siRNA screening of the kinome identifies ULK1 as a multidomain modulator of autophagy

Autophagy is a vital response to nutrient starvation. Here, we screened a kinase-specific siRNA library using an autophagy assay in human embryonic kidney 293 cells that measures lipidation of the marker protein GFP-LC3 following amino acid starvation. This screen identified ULK1 in addition to other novel candidates that could be confirmed with multiple siRNAs. Knockdown of ULK1, but not the related kinase ULK2, inhibited the autophagic response. Also, ULK1 knockdown inhibited rapamycin-induced autophagy consistent with a role downstream of mTOR. Overexpression of ULK1 inhibited autophagy and this inhibition was independent of its kinase activity. Deletion of the PDZ domain-binding Val-Tyr-Ala motif at the ULK1 C terminus generated a more potent dominant-negative protein. Further deletions revealed that the minimal ULK1 dominant-negative region could be mapped to residues 1-351. Full-length ULK1 localized to cytoplasmic structures, some of which were GFP-LC3-positive, and this localization required the conserved C-terminal domain. In contrast, ULK1-(1-351) was diffuse in the cytoplasm. These experiments reveal at least two domains in ULK1 which likely function via unique sets of effectors to regulate autophagy.     

Inducible trehalase enzyme activity of Morchella conica Persoon mycelium

Morchella conica Pers. strains of the study were isolated from fruit bodies collected in ash-mixed forests. At first, the strains were cultured on potato dextrose agar (PDA), then on modified Murashige and Skoog (MS) solid agar media. A normal-growing strain was chosen for the trehalase induction experiments. During the trehalase induction treatment, mycelia were grown in liquid culture containing different concentrations of trehalose. After the induction period of trehalase enzymes, physiological state of the mycelium and the oxidative stress were monitored in the vegetative mycelia by measuring the change of the malondialdehyde content, superoxide dismutase enzyme activity, the fresh and dry weight. The examined Morchella conica strain utilized the trehalose properly. The rising amount of the trehalose triggered the increase of the mycelial trehalase enzyme activity. Our results clearly proved that both neutral and acidic trehalase isoenzyme activity of the Morchella conica mycelium are inducible and are playing important role in the utilization of external trehalose.     

Plants ectopically expressing the iron-binding protein, ferritin, are tolerant to oxidative damage and pathogens

Transgenic tobacco plants that synthesize alfalfa ferritin in vegetative tissues--either in its processed form in chloroplasts or in the cytoplasmic nonprocessed form--retained photosynthetic function upon free radical toxicity generated by iron excess or paraquat treatment. Progeny of transgenic plants accumulating ferritin in their leaves exhibited tolerance to necrotic damage caused by viral (tobacco necrosis virus) and fungal (Alternaria alternata, Botrytis cinerea) infections. These transformants exhibited normal photosynthetic function and chlorophyll content under greenhouse conditions. We propose that by sequestering intracellular iron involved in generation of the very reactive hydroxyl radicals through a Fenton reaction, ferritin protects plant cells from oxidative damage induced by a wide range of stresses.     

Assessment of endangered synanthropic plants of Hungary with special attention to arable weeds

Abstract

In the present study, species were selected from the new Red List of the vascular flora of Hungary which can be regarded as a weed. For each species, current conservation status and the most important traits were assessed. Altogether 149 weed species were found to be at risk according to the International Union for Conservation of Nature (IUCN) categories: 11 species are extinct, 11 are critically endangered, 27 are endangered, 26 are vulnerable, 62 are near threatened and 12 are data deficient. These species belong to 37 plant families, from which the most important are Caryophyllaceae, Brassicaceae, Asteraceae, Scrophulariaceae, Chenopodiaceae, Poaceae and Fabaceae. The most significant chorological elements are Mediterranean (28%) and Eurasian (27%); endemic (Pannonian) taxa constitute only 5.4%. Over 90% of these species are of native or archaeophyte origin, according to their residence time. Considering the main habitat types, 46% of the species are originated from dry habitats, 23% from arable lands, 17.5% from wet habitats and 13.5% from ruderal habitats. In the life form spectra, a pronounced dominance of therophytes (81%) is represented. The factor that currently offers the greatest conflict to the conservation of endangered weed species in Hungary are side effects of strong eradication campaigns against the invasive Ambrosia artemisiifolia.     

The effect of light conditions on herbs, bryophytes and seedlings of temperate mixed forests in ?rség, Western Hungary

A vegetation survey was carried out in a relatively intact Atlantic blanket bog in Southwest Ireland to study the vegetation patterns in relation to environmental variation, and to quantify the effect of artificial and natural borders on compositional variation. The data were analysed using canonical correspondence analysis. In terms of both vegetation and water chemistry, the study site can be categorized as typical of Atlantic blanket bogs in the maritime regions of North-western Europe. The distribution of plant species was explained mainly by depth of the water table. The distribution of bryophytes was secondarily explained by the pH of the bog water, while the distribution of vascular plants was secondarily explained by concentrations of ammonia. The vegetation distribution exhibited little variation between the central sector of the peatland and its disturbed edges (hill-grazing and restoration areas), but a substantial variation was observed between the area along a natural edge (stream) and the areas close to the other peatland borders or centre. Similarly, the internal variation within each sector (centre, hill-grazing edge and restoration area edge) was small, but substantial vegetation variation was observed within the area located along the stream. The area along the stream was associated with relatively deep water table, shallow peat depth, high water colour, pH and NH₄ ⁺ concentrations, and low Cl⁻ concentrations in the bog water. Our results suggest the existence of strong centre-natural margin gradients, as in raised bogs, and indicate that human or animal disturbance do not give rise to the marked transition zones that often characterize natural margins of mire systems. This indicates that even small areas and remnants of Atlantic blanket bogs are worthy of conservation and that their conservation value would benefit from the inclusion of sectors close to the natural peatland borders, which would increase the plant biodiversity of the conserved area.     

A modified semipermeable membrane technique for carbonic anhydrase histochemistry of the nervous system

We present a modification of Hansson's method for the demonstration of carbonic anhydrase activity. Using a semipermeable membrane together with a fluid incubation medium, frozen sections of aldehyde-fixed tissue were incubated without floating or dipping. Thin sections (thickness, 20-40 microns) were mounted on the outer surface of a tubular-shaped, semipermeable cellophane dialysis membrane containing the incubation fluid. After incubation for 25-30 min at room temperature, the sections were rinsed in buffer and treated with 0.5% (NH4)2S solution. The histochemical reaction was fully inhibited by 10(-4) M acetazolamide.