Three endo-β-mannanase genes expressed in the micropylar endosperm and in the radicle influence germination of Arabidopsis thaliana seeds

Mannans are hemicellulosic polysaccharides in the plant primary cell wall (CW). Mature seeds, specially their endosperm cells, have CWs rich in mannan-based polymers that confer a strong mechanical resistance for the radicle protrusion upon germination. The rupture of the seed coat and endosperm are two sequential events during the germination of Arabidopsis thaliana. Endo-β-mannanases (MAN; EC. 3.2.1.78) are hydrolytic enzymes that catalyze cleavage of β1 → 4 bonds in the mannan-polymer. In the genome of Arabidopsis, the endo-β-mannanase (MAN) family is represented by eight members. The expression of these eight MAN genes has been systematically explored in different organs of this plant and only four of them (AtMAN7, AtMAN6, AtMAN2 and AtMAN5) are expressed in the germinating seeds. Moreover, in situ hybridization analysis shows that their transcript accumulation is restricted to the micropylar endosperm and to the radicle and this expression disappears soon after radicle emergence. T-DNA insertion mutants in these genes (K.O. MAN7, K.O. MAN6, K.O. MAN5), except that corresponding to AtMAN2 (K.O. MAN2), germinate later than the wild type (Wt). K.O. MAN6 is the most affected in the germination time course with a t 50 almost double than that of the Wt. These data suggest that AtMAN7, AtMAN5 and specially AtMAN6 are important for the germination of A. thaliana seeds by facilitating the hydrolysis of the mannan-rich endosperm cell walls

Two Group A Streptococcal Peptide Pheromones Act through Opposing Rgg Regulators to Control Biofilm Development

Streptococcus pyogenes (Group A Streptococcus, GAS) is an important human commensal that occasionally causes localized infections and less frequently causes severe invasive disease with high mortality rates. How GAS regulates expression of factors used to colonize the host and avoid immune responses remains poorly understood. Intercellular communication is an important means by which bacteria coordinate gene expression to defend against host assaults and competing bacteria, yet no conserved cell-to-cell signaling system has been elucidated in GAS. Encoded within the GAS genome are four rgg-like genes, two of which (rgg2 and rgg3) have no previously described function. We tested the hypothesis that rgg2 or rgg3 rely on extracellular peptides to control target-gene regulation. We found that Rgg2 and Rgg3 together tightly regulate two linked genes encoding new peptide pheromones. Rgg2 activates transcription of and is required for full induction of the pheromone genes, while Rgg3 plays an antagonistic role and represses pheromone expression. The active pheromone signals, termed SHP2 and SHP3, are short and hydrophobic (DI[I/L]IIVGG), and, though highly similar in sequence, their ability to disrupt Rgg3-DNA complexes were observed to be different, indicating that specificity and differential activation of promoters are characteristics of the Rgg2/3 regulatory circuit. SHP-pheromone signaling requires an intact oligopeptide permease (opp) and a metalloprotease (eep), supporting the model that pro-peptides are secreted, processed to the mature form, and subsequently imported to the cytoplasm to interact directly with the Rgg receptors. At least one consequence of pheromone stimulation of the Rgg2/3 pathway is increased biogenesis of biofilms, which counteracts negative regulation of biofilms by RopB (Rgg1). These data provide the first demonstration that Rgg-dependent quorum sensing functions in GAS and substantiate the role that Rggs play as peptide receptors across the Firmicute phylum

IMPROVING THE EFFICIENCYOF NATIONAL STUDENT COMPETITION

The article considers the new ways and methods for improving the efficiency of national student contests and Olympiads as a tool for identifying and supporting young talents. The authors suggest a new approach to the organization of the Olympiad movement including such principles as the limitation of the state’s role (it should be only a general initiator and supporter), segmentation of contest types, determination of contestants’ level, finding the optimal combinationbetween of the system’s stability and its capability to develop

Technology for Obtaining and Tribotechnical Characteristics of Oxidized Aluminum Coatings Applied to Polymers

Определены режимы гиперзвуковой металлизации алюминиевых покрытий на основу из термопластичных полимеров, позволяющие обеспечить прочность сцепления покрытий до 7,5 МПа. Разработано оборудование микродугового оксидирования для формирования оксидокерамических слоев на поверхности газотермических покрытий из Al, нанесенных на полимерные материалы. Показано, что износостойкость оксидированных поверхностей алюминиевых покрытий при сухом трении в 2 и более раз превышает износостойкость высокопрочного чугуна марки ВЧ50-7.= The modes of hypersonic metallization of aluminum coatings on a base of thermo-plastic polymers are determined, which allow ensuring the adhesion strength of coatings up to 7.5 MPa. MDO equipment has been developed for the formation of oxide-ceramic layers on the surface of gas-thermal coatings made of Al deposited on polymer materials. It is shown that the wear resistance of oxidized surfaces of aluminum coatings under dry friction is 2 or more times higher than the wear resistance of high-strength cast iron of the VCH50-7 brand

An extracellular bacterial pathogen modulates host metabolism to regulate its own sensing and proliferation

10.1016/j.cell.2013.12.007Cell1561-297-108CELL

Определение адгезионной и когезионной прочности металлических покрытий, нанесенных гиперзвуковой металлизацией

. It is known that at present, methods of thermal spraying are widely used to restore and strengthen various worn-out machine parts. As a rule, metal coatings applied by thermal spraying have lower strength characteristics than solid materials. It is believed that the strength of coatings is proportional to their adhesive and cohesive strength. The value of adhesive and cohesive strength depends on various factors, including the nature of the materials and the technology of coating. An important factor characterizing the possibility of using metal coatings in various industries is the strength of adhesion of coatings to the base metal. The paper presents the determination of the adhesive and cohesive strength of coatings from different materials, applied by the method of hypersonic metallization. The results of testing the strength of metal coatings made of ER316LSi-grade wire, nichrome (Cr20Ni80) and molybdenum wire are given in the paper. Based on the results of metallographic studies, the proportion of the participation of cohesive and adhesive components in the strength of coatings has been determined, and some features of coating destruction have been described. It has been found that the participation of the cohesive and adhesive components of the coating strength differs depending on the material used. The cohesive component prevails in the strength of coatings made of high-alloy wire of the ER316LSi-grade, at which destruction mainly occurs along the coating-base boundary. For nichrome coatings and especially for coatings made of molybdenum, the cohesive component is predominant, in which the destruction of the coating occurs not along the coating-base boundary, but between the coating layers.Известно, что в настоящее время для восстановления и упрочнения различных изношенных деталей машин широко применяются методы газотермического напыления. Как правило, металлические покрытия, нанесенные газотермическим напылением, обладают худшими прочностными характеристиками, чем сплошные материалы. Считается, что прочность покрытий пропорциональна их адгезионной и когезионной прочности. Величины последних зависят от различных факторов, связанных в том числе с природой материалов и технологией нанесения покрытий. Важным показателем, характеризующим возможность применения металлических покрытий в различных отраслях промышленности, является прочность сцепления (адгезия) покрытий с основным металлом. В статье представлено определение адгезионной и когезионной прочности покрытий из разных материалов, нанесенных методом гиперзвуковой металлизации. Приведены результаты испытаний прочности металлических покрытий из проволоки марки ER316LSi, нихрома (Х20Н80) и молибденовой проволоки. По результатам металлографических исследований определена доля участия когезионной и адгезионной составляющих в прочности покрытий, а также описаны некоторые особенности разрушения покрытий. Установлено, что участие когезионной и адгезионной составляющих в прочности покрытий отличается в зависимости от применяемого материала. В прочности покрытий из высоколегированной проволоки марки ER316LSi преобладает когезионная составляющая, при которой разрушение в основном происходит по границе покрытие – основа. Для покрытий из нихрома и особенно из молибдена преобладающей является когезионная составляющая прочности, при которой разрушение происходит не по границе покрытие – основа, а между слоями покрытия