41 research outputs found
A második fotokĂ©miai rendszer alternatĂv elektrondonorának kĂ©miai termĂ©szete Ă©s Ă©lettani szerepe cianobaktĂ©riumokban, algákban Ă©s növĂ©nyekben; potenciális biotechnolĂłgiai alkalmazások = Identification, physiological role and potential biotechnological applications of the alternative electron donors of photosystem II in cyanobacteria, algae and plants
Az aszkorbát (C-vitamin) esszenciális antioxidáns az ember Ă©s az állatok számára egyaránt. NövĂ©nyekben nagy mennyisĂ©gben (2-20 mM) szintetizálĂłdik Ă©s fontos antioxidáns szerepe mellett más egyĂ©b enzimatikus folyamatokhoz is szĂĽksĂ©ges. Munkánk során az aszkorbát a fotoszintĂ©zisben betöltött, eddig ismeretlen szerepĂ©t vizsgáltuk. I. BizonyĂtottuk, hogy az aszkorbát a második fotokĂ©miai rendszer alternatĂv elektrondonora növĂ©nyekben Ă©s zöldalgákban egyaránt Ă©s hĹ‘ által inaktivált vĂzbontĂł aktivitás mellett jelentĹ‘s mennyisĂ©gű elektront szolgáltat az elektrontranszport-lánc számára. Az elektronátadás fĂ©lideje kb. 25 ms vadtĂpusĂş Ă©s 55 ms aszkorbát-deficiens mutánsokban, ami a környezeti körĂĽlmĂ©nyektĹ‘l is fĂĽgg. II. A donor oldal által indukált fotoinhibĂciĂłt mĂ©rsĂ©kelve az aszkorbát jelentĹ‘s szerepet tölt be a növĂ©nyek hĹ‘stresszel szembeni vĂ©dekezĂ©sĂ©ben. III. Az aszkorbáttĂłl második fotokĂ©miai rendszerhez irányulĂł alternatĂv elektrontranszport jelensĂ©gĂ©t sikeresen hasznosĂtottuk a Chlamydomonas reinhardtii zöldalga biohidrogĂ©n-termelĂ©sĂ©nek serkentĂ©sĂ©re. | In humans and all animals ascorbate (vitamin C) is an essential antioxidant. In plants ascorbate is synthesized in large quantities (2-20 mM), and has been shown to play a role as antioxidant and it is required for several other enzymatic processes. In this project a novel role of this compound in photosynthesis was explored. I. We have shown that ascorbate is an alternative electron donor of photosystem II in higher plants and green algae and it is capable of supporting a sustained electron transport activity in heat-stressed leaves containing inactivated oxygen-evolving complexes. The halftime of electron donation is about 25 ms in wild-type Arabidopsis leaves, and 55 ms in ascorbate-deficient mutants and the rate is also dependent on the environmental conditions. II. By slowing down donor-side-induced photodamage to photosystem II, ascorbate contributes significantly to the ability of plants to withstand heat-stress conditions. III. The phenomenon of alternative electron transport from ascorbate through photosystem II was successfully exploited in enhancing biohydrogen production in the green alga Chlamydomonas reinhardtii
Alternative electron donors to photosystem II play an important role in the reduction of the electron transport chain in heat-treated barley leaves
Electron donation to TyrZ in heat-inactivated photosystem II (PSII) reaction centers by alternative donors was evaluated. Chl a fluorescence transients indicate that in the 0.1-3 ms range (K-step) only one electron is available, but that in the 0.2-2 s range accumulation of QA- took place that coincided with the re-reduction of plastocyanin PC+ and P700+. Using Chl a fluorescence emission induced by short repetitive pulses and simultaneous 820 nm transmission and Chl a fluorescence transient measurements we show that electron donation to photosystem II takes place with a halftime of ~10 ms. There is a large pool of such alternative donors and they significantly contribute to the reduction of the linear electron transport chain since inhibition of PS II by DCMU prevented the re-reduction of PC+ and P700+
Az aszkorbát (C-vitamin) bioszintézise és szerepei a fotoszintézisben és a zöldalgák hidrogéntermelésében
Concentration does matter: The beneficial and potentially harmful effects of ascorbate in humans and plants
Probing the photosynthetic apparatus noninvasively in the laboratory of Reto Strasser in the countryside of Geneva between 2001 and 2009
Elimination of the flavodiiron electron sink facilitates long-term H2 photoproduction in green algae
The development of renewable and sustainable biofuels to cover the future energy demand is one of the most challenging issues of our time. Biohydrogen, produced by photosynthetic microorganisms, has the potential to become a green biofuel and energy carrier for the future sustainable world, since it provides energy without CO2 emission. The recent development of two alternative protocols to induce hydrogen photoproduction in green algae enables the function of the O2-sensitive [FeFe]-hydrogenases, located at the acceptor side of photosystem I, to produce H2 for several days. These protocols prevent carbon fixation and redirect electrons toward H2 production. In the present work, we employed these protocols to a knockout Chlamydomonas reinhardtii mutant lacking flavodiiron proteins (FDPs), thus removing another possible electron competitor with H2 production.The deletion of the FDP electron sink resulted in the enhancement of H2 photoproduction relative to wild-type C. reinhardtii. Additionally, the lack of FDPs leads to a more effective obstruction of carbon fixation even under elongated light pulses.We demonstrated that the rather simple adjustment of cultivation conditions together with genetic manipulation of alternative electron pathways of photosynthesis results in efficient re-routing of electrons toward H2 photoproduction. Furthermore, the introduction of a short recovery phase by regular switching from H2 photoproduction to biomass accumulation phase allows to maintain cell fitness and use photosynthetic cells as long-term H2-producing biocatalysts
Problémamegoldás barátok és nem barátok között serdülők körében
Háttér és célkitűzések: A vizsgálat célja az azonos és ellentétes nemű baráti viszony és az ezekben törté-
nő problémamegoldás jellemzőinek, illetve kapcsolatuknak a feltárása volt 12–13 és 16–17 évesek körében
(N = 304).
Módszer: A személyközi problémák megoldásának jellemzőit a Social Problem-Solving Inventory–Revised
(SPSI–R, D’Zurilla, Nezu és Maydeu-Olivares, 2002; magyarul: Kasik, Nagy és Fűzy, 2010), a barátság-
funkciókat a McGill Friendship Questionnaire (MFQ, Mendelson és Aboud, 2014; magyarul: Kasik, Jám-
bori, Gál Ă©s TĂłth, 2021) eszközzel tártuk fel, mindkĂ©t kĂ©rdĹ‘Ăv jĂł megbĂzhatĂłsági mutatĂłkkal rendelkezett.
EredmĂ©nyek: Az MFQ által mĂ©rt serkentĹ‘ egyĂĽttlĂ©t, segĂtsĂ©gnyĂşjtás, bensĹ‘sĂ©gessĂ©g, Ă©rzelmi biztonság, ki-
tartás és elismertség közül az idősebbek számára fontosabb a kitartás és az elismertség azonos és ellentétes
nemű barát esetében egyaránt. A baráti viszonyban előforduló problémák megoldásához mindkét életkorban
pozitĂvan viszonyulnak, megoldási stĂlusuk racionális, ám ez jobban jellemzĹ‘ az azonos nemű barátságok-
ra, hiszen az ellentĂ©tes neműeknĂ©l – akárcsak a nem baráti viszonyban – megjelenik a negatĂv viszonyulás,
ehhez kapcsoltan az impulzĂv Ă©s az elkerĂĽlĹ‘ megoldási stĂlus.
KövetkeztetĂ©sek: Az eredmĂ©nyek a korábban feltárt Ă©letkor Ă©s nem szerinti sajátosságok megerĹ‘sĂtĂ©se mel-
lett igen sok mĂłdszertani kĂ©rdĂ©st is felvetnek, Ăşjabb kutatásokra ösztönöznek, valamint felhĂvják a figyelmet
arra, hogy a baráti kapcsolatoknak milyen fontos szerepük van a serdülők társas életében, hiszen a baráti
kapcsolatban felmerĂĽlĹ‘ problĂ©mamegoldás rendelkezik azokkal a jellemzĹ‘kkel (pozitĂv viszonyulás, racioná-
lis stĂlus), amelyek kialakĂtása, erĹ‘sĂtĂ©se általános nevelĂ©si, fejlesztĂ©si cĂ©l ebben az Ă©letkorban a nem baráti
kortársi viszonyok esetében
Ascorbate deficiency does not limit non-photochemical quenching in Chlamydomonas reinhardtii
Ascorbate (Asc, vitamin C) plays essential roles in development, signaling, hormone biosynthesis, regulation of gene expression, stress resistance and photoprotection. In vascular plants, violaxanthin de-epoxidase (VDE) requires Asc as reductant, thereby it is required for the energy-dependent component of non-photochemical quenching (NPQ). To assess the role of Asc in NPQ in green algae, which are known to contain low amounts of Asc, we searched for an insertional Chlamydomonas reinhardtii mutant affected in the VTC2 gene encoding GDP-L-galactose phosphorylase, which catalyzes the first committed step in the biosynthesis of Asc.. The Crvtc2-1 knockout mutant was viable and, depending on the growth conditions, contained 10 to 20% Asc relative to its wild type. When C. reinhardtii was grown photomixotrophically at moderate light, the zeaxanthin-dependent component of NPQ emerged upon strong red illumination both in the Crvtc2-1 mutant and in its wild type. Deepoxidation was unaffected by Asc deficiency, demonstrating the Chlorophycean VDE found in C. reinhardtii does not require Asc as a reductant. The rapidly induced, energy-dependent NPQ component characteristic of photoautotrophic C. reinhardtiicultures grown at high light was not limited by Asc deficiency either. On the other hand, a reactive oxygen species-induced photoinhibitory NPQ component was greatly enhanced upon Asc deficiency, both under photomixotrophic and photoautotrophic conditions. These results demonstrate Asc has distinct roles in NPQ formation in C. reinhardtiithan in vascular plants