Antimicrobial activity and properties of de novo design of short synthetic lipopeptides

The aim of this article is to introduce the topic of newly designed peptides as well as their biological activity. We designed nine encoded peptides composed of six amino acids. All these peptides were synthesized with C-terminal amidation. To investigate the importance of increased hydrophobicity at the amino end of the peptides, all of them were subsequently synthesized with palmitic or lithocholic acid at the N-terminus. Antimicrobial activity was tested on Gram-positive and Gram-negative bacteria and fungi. Cytotoxicity was measured on HepG2 and HEK 293 T cell cultures. Peptides bearing a hydrophobic group exhibited the best antimicrobial activity. Lipopeptides with palmitic or lithocholic acid (PAL or LCA peptides) at the N-terminus and with C-terminal amidation were highly active against Gram-positive bacteria, especially against strains of Staphylococcus aureus and Candida tropicalis. The LCA peptide SHP 1.3 with the sequence LCA-LVKRAG-NH2, had high efficiency on HepG2 human liver hepatocellular carcinoma cells (97%).

Plant Growth-Promoting Endophytic Bacteria Isolated from Miscanthus giganteus and Their Antifungal Activity

Modern technologies can satisfy human needs only with the use of large quantities of fertilizers and pesticides that are harmful to the environment. For this reason, it is possible to develop new technologies for sustainable agriculture. The process could be carried out by using endophytic microorganisms with a (possible) positive effect on plant vitality. Bacterial endophytes have been reported as plant growth promoters in several kinds of plants under normal and stressful conditions. In this study, isolates of bacterial endophytes from the roots and leaves of Miscanthus giganteus plants were tested for the presence of plant growth-promoting properties and their ability to inhibit pathogens of fungal origin. Selected bacterial isolates were able to solubilize inorganic phosphorus, fix nitrogen, and produce phytohormones, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, and siderophore. Leaf bacterial isolate Pantoea ananat is 50 OL 2 had high production of siderophores (zone ≥ 5 mm), and limited phytohormone production, and was the only one to show ACC deaminase activity. The root bacterial isolate of Pseudomonas libanensis 5 OK 7A showed the best results in phytohormone production (N6-(Δ2-isopentenyl)adenine and indole-3-acetic acid, 11.7 and 12.6 ng·mL-1, respectively). Four fungal cultures-Fusarium sporotrichioides DBM 4330, Sclerotinia sclerotiorum SS-1, Botrytis cinerea DS 90 and Sphaerodes fimicola DS 93-were used to test the antifungal activity of selected bacterial isolates. These fungal cultures represent pathogenic families, especially for crops. All selected root endophyte isolates inhibited the pathogenic growth of all tested fungi with inhibition percentages ranging from 30 to 60%. Antifungal activity was also tested in two forms of immobilization of selected bacterial isolates: one in agar and the other on dextrin-coated cellulose carriers. These results demonstrated that the endophytic Pseudomonas sp. could be used as biofertilizers for crops.

Silver Nanoparticles Alter Microtubule Arrangement, Dynamics and Stress Phytohormone Levels

The superior properties of silver nanoparticles (AgNPs) has resulted in their broad utilization worldwide, but also the risk of irreversible environment infestation. The plant cuticle and cell wall can trap a large part of the nanoparticles and thus protect the internal cell structures, where the cytoskeleton, for example, reacts very quickly to the threat, and defense signaling is subsequently triggered. We therefore used not only wild-type Arabidopsis seedlings, but also the glabra 1 mutant, which has a different composition of the cuticle. Both lines had GFP-labeled microtubules (MTs), allowing us to observe their arrangement. To quantify MT dynamics, we developed a new microscopic method based on the FRAP technique. The number and growth rate of MTs decreased significantly after AgNPs, similarly in both lines. However, the layer above the plasma membrane thickened significantly in wild-type plants. The levels of three major stress phytohormone derivatives—jasmonic, abscisic, and salicylic acids—after AgNP (with concomitant Ag⁺) treatment increased significantly (particularly in mutant plants) and to some extent resembled the plant response after mechanical stress. The profile of phytohormones helped us to estimate the mechanism of response to AgNPs and also to understand the broader physiological context of the observed changes in MT structure and dynamics.

Loss of membrane fluidity and endocytosis inhibition are involved in rapid aluminum-induced root growth cessation in Arabidopsis thaliana

Aluminum (Al) toxicity is the main limiting factor in crop production on acid soils. The main symptom of Al toxicity is a rapid inhibition of root growth, but the mechanism of root growth cessation remains unclear. Here we examined the earliest changes in the plasma membrane and processes related to the membrane in the Arabidopsis thaliana root tip cells of roots grown in a hydropony. Al suppressed root growth within 2 min, inhibited endocytosis within 10 min of exposure and stabilized cortical microtubules within the first 30 min. Spectrofluorometric measurements of the plasma membrane isolated from Arabidopsis plants and labeled with the fluorescent probe laurdan showed that Al induced a reduction in membrane fluidity. Application of the membrane fluidizer, benzyl alcohol, restored partially membrane fluidity and also partially restored root growth during first 30 min of Al treatment. We concluded that Al-induced loss of membrane fluidity and endocytosis inhibition occurred very early during Al toxicity in plant roots and could be the earliest targets of Al treatment.

Aluminium ions inhibit the formation of diacylglycerol generated by phosphatidylcholine-hydrolysing phospholipase C in tobacco cells

• Aluminium ions (Al) have been recognized as a major toxic factor for crop production in acidic soils. This study aimed to assess the impact of Al on the activity of phosphatidylcholine-hydrolysing phospholipase C (PC-PLC), a new member of the plant phospholipase family. • We labelled the tobacco cell line BY-2 and pollen tubes with a fluorescent derivative of phosphatidylcholine and assayed for patterns of fluorescently labelled products. Growth of pollen tubes was analysed. • We observed a significant decrease of labelled diacylglycerol (DAG) in cells treated with AlCl(3). Investigation of possible metabolic pathways that control DAG generation and consumption during the response to Al showed that DAG originated from the reaction catalysed by PC-PLC. The growth of pollen tubes was retarded in the presence of Al and this effect was accompanied by the decrease of labelled DAG similar to the case of the BY-2 cell line. The growth of pollen tubes arrested by Al was rescued by externally added DAG. • Our observation strongly supports the role of DAG generated by PC-PLC in the response of tobacco cells to Al.

Mutual regulation of plant phospholipase D and the actin cytoskeleton

Membrane lipids and cytoskeleton dynamics are intimately inter-connected in the eukaryotic cell; however, only recently have the molecular mechanisms operating at this interface in plant cells been addressed experimentally. Phospholipase D (PLD) and its product phosphatidic acid (PA) were discovered to be important regulators in the membrane-cytoskeleton interface in eukaryotes. Here we report the mechanistic details of plant PLD-actin interactions. Inhibition of PLD by n-butanol compromises pollen tube actin, and PA rescues the detrimental effect of n-butanol on F-actin, showing clearly the importance of the PLD-PA interaction for pollen tube F-actin dynamics. From various candidate tobacco PLDs isoforms, we identified NtPLDbeta1 as a regulatory partner of actin, by both activity and in vitro interaction assays. Similarly to published data, the activity of tobacco PIP(2)-dependent PLD (PLDbeta) is specifically enhanced by F-actin and inhibited by G-actin. We then identified the NtPLDbeta1 domain responsible for actin interactions. Using sequence- and structure-based analysis, together with site-directed mutagenesis, we identified Asn323 and Thr382 of NtPLDbeta1 as the crucial amino acids in the actin-interacting fold. The effect of antisense-mediated suppression of NtPLDbeta1 or NtPLDdelta on pollen tube F-actin dynamics shows that NtPLDbeta1 is the active partner in PLD-actin interplay. The positive feedback loop created by activation of PLDbeta by F-actin and of F-actin by PA provides an important mechanism to locally increase membrane-F-actin dynamics in the cortex of plant cells.

Aluminum ions inhibit phospholipase D in a microtubule-dependent manner

Aluminum is a highly cytotoxic metal to plants, but the molecular base and the primary target of Al toxicity are still unknown. The most important physiological consequence of Al toxicity is a cessation of root growth and changes in root morphology suggesting a role of the root cytoskeleton as a target structure. The important role of phospholipid degrading enzyme phospholipase D in regulation of cytoskeleton remodelling in both animal and plant organisms is now evident. Both the phospholipid pathway and the cytoskeleton are influenced by Al(3+), but their relationship with Al stress remains to be explored. Therefore, we tested the possibility that Al stress could be sensed by plants through microtubules in close interaction with phospholipases. We have shown that Al(3+) reduced the formation of phosphatidic acid in vivo, inhibited activity of phosphatidylinositol-4,5-bisphosphate-dependent phospholipase D in vitro and that the phosphatidic acid production is modified by microtubule dynamics.

Inositol trisphosphate receptor in higher plants: is it real?

The receptor for D-myo-inositol 1,4,5-trisphosphate (InsP3-R) has been well documented in animal cells. It constitutes an important component of the intracellular calcium signalling system. Today the corresponding genes in many species have been sequenced and the antibodies against some of the InsP3-Rs are available. In contrast, very little is known about its plant counterpart. Only a few published works have dealt directly with this topic. This review summarizes the available relevant data and determines some properties of putative plant receptor(s) including the in silico search for its gene in plant genomes, in vivo evidence, its electrophysiology, the parameters of InsP3-induced calcium release and InsP3 binding, immunological cross-reactivity, and subcellular localization. Future progress in this area seems to be inevitable as, despite the efforts, its gene in plants has not been identified yet.

Involvement of phospholipases C and D in early response to SAR and ISR inducers in Brassica napus plants

Phospholipid signaling is an important component in eukaryotic signal transduction pathways. In plants, it plays a key role in growth and development as well as in responses to environmental stresses, including pathogen attack. We investigated the involvement of both phospholipase C (PLC, EC 3.1.4.11) and D (PLD, EC 3.1.4.4) in early responses to the treatment of Brassica napus plants with the chemical inducers of systemic acquired resistance (SAR): salicylic acid (SA), benzothiadiazole (BTH), and with the inducer mediating the induced systemic resistance (ISR) pathway, methyl jasmonate (MeJA). Rapid activation (within 0.5-6 h treatment) of the in vitro activity level was found for phosphatidyl inositol 4,5 bisphosphate (PIP2)-specific PLC (PI-PLC) and three enzymatically different forms of PLD: conventional PLDalpha, PIP2-dependent PLD beta/gamma, and oleate-stimulated PLDdelta. The strongest response was found in case of cytosolic PIP2-dependent PLD beta/gamma after BTH treatment. PLDdelta was identified in B. napus leaves and was very rapidly activated after MeJA treatment with the highest degree of activation compared to the other PLD isoforms. Interestingly, an increase in the amount of protein was observed only for PLDgamma and/or delta after ISR induction, but later than the activation occurred. These results show that phospholipases are involved in very early processes leading to systemic responses in plants and that they are most probably initially first activated on post translational level.

Acid sphingomyelinase deficiency. Phenotype variability with prevalence of intermediate phenotype in a series of twenty-five Czech and Slovak patients. A multi-approach study

A multi-approach study in a series of 25 Czech and Slovak patients with acid sphingomyelinase deficiency revealed a broad phenotypic variability within Niemann-Pick disease types A and B. The clinical manifestation of only 9 patients fulfilled the historical classification: 5 with the rapidly progressive neurovisceral infantile type A and 4 with a slowly progressive visceral type B. Sixteen patients (64%) represented a hitherto scarcely documented 'intermediate type' (IT). Twelve patients showed a protracted neurovisceral course with overt or mild neurological symptoms, three a rapidly progressing fatal visceral affection with rudimentary neurological lesion. One patient died early from a severe visceral disease. The genotype in our patients was represented by 4 frameshift and 14 missense mutations. Six were novel (G166R, R228H, A241V, D251E, D278A, A595fsX601). The Q292K mutation (homoallelic, heteroallelic) was strongly associated with a protracted neurovisceral phenotype (10 of 12 cases). The sphingomyelin loading test in living fibroblasts resulted in total degradation from less than 2% in classical type A to 70-80% in classical type B. In the IT group it ranged from 5% to 49% in a 24 h chase. The liver storage showed three patterns: diffuse, zonal (centrolobular), and discrete submicroscopic. Our series showed a notable variability in both the neurological and visceral lesions as well as in their proportionality and synchrony, and demonstrates a continuum between the historical 'A' and 'B' phenotypes of ASM deficiency. This points to a broad phenotypic potential of ASM deficiency, suggesting the existence of still unknown factors independently controlling the storage level in the visceral and neuronal compartments. This report highlights the important position of the IT in the ASM deficiency phenotype classification. We define IT as a cluster of variants combining clinical features of both the classical types. The protracted neuronopathic variant with overt, borderline or subclinical neurology prevails and is important in view of future enzyme replacement therapy. It appears more common in central Europe. The visceral, rapidly progressing early fatal type has been recognized rarely so far.

Plant PIP2 -dependent phospholipase D activity is regulated by phosphorylation

Phospholipase D (PLD) forms the major family of phospholipases that was first discovered and cloned in plants. In this report we have shown, for the first time, that C2 phosphatidylinositol-4,5-bisphosphate (PIP2)-dependent PLD(s) from 5 day hypocotyls of Brassica oleracea associated with plasma membrane is covalently modified-phosphorylated. Pre-incubation of the plasma membrane fraction with acid phosphatase resulted in concentration-dependent inhibition of PIP2-dependent PLD activity. Using matrix-assisted laser desorption/ionization time of flight mass spectrometry of tryptic in-gel digests, the BoPLDgamma(1,2) isoform was identified. Comparing the spectra of the proteins obtained from the plasma membrane fractions treated and non-treated with acid phosphatase, three peptides differing in the mass of the phosphate group (80 Da) were revealed: TMQMMYQTIYK, EVADGTVSVYNSPR and KASKSRGLGK which possess five potential Ser/Thr phosphorylation sites. Our findings suggest that a phosphorylation/dephosphorylation mechanism may be involved in the regulation of plant PIP2-dependent PLDgamma activity.

Phosphatidic acid produced by phospholipase D is required for tobacco pollen tube growth

Phospholipase D (PLD) and its product phosphatidic acid (PA) are involved in a number of signalling pathways regulating cell proliferation, membrane vesicle trafficking and defence responses in eukaryotic cells. Here we report that PLD and PA have a role in the process of polarised plant cell expansion as represented by pollen tube growth. Both phosphatidylinositol-4,5-bisphosphate-dependent and independent PLD activities were identified in pollen tube extracts, and activity levels during pollen tube germination and growth were measured. PLD-mediated PA production in vivo can be blocked by primary alcohols, which serve as a substrate for the transphosphatidylation reaction. Both pollen germination and tube growth are stopped in the presence 0.5% 1-butanol, whereas secondary and tertiary isomers do not show any effect. This inhibition could be overcome by addition of exogenous PA-containing liposomes. In the absence of n-butanol, addition of a micromolar concentration of PA specifically stimulates pollen germination and tube elongation. Furthermore, a recently established link between PLD and microtubule dynamics was supported by taxol-mediated partial rescue of the 1-butanol-inhibited pollen tubes. The potential signalling role for PLD-derived PA in plant cell expansion is discussed.

In vitro distribution and characterization of membrane-associated PLD and PI-PLC in Brassica napus

Two types of phospholipid degrading enzyme, phospholipase D (PLD; EC 3.1.4.4) and phosphatidyl- inositol-specific phospholipase C (PIP(2)-PLC; PI-PLC 3.1.4.11) were studied during the development of seeds and plants of Brassica napus. PLD exhibits two types of activity; polyphosphoinositide-requiring (PIP(2)-dependent PLD) and polyphosphoinositide-independent requiring millimolar concentrations of calcium (PLDalpha). Significantly different patterns of activity profiles were found for soluble and membrane-associated forms of all three enzymes within both processes. Membrane-associated PIP(2)-dependent PLD activity shows the opposite trend when compared to PLDalpha, while the highest PI-PLC activity appears in the same stages of development of seeds and plants as for PLDalpha. In subcellular fractions of hypocotyls of young plants, phospholipases were localized predominantly on plasma membranes. The biochemical characteristics (Ca(2+), pH) of all three enzymes associated with plasma membrane vesicles, isolated by partitioning in an aqueous dextran- polyethylene glycol two-phase system, are also described. Direct interaction of PLDalpha with G-proteins under in vitro conditions was not confirmed.