Experimental system for studying long-term drought stress adaptation of wheat cultivars

Water limitation is a well-known problem for plants. Lack of water affects their biomass, their yield that is the most conspicuous in case of crops causing severe uncertainty of agricultural productivity. Under drought stress, plants generally display many physiological responses such as stomata closure, decreased/stopped photosynthetic activity, increased root/shoot ratio, reduced growth of vegetative parts. Many of the physiological changes are caused by underlying transcriptional alterations of high number of genes in many cases. One of the most studied phenomenon is the accumulation of proline as an osmoprotectant. Proline biosynthesis is increased by water deficit due to increased expression of the key enzyme, namely Δ1-pyrroline-5-carboxylate synthetase (P5CS). In our experiments, we applied P5CS as a positive control to evaluate our new experimental system, which will allow to follow transcriptional changes in shoots, as well as in roots during drought adaptation. Our alternative approach allows greenhouse or growth chamber experiments that are more similar to natural conditions than the widely used experimental systems based on osmotic agents such as polyethylene glycol (PEG)

Víztakarékos öntözéstechnikával termeszthető rizsfajtákra jellemző génexpressziós mintázatok = Gene expression profiles characteristic to rice varieties cultivated under water-saver irrigation regime

Eltérő vízigényű rizsfajták (''szárazrizsek'' és hagyományos fajták) növekedési, termesztési paramétereit határoztuk meg árasztásos ill csak kiegészítő öntözéses körülmények között annak érdekében, hogy a korlátozott vízellátáshoz jól adaptálódó fajtákra jellemző tulajdonságokat megállapíthassuk. Kidolgoztunk egy olyan kísérleti rendszert, melyben ezeknek a fajtáknak a gyökérnövekedését vizsgálhatjuk, illetve génexpressziós vizsgálatokhoz mintát gyűjthetünk. Transzkript profilok microarray hibridizációs felvételével megállapítottuk, hogy a mélyrehatoló, erőteljes gyökérzet meghatározó jellemzője a száraz körülmények között is jól teljesítő fajtáknak, és több száz olyan gént találtunk, melynek transzkript-szintje vízellátástól függő napszakos változásokat mutat a legnagyobb tűrőképességű Sandora fajta gyökérzetében. Valósidejű kvantitatív PCR-rel ellenőriztük számos gén expressziós mintázatát, ez döntő többségében megerősítette a microarray hibridizációval kapottakat, egyúttal más aszályérzékenységű rizsfajtákban is meghatároztuk ezen gének expressziós mintázatát. | Rice cultivars featuring different water demand (upland and traditional cultivars) were studied in this project. Growth and harvest parameters of these cultivars were determined under flooding and limited sprinkle irrigation in order to find features characteristic to genotypes adapting well to water limitation. An experimental system was established that allows studies of root growth as well as collection of samples for gene expression experiments. Microarray hybridizations revealed the transcript profile of Sandora cultivar that develops strong and deep root system which is an important component of good yield performance under drought stress. Several hundred genes were found which showed water supply dependent transcript level changes in the roots of this cultivar on a daily manner. Microarray results were confirmed by quantitative real-time PCR for several genes. The expression patterns of these genes were also checked in cultivars being less drought tolerant

Investigation of the in vitro photocatalytic antibacterial activity of nanocrystalline TiO2 and coupled TiO2/Ag containing copolymer on the surface of medical grade titanium

Antibacterial surfaces have been in the focus of research for years, driven by an unmet clinical need to manage an increasing incidence of implant-associated infections. The use of silver has become a topic of interest because of its proven broad-spectrum antibacterial activity and track record as a coating agent of soft tissue implants and catheters. However, for the time being, the translation of these technological achievements for the improvement of the antibacterial property of hard tissue titanium (Ti) implants remains unsolved. In our study, we focused on the investigation of the photocatalysis mediated antibacterial activity of silver (Ag), and Ti nanoparticles instead of their pharmacological effects. We found that the photosensitisation of commercially pure titanium discs by coating them with an acrylate-based copolymer that embeds coupled Ag/Ti nanoparticles can initiate the photocatalytic decomposition of adsorbed S. salivarius after the irradiation with an ordinary visible light source. The clinical isolate of S. salivarius was characterised with MALDI-TOF mass spectrometer, while the multiplication of the bacteria on the surface of the discs was followed-up by MTT assay. Concerning practical relevance, the infected implant surfaces can be made accessible and irradiated by dental curing units with LED and plasma arc light sources, our research suggests that photocatalytic copolymer coating films may offer a promising solution for the improvement of the antibacterial properties of dental implants

Genome-wide identification of the glutathione transferase superfamily in the model organism Brachypodium distachyon

The detoxification of harmful metabolites can determine the effectiveness of plant stress responses. Scavenging some of these toxic stress by-products through the reduced form of glutathione is catalysed by members of the glutathione transferase (GST) enzyme superfamily. The involvement of these enzymes was studied in the model organism Brachypodium distachyon (L.) P.Beauv. Bd21 and in its derivative Bd21-3, a more drought tolerant line. Osmotic stress treatment resulted in a decrease in the water potential of both Brachypodium genotypes, the difference between the control and treated plant's psi(w) decreased by the last sampling day in Bd21-3, suggesting some degree of adaptation to the applied osmotic stress. Increased GST activity revealed a severe defence reaction against the harmful imbalance of the redox environment. Screening for the gene sequences led to the identification of 91 full-length or partial GST sequences. Although purple false brome has a relatively small genome, the number of identified GST genes was almost as high as the number predicted in wheat. The estimation of GST expression showed stress-induced differences: higher expression levels or the fast induction of BdGSTF8, BdGSTU35 and BdGSTU42 gene products presumably indicate a strong detoxification under osmotic stress

Monitoring of Transcriptional Responses in Roots of Six Wheat Cultivars during Mild Drought Stress

In order to study drought stress responses in roots during moderate water shortage, our group has designed an oligonucleotide microarray containing probes for genes annotated as either stress-related or general ones to examine six wheat cultivars. These include two drought-tolerant and four drought-sensitive genotypes, having different root morphology either during optimal or water-deficit stress conditions. After a two-week-long water withdrawal, no significant changes were detected in root weights but various trends were observed in the cultivars. These tendencies showed relevant correlations with expression kinetics of genes encoding proteins related to root growth and development. On the other hand, probes indicating variation in distinct genotypes mainly belonged to the group of stress-related genes which encode proteins that contribute to carbohydrate remodeling, osmoprotectant accumulation, amino acid metabolism, defense against oxidative stress, and regulation of transcription. Hence, these data allow us to focus on major metabolic processes involved in drought adaptation as well as provide a wide selection of candidate genes for further detailed studies