Role of molecular polymorphism in defining tau filament structures in neurodegenerative diseases

Misfolding and aggregation of tau protein is implicated in many neurodegenerative diseases that are typified by the presence of large, filamentous tau inclusions. The aggregation of tau in human brain is disease-specific with characteristic filaments defining the neuropathology. An understanding of how identical tau isoforms aggregate into disparate filament morphologies in phenotypically distinct tau-related diseases remains elusive. Here, we determine the structure of a brain-derived twisted tau filament in progressive supranuclear palsy and compare it to a dissimilar tau fold found in corticobasal degeneration. While the tau filament core in both diseases is comprised of residues 274 to 380, molecular-level polymorphism exists. Potential origins of the molecular polymorphism, such as noncovalent cofactor binding, are identified and predicted to modulate tau filament structures in the brain.

Genotype identification and diversity analysis in Kiwifruit (Actinidia spp.) using RAPD markers

Kiwifruit (Actinidia spp.) is a significant plantation crop belonging to family Actinidiaceae, having deciduous, dioecious, and scrambling vines with chromosome number 2n=58. Dioecy in kiwifruit forms the basis for several breeding programs. The present study was carried out for diversity analysis in kiwifruit genotypes using RAPD markers. 7 kiwifruit genotypes (2 males viz. Allision & Tomuri and 5 females viz. Hayward, Bruno, Allision, Monty & Abbott) were analysed for molecular polymorphism using 94 RAPD primers, out of which 23 primers amplified the genomic DNA in all the genotypes. RAPD data was analysed using NTSYS-pc software and dendrogram construction was done using UPGMA method. Two separate clusters of male and female genotypes were formed. Similarity matrix indices showed maximum similarity between Tomuri (M) and Allision (M) with a similarity coefficient of 0.719 while Abbott (F) and Allision (M) were found to have least similarity having a similarity coefficient of 0.521. Four RAPD primers amplified unique amplicons in Monty, Hayward, Bruno, Allision (M) and Abbott and two primers amplified unique amplicons in Allision (M) & Tomuri (M) along with the male and female plants of Allision genotype respectively. Therefore, these primers can help in distinguishing the genotypes of kiwifruit and can also be validated as putative markers for the sex identification in kiwifruit.

Synergistic role of nucleotides and lipids for the self-assembly of Shs1 septin oligomers

Budding yeast septins are essential for cell division and polarity. Septins assemble as palindromic linear octameric complexes. The function and ultra-structural organization of septins are finely governed by their molecular polymorphism. In particular, in budding yeast, the end subunit can stand either as Shs1 or Cdc11. We have dissected, here, for the first time, the behavior of the Shs1 protomer bound to membranes at nanometer resolution, in complex with the other septins. Using electron microscopy, we have shown that on membranes, Shs1 protomers self-assemble into rings, bundles, filaments or two-dimensional gauzes. Using a set of specific mutants we have demonstrated a synergistic role of both nucleotides and lipids for the organization and oligomerization of budding yeast septins. Besides, cryo-electron tomography assays show that vesicles are deformed by the interaction between Shs1 oligomers and lipids. The Shs1–Shs1 interface is stabilized by the presence of phosphoinositides, allowing the visualization of micrometric long filaments formed by Shs1 protomers. In addition, molecular modeling experiments have revealed a potential molecular mechanism regarding the selectivity of septin subunits for phosphoinositide lipids.

Genetic Diversity Among Saudi Peganum harmala and Rhazya stricta Populations Using Chemical and ISSR Markers

Background:The vernacular name 'Harmal' is used for two plant species in Saudi Arabia, i.e. Peganum harmala L. and Rhazya stricta Decne. Both are important medicinal plants which offer interesting pharmacological properties.Objective:This study aimed to evaluate the genetic diversity among different populations of harmal based on chemical variations of alkaloids and molecular polymorphism.Methods:Total alkaloids were extracted from plants of three populations of each species and estimated by using spectrophotometer and the chemical compounds were analyzed by Gas chromatography mass spectrometry (GC-MS). Molecular polymorphism was estimated by using the Inter Simple Sequence Repeat (ISSR) fingerprints.Results:The results showed that the alkaloids content of R. stricta was higher than P. harmala populations. The GC-MS analysis revealed the presence of (65-53) compounds in R. stricta and P. harmala, and the percentage of polymorphism was found to be 93.2%. Sixteen ISSR primers produced 170 scorable bands with an average of 9.6 bands per primer and 75%-100% polymorphism. The cluster analysis using the unweighted pair-group method of the arithmetic average (UPGMA) method based on combined data of GC-MS and ISSR markers divided the six harmal genotypes into two major groups.Conclusion:The existence of variations in chemical and genetic markers is useful for the selection of potential genotypes for medicinal use, and for breeding lines for medicinal substances production to spare wild plants from uncontrolled harvesting for folk medicine.

Molecular Polymorphism of Pectinase Genes PGU of the Yeast Saccharomyces bayanus var. uvarum

We have conducted a molecular genetic study of the pectinase PGU genes of 74 strains of the yeast Saccharomyces bayanus var. uvarum, isolated from various fermentation processes and natural sources in different regions of Europe and in the USA. Unlike S. cerevisiae, each having a PGU gene, strains of S. bayanus var. uvarum have three divergent genes PGU1b, PGU2b and PGU3b, located respectively on chromosomes X, I and XIV. The high pectinolytic activity of these yeasts appears to be related to the presence of several PGU polymeric genes in their genome. Saccharomyces bayanus var. uvarum, endo-polygalacturonase, yeast pectinase, genes PGU1b, PGU2b and PGU3b, molecular karyotyping, Southern-hybridization This study was supported by Budget-supported project No. 595-00004-18PR. doi: 10.21519/0234-2758-2019-35-2-30-37