Ricerche sulla flsiologia della produzione di tossine in colture di Helminthospobium maydis Nishik. et Miy

Abstract

STUDIES ON THE PHYSIOLOGY OF TOXIN PRODUCTION BY HELMINTHO-SPORIUM MAYDIS NISHIK. ET MIY. CULTURES. — Helminthosporium maydis produces under artificial culture toxic metabolites, which are responsible of a reduction of wheat and corn rootlets growth, severe alterations in tomato shoots and young corn plants, and growth inhibition of some microrganisms.

Cultural conditions for growth and toxin production were studied. Different strains of the fungus vary in their ability of toxin production, the highest amounts being produced by each strain by somewhat different conditions. At least one toxic metabolite can be extracted by chloroform from the cultural filtrates, but probably more than one toxin is produced, and of them at least one is not extracted with organic solvents. Toxic substances can be extracted from the mycelia, but it is not yet possible identify the toxins obtained by the extraction of the mycelia with one or more of the toxic metabolites obtained by extraction of the cultural filtrates.     

Hotspots of (sub)alpine plants in the Irano-Anatolian global biodiversity hotspot are insufficiently protected

Aim

The mountainous regions in SW Asia harbour a high number of endemic species, many of which are restricted to the high-elevation zone. The (sub)alpine habitats of the region are under particular threat due to global change, but their biodiversity hotspots and conservation status have not been investigated so far.

Location

Subalpine-alpine habitats of SW Asia.

Methods

Distribution data of all (sub)alpine vascular plant species of the region were compiled, resulting in 19,680 localities from 1672 (sub)alpine species, the majority of them being restricted to the region (76%). Six quantitative indices of species diversity were used on the basis of 0.5° × 0.5° grid cells to identify (sub)alpine hotspots. Hotspots whose surface area in the (sub)alpine zone was covered by nature reserves maximally by 10% were defined as conservation gaps.

Results

A high proportion (80%) of the endemic species of the study area is range-restricted and narrowly distributed. The results of all six indices were highly correlated. Using the top 5%, 10% and 20% richest cells supported by any index, 32, 53 and 98 cells, respectively, were identified as Hotspots. Almost 60% of these Hotspots at all three levels were identified as unprotected (i.e. constituted Conservation Gaps). Generally, only 22%, 18% and 16%, respectively, of the alpine surface area of the identified Hotspots were covered by nature reserves for the top 5%, 10% and 20% richest cells, respectively.

Main conclusions

Although the rate of protection in (sub)alpine Hotspots exceeds that of the entire region it is still insufficient, because these Hotspots are much richer in endemic and in range-restricted species, but at the same time are under high pressure of global change. Therefore, the establishment of new nature reserves with high conservation efficiency in (sub)alpine habitats with a particular focus on the identified Hotspots is strongly recommended.     

High Content Image-Based Screening of a Protease Inhibitor Library Reveals Compounds Broadly Active against Rift Valley Fever Virus and Other Highly Pathogenic RNA Viruses

High content image-based screening was developed as an approach to test a protease inhibitor small molecule library for antiviral activity against Rift Valley fever virus (RVFV) and to determine their mechanism of action. RVFV is the causative agent of severe disease of humans and animals throughout Africa and the Arabian Peninsula. Of the 849 compounds screened, 34 compounds exhibited ≥50% inhibition against RVFV. All of the hit compounds could be classified into 4 distinct groups based on their unique chemical backbone. Some of the compounds also showed broad antiviral activity against several highly pathogenic RNA viruses including Ebola, Marburg, Venezuela equine encephalitis, and Lassa viruses. Four hit compounds (C795-0925, D011-2120, F694-1532 and G202-0362), which were most active against RVFV and showed broad-spectrum antiviral activity, were selected for further evaluation for their cytotoxicity, dose response profile, and mode of action using classical virological methods and high-content imaging analysis. Time-of-addition assays in RVFV infections suggested that D011-2120 and G202-0362 targeted virus egress, while C795-0925 and F694-1532 inhibited virus replication. We showed that D011-2120 exhibited its antiviral effects by blocking microtubule polymerization, thereby disrupting the Golgi complex and inhibiting viral trafficking to the plasma membrane during virus egress. While G202-0362 also affected virus egress, it appears to do so by a different mechanism, namely by blocking virus budding from the trans Golgi. F694-1532 inhibited viral replication, but also appeared to inhibit overall cellular gene expression. However, G202-0362 and C795-0925 did not alter any of the morphological features that we examined and thus may prove to be good candidates for antiviral drug development. Overall this work demonstrates that high-content image analysis can be used to screen chemical libraries for new antivirals and to determine their mechanism of action and any possible deleterious effects on host cellular biology.     

Amber microfossils: On the validity of species concept

Do terrestrial micro-organisms evolve morphologically? A recent concept suggests that morphological stasis over dozens of millions of years has persisted in microbial lineages. However, it is based on a weak fossil record. Indeed, it is already difficult to define a species with extant microbes, and this task is even harder when dealing with fossil micro-organisms. Based on research on fossils in amber, we highlighted the different problems that are raised when describing a new fossil species of micro-organisms and we discuss the concept of morphological stasis.     

NMR resonance assignments of an engineered neomycin-sensing riboswitch RNA bound to ribostamycin and tobramycin

The neomycin-sensing riboswitch is an engineered riboswitch developed to regulate gene expression in vivo in the lower eukaryote Saccharomyces cerevisiae upon binding to neomycin B. With a size of only 27nt it is the smallest functional riboswitch element identified so far. It binds not only neomycin B but also related aminoglycosides of the 2′-deoxystreptamine class with high affinity. The regulatory activity, however, strongly depends on the identity of the aminoglycoside. As a prerequisite for the structure determination of riboswitch-ligand complexes we report here the ¹H, ¹⁵N, ¹³C and partial ³¹P chemical shift assignments for the minimal functional 27nt neomycin sensing riboswitch RNA in complex with the 4,5-linked neomycin analog ribostamycin and the 4,6-linked aminoglycoside tobramycin.     

Phytochemical composition and in vitro biological activities of Morinda citrifolia fruit juice

Morinda citrifolia is a plant with broad nutraceutical and therapeutic effects and used in the traditional treatment of several ailments. The objective of this work is to investigate the phytochemistry of the fruit juice of M. citrifolia on one hand and on other hand to evaluate its antiradical and antibacterial activity. The phytochemical investigation was carried out by tube staining tests of the extract of two types of fruit juice of M. citrifolia. The antioxidant activity of these juices was evaluated by reducing the DPPH radical method. Concerning the antibacterial activity, it was tested on the in vitro growth of 10 reference bacterial strains using the well diffusion method. Qualitative phytochemistry of M. citrifolia fruit juices revealed the presence of large groups of secondary metabolites including polyphenols, reducing compounds, mucilage and terpernoids. The antioxidant activity of M. citrifolia fruit juices is dose-dependent and higher than that of ascorbic acid. Antimicrobial activity on other hand revealed that fruit juices inhibit growth inhibitory activity of Staphylococcus aureus, Pseudomonas aeruginosa, Proteus mirabilis, S. epidermidis, Proteus vulgaris, Streptococcus oralis, Enterococcus faecalis and Escherichia coli. This observed difference is significant for each juices on the strains (p < 0.001). These results support the use of M. citrifolia in traditional medicine and are the starting points for the development of a new drug to combat both dietary conditions and chronic conditions associated with oxidative stress.     

<Emphasis Type="Italic">KNOX</Emphasis> overexpression in transgenic <Emphasis Type="Italic">Kohleria</Emphasis> (Gesneriaceae) prolongs the activity of proximal leaf blastozones and drastically alters segment fate

KNOX (knotted1-like homeobox) genes have a widely conserved role in the generation of dissected leaves. Ectopic KNOX activity in leaves in various angiosperm lineages causes leaf form changes that can elucidate how the configuration of leaf development evolved. We present an analysis of leaf morphology and morphogenesis in transgenic Kohleria lines overexpressing a heterologous KNOX gene. Kohleria, like many members of Gesneriaceae, has simple-serrated leaves with pinnate venation. KNOX overexpression causes prolonged segment proliferation in proximal, but not distal, parts of leaf blades. Elaborate dissected segments reiterate the zonation of the whole leaf, with organogenic activity persisting between a distal maturation zone and a proximal intercalary elongation zone. The architecture of vascular bundles is severely altered, with a reduced midvein and a more palmate venation. The initial establishment of organogenically competent primordial margins (marginal blastozones) and the onset of tissue differentiation in early stages of leaf development were similar in wild-type and KNOX overexpressing lines. However, leaves overexpressing KNOX often failed to fully mature, and persistent marginal blastozones were found at the base of blades in mature portions of the shoot. We conclude that KNOX-mediated perpetuation of marginal blastozones in Kohleria is sufficient to induce a set of processes that result in highly dissected leaflets, which are unusual in this plant family. Spatial confinement of blastozones between an early maturing tip and a late elongating petiole zone reflects the presence of distinct maturation processes that limit the ability of the leaf margins to respond to ectopic KNOX gene expression.