Peroxidase Isoenzyme Patterns in Cell Cultures derived from Cotyledon, Stem, Leaf and Fruit from Grapevine (Vitis vinifera cv. Monastrell)

The expression of peroxidase isoenzymes capable of oxidizing4-hydroxystilbenes was studied during the establishment of cellcultures derived from different tissues (cotyledon, stem, leafand fruit) of Vitis vinifera cv. Monastrell vines. This wascarried out in order to elucidate whether different tissuesof the same plant maintain persistent tissue-specific patternsof gene expression during in vitro culture or whether in vitrocultures are characterized by identical patterns of gene expressionirrespective of the tissue's origin. The results illustratedthat both the isozyme patterns and the substrate specificityof the peroxidase activity secreted to the medium are analogousfor the profile of acidic (Prx A) and basic (Prx B) peroxidaseisoenzymes, only quantitative differences being shown in theneutral peroxidase isoenzyme (Prx N) pattern. These resultssuggest that in vitro cultures of grapevines are characterizedby similar patterns of gene expression, no matter what theirtissue of origin.Copyright 1995, 1999 Academic Press Grapevine, vitis vinifera, cell cultures, 4-hydroxystilbene oxidizing peroxidase isoenzyme, substrate specificity     

Molecular modeling and analysis of human and plant endo-β-N-acetyl- glucosaminidases for mutations effects on function

Endo- β-N-acetylgucosaminidases (ENGases) are the enzymes that catalyze both hydrolysis and transglycosylation reactions. It is of interest to study ENGases because of their ability to synthesize glycopeptides. Homology models of Human, Arabidopsis thaliana and Sorghum ENGases were developed and their active sites marked based on information available from Arthrobacter protophormiae (PDB ID: 3FHQ) ENGase. Further, these models were docked with the natural substrate GlcNAc-Asn and the inhibitor Man₃GlcNAc-thiazoline. The catalytic triad of Asn, Glu and Tyr (N171, E173 and Y205 of bacteria) were found to be conserved across the phyla. The crucial Y299F mutation showing 3 times higher transglycosylation activity than in wild type Endo-A is known. The hydrolytic activity remained unchanged in bacteria, while the transglycosylation activity increased. This Y to F change is found to be naturally evolved and should be attributing higher transglycosylation rates in human and Arabidopsis thaliana ENGases. Ligand interactions Ligplots revealed the interaction of amino acids with hydrophobic side chains and polar uncharged side chain amino acids. Thus, structure based molecular model-ligand interactions provide insights into the catalytic mechanism of ENGases and assist in the rational engineering of ENGases.     

More than just a pair of blue genes: how cyanobacteria adapt to changes in their light environment

Cyanobacteria require light to perform photosynthesis, but not all colors of light are equally useable for them. In particular, blue light-grown cyanobacterial strains, including the well-studied model organism Synechocystis sp. PCC 6803 (Synechocystis), have been observed to exhibit slower growth rates than white or red light-grown cells. In this issue of Physiologia Plantarum, Luimstra et al. (2020) have attempted to understand why cyanobacterial cells suffer under blue light. They measured the molecular and genetic responses of Synechocystis cells to being shifted from white light to blue light. They found that blue light-grown cells make changes that lead to a redistribution of energy flow between the two photosystems that power photosynthesis. These findings could help researchers identify avenues for optimizing photosynthesis in cyanobacterial species, a group of organisms which show great promise as potential solar-powered factories for the production of biofuels and other high-value products.     

TAC from Mycobacterium tuberculosis: a paradigm for stress-responsive toxin–antitoxin systems controlled by SecB-like chaperones

Bacterial type II toxin–antitoxins (TAs) are two-component systems that modulate growth in response to specific stress conditions, thus promoting adaptation and persistence. The major human pathogen Mycobacterium tuberculosis potentially encodes 75 TAs and it has been proposed that persistence induced by active toxins might be relevant for its pathogenesis. In this work, we focus on the newly discovered toxin–antitoxin–chaperone (TAC) system of M. tuberculosis, an atypical stress-responsive TA system tightly controlled by a molecular chaperone that shows similarity to the canonical SecB chaperone involved in Sec-dependent protein export in Gram-negative bacteria. We performed a large-scale genome screening to reconstruct the evolutionary history of TAC systems and found that TAC is not restricted to mycobacteria and seems to have disseminated in diverse taxonomic groups by horizontal gene transfer. Our results suggest that TAC chaperones are evolutionary related to the solitary chaperone SecB and have diverged to become specialized toward their cognate antitoxins.     

Circulating antigens and antibodies in human and mouse dermatophytosis: use of monoclonal antibody reactive to phosphorylcholine-like epitopes

The presence of circulating antibodies in the sera of patients infected with either Trichophyton concentricum or Trichophyton rubrum, and in the sera of BALB/c mice chronically infected with Trichophyton quinckeanum, was determined by ELISA. High levels of antibody to dermatophyte cytoplasmic antigens were detected both in infected humans and in mice. Partial inhibition of this reaction was observed by pretreatment of the sera with the hapten phosphorylcholine (PC). Moreover, antibodies were shown to have some reactivity with PC when tested by ELISA against PC conjugated to bovine serum albumin. Significant levels of circulating antigen were detected in patients with T. concentricum and T. rubrum infections, but not in uninfected subjects, by an immunoradiometric assay using a monoclonal antibody, Tq-1, which reacts with the PC-like epitopes of dermatophytes. It is possible that this dermatophyte antigen may play a role in modulating the cell-mediated immune responses, which would appear to be defective in most patients with these chronic forms of dermatophytosis.     

Blind killing of both male and female Drosophila embryos by a natural variant of the endosymbiotic bacterium Spiroplasma poulsonii

Spiroplasma poulsonii is a vertically transmitted endosymbiont of Drosophila melanogaster that causes male‐killing, that is the death of infected male embryos during embryogenesis. Here, we report a natural variant of S. poulsonii that is efficiently vertically transmitted yet does not selectively kill males, but kills rather a subset of all embryos regardless of their sex, a phenotype we call ‘blind‐killing’. We show that the natural plasmid of S. poulsonii has an altered structure: Spaid, the gene coding for the male‐killing toxin, is deleted in the blind‐killing strain, confirming its function as a male‐killing factor. Then we further investigate several hypotheses that could explain the sex‐independent toxicity of this new strain on host embryos. As the second non‐male‐killing variant isolated from a male‐killing original population, this new strain raises questions on how male‐killing is maintained or lost in fly populations. As a natural knock‐out of Spaid, which is unachievable yet by genetic engineering approaches, this variant also represents a valuable tool for further investigations on the male‐killing mechanism.