Tissue- and organ specific plastid differentiation in various plant species

Plastid differentiation and the greening process are usually studied in etiolated leaves. In this work, we studied stems or stem related organs of various plant species. Electron microscopy studies combined with fluorescence spectroscopy showed the formation of protochlorophyllide forms similar to those of etiolated leaves but their ratio had a big variation, even more in different tissues of the same organ. In a series of measurements, we proved that etiolation conditions can occur in the nature in closed cabbage head or inside closed leaf buds

Dynamic interconversion and phototransformation processes of protochlorophyllide complexes during greening

Photoreduction and interconversion processes of different protochlorophyllide complexes were studied in epicotyl segments of dark-germinated pea (Pisum sativum L.) seedlings illuminated with low-intensity white or 632.8 nm laser light. Analyses of 77 K fluorescence emission spectra showed the direct phototransformation of the monomer, 636 nm emitting complex. The 629 nm emitting complex containing also monomer pigment, regenerated all longer wavelength, flash-photoactive complexes. A dynamic transformation of the protochlorophyllide complexes was also detected during the illumination and/or the subsequent dark-incubation. On the basis of these results, the protochlorophyllide phototransformation schemes can be completed with new pathways

Special features of the greening of Ginkgo biloba L.

Most studies on chlorophyll biosynthesis and greening are carried out on angiosperm leaves. Unlike angiosperms, most gymnosperms can synthesize chlorophyll in the dark and cannot be etiolated. Ginkgo (Ginkgo biloba L.) is an exception. In this work, the greening of the stems and the leaves of ginkgo were analyzed. Pigment content changes, changes in the 77 K fluorescence emission spectra and plastid ultrastructure were studied and compared at different temperatures

Vírusfertőzés hatása a növények fotokémiai rendszereinek kialakulására és működésére = Effect of virus infection on the development and function of plant photosystems

A fotoszintetikus rendszer vírusfertőzésre kialakult morfológiai és molekuláris összetételben bekövetkezett változásait két fő gazdanövény-kórokozó kapcsolatban vizsgáltuk, egyrészt a teljes sötétben nevelt, árpa csíkos mozaik vírussal magátvitel formájában fertőzött árpa csíranövények leveleiben, másrészt Tobamovírusokkal fertőzött paprika növényekben. A fertőzött árpa növények sejtjeiben már az etioplasztiszok kialakulása is gátlást szenvedett, amit a prolammelláris testek (PLB) és a protilakoid membránok rendellenességeivel jellemeztünk. Bár a fertőzés közvetlenül nem befolyásolta a protoklorofillid oxidoreduktáz (POR) enzim szerepét, mégis a megvilágítás hatására a fertőzött szövetekben a zöldülési folyamatok jelentős gátlást, késést szenvedtek, ami arra utal, hogy ebben a folyamatban a membrán-protein rendszer térbeli kialakulásában is zavar támad. A POR enzim immunolokalizálása során a kontroll csíranövényekben a jelölés nagymértékben a PLB-kra koncentrálódott. A vírusfertőzés csökkentette a POR enzim jelölést. A vírusfertőzés csökkentette a telítetlen zsírsavak és a galaktolipidek mennyiségét, és azok arányait is. A tobamovirusok fertőzése a különböző paprika fajták illetve vonalak leveleinek kloroplasztiszaiban a tilakoid membránok szerkezetében és összetételében is jellemző változásokat okozott az enyhe serkentéstől a súlyos károsításig, és rámutatott a PSII fotokémiai rendszer mellett a PSI károsodására is. | Effects of virus infections on the morphology and molecular structure of chloroplasts were studied in two host-parasite systems: in etiolated barley seedlings infected with Barley stripe mosaic virus (BSMV); and in pepper varieties infected by different Tobamoviruses. Seed transmission of BSMV altered the membrane structure of dark-grown barley etioplasts and caused the delay of greening processes after illumination, suggesting the early damage of chloroplast development. Immunolabeling intensity of protochlorophyllide oxidoreductase enzyme (POR) in etioplasts of infected barley leaves was weaker and the amount of the enzyme was lower than in non-infected plants. The lower amount of highly unsaturated fatty acids and the reduced abundance of galactolipids correlated with the previously detected reduction in prolamellar body to prothylakoid membrane ratio. The effect pathogenically different Tobamoviruses on the photosynthetic structures and the chlorophyll protein complexes were studied. Virus infection caused characteristic differences in the chlorophyll-protein complexes from the slight increase to the serious damage, including the alterations in PSII as well as in PSI photosystems

Plasztisz-differenciálódás: a szerkezet és a működés összefüggései = Plastid differentiation: connection between structure and function

A plasztisz-differenciálódás folyamatában a struktúra és a funkció közötti összefüggéseket vizsgáltuk különböző szerveződési szinteken. Sötétben nevelt csíranövényeket, szerv- és szövettenyészetet, szövet-homogenátumokat, membrán-preparátumokat, intakt növényeket és a természetből begyűjtött rügyeket és egyéb szerveket használtunk. A folyamat indikátoraként a NADPH:protoklorofillid oxidoreduktáz (POR) enzim, illetve a pigmentek komplexeit használtuk. Különböző fluoreszcencia spektroszkópiai módszereket és elektronmikroszkópos vizsgálatokat végeztünk. Megállapítottuk, hogy a POR monomer, dimer és oligomer komplexei is flash fotoaktívak, és dinamikusan egymásba alakulnak. A nem levél eredetű szervekben proplasztisz jellegű etioplasztiszok vannak, amelyekben a POR- és nem kötött pigment-monomerek dominálnak, valamint NADPH hiány jellemző. Emiatt a monomer dominanciájú szervek természetes fényen fotodegradálódnak. A makrodomén szerveződés együtt jár a prolamelláris test kialakulásával, fejlett etioplasztiszok képződésével, növeli a fotoredukció hatékonyságát, és véd a fotodegradáció ellen. A plasztisz-differenciálódást a citokinin szint és a N-ellátottság szabályozza. Proplasztiszok, etioplasztiszok és átmeneti állapotú plasztiszok természetes körülmények között is kialakulnak, egyes kiválasztásra differenciálódott szövetekben a kloroplasztisz speciálisan módosul. Eredményeink alapján a klorofill bioszintézis befejező lépését és a plasztisz-differenciálódást leíró reakciósémákat módosítani kell. | Relationships between the structure and function were studied in the process of plastid differentiation, on different organizational levels. Dark-grown seedlings, organ- and tissue cultures, tissue homogenates, membrane preparations, intact plants, buds and other organs collected from the nature were used. Different complexes of the NADPH:protochlorophyllide oxidoreductase (POR) enzyme and of pigments were used as indicators of the differentiation process. Various fluorescence spectroscopic measurements and electron microscopy studies were done. We have proved that the monomer, dimer and oligomer complexes of POR are flash-photoactive and they transform into each other dinamically. In non-leaf organs, proplastid type etioplasts can be found in which monomers of POR and of non-bound pigments are dominant and NADPH shortage is characteristic. Therefore, these organs undergo photodegradation at natural light conditions. The macrodomain organization proceeds together with the formation of prolamellar bodies, i.e. of developed etioplasts, it increases the efficiency of photoreduction and provides protection against photodegradation. Plastid differentiation is regulated by citokinin concentrations and nitrogen supply. Proplastids, etioplasts and plastids of transitional developmental stages can be found in the nature. In certain secretion tissues, the chloroplasts are specifically modified. On the basis of our results, the reaction schemes describing the terminal steps of chlorophyll biosynthesis and plastid differentiation should be modified

Colistin resistance associated with outer membrane protein change in Klebsiella pneumoniae and Enterobacter asburiae

In this study, outer membrane proteins (OMPs) of colistin-resistant Klebsiella pneumoniae and Enterobacter asburiae were analyzed. One colistin-susceptible and three colistin-resistant K. pneumoniae sequence type 258 strains as well as one colistin-susceptible E. asburiae and its colistin-heteroresistant counterpart strain were involved in the study. OMP analysis of each strain was performed by microchip method. Matrix-assisted laser desorption ionization time of flight/mass spectrometry (MALDI-TOF/MS) investigation was carried out after separation of OMPs by two-dimensional gel electrophoresis and in-gel digestion. The MALDI-TOF/MS analysis of OMPs in the colistin-susceptible K. pneumoniae found 16 kDa proteins belonging to the LysM domain/BON superfamily, as well as DNA starvation proteins, whereas OmpX and OmpW were detected in the colistin-resistant counterpart strains. OmpC and OmpW were detected in the colistin-susceptible E. asburiae, whereas OmpA and OmpX were identified in the colistin-resistant counterpart. This study demonstrated that OMP differences were between colistin-susceptible and -resistant counterpart strains. The altered Gram-negative cell wall may contribute to acquired colistin resistance in Enterobacteriaceae

One step closer to eliminating the nomenclatural problems of minute coccoid green algae: Pseudochloris wilhelmii, gen. et sp. nov. (Trebouxiophyceae, Chlorophyta)

‘Chlorella’ and ‘Nannochloris’ were traditional genera of minute coccoid green algae with numerous species described in the past century, including isolates used as experimental test organisms. In the last few years, the introduction of DNA-based phylogenetic analyses resulted in a large number of taxonomic revisions. We investigated and reclassified a taxonomically problematic group within the Trebouxiophyceae (comprising ‘Nannochloris eucaryotum’ UTEX 2502, ‘N. eucaryotum’ SAG 55.87 and ‘Chlorella minutissima’ SAG 1.80), distantly related to the recently described Chloroparva isolates (97.5–97.9 % 18S rRNA gene pairwise similarity). Cryopreserved material of SAG 55.87 was selected as holotype for a novel species – Pseudochloris wilhelmii Somogyi, Felföldi & Vörös – whose phylogenetic position confirmed the proposal of a new genus. Pseudochloris wilhelmii had spherical to oval cells with an average diameter of 2.6 × 2.8 µm and a simple ultrastructure characteristic of small green algae. Vegetative cells sometimes contained several lipid droplets occupying a large portion of the cells. The cell wall consisted of an outer trilaminar layer and an inner microfibrillar sheet. Cells divided by autosporulation, forming two or four daughter cells per autosporangium. The pigment composition was typical of green algae, with chlorophylls a and b, and lutein as the dominant carotenoid

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