Seasonal changes in cambium activity from active to dormant stage affect the formation of secondary xylem in Pinus tabulaeformis Carr

Understanding the changing patterns of vascular cambium during seasonal cycles is crucial to reveal the mechanisms that control cambium activity and wood formation, but this area has been underexplored, especially in conifers. Here, we quantified the changing cellular morphology patterns of cambial zones during the active, transition and dormant stages. With the help of toluidine blue and periodic acid Schiff staining to visualize cell walls and identify their constituents, we observed decreasing cambial cell layers, thickening of newly formed xylem cell walls and increased polysaccharide granules in phloem from June to the following March over the course of our collecting period. Pectin immunofluorescence showed that dormant stage cambium can produce highly abundant de-esterified homogalacturonan and (1–4)-β-D-galactan epitopes, while active cambium can strong accumulate high methylesterified homogalacturonan. Calcofluor white staining and confocal Raman spectroscopy analysis revealed regular changes in the chemical composition of cell walls, such as relative lower cellulose deposition in transition stage in vascular cambium, and higher lignin accumulation was found in dormant stage in secondary xylem. Moreover, RT-qPCR analysis suggested that various IAA (Aux/IAA protein), CesA, CslA and HDZ genes, as well as NAC, PME3 and PME4, may be involved in cambium activities and secondary xylem formation. Taken together, these findings provide new information about cambium activity and cell differentiation in the formation, structure, and chemistry in conifers during the active–dormant transition.

The Effect of an Accelerator on Cement Paste Capillary Pores: NMR Relaxometry Investigations

Nuclear Magnetic Resonance (NMR) relaxometry is a valuable tool for investigating cement-based materials. It allows monitoring of pore evolution and water consumption even during the hydration process. The approach relies on the proportionality between the relaxation time and the pore size. Note, however, that this approach inherently assumes that the pores are saturated with water during the hydration process. In the present work, this assumption is eliminated, and the pore evolution is discussed on a more general basis. The new approach is implemented here to extract information on surface evolution of capillary pores in a simple cement paste and a cement paste containing calcium nitrate as accelerator. The experiments revealed an increase of the pore surface even during the dormant stage for both samples with a faster evolution in the presence of the accelerator. Moreover, water consumption arises from the beginning of the hydration process for the sample containing the accelerator while no water is consumed during dormant stage in the case of simple cement paste. It was also observed that the pore volume fractal dimension is higher in the case of cement paste containing the accelerator.

Clostridioides difficile SpoVAD and SpoVAE interact and are required for DPA packaging into spores

Clostridioides difficile spores, like the spores from most endospore-forming organisms, are a metabolically dormant stage of development with a complex structure that conveys considerable resistance to environmental conditions, e.g., dry heat. This resistance is due to the large amount of dipicolinic acid (DPA) that is packaged into the spore core, thereby replacing the majority of water. DPA is synthesized by the mother cell and its packaging into the spore core is regulated by the spoVA operon that has a variable number of genes, depending on the organism. C. difficile encodes 3 spoVA orthologues, spoVAC, spoVAD, and spoVAE. Prior work has shown that C. difficile SpoVAC is a mechanosensing protein responsible for DPA release from the spore core upon the initiation of germination. However, the roles of SpoVAD and SpoVAE remain unclear in C. difficile. In this study we analyzed the roles of SpoVAD and SpoVAE and found that they are essential for DPA packaging into the spore, similar to SpoVAC. Using split luciferase protein interaction assays we found that these proteins interact, and we propose a model where SpoVAC / SpoVAD / SpoVAE proteins interact at or near the inner spore membrane, and each member of the complex is essential for DPA packaging into the spore

Downwind Spray Drift Assessment for Airblast Sprayer Applications in a Modern Apple Orchard System

HighlightsAirblast sprayer drift potential was evaluated up to 183 m (600 ft) downwind from an orchard edge.A central leader apple orchard was sprayed at dormant and full canopy stage.Higher drift at full canopy stage was likely due to higher wind speeds and lower humidity.String and artificial foliage samplers had higher collection efficiencies than Mylar cards.Abstract. Risk assessment of orchard pesticide spraying is currently based on spray drift estimation using a worst-case scenario (dormant stage). However, most spray applications are conducted during non-dormant canopy growth stages. Such overestimation leads to restrictive operational regulations in pest management activities. Therefore, field data were generated and studied for a mechanistic model that will predict spray drift from airblast spray applications in tree fruit orchards. Spray trials were conducted at dormant and full canopy growth stages in a central leader trained apple orchard. An axial-fan airblast sprayer sprayed fluorescent tracer in the third row from the orchard’s downwind edge, with four passes being one run. A total of 20 runs, i.e., 17 spray runs and three blanks, were performed during each of the two crop growth stages. Mylar cards, artificial foliage (AF), and horizontal strings (HS) were used to quantify drifting spray deposition up to 183 m (600 ft) downwind. Within the orchard, the deposition on card samplers 3 m upwind of the sprayed row was 21.94% ±4.63% (mean ± standard deviation) of applied dose (AD) at dormant stage and 16.02% ±2.86% AD at full canopy stage. Deposition downwind and adjacent (-3 m) to the sprayed row was 17.92% ±2.70% AD and 7.15% ±1.78% AD at dormant and full canopy stages, respectively. Spray drift decreased substantially at the orchard edge to 3.18% ±1.30% AD at dormant stage and 2.30% ±1.16% AD at full canopy stage. Spray drift was very low at 183 m (600 ft) downwind of the orchard, with deposition of 0.002% ±0.003% AD at dormant stage and 0.003% ±0.004% AD at full canopy stage. Deposition data collected at common sampler locations showed that HS and AF samplers collected significantly (p < 0.05) more drifting spray than card samplers. Downwind speeds had a strong linear relationship with spray drift at both growth stages (dormant: R2= 0.80, full canopy: R2= 0.86), while the influence of temperature and humidity could not be directly observed from the collected data. Keywords: Airblast spraying, Deposit samplers, Dormant and full canopy, Drift, Modern orchard systems.

Demystifying the catalytic pathway of Mycobacterium tuberculosis isocitrate lyase

Pulmonary tuberculosis, caused by Mycobacterium tuberculosis, is one of the most persistent diseases leading to death in humans. As one of the key targets during the latent/dormant stage of M. tuberculosis, isocitrate lyase (ICL) has been a subject of interest for new tuberculosis therapeutics. In this work, the cleavage of the isocitrate by M. tuberculosis ICL was studied using quantum mechanics/molecular mechanics method at M06-2X/6-31+G(d,p): AMBER level of theory. The electronic embedding approach was applied to provide a better depiction of electrostatic interactions between MM and QM regions. Two possible pathways (pathway I that involves Asp108 and pathway II that involves Glu182) that could lead to the metabolism of isocitrate was studied in this study. The results suggested that the core residues involved in isocitrate catalytic cleavage mechanism are Asp108, Cys191 and Arg228. A water molecule bonded to Mg2+ acts as the catalytic base for the deprotonation of isocitrate C(2)–OH group, while Cys191 acts as the catalytic acid. Our observation suggests that the shuttle proton from isocitrate hydroxyl group C(2) atom is favourably transferred to Asp108 instead of Glu182 with a lower activation energy of 6.2 kcal/mol. Natural bond analysis also demonstrated that pathway I involving the transfer of proton to Asp108 has a higher intermolecular interaction and charge transfer that were associated with higher stabilization energy. The QM/MM transition state stepwise catalytic mechanism of ICL agrees with the in vitro enzymatic assay whereby Asp108Ala and Cys191Ser ICL mutants lost their isocitrate cleavage activities.

A Never-Ending Story of Anogenital Warts: Review Article

Anogenital wart (AGW) has long been one of the most common sexually transmitted infections, which has negative effects on psychological and social issues. Its slowly progressive nature and long dormant stage prevent AGW from elimination. Although diagnosis is as simple as inspection using the naked eyes or a magnifying glass and basic medical treatment is the main treatment modality, the long period of clinical response appears to be the biggest challenge. Many patients suffer from this non-fatal disease for over half a year. Onward transmission obviously continues during the occurrence of lesions. Primary prevention, particularly vaccination against human papillomavirus (HPV vaccine), is an ideal method. HPV vaccine is a promising method; however, its high cost limits wide accessibility. In addition, despite being vaccinated, some women present with AGW. Therefore, a never-ending story of AGW remains to be explored. The Siriraj Female STI Clinic, which has over 20 years of experience in treating women with AGW, would like to share some experience so that these patients will be treated with more understanding. Keywords: Anogenital wart, Prevention, Surveillance, Siriraj experience

Caenorhabditis elegans dauers vary recovery in response to bacteria from natural habitat

Many species use dormant stages for habitat selection by tying recovery from the stage to informative external cues. Other species have an undiscerning strategy in which they recover randomly despite having advanced sensory systems. We investigated whether elements of a species’ habitat structure and life history can bar it from developing a discerning recovery strategy. The nematode Caenorhabditis elegans has a dormant stage called the dauer larva that disperses between habitat patches. On one hand, C. elegans colonization success is profoundly influenced by the bacteria found in its habitat patches, so we might expect this to select for a discerning strategy. On the other hand, C. elegans’ habitat structure and life history suggest that there is no fitness benefit to varying recovery, which might select for an undiscerning strategy. We exposed dauers of three genotypes to a range of bacteria acquired from the worms’ natural habitat. We found that C. elegans dauers recover in all conditions but increase recovery on certain bacteria depending on the worm’s genotype, suggesting a combination of undiscerning and discerning strategies. Additionally, the worms’ responses did not match the bacteria’s objective quality, suggesting that their decision is based on other characteristics.

The Bradyzoite: A Key Developmental Stage for the Persistence and Pathogenesis of Toxoplasmosis

Toxoplasma gondii is a ubiquitous parasitic protist found in a wide variety of hosts, including a large proportion of the human population. Beyond an acute phase which is generally self-limited in immunocompetent individuals, the ability of the parasite to persist as a dormant stage, called bradyzoite, is an important aspect of toxoplasmosis. Not only is this stage not eliminated by current treatments, but it can also reactivate in immunocompromised hosts, leading to a potentially fatal outcome. Yet, despite its critical role in the pathology, the bradyzoite stage is relatively understudied. One main explanation is that it is a considerably challenging model, which essentially has to be derived from in vivo sources. However, recent progress on genetic manipulation and in vitro differentiation models now offers interesting perspectives for tackling key biological questions related to this particularly important developmental stage.