The 3D architecture and molecular foundations of de novo centriole assembly via bicentrioles

Centrioles are structurally conserved organelles, composing both centrosomes and cilia. In animal cycling cells, centrioles often form through a highly characterized process termed canonical duplication. However, a large diversity of eukaryotes assemble centrioles de novo through uncharacterized pathways. This unexplored diversity is key to understanding centriole assembly mechanisms and how they evolved to assist specific cellular functions. Here, we show that, during spermatogenesis of the bryophyte Physcomitrium patens, centrioles are born as a co-axially oriented centriole pair united by a cartwheel. Interestingly, we observe that these centrioles are twisted in opposite orientations. Microtubules emanate from the bicentrioles, which localize to the spindle poles during cell division. After their separation, the two resulting sister centrioles mature asymmetrically, elongating specific microtubule triplets and a naked cartwheel. Subsequently, two motile cilia are assembled that appear to alternate between different motility patterns. We further show that centriolar components SAS6, Bld10, and POC1, which are conserved across eukaryotes, are expressed during spermatogenesis and required for this de novo biogenesis pathway. Our work supports a scenario where centriole biogenesis, while driven by conserved molecular modules, is more diverse than previously thought.

The 3D architecture and molecular foundations of de novo centriole assembly via bicentrioles

Centrioles are structurally conserved organelles, composing both centrosomes and cilia. In animal cycling cells, centrioles often form through a highly characterized process termed canonical duplication. However, a large diversity of eukaryotes assemble centrioles de novo through uncharacterized pathways. This unexplored diversity is key to understanding centriole assembly mechanisms and how they evolved to assist specific cellular functions. Here, we show that, during spermatogenesis of the bryophyte Physcomitrium patens, centrioles are born as a co-axially oriented centriole pair united by a cartwheel. Interestingly, we observe that these centrioles are twisted in opposite orientations. Microtubules emanate from the bicentrioles, which localize to the spindle poles during cell division. After their separation, the two resulting sister centrioles mature asymmetrically, elongating specific microtubule triplets and a naked cartwheel. Subsequently, two motile cilia are assembled that appear to alternate between different motility patterns. We further show that centriolar components SAS6, Bld10, and POC1, which are conserved across eukaryotes, are expressed during spermatogenesis and required for this de novo biogenesis pathway. Our work supports a scenario where centriole biogenesis, while driven by conserved molecular modules, is more diverse than previously thought.

Comparative transcriptomic analysis reveals conserved programmes underpinning organogenesis and reproduction in land plants

The appearance of plant organs mediated the explosive radiation of land plants, which shaped the biosphere and allowed the establishment of terrestrial animal life. The evolution of organs and immobile gametes required the coordinated acquisition of novel gene functions, the co-option of existing genes and the development of novel regulatory programmes. However, no large-scale analyses of genomic and transcriptomic data have been performed for land plants. To remedy this, we generated gene expression atlases for various organs and gametes of ten plant species comprising bryophytes, vascular plants, gymnosperms and flowering plants. A comparative analysis of the atlases identified hundreds of organ- and gamete-specific orthogroups and revealed that most of the specific transcriptomes are significantly conserved. Interestingly, our results suggest that co-option of existing genes is the main mechanism for evolving new organs. In contrast to female gametes, male gametes showed a high number and conservation of specific genes, which indicates that male reproduction is highly specialized. The expression atlas capturing pollen development revealed numerous transcription factors and kinases essential for pollen biogenesis and function.

Comparative transcriptomic analysis reveals conserved programmes underpinning organogenesis and reproduction in land plants

The appearance of plant organs mediated the explosive radiation of land plants, which shaped the biosphere and allowed the establishment of terrestrial animal life. The evolution of organs and immobile gametes required the coordinated acquisition of novel gene functions, the co-option of existing genes and the development of novel regulatory programmes. However, no large-scale analyses of genomic and transcriptomic data have been performed for land plants. To remedy this, we generated gene expression atlases for various organs and gametes of ten plant species comprising bryophytes, vascular plants, gymnosperms and flowering plants. A comparative analysis of the atlases identified hundreds of organ- and gamete-specific orthogroups and revealed that most of the specific transcriptomes are significantly conserved. Interestingly, our results suggest that co-option of existing genes is the main mechanism for evolving new organs. In contrast to female gametes, male gametes showed a high number and conservation of specific genes, which indicates that male reproduction is highly specialized. The expression atlas capturing pollen development revealed numerous transcription factors and kinases essential for pollen biogenesis and function.

Biophysical and Quantitative Principles of Centrosome Biogenesis and Structure

The centrosome is a main orchestrator of the animal cellular microtubule cytoskeleton. Dissecting its structure and assembly mechanisms has been a goal of cell biologists for over a century. In the last two decades, a good understanding of the molecular constituents of centrosomes has been achieved. Moreover, recent breakthroughs in electron and light microscopy techniques have enabled the inspection of the centrosome and the mapping of its components with unprecedented detail. However, we now need a profound and dynamic understanding of how these constituents interact in space and time. Here, we review the latest findings on the structural and molecular architecture of the centrosome and how its biogenesis is regulated, highlighting how biophysical techniques and principles as well as quantitative modeling are changing our understanding of this enigmatic cellular organelle. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Noncanonical Biogenesis of Centrioles and Basal Bodies

Centrioles and basal bodies (CBBs) organize centrosomes and cilia within eukaryotic cells. These organelles are composed of microtubules and hundreds of proteins performing multiple functions such as signaling, cytoskeleton remodeling, and cell motility. The CBB is present in all branches of the eukaryotic tree of life and, despite its ultrastructural and protein conservation, there is diversity in its function, occurrence (i.e., presence/absence), and modes of biogenesis across species. In this review, we provide an overview of the multiple pathways through which CBBs are formed in nature, with a special focus on the less studied, noncanonical ways. Despite the differences among each mechanism herein presented, we highlighted some of their common principles. These principles, governing different steps of biogenesis, ensure that CBBs may perform a multitude of functions in a huge diversity of organisms but yet retained their robustness in structure throughout evolution.

Durum wheat diversity for heat stress tolerance during inflorescence emergence is correlated to TdHSP101C expression in early developmental stages

The predicted world population increase along with climate changes threatens sustainable agricultural supply in the coming decades. It is therefore vital to understand crops diversity associated to abiotic stress response. Heat stress is considered one of the major constrains on crops productivity thus it is essential to develop new approaches for a precocious and rigorous evaluation of varietal diversity regarding heat tolerance. Plant cell membrane thermostability (CMS) is a widely used method for wheat thermotolerance assessment although its limitations require complementary solutions. In this work we used CMS assay and explored TdHSP101C genes as an additional tool for durum wheat screening. Genomic and transcriptomic analyses of TdHSP101C genes were performed in varieties with contrasting CMS results and further correlated with heat stress tolerance during fertilization and seed development. Although the durum wheat varieties studied presented a very high homology on TdHSP101C genes (>99%) the transcriptomic assessment allowed the discrimination between varieties with good CMS results and its correlation with differential impacts of heat treatment during inflorescence emergence and seed development on grain yield. The evidences here reported indicate that TdHSP101C transcription levels induced by heat stress in fully expanded leaves may be a promising complementary screening tool to discriminate between durum wheat varieties identified as thermotolerant through CMS.

Virulence factors and infection ability of Pseudomonas aeruginosa isolates from a hydropathic facility and respiratory infections

AIMS

To compare the virulence pool and acute infection ability of Pseudomonas aeruginosa isolates from a hydropathic facility, used to treat respiratory conditions by inhalation of untreated natural mineral water, with clinical isolates from respiratory infections.

METHODS AND RESULTS

Pseudomonas aeruginosa isolates from a hydropathic facility and from respiratory infections were typed by pulsed-field gel electrophoresis. Nonclonal representatives of each population were selected. 18 virulence-encoding genes were screened by polymerase chain reaction and statistically compared by multiple correspondence analysis. Homogeneous distribution of genes between populations but higher genetic association in aquatic isolates was observed, as well as distinct virulence pool according to location in the water system. Acute infection ability of selected isolates from each population, in Galleria mellonella model, showed lower LD50 of the majority of the hydropathic isolates and significant variations in LD50 of biofilm isolates from different equipments.

CONCLUSIONS

Hydrotherapy Ps. aeruginosa isolates present similar virulence to isolates from respiratory infections. Hydrotherapy users may be exposed to different microbiological risks when using different treatment equipments.

SIGNIFICANCE AND IMPACT OF THE STUDY

Twenty-one million people use hydropathic facilities in Europe, and the majority present risk factors to pneumonia. This study demonstrates the health risk associated with this practice. Revision of European regulations should be considered.

Mobile genetic elements of Pseudomonas aeruginosa isolates from hydrotherapy facility and respiratory infections

The content of mobile genetic elements in Pseudomonas aeruginosa isolates of a pristine natural mineral water system associated with healthcare was compared with clinical isolates from respiratory infections. One isolate, from the therapy pool circuit, presented a class 1 integron, with 100% similarity to a class 1 integron contained in plasmid p4800 of the Klebsiella pneumoniae Kp4800 strain, which is the first time it has been reported in P. aeruginosa. Class 1 integrons were found in 25.6% of the clinical isolates. PAGI1 orf3 was more prevalent in environmental isolates, while PAGI2 c105 and PAGI3 sg100 were more prevalent in clinical isolates. Plasmids were not observed in either population.

Towards a controlled photopolymerization of dental dimethacrylate monomers: EPR studies on effects of dilution, filler loading, storage and aging

Electron paramagnetic resonance (EPR) was used to study the kinetics of methacrylate radical formation in the monomer mixture 2,2-bis [4-(2-hydroxy-3-methacryloxyprop-1-oxy) phenyl] propane (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA), in the presence of a photo-initiator system (camphorquinone, CQ/N,N-dimethyl-p-toluidine, DET). Curing-time dependences on the filler (0-40 wt%) and TEGDMA content (15-90 wt%) were evaluated; the influence of irradiation protocol, uncured sample storage time and aging of cured systems were also studied. EPR enabled observing at least two different kinetic regimes during polymerization. The final radical concentration decreased both with Bis-GMA and filler content. However, a reverse trend was obtained when the relative photo-initiator concentrations were considered. Filler also showed a significant effect on the radical life-time reduction. Irradiation protocol and storage time of uncured matrices showed to affect the free radical concentration. The observed changes on the EPR signal lineshape with post-curing time suggests that the distribution of CH(2) conformations also changes with time.

Effect of treated filler loading on the photopolymerization inhibition and shrinkage of a dimethacrylate matrix

This study shows how treated filler loading influences the photopolymerization of a dimethacrylate comonomer mixture, regarding, in particular, shrinkage and inhibition under atmospheric oxygen, present in oral environment. Bis-GMA/TEGDMA (75/25 wt.%) resins were loaded with hybrid filler (Ba aluminosilicate glass and pyrogenic silica), treated with gamma-methacryloxy(propyl)trimethoxysilane, at 0-50 wt.% and light cured over a total of 30 s (45 mW/cm2). Degree of double-bond conversion (DC), obtained using FTIR, decreased with filler content. 1H MAS spectra (293-340 K) and STRAFI images (293 K) were obtained as a function of irradiation time and filler concentration. 1H signals of unreacted methacrylate groups were more intense for higher loaded resins and resonances from -CH2SiO2(OH) (T2) and -CH2SiO3- (T3) units, also observed by 29Si NMR, were resolved and suggest the presence of T2-resin bonds. 1D images show a reduction on polymerization contraction and reaction inhibition at the composite resin surface with filler loading. 2D resin images present a highly mobile surface layer, hence with lower DC.

Serum leptin levels after bariatric surgery across a range of glucose tolerance from normal to diabetes

BACKGROUND

A longitudinal, clinical intervention study with bariatric surgery was done to investigate the relationship between leptin levels, BMI, and insulin during weight loss across a range of glucose tolerance from normal to diabetes.

METHODS

43 morbidly obese patients (BMI: 42-75 kg/m2) undergoing vertical banded gastroplasty Roux-en-Y gastric bypass (VBG-RGB), were divided into 3 groups: 21 normal (NGT), 12 impaired glucose tolerance (IGT) and 10 type 2 diabetes (DM). Leptin, insulin, glucose, lipids and uric acid were measured at baseline and 2, 4, 6, and 12 months following surgery.

RESULTS

BMI fell from 54.1 +/- 9.1 to 34.6 +/- 6.3 kg/m2, similarly in all groups. Leptin decreased from 73.9 +/- 8.7 to 16.9 +/- 10.2 ng/ml and was strongly correlated with BMI during 1-year follow-up (r = 0.78; p < 0.001). Linear univariate analysis for repeated evaluation showed a positive correlation between leptin and glucose, triglycerides, uric acid, and insulin. Multivariate regression analysis indicated that BMI was independently correlated with the decrease in leptin (p < 0.001), accounting for 66% of the variance in leptin levels during weight loss. These results were found in the NGT and IGT groups. In the DM group, a small additional influence in leptin levels was attributed to glucose decrease.

CONCLUSIONS

A strong link between leptin and BMI was found after surgery. BMI was the main determinant of the decrease of leptin. In these patients submitted to bariatric surgery, ranging from normal glucose tolerance to diabetes, changes in insulin levels and metabolic parameters, except for glucose in the DM group, did not appear to be correlated with changes in leptin levels.

Laparoscopic wedge resection of a gastric leiomyoma

Gastric stromal tumors represent a small percentage of gastric neoplasms. Establishing a diagnosis when these lesions are encountered usually is not possible with limited biopsies. Benign and malignant gastric stromal tumors require only local excision for definitive treatment. However, most lesions are not amenable to endoscopic excision. As a result, laparoscopic local excision offers the ideal method to establish a diagnosis and to treat patients with gastric smooth muscle tumors. We present a minimally invasive local excision of a gastric stromal tumor. We also review the previously published management of gastric stromal tumors and show how it is being influenced by laparoscopy.

United states research published in major surgical journals is decreasing

OBJECTIVE

The authors hypothesized that less research performed in the United States was reported in the five major general surgical journals in 1993 than in 1983.

SUMMARY BACKGROUND DATA

Academic surgeons believe they have less time and fewer funds for research than previously.

METHODS

Five journals were analyzed for the number of pages and articles devoted to basic and clinical research in 1983 and 1993 and for the country in which the research was performed.

RESULTS

The number of U.S. research pages and articles decreased over the past decade, and the number of non-U.S. pages and articles increased.

CONCLUSIONS

The reason(s) for the decrease in U.S. research reported in the general surgical journals should be studied, identified, and, if possible, rectified.