The Emergence of New Aggressive Leaf Rust Races with the Potential to Supplant the Resistance of Wheat Cultivars

Characterization of the genetic structure and the physiological races of Puccinia triticina is a growing necessity to apply host genetic resistance against wheat leaf rust as a successful control strategy. Herein, we collected and identified about 130 isolates of P. triticina from 16 Egyptian commercial wheat cultivars grown at different locations, over two seasons (2019/2020 and 2020/2021). The 130 isolates of P. triticina were segregated into 17 different physiological races. TTTST and TTTKS were the most common virulent races, whereas TTTST and MTTGT were the most frequent races. The races were classified into three groups, based on their distinct DNA band sizes (150 bp, 200 bp, and 300 bp) after RAPD analysis. The new wheat cultivars (Sakha-94, Sakha-95, and Shandweel-1) infected with the most virulent race (TTTST), Gemmeiza-12, and Misr-3 were resistant to all physiological races. The resistance of these cultivars was mostly due to the presence of Lr19- and Lr28-resistant genes. Our results serve as a warning about emerging aggressive races capable of supplanting resistance to leaf rust, and help in the understanding of the pathotype–cultivar–location association and its role in the susceptibility/resistance of new wheat cultivars to P. triticina.

Interactions of Truncated Menaquinones in Lipid Monolayers and Bilayers

Menaquinones (MK) are hydrophobic molecules that consist of a naphthoquinone headgroup and a repeating isoprenyl side chain and are cofactors used in bacterial electron transport systems to generate cellular energy. We have previously demonstrated that the folded conformation of truncated MK homologues, MK-1 and MK-2, in both solution and reverse micelle microemulsions depended on environment. There is little information on how MKs associate with phospholipids in a model membrane system and how MKs affect phospholipid organization. In this manuscript, we used a combination of Langmuir monolayer studies and molecular dynamics (MD) simulations to probe these questions on truncated MK homologues, MK-1 through MK-4 within a model membrane. We observed that truncated MKs reside farther away from the interfacial water than ubiquinones are are located closer to the phospholipid tails. We also observed that phospholipid packing does not change at physiological pressure in the presence of truncated MKs, though a difference in phospholipid packing has been observed in the presence of ubiquinones. We found through MD simulations that for truncated MKs, the folded conformation varied, but MKs location and association with the bilayer remained unchanged at physiological conditions regardless of side chain length. Combined, this manuscript provides fundamental information, both experimental and computational, on the location, association, and conformation of truncated MK homologues in model membrane environments relevant to bacterial energy production.

Fluoroquinolone Metalloantibiotics to Bypass Antimicrobial Resistance Mechanisms: Decreased Permeation through Porins

Fluoroquinolones (FQs) are broad-spectrum antibiotics largely used in the clinical practice against Gram-negative and some Gram-positive bacteria. Nevertheless, bacteria have developed several antimicrobial resistance mechanisms against such class of antibiotics. Ternary complexes of FQs, copper(II) and phenanthroline, known as metalloantibiotics, arise in an attempt to counteract an antibiotic resistance mechanism related to low membrane permeability. These metalloantibiotics seem to use an alternative influx route, independent of porins. The translocation pathways of five FQs and its metalloantibiotics were studied through biophysical experiments, allowing us to infer about the role of OmpF porin in the influx. The FQ-OmpF interaction was assessed in mimetic membrane systems differing on the lipidic composition, disclosing no interference of the lipidic composition. The drug-porin interaction revealed similar values for the association constants of FQs and metalloantibiotics with native OmpF. Therefore, OmpF mutants and specific quenchers were used to study the location-association relationship, comparing a free FQ and its metalloantibiotic. The free FQ revealed a specific association, with preference for residues on the centre of OmpF, while the metalloantibiotic showed a random interaction. Thereby, metalloantibiotics may be an alternative to pure FQs, being able to overcome some antimicrobial resistance mechanism of Gram-negative bacteria related to decreased membrane permeability.

Forward Processing of Object–Location Association from the Ventral Stream to Medial Temporal Lobe in Nonhuman Primates

While the hippocampus (HPC) is a prime candidate combining object identity and location due to its strong connections to the ventral and dorsal pathways via surrounding medial temporal lobe (MTL) areas, recent physiological studies have reported spatial information in the ventral pathway and its downstream target in MTL. However, it remains unknown whether the object–location association proceeds along the ventral MTL pathway before HPC. To address this question, we recorded neuronal activity from MTL and area anterior inferotemporal cortex (TE) of two macaques gazing at an object to retain its identity and location in each trial. The results showed significant effects of object–location association at a single-unit level in TE, perirhinal cortex (PRC), and HPC, but not in the parahippocampal cortex. Notably, a clear area difference emerged in the association form: 1) representations of object identity were added to those of subjects’ viewing location in TE; 2) PRC signaled both the additive form and the conjunction of the two inputs; and 3) HPC signaled only the conjunction signal. These results suggest that the object and location signals are combined stepwise at TE and PRC each time primates view an object, and PRC may provide HPC with the conjunctional signal, which might be used for encoding episodic memory.

Marjolin's Tumor Complicating Chronic Periprosthetic Infection of a Total Knee Arthroplasty

Marjolin's tumor is a term used to describe a malignancy developing in the setting of a chronic wound, infection, or other tissue subject to chronic inflammatory changes. These malignancies usually present after many years of chronicity, and can range from lower grade basal cell carcinomas to high-grade sarcomas. We present the case of a squamous cell carcinoma that developed within a chronic periprosthetic infection of a total knee arthroplasty of 7 years duration. The intra-articular location, association with an orthopaedic implant, and brief latency period are all unique features of this case.