Different approaches for Agrobacterium-mediated genetic transformation of Brachypodium distachyon, a new model plant for temperate grasses

Cereal crops belonging to temperate grasses are fundamental sources of human nutrition therefore their agronomical improvement is centrally important. For this purpose the establishment of an experimental model system for these monocot plants is essential in plant biology research. Considering its advantageous morphological and physiological virtues taken together with the results of the advanced genomics research the Brachypodium distachyon became the new model plant for the Poaceae. The aim of our work is to adapt and possibly improve the Agrobacterium-mediated transformation method using embryogenic callus from in vitro cultures and furthermore develop an in planta methodology via Agrobacterium tumefaciens for Brachypodium in order to simplify the transformation procedure

Transcriptional changes in ascorbate-glutathione cycle under drought conditions

Ascorbate-glutathione cycle has an important role in defensive processes against oxidative damage generated by drought stress. Changes in expression patterns, subjected to reduced amount of irrigation solution, of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDAR) and dehydroascorbate reductase (DHAR) as enzyme families of this cycle were studied comparing a drought tolerant (Triticum aestivum cv. Plainsman V) and a drought sensitive (Triticum aestivum cv. Cappelle Desprez) wheat genotype. Relative transcript level of isoenzymes localized in distinct subcellular organelles showed significant differences between the two genotypes at the beginning of treatment. Among APX isoenzymes, a thylakoid-bound (tAPX), two stromal (sAPX1, sAPX2), one of the two cytosolic (cAPX1) and a peroxisomal (mAPX) APXs displayed higher relative transcript level in the drought tolerant genotype. The same was observed in case of cytosolic (cDHAR) and stromal (sDHAR) DHARs. However, relative transcript levels of MDHAR isoenzymes were similar in both genotypes. Under drought conditions, the initial relative transcript levels of distinct isoenzymes changed differently comparing the two genotypes leading to the final conclusion that the drought tolerant genotype up-regulates mostly the cytosolic APXs and MDARs to maintain the cellular ascorbate redox state, however in the drought sensitive genotype, sAPX and sDHAR are induced to fill the same function

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)

Comparative approach for the isolation of genes involved in the osmotolerance of wheat

Improving drought tolerance of wheat is of great agronomical importance. Gene isolation techniques based on expression properties may provide new tools for breeders both in early characterization of new cultivars and in improving drought tolerance via molecular breeding. The main aim of our project is to isolate new drought activated genes which may serve both purposes. As a first step, a subtracted cDNA library was prepared, which represents the difference in the mRNA populations of wheat plantlets grown under 400 mOsm polyethylene-glycol derived osmotic stress versus plantlets grown in optimal conditions. By applying the subtraction approach, the resulted cDNA library becomes enriched in clones of differentially expressed genes including the ones of rare messages as well. This allows us to clone these genes, sequence them and, later, perform in silico analysis. Our first results indicate that the resulted library is enriched in clones coding for membrane associated channel proteins as well as abscisic acid and stress responsive ones

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

Limited water stress modulates expression of circadian clock genes in Brachypodium distachyon roots

Organisms have evolved a circadian clock for the precise timing of their biological processes. Studies primarily on model dicots have shown the complexity of the inner timekeeper responsible for maintaining circadian oscillation in plants and have highlighted that circadian regulation is more than relevant to a wide range of biological processes, especially organ development and timing of flowering. Contribution of the circadian clock to overall plant fitness and yield has also long been known. Nevertheless, the organ- and species-specific functions of the circadian clock and its relation to stress adaptation have only recently been identified. Here we report transcriptional changes of core clock genes of the model monocot Brachypodium distachyon under three different light regimes (18:6 light:dark, 24:0 light and 0:24 dark) in response to mild drought stress in roots and green plant parts. Comparative monitoring of core clock gene expression in roots and green plant parts has shown that both phase and amplitude of expression in the roots of Brachypodium plants differ markedly from those in the green plant parts, even under well-watered conditions. Moreover, circadian clock genes responded to water depletion differently in root and shoot. These results suggest an organ-specific form and functions of the circadian clock in Brachypodium roots

Secondary resonances of co-orbital motions

The size distribution of the stability region around the Lagrangian point L4 is investigated in the elliptic restricted three-body problem as the function of the mass parameter and the orbital eccentricity of the primaries. It is shown that there are minimum zones in the size distribution of the stability regions, and these zones are connected with secondary resonances between the frequencies of librational motions around L4. The results can be applied to hypothetical Trojan planets for predicting values of the mass parameter and the eccentricity for which such objects can be expected or their existence is less probable.Comment: 9 pages, 7 figures, accepted for publication in MNRA

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