Preliminary algological study on biofouling in industrial water systems

This paper deals with the algological investigation and the elimination of biofouling in industrial cooling water systems. Samples were taken from cooling water systems of different Hungarian Works in 1982. The algal fouling of different sampling sites was compared by cluster analysis. We given an outline about the possibilities of protective measures

Changes in the mosaic-like water surfaces of the Lake Velence as reflected by reed periphyton studies

Long term changes of the reed cover of the Lake Velence (12 years) were summarised for this paper, with emphasis on the results of investigations in 1989 and 1990. Ont he basis of the analyses it appeared that the water surface of the lake had lost its former mosaic-like character, which was primarily caused by intensive reed harvesting. Due to the scarcity of water since 1989, the salinity of the lake was increasing, as indicated by the increasing relative abundance of Chaetoceros muelleri as well as other factors. Scarcity of water also explains that algal fields detached from the basement are getting wide-spread even in protected areas (still preserving the water quality characteristic of the dark brown water surfaces), especially species of filamentours blue algae

Study on reed-periphyton in Lake Velence

In this paper we given an account of our findings between 1978 and 1988, while measuring the trends and tendencies of water quality due to the rehabilitation of Lake Velence. Dry mass and phytotecton analyses of reed-periphyton collected in 1978 and 1988 are presented. With 5 tables, 1 figure and 2 photoplates

Two Plant Viral Suppressors of Silencing Require the Ethylene-Inducible Host Transcription Factor RAV2 to Block RNA Silencing

RNA silencing is a highly conserved pathway in the network of interconnected defense responses that are activated during viral infection. As a counter-defense, many plant viruses encode proteins that block silencing, often also interfering with endogenous small RNA pathways. However, the mechanism of action of viral suppressors is not well understood and the role of host factors in the process is just beginning to emerge. Here we report that the ethylene-inducible transcription factor RAV2 is required for suppression of RNA silencing by two unrelated plant viral proteins, potyvirus HC-Pro and carmovirus P38. Using a hairpin transgene silencing system, we find that both viral suppressors require RAV2 to block the activity of primary siRNAs, whereas suppression of transitive silencing is RAV2-independent. RAV2 is also required for many HC-Pro-mediated morphological anomalies in transgenic plants, but not for the associated defects in the microRNA pathway. Whole genome tiling microarray experiments demonstrate that expression of genes known to be required for silencing is unchanged in HC-Pro plants, whereas a striking number of genes involved in other biotic and abiotic stress responses are induced, many in a RAV2-dependent manner. Among the genes that require RAV2 for induction by HC-Pro are FRY1 and CML38, genes implicated as endogenous suppressors of silencing. These findings raise the intriguing possibility that HC-Pro-suppression of silencing is not caused by decreased expression of genes that are required for silencing, but instead, by induction of stress and defense responses, some components of which interfere with antiviral silencing. Furthermore, the observation that two unrelated viral suppressors require the activity of the same factor to block silencing suggests that RAV2 represents a control point that can be readily subverted by viruses to block antiviral silencing

Regulation of microRNA biogenesis and turnover by animals and their viruses

Item does not contain fulltextMicroRNAs (miRNAs) are a ubiquitous component of gene regulatory networks that modulate the precise amounts of proteins expressed in a cell. Despite their small size, miRNA genes contain various recognition elements that enable specificity in when, where and to what extent they are expressed. The importance of precise control of miRNA expression is underscored by functional studies in model organisms and by the association between miRNA mis-expression and disease. In the last decade, identification of the pathways by which miRNAs are produced, matured and turned-over has revealed many aspects of their biogenesis that are subject to regulation. Studies in viral systems have revealed a range of mechanisms by which viruses target these pathways through viral proteins or non-coding RNAs in order to regulate cellular gene expression. In parallel, a field of study has evolved around the activation and suppression of antiviral RNA interference (RNAi) by viruses. Virus encoded suppressors of RNAi can impact miRNA biogenesis in cases where miRNA and small interfering RNA pathways converge. Here we review the literature on the mechanisms by which miRNA biogenesis and turnover are regulated in animals and the diverse strategies that viruses use to subvert or inhibit these processes

Antiviral Silencing and Suppression of Gene Silencing in Plants

RNA silencing is an evolutionary conserved sequence-specific gene inactivation mechanism that contributes to the control of development, maintains heterochromatin, acts in stress responses, DNA repair and defends against invading nucleic acids like transposons and viruses. In plants RNA silencing functions as one of the main immune systems. RNA silencing process involves the small RNAs and trans factor components like Dicers, Argonautes and RNA-dependent RNA poly- merases. To deal with host antiviral silencing responses viruses evolved mecha- nisms to avoid or counteract this, most notably through expression of viral suppressors of RNA silencing. Due to the overlap between endogenous and antiviral silencing pathways while blocking antiviral pathways viruses also impact endogenous silencing processes. Here we provide an overview of antiviral silencing pathway, host factors implicated in it and the crosstalk between antiviral and endogenous branches of silencing. We summarize the current status of knowledge about the viral counter-defense strategies acting at various steps during virus infection in plants with the focus on representative, well studied silencing suppres- sor proteins. Finally we discuss future challenges of the antiviral silencing and counter-defense research field

Photochemical activity and osmotic adjustment of some halophyte and xerophyte species in different microtopographic conditions

The saline area of the Kiskunság region of Hungary has varied micro-topographic conditions with different plant communities. This study was performed in a dry sandy grassland community ( Potentillo arenariae-Festucetum pseudovinae Soó (1938) 1940) and a neighbouring saline sandy grassland community ( Lepidio crassifolii-Puccinellietum limosae Soó (1947) 1957). These are located at different elevations and have completely different floristic composition and physiognomy due to the soil characteristics and water availability. We assessed how the different environmental conditions during summer period might alter some physiological traits of two dominant xerophytes of sandy grassland ( Achillea collina L., Festuca pseudovina Hack. ex Wiesb.) and two halophytes of saline grassland ( Lepidium crassifolium (W. et K.), Puccinellia limosa (Schur) Holmbg.). The relationship between soil water potential and water content showed lower water availability for plants in the saline habitat as the high water soluble sodium content (900–2000 ppm) of this soil type limits water absorption. Both halophyte species in this study exhibited lower K/Na ratio than xerophyte species. Between the two halophytes L. crassifolium can be described as a “leaf/shoot sodium accumulator” species while P. limosa as a “leaf sodium avoider” species. The four species differed in proline accumulation. The salt adapted species had multifold accumulation of proline as compared to species of dry sandy grassland. The three microhabitats differing in total plant cover offered different microenvironmental conditions for L. crassifolium . Proline content was twice higher in leaves of this species in the microhabitats with high soil Na+ content than in the closed microhabitat. Every species showed a transient reversible decrease of potential photochemical efficiency of PSII (Fv/Fm ) at midday during the study period. In the saline habitat the midday depression of Fv/Fm for L. crassifolium was much larger than in case of P. limosa which reflected its higher susceptibility to photoinhibition. In sandy grassland Fv/Fm of A. collina was smaller than that of F. pseudovina . Mesophyll succulence index (Sm) expressing the ratio of water content to chlorophyll content was the highest in L. crassifolium (1.6–2.2 g H2O mg-1 Chl). Sm was low in xerophyte species (0.5–1.1 g H2O mg-Chl), and the lowest value was found for the F. pseudovina (0.54 g H2O mg- Chl)