Patterns of ribosomal DNA spacer lengths are inherited

The non-transcribed spacer regions in Xenopus laevis ribosomal DNA vary in length, even within a single nucleolar organizer. The pattern of spacer lengths is sufficiently different from one nucleolar organizer to another to allow the pattern to be used as a genetic marker. We have analyzed the spacer patterns of rDNA² from a total of 50 progeny from three separate matings. Spacer patterns were inherited with no detectable change in all but two cases. The reproducibility of the patterns among siblings and their stable inheritance between generations rule out sudden mechanisms for gene evolution, such as the master-slave model, and support more gradual mechanisms.Two animals out of 50 showed marked changes in their rDNA spacer patterns. It is not possible at present to decide which of several possible mechanisms were responsible for the observed changes.     

Structure-selected RBM immunogens prime polyclonal memory responses that neutralize SARS-CoV-2 variants of concern

Successful control of the COVID-19 pandemic depends on vaccines that prevent transmission. The full-length Spike protein is highly immunogenic but the majority of antibodies do not target the virus: ACE2 interface. In an effort to affect the quality of the antibody response focusing it to the receptor-binding motif (RBM) we generated a series of conformationally-constrained immunogens by inserting solvent-exposed RBM amino acid residues into hypervariable loops of an immunoglobulin molecule. Priming C57BL/6 mice with plasmid (p)DNA encoding these constructs yielded a rapid memory response to booster immunization with recombinant Spike protein. Immune sera antibodies bound strongly to the purified receptor-binding domain (RBD) and Spike proteins. pDNA primed for a consistent response with antibodies efficient at neutralizing authentic WA1 virus and three variants of concern (VOC), B.1.351, B.1.617.2, and BA.1. We demonstrate that immunogens built on structure selection can be used to influence the quality of the antibody response by focusing it to a conserved site of vulnerability shared between wildtype virus and VOCs, resulting in neutralizing antibodies across variants.     

Epitope mapping of the major capsid protein of type 2 porcine circovirus (PCV2) by using chimeric PCV1 and PCV2

Type 2 porcine circovirus (PCV2) is associated with postweaning multisystemic wasting syndrome in pigs, whereas the genetically related type 1 PCV (PCV1) is nonpathogenic. In this study, seven monoclonal antibodies (MAbs) against PCV2-ORF2 capsid protein were generated, biologically characterized, and subsequently used to map the antigenic sites of PCV2 capsid protein by using infectious PCV DNA clones containing PCV1/PCV2-ORF2 chimeras. The PCV1/PCV2-ORF2 chimeras were constructed by serial deletions of PCV2-ORF2 and replacement with the corresponding sequences of the PCV1-ORF2. The reactivities of chimeric PCV1/PCV2 clones in transfected PK-15 cells with the seven MAbs were detected by an immunofluorescence assay (IFA). The chimera (r140) with a deletion of 47 amino acids at the N terminus of PCV2-ORF2 reacted strongly to all seven MAbs. Expanding the deletion of PCV2-ORF2 from residues 47 to 57 (r175) abolished the recognition of MAb 3B7, 3C11, 4A10, 6H2, or 8F6 to the chimera. Further deletion of PCV2-ORF2 to 62 residues disrupted the binding of this chimera to all seven MAbs. IFA reactivities with all MAbs were absent when residues 165 to 233 at the C terminus of PCV2-ORF2 was replaced with that of PCV1-ORF2. Extending the sequence of PCV2-ORF2 from residues 165 (r464) to 185 (r526), 200 (r588), or 224 (r652) restored the ability of the three chimeras to react with MAbs 3C11, 6H2, 9H7, and 12G3 but not with 8F6, 3B7, or 4A10. When the four amino acids at the C terminus of r588 were replaced with that of PCV2-ORF2, the resulting chimera (r588F) reacted with all seven MAbs. The results from this study suggest that these seven MAbs recognized at least five different but overlapping conformational epitopes within residues 47 to 63 and 165 to 200 and the last four amino acids at the C terminus of the PCV2 capsid protein.     

Are fire,soil fertility and toxicity,water availability,plant functional diversity,and litter decomposition related in a Neotropical savanna?

Understanding how biodiversity and ecosystem functioning respond to changes in the environment is fundamental to the maintenance of ecosystem function. In realistic scenarios, the biodiversity-ecosystem functioning path may account for only a small share of all factors determining ecosystem function. Here, we investigated the strength to which variations in environmental characteristics in a Neotropical savanna affected functional diversity and decomposition. We sought an integrative approach, testing a number of pairwise hypotheses about how the environment, biodiversity, and functioning were linked. We used structural equation modelling to connect fire frequency, soil fertility, exchangeable Al, water availability, functional diversity of woody plants, tree density, tree height, and litter decomposition rates in a causal chain. We found significant effects of soil nutrients, water availability, and Al on functional diversity and litter decomposition. Fire did not have a significant direct effect on functional diversity or litter decomposition. However, fire was connected to both variables through soil fertility. Functional diversity did not influence rates of litter decomposition. The mediated effects that emerged from pairwise interactions are encouraging not only for predicting the functional consequences of changes in environmental variables and biodiversity, but also to caution against predictions based on only environmental or only biodiversity change.     

Characterization of Lipids and Proteins Associated to the Cell Wall of the Acapsular Mutant Cryptococcus neoformans Cap 67

Cryptococcus neoformans is an opportunistic human pathogen that causes life‐threatening meningitis. In this fungus, the cell wall is exceptionally not the outermost structure due to the presence of a surrounding polysaccharide capsule, which has been highly studied. Considering that there is little information about C. neoformans cell wall composition, we aimed at describing proteins and lipids extractable from this organelle, using as model the acapsular mutant C. neoformans cap 67. Purified cell wall preparations were extracted with either chloroform/methanol or hot sodium dodecyl sulfate. Total lipids fractionated in silica gel 60 were analyzed by electrospray ionization tandem mass spectrometry (ESI‐MS/MS), while trypsin digested proteins were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC‐MS/MS). We detected 25 phospholipid species among phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and phosphatidic acid. Two glycolipid species were identified as monohexosyl ceramides. We identified 192 noncovalently linked proteins belonging to different metabolic processes. Most proteins were classified as secretory, mainly via nonclassical mechanisms, suggesting a role for extracellular vesicles (EV) in transwall transportation. In concert with that, orthologs from 86% of these proteins have previously been reported both in fungal cell wall and/or in EV. The possible role of the presently described structures in fungal–host relationship is discussed.     

Effects of age and caloric restriction on glutathione redox state in mice

The main purpose of this study was to determine whether the aging process in the mouse is associated with a pro-oxidizing shift in the redox state of glutathione and whether restriction of caloric intake, which results in the extension of life span, retards such a shift. Amounts of reduced and oxidized forms of glutathione (GSH and GSSG, respectively) and protein-glutathione mixed disulfides (protein-SSG) were measured in homogenates and mitochondria of liver, kidney, heart, brain, eye, and testis of 4, 10, 22, and 26 month old ad libitum-fed (AL) mice and 22 month old mice fed a diet containing 40% fewer calories than the AL group from the age of 4 months. The concentrations of GSH, GSSG, and protein-SSG vary greatly (approximately 10-, 30-, and 9-fold, respectively) from one tissue to another. During aging, the ratios of GSH:GSSG in mitochondria and tissue homogenates decreased, primarily due to elevations in GSSG content, while the protein-SSG content increased significantly. Glutathione redox potential in mitochondria became less negative, i.e., more pro-oxidizing, as the animal aged. Caloric restriction (CR) lowered the GSSG and protein-SSG content. Results suggest that the aging process in the mouse is associated with a gradual pro-oxidizing shift in the glutathione redox state and that CR attenuates this shift.     

The Functional Role of the Hollow Region of the Butterfly Pyrameis atalanta （L.） Scale

Questions concerning the functional role of the hollow region of the butterfly Pyrameis atalanta （L.） scale are experimentally investigated. Attention was initially directed to this problem by observation of the complex microstrucmre of the butterfly scale as well as other studies indicating higher lift on butterfly wings covered with scale. The aerodynamic forces were measured for two oscillating scale models. Results indicated that the air cavity of an oscillating model of the Pyrameis atalanta （L.） scale increased the lift by a factor of 1.15 and reduced the damping coefficients by a factor of 1.38. The modification of the aerodynamic effects on the model of butterfly scale was due to an increase of the virtual air mass, which influenced the body. The hollow region of the scale increased the virtual air mass by a factor of 1.2. The virtual mass of the butterfly scale with the hollow region was represented as the sum of air mass of two imaginary geometrical figures： a circular cylinder around the scale and a right-angled parallelepiped within the hollow region. The interaction mechanism of the butterfly Pyrameis atalanta （L.） scale with a flow was described. This novel interaction mechanism explained most geometrical features of the airpermeable butterfly scale （inverted V-profile of the ridges, nozzle of the tip edge, hollow region, and openings of the upper lamina） and their arrangement.