Effect of Cd on the iron re-supply-induced formation of chlorophyll-protein complexes in cucumber

Cd induced changes in the accumulation of chlorophyll-protein complexes were studied during the iron induced re-greening of iron deficient cucumber plants to see how the Cd-induced alterations develop during the thylakoid biogenesis, and whether the altered development of chlorophyll-protein complexes and the changed iron metabolism are connected. Treatment with 1 μM Cd resulted in strong decrease in iron content of leaves compared to the controls, but Cd could not be detected in the leaves. It was accompanied with strong retardation of chlorophyll synthesis and biogenesis of chlorophyll-protein complexes, particularly photo-system I, the amount of which even decreased at the later period of greening. During the re-greening, the actual efficiency of photosystem II and CO2 fixation capacity recovered totally and partially, respectively. It was concluded that both retardation of the biogenesis of the complexes due to iron and chlorophyll deficiency and degradation processes affecting mainly photosystem I were involved in Cd induced changes in the pattern of chlorophyll-protein complexes

Comparison of the effects of Pb treatment on thylakoid development in poplar and cucumber plants

Pb (10 to 100 uM ) effects on the development of thylakoids were investigated in Fe-EDTA an d Fe-citrate grown cucumber and poplar to compare the symptoms in different plant species. Increased chlorophyll content of leaves appeared either in PSII core or LHCII depending on the treatment. Lowering of the chlorophyll content, however, was accompanied by decrease in PSI and LHCII, and relatively high stability of PSII core. PSII efficiency and C02 fixation were mostly unchanged or decreased moderately, but rise in the non-photochemical quenching was observed in all kinds of treatment. While Pb could not be detected and Mn content decreased in poplar leaves, changes in photosynthetic parameters paralleled with the Pb content in cucumber, and increase in Fe, Mn, and Ca content was measured. The direct effects of Pb or oxidative stress may evoke the changes in cucumber, while Pb induced Mn deficiency seems to play a role in poplar. Alterations in the composition of thylakoids were probably triggered by regulatory processes, which optimise the structure and function under stress conditions

Investigations into the »inverse contrast« of chloroplast thylakoids

We detected an »inverse contrast« (i. e. dense lumen and lightly staining membrane) of thylakoids in some species or organs where it has not previously been described. We probed the chemical character of the dense lumenal substance by in situ extraction on ultrathin sections, and found that it was less hydrophilic in Perilla frutescens, than in Helianthus annuus, where it could be neither lipid nor protein. Its disappearance from the lumen upon prolonged illumination was accompanied by a drop in the plastidial polyphenol oxidase activity, so it may be a phenolic compound. Growing Helianthus seedlings at 30 °C (rather than at 25 °C) resulted in the density appearing in the stroma (rather than in the lumen), but still preventing the strong staining of the thylakoid membrane. Upon the removal of the dense substance from the stroma by plastid isolation the staining pattern reverted to its usual appearance in the plastids. This excludes the explanation that light membrane staining is produced by some compositional deficiency. This conclusion was supported also by gel electrophoretograms of polypeptides from such membranes. We think that the dense substance on either side of the membrane protects lipid molecules from a conformational change during solvent dehydration, which normally leads to the strong staining of the membrane

Fémionok homeosztázisa növényekben = Studies on metal homeostasis in plants

A pályázat keretében a spanyol Tudományos Akadémia Aula Dei Kutató Intézetével együttműködésben vizsgáltuk a növények (gyökér, levél, kloroplasztisz) vasfelvételének mechanizmusát, ezen belül a növényben kialakuló Fe(II) és Fe(III) ion- és vegyületformákat, komplexeket, valamint a felvétel kinetikáját eltérő Fe és Zn ellátás, illetve Cd kezelés mellett. Vizsgáltuk a növényi proteom változását különböző szintű fémellátás mellett: a vasellátás és a Cd indukálta változásokat a kloroplasztisz envelop proteomban és a lehetséges kloroplasztisz transzporterek transzkript szintjében, továbbá a különböző tilakoid doménekben lévő komplexek összetételében és szerveződésében bekövetkező változásokat. A hazai laboratóriumokban Mössbauer spektroszkópiával, ICP-MS-rel, BN/SDS PAGE-sel, illetve qRT-PCR-rel, míg a spanyol laboratóriumban IEF/SDS PAGE-sel, HPLC ESI-TOF-MS, illetve nano-HPLC-MS technikával végeztük a méréseket. A tudományterületen jelentős, új eredményeket értünk el 1. a gyökér vas felvétele és szállítása során kialakuló vasformák leírása, 2. a Cd vasfelvétel kinetikájára gyakorolt hatása, 3. a kloroplasztisz vasfelvételének mechanizmusa, 4. a kloroplasztisz borítómembrán proteomikai vizsgálata, valamint különböző tilakoid doménekben a Fe ellátás és a Zn és Cd kezelések a fotoszintetikus komplexek összetételére és szerveződésére gyakorolt hatása terén. Az eredményeket referált tudományos folyóiratokban és nemzetközi konferenciákon közöltük és közöljük. A tudományos kooperáció igen sikeres volt a hazai kutatók külföldi tapasztalatszerzése terén is. | In the framework of the project we have studied the iron uptake mechanism of plants (roots, leaves, chloroplasts), more specifically the Fe(II) and Fe(III) ionic forms and complexes as well as the kinetics of the uptake under different Fe and Zn supply and Cd treatments in cooperation with the Aula Dei Research Station (CSIC), Zaragoza, Spain. We have investigated the changes in the plant proteom at different levels of metal supply: the changes induced by Fe-supply and Cd in the chloroplast envelope proteom, the candidate chloroplast transporter’s transcript level and the complex composition and organisation in different thylakoid domains. The measurements were made in the Hungarian labs by Mössbauer spectroscopy, ICP-MS, BN/SDS PAGE and qRT-PCR while in the Spanish lab by IEF/SDS PAGE, HPLC ESI-TOF-MS and nano-HPLC-MS. Significant results have been achieved in the field of 1. identifying the Fe species formed during its uptake and transport processes, 2. the effect of Cd on the kinetics of Fe uptake, 3. the Fe uptake mechanism of chloroplasts, 4. the proteomic study of the chloroplast envelope and the effect of Fe supply and Zn and Cd treatments on the composition and organisation of photosynthetic complexes in the different thylakoid domains. The results have been and being published in scientific journals with high impact factor and international conferences. The scientific cooperation has been very successful regarding the experience of Hungarian researchers in foreign laboratories, too

A kompetenciafejlesztés lehetőségei a kisiskoláskori idegennyelv-oktatásban

This paper examines competence development in the lower-primary second-language class. The activities presented clearly illustrate that language learning is more than just a purpose in itself; instead, it is part of a more extensive educational program. From this end, it is important to stress that second-language learning can only be successful if one teaches through the language, not only about the language. In order to achieve this goal, the use of content from other subjects can be used and through this one can develop pupils' communicative and general competences, with special emphasis on the intercultural. To achieve this objective, we need teachers who are familiar with the theory and practice of competence development, and are able to make the target-language understandable for the pupils, and who use the target-language in the second language classroom. This new role of the teacher poses new challenges for teacher-training and for the continuing education of professional teachers

Antioxidative defence mechanism contributes to desiccation tolerance in Haberlea rhodopensis population naturally exposed to high irradiation

Drought induced stress is one of the most important among the environmental challenges. Haberlea rhodopensis, a chlorophyll-retaining resurrection plant, can survive desiccation to air-dry stage in its usual low irradiance habitat (“shade” plants). Nevertheless, in the past years, some populations living under high irradiance (“sun” plants) have been also discovered with the same ability to survive dehydration. In order to clarify the adaptation mechanisms to a high irradiation habitat, superoxide dismutase (SOD) activity determined by activity staining on polyacrylamide gels and malondialdehyde (MDA) content of sun and shade plants collected from high and low irradiance environment, respectively, were studied. Desiccation induced a significantly higher induction in SOD activity and thus a smaller increase in the MDA content in sun compared to shade plants. The MDA content and SOD activity was restored in both sun and shade plants after six-day rehydration. Nevertheless, the SOD activity remained higher in rehydrated sun leaves compared to the well-hydrated initial stage. The early enhancement of SOD activity in dehydrating sun plants contributes to the higher stress tolerance of these populations

Light piping driven photosynthesis in the soil: low-light adapted active photosynthetic apparatus in the under-soil hypocotyl segments of bean (Phaseolus vulgaris)

Photosynthetic activity was identified in the under-soil hypocotyl part of 14-day-old soil-grown bean plants (Phaseolus vulgaris L. cv. Magnum) cultivated in pots under natural light-dark cycles. Electron microscopic, proteomic and fluorescence kinetic and imaging methods were used to study the photosynthetic apparatus and its activity. Under-soil shoots at 0-2 cm soil depth featured chloroplasts with low grana and starch grains and with pigment-protein compositions similar to those of the above-soil green shoot parts. However, the relative amounts of photosystem II (PSII) supercomplexes were higher; in addition a PIP-type aquaporin protein was identified in the under-soil thylakoids. Chlorophyll-a fluorescence induction measurements showed that the above- and under-soil hypocotyl segments had similar photochemical yields at low (10-55 µmol photons m-2 s-1) light intensities. However, at higher photon flux densities the electron transport rate decreased in the under-soil shoot parts due to inactivation of the PSII reaction centers. These properties show the development of a low-light adapted photosynthetic apparatus driven by light piping of the above-soil shoot. The results of this paper demonstrate that the classic model assigning source and sink functions to above- and under-soil tissues is to be refined, and a low-light adapted photosynthetic apparatus in under-soil bean hypocotyls is capable of contributing to its own carbon supply

Ionic, not the osmotic component, is responsible for the salinity-induced inhibition of greening in etiolated wheat (Triticum aestivum L. cv. Mv Béres) leaves : a comparative study

Main conclusion Greening was partially (in 300 mM NaCl, $CaCl_{2}$, 600 mM $KNO_{3}$ or KCl) or fully inhibited (in 600 mM NaCl, $NaNO_{3}$ or NaCl:KCl) by the ionic and not the osmotic component of salinity. Abstract Although high soil salinity is an increasing global problem, not much is known about how direct exposure to salinity affects etiolated leaves of seedlings germinating in the soil and then reaching the surface. We investigated the effect of various salt treatments on the greening process of leaves in 8- to 11-day-old etiolated wheat (Triticum aestivum L. Mv. Béres) seedlings. Etiolated leaf segments pre-treated on different salt (600 mM NaCl:KCl 1:1, 600 mM NaCl, 600 mM KCl, 600 mM $NaNO_{3}$, 600 mM KNO3, 300 mM KCl, 300 mM NaCl or 300 mM $CaCl_{2}$) or isosmotic polyethylene glycol 6000 (PEG) solutions for 1.5 h in the dark and then greened for 16 h on the same solutions were studied. Leaf segments greened on PEG (osmotic stress) or on 300 mM KCl had similar chloroplasts compared to control samples greened on Hoagland solution. Slightly slower development of chloroplast structure and function (photosynthetic activity) was observed in segments greened on 300 mM NaCl or $CaCl_{2}$, 600 mM KNO3 or KCl. However, etioplast-to-chloroplast transformation and chlorophyll accumulation were fully inhibited and peculiar prothylakoid swelling occurred in segments greened on 600 mM NaCl, $NaNO_{3}$ or NaCl:KCl (1:1) solutions. The data indicate that not the high osmolarity of the used salt solution, but its ions, especially $Na^{+}$, had the strongest negative impact on these processes