells.

Cardiac hypertrophy is a well-established risk factor for cardiovascular mortality worldwide. According to a recent study, hypoxia-induced endoplasmic reticulum stress regulating long noncoding RNA (HypERlnc) is significantly reduced in the left ventricular myocardium of heart failure (HF) patients compared with healthy controls. However, the effect of HypERlnc on hypertrophy is unclear. In this study, the expression level of HypERlnc in serum of patients with chronic HF was analyzed. Moreover, the cardioprotective effect and mechanism of HypERlnc against cardiomyocyte hypertrophy were explored. Here, the level of HypERlnc expression was reduced in serum of patients with HF and in Angiotensin II (Ang II)-stimulated AC16 cells. HypERlnc overexpression could reduce cell size and inhibit expression of hypertrophy genes (ANP, BNP, and β-MHC) in the Ang II-induced cardiomyocyte hypertrophy. Meanwhile, HypERlnc could improve the Ang II-induced energy metabolism dysfunction and mitochondrial damage via upregulating PGC-1α/PPARα signaling pathway. Furthermore, it is found that SIRT1 SUMOylation mediated the HypERlnc-induced inhibition of cardiomyocyte hypertrophy and the improvement of energy metabolism. Taken together, this study suggests that HypERlnc suppresses cardiomyocyte hypertrophy and energy metabolism dysfunction via enhancing SUMOylation of SIRT1 protein. HypERlnc is a potential novel molecular target for preventing and treating pathological cardiac hypertrophy.

TRF2 rescues telomere attrition and prolongs cell survival in Duchenne muscular dystrophy cardiomyocytes derived fromhuman iPSCs.

Duchenne muscular dystrophy (DMD) is a severe muscle wasting disease caused by the lack of dystrophin. Heart failure, driven by cardiomyocyte death, fibrosis, and the development of dilated cardiomyopathy, is the leading cause of death in DMD patients. Current treatments decrease the mechanical load on the heart but do not address the root cause of dilated cardiomyopathy: cardiomyocyte death. Previously, we showed that telomere shortening is a hallmark of DMD cardiomyocytes. Here, we test whether prevention of telomere attrition is possible in cardiomyocytes differentiated from patient-derived induced pluripotent stem cells (iPSC-CMs) and if preventing telomere shortening impacts cardiomyocyte function. We observe reduced cell size, nuclear size, and sarcomere density in DMD iPSC-CMs compared with healthy isogenic controls. We find that expression of just one telomere-binding protein, telomeric repeat-binding factor 2 (TRF2), a core component of the shelterin complex, prevents telomere attrition and rescues deficiencies in cell size as well as sarcomere density. We employ a bioengineered platform to micropattern cardiomyocytes for calcium imaging and perform Southern blots of telomere restriction fragments, the gold standard for telomere length assessments. Importantly, preservation of telomere lengths in DMD cardiomyocytes improves their viability. These data provide evidence that preventing telomere attrition ameliorates deficits in cell morphology, activation of the DNA damage response, and premature cell death, suggesting that TRF2 is a key player in DMD-associated cardiac failure.

Cytotoxic Effect of the Alcoholic Extract of Conocarpus erectus Leaves on MDA-MB 231 and MCF7 Breast Cancer Cell Lines

Currently, there is a growing interest in medicinal plants extracts as some plants have shown antitumor potential. The goal of this study was to test the anticancer activity of methanol extract of Conocarpous erectus leaves in breast cancer cells. Cytotoxicity was tested in vitro on breast cancer cell lines, MCF7 [Estrogen receptor + (ER+)] and MDA-MB231 [Estrogen receptor - (ER-)], in addition to normal fibroblast cells (REF). MTT assay was utilized to measure the growth inhibitory effects after 48 hours exposure to extracts. Viability results indicated that MDA-MB231 were sensitive (GI50 = 56.1µg/ml).However, no sensitivity was seen in both MCF7 and REF cells (GI50>100 µg/ml). Interestingly the sensitivity seen in MDA-MB231 cells was associated with a significant reduction in cell number and size. It can be concluded from this study that leaves extracts may provide a candidate therapy against breast cancer cells and sensitivity was not linked with ER expression. No effect was observed in normal cells.

The thermal and combustion properties of soybean oil phosphate-based polyurethane foam composites containing polyol of etidronic acid

In this work, a phosphorus-containing soybean oil-based polyol (PSOP) was successfully synthesized from epoxidized soybean oil by a ring-opening reaction with dibutyl phosphate. A phosphorous polyol (HEDP-PO) was synthesized by polymerization between 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and propylene oxide (PO). The two new polyols were used together in the formation of flame-retardant polyurethane foams (FRPUF), which depicted good thermal stability and flame retardancy performance. The addition of PSOP/HEDP-PO polyols resulted in a reduction of cell size and an increasement of cell numbers of PUF composites, whose apparent density was observed to increase. Besides, the LOI value of PUF-80 could reach 23.7% and satisfy the V-0 rating in the vertical burning test. The cone calorimeter test showed a reduction in the heat release rate from 395 kW/m2 to 251 kW/m2 and the total heat release from 24.9 MJ/m2 to 18.0 MJ/m2. Polyurethane foam exhibited good flame retardancy because PSOP/HEDP-PO played a great free radical quenching effect in the gas phase by releasing the PO* and PO2* free radicals. Meanwhile, a more dense and complete carbon layer was formed to cut off the transfer of heat and oxygen between the matrix and the ambient.

Water absorption properties of polyurethane foam reinforced with paper pulp

Polyurethane foams are widely used for furniture, cushioning and thermal insulation applications. However, there has been limited research on polyurethane foam applications that focus on water absorptivity, as the polyurethane foam is hydrophobic in nature. Hence, this research aims to reinforce polyurethane foam with paper pulp to enhance its water- absorbing properties, potentially allowing it to be utilized in new applications like growing plants. This study conducted an investigation on the effect of filler loading, cellular structure, and water-absorbing properties. It has been noted that the addition of paper pulp filler causes a reduction in cell size and wall thickness. Water absorptivity and water retention are found to be correlated with the cell structure, and they improve as the cell size increases. It was found that 4 wt% of paper pulp reinforced polyurethane foam demostrated satisfactory water absorption (11.5%) and water retention properties (75.9%) among the samples, potentially to apply as plantation foam.

Photosynthetic picoeukaryotes significantly affect global oceanic meta-metabolism: cellular and genome streamlining confer ecological success

Photosynthetic picoeukaryotes (PPEs) are characterized by a reduction in cell and genome size but are free living, in contrast to many other organisms that have undergone such reductions. The relative abundance of PPEs in the oceans remains to be determined, as do the evolutionary imperatives behind their cell and genome reduction. Their enigmatic nature may be deciphered through metagenomics approaches; consequently, we utilized shotgun data from the Tara Oceans database to better understand both their ecological and genomic features. The clustering of meta-metabolomic networks constructed from shotgun data from 10 different sampling sites was influenced by the proportion of PPEs in the data sets. This, along with the relative abundance of RUBISCO sequences belonging to PPEs, indicates that they have a significant effect on oceanic meta-metabolism, emphasizing the evolutionary success of the streamlining strategy. Using rRNA sequences extracted from the shotgun data, a global oceanic distribution of PPEs showed little variation, including those lineages with reduced genome sizes. This indicates that genome and cellular streamlining is not an adaptation to environmental parameters but may rather be a community-driven effect. Lastly, and surprisingly given their role as primary producers, PPEs were found to comprise only 2 to 49% (17% on average) of all picoeukaryotes across 93 metagenomes. We show that contamination of the data set by eukaryotes with larger cell sizes is not responsible for the anomaly, and so the observation remains to be explained. The approaches described here allow us to draw a direct link between taxonomic composition and meta-metabolomic capacity, with implications for better understanding carbon fixation, biogeochemical cycling, and planetary self-regulation.

Regulation of cell size and Wee1 kinase by elevated levels of the cell cycle regulatory protein kinase Cdr2

Many cell cycle regulatory proteins catalyze cell cycle progression in a concentration-dependent manner. In the fission yeast Schizosaccharomyces pombe, the protein kinase Cdr2 promotes mitotic entry by organizing cortical oligomeric nodes that lead to inhibition of Wee1, which itself inhibits the cyclin-dependent kinase Cdk1. cdr2Δ cells lack nodes and divide at increased size due to overactive Wee1, but it has not been known how increased Cdr2 levels might impact Wee1 and cell size. It also has not been clear if and how Cdr2 might regulate Wee1 in the absence of the related kinase Cdr1/Nim1. Using a tetracycline-inducible expression system, we found that a 6× increase in Cdr2 expression caused hyperphosphorylation of Wee1 and reduction in cell size even in the absence of Cdr1/Nim1. This overexpressed Cdr2 formed clusters that sequestered Wee1 adjacent to the nuclear envelope. Cdr2 mutants that disrupt either kinase activity or clustering ability failed to sequester Wee1 and to reduce cell size. We propose that Cdr2 acts as a dosage-dependent regulator of cell size by sequestering its substrate Wee1 in cytoplasmic clusters, away from Cdk1 in the nucleus. This mechanism has implications for other clustered kinases, which may act similarly by sequestering substrates.

Oxidative damage by 1,10-phenanthroline-5,6-dione and its silver and copper complexes lead to apoptotic-like death in Trichomonas vaginalis

Trichomoniasis is a neglected, parasitic, sexually transmitted infection. Resistance to the only approved drugs is increasing worldwide, leaving millions of people without alternative medications. Thus, the search for new therapeutic options against this infection is necessary. Previously, our group reported that 1,10-phenanthroline-5,6-dione (phendione) and its silver(I) and copper (II) complexes (abbreviated as Ag-phendione and Cu-phendione, respectively) presented activity against the amitochondriate parasite T. vaginalis, with Cu-phendione being the most effective (IC50 = 0.84 μM). Methods: qRT-PCR, SEM, flow cytometry. The current study on the effects of Cu-phendione on the antioxidant metabolism of T. vaginalis by qRT-PCR revealed that the complex causes a decrease in the relative expression of mRNA of NADH oxidase, flavin reductase, superoxide dismutase, peroxiredoxin, iron-sulfur flavoprotein, rubrerythrin and osmotically inducible proteins. In contrast, the mRNA expression of flavodiiron protein was increased. Detoxification-related enzymes were downregulated, impairing oxygen metabolism in trophozoites and triggering a subsequent accumulation of the superoxide anion. Although no DNA fragmentation was observed, the treatment of parasites with Cu-phendione led to a significant reduction in cell size and a concomitant increase in granularity. The complex promoted phosphatidylserine exposure at the plasma membrane (as judged by Annexin V binding) and propidium iodide was unable to passively permeate the parasites. All of these outcomes are classical hallmarks of cell death by apoptosis. In essence, the trichomonacidal effect of Cu-phendione operates through redox homeostasis imbalance, which is a mode of action that is quite distinct from that caused by metronidazole.

Endoreplication mediates cell size control via mechanochemical signaling from cell wall

Endoreplication is an evolutionarily conserved mechanism for increasing nuclear DNA content (ploidy). Ploidy frequently scales with final cell and organ size, suggesting a key role for endoreplication in these processes. However, exceptions exist, and, consequently, the endoreplication-size nexus remains enigmatic. Here, we show that prolonged tissue folding at the apical hook in Arabidopsis requires endoreplication asymmetry under the control of an auxin gradient. We identify a molecular pathway linking endoreplication levels to cell size through cell wall remodeling and stiffness modulation. We find that endoreplication is not only permissive for growth: Endoreplication reduction enhances wall stiffening, actively reducing cell size. The cell wall integrity kinase THESEUS plays a key role in this feedback loop. Our data thus explain the nonlinearity between ploidy levels and size while also providing a molecular mechanism linking mechanochemical signaling with endoreplication-mediated dynamic control of cell growth.

Achiral Nanoparticle-Enhanced Chiral Twist and Thermal Stability of Blue Phase Liquid Crystals.

Blue phase liquid crystals (BPLCs) are chiral mesophases with 3D order, which makes them a promising template for doping nanoparticles (NPs), yielding tunable nanomaterials attractive for microlasers and numerous microsensor applications. However, doping NPs to BPLCs causes BP lattice extension, which translates to elongation of operating wavelengths of light reflection. Here, it is demonstrated that small (2.4 nm diameter) achiral gold (Au) NPs decorated with designed LC-like ligands can enhance the chiral twist of BPLCs (i.e., reduce cell size of the single BP unit up to ∼14% and ∼7% for BPI and BPII, respectively), translating to a blue-shift of Bragg reflection. Doping NPs also significantly increases the thermal stability of BPs from 5.5 °C (for undoped BPLC) up to 22.8 °C (for doped BPLC). In line with our expectations, both effects are saturated, and their magnitude depends on the concentration of investigated nanodopants as well the BP phase type. Our research highlights the critical role of functionalization of Au NPs on the phase sequence of BPLCs. We show that inappropriate selection of surface ligands can destabilize BPs. Our BPLC and Au NPs are photochemically stable and exhibit great miscibility, preventing NP aggregation in the BPLC matrix over the long term. We believe that our findings will improve the fabrication of advanced nanomaterials into 3D periodic soft photonic structures.

Mate Perception and Gene Networks Regulating the Early Phase of Sex in Pseudo-nitzschia multistriata

Diatoms are photosynthetic microorganisms playing a key role in the functioning of aquatic ecosystems; they are at the base of the food web and are the main drivers of biogeochemical processes. These microalgae have a unique diplontic life cycle in which the vegetative phase entails a cell size reduction that would lead to the extinction of the cell population if the size was not restored, usually by sexual reproduction. The switch from asexual to sexual reproduction needs to be finely synchronized and regulated to ensure its success; to this aim, cells evolved complex chemical crosstalk that mediates mating. We focused our attention on the marine diatom Pseudo-nitzschia multistriata, investigating the reciprocal perception of the opposite mating type (MT) and the genes and signaling molecules putatively involved in the process. From previously available transcriptomic data, we selected a panel of genes deregulated during the early phase of sexual reproduction, confirming for some of them a role during mate perception and establishing a hierarchy governing their behavior. Moreover, we explored the nature of the molecules controlling sexual reproduction in this species, unveiling that the signaling is mediated by the secretion of protein and non-protein cues from the MT− and MT+, respectively. Our results point to a model in which the two MTs stimulate each other, but the stimulation by the MT− is amplified after MT+ perception in a positive feedback manner.