Razvoj plastida u listovima svojte Ligustrum ovalifolium Hassk. var. aureum na svjetlosti različitih intenziteta

Istražen je utjecaj intenziteta svjetlosti na ultrastrukturu, sadržaj pigmenata i fotosintetsku aktivnost plastida kaline tipa aurea (Ligustrum ovalifolium Hassk. var aureum). Rezultati su uspoređeni s onima dobivenim za plastide kaline divljeg tipa. Listovi tipa aurea mogu normalno ozelenjeti samo na slaboj svjetlosti u sjeni, dok na intenzivnoj sunčevoj svjetlosti postaju zlatnožuti i na kraju izblijede. Plastidi zelenih listova imaju normalno razvijen tilakoidni sustav i gotovo se ne razlikuju od plastida divljeg tipa. U plastidima žutih listova izloženih suncu postoje samo pojedinačni tilakoidi, ili čak brojne vezikule i plastoglobuli. Koncentracija pigmenata u žutim listovima je vrlo niska, a također i njihova fotosintetska aktivnost. Fotosintet- ska efikasnost (fotosintetska aktivnost izražena na jedinicu klorofila) u njih je, naprotiv, 2 puta viša od one u zelenim listovima tipa aurea i 3,5 puta viša od one u listovima divljeg tipa. Strukturne i funkcionalne osobine plastida tipa aurea na jakoj sunčevoj svjetlosti vjerojatno su posljedica promjena u sastavu antenskih kompleksa klorofila i proteina (light harvesting complex)

Ultrastrukturne promjene u plastidima listova pšenice izazvane kadmijem

Cadmium, when applied directly through the leaf surface, affects the greening of etiolated leaves in light and eventually produces their bleaching. After 2 days on 1 mmol solution of CdCl2, in yellow leaf portions the transformation of etioplasts into chloroplasts is strongly inhibited. The plastids contain tubular complexes (remnants of prolamellar bodies), some dilated prothylakoids, and stacks of appressed and bent cup shaped thy- lakoids. The chlorophyll synthesis and the photosynthetic activity (Hill reaction) of these plastids are very low, although the photosynthetic efficiency is higher than in the control. The changes described are discussed in connection with similar changes in some chlorophyll deficient mutants. Athough the fine structure of chloroplasts of green leaves treated with cadmium is not considerably altered, the concentration of chlorophyll and the photosynthetic activity (Hill reaction) are much lower than in the control leaves.Ako se etiolirani listovi pšenice izlože djelovanju kadmija, njihovo je ozelenjavanje snažno zakočeno. Listovi ostanu pretežno žuti, a nakon nekoliko dana posve izblijede. U žutim dijelovima listova, koji su dva dana bili na površini otopine CdCl2 (1 mmol), prijetvorba etioplasta u kloro- plaste je zakočena. Plastidi sadržavaju tubularne komplekse (ostatke prolamelarnih tjelešaca), malobrojne dilatirane protilakoide i svežnjeve čaškasto svinutih tilakoida. Sinteza klorofila i fotosintetska aktivnost (Hillova reakcija) plastida vrlo su niske, dok je fotosintetska efikasnost viša nego u kontroli. Opisane promjene uspoređene su sa sličnim promjenama u nekim mutantama deficijentnim u klorofilu. Ultrastruktura kloroplasta zelenih listova tretiranih kadmijem nije bitnije izmijenjena, iako je i koncetracija klorofila i fotosintetska aktivnost znatno niža od one kontrolnih listova

Intracellular Localization of Heavy Metals in Yeast by X-Ray Microanalysis

The intracellular localization of heavy metals in yeast cells was studied by means of energy-dispersive X-ray microanalysis. The yeast, Saccharomyces cerevisiae, was pretreated with phosphate and then loaded with different metal ions, by suspending the cells in salt solutions (Ni, Zn, Cd, Pb, Al and Cr). For the analysis, the cells were embedded in gelatin, rapidly frozen, and thin cryosections were cut on a dry knife. A considerable uptake of divalent cations by the yeast cells was found to occur. The cations were bound to the polyphosphate granules localized in or close to the cell vacuoles. Immediately after phosphate loading, the polyphosphate granules were predominantly located in the cytoplasm, but as the incubation progressed, they migrated to the vacuole. As for trivalent cations, Cr was taken up and also stored in the polyphosphate granules, but Al could not be demonstrated with certainty in the cells, only in the cell walls. Incubation of the cells with zinc, cadmium or lead ions caused a significant decrease of the relative size of the vacuole

Expression of the FAE1 gene and FAE1 promoter activity in developing seeds of Arabidopsis thaliana

Abstract Plant fatty acid elongase which catalyzes very-long-chain fatty acid (VLCFA) biosynthesis is a membrane-bound multienzyme complex. It is composed of four enzymes, a 3-ketoacyl-CoA synthase (condensing enzyme), a 3-ketoacyl-CoA reductase, a 3-hydroxyacyl-CoA dehydrase, and an enoyl-CoA reductase required for completion of each step of 2-carbon elongation of fatty acids. To improve our understanding of the overall regulation of the fatty acid elongase, we investigated the spatial and temporal expression of its key component, the FAE1-condensing enzyme, and examined the activity of the promoter of the FAE1 gene in Arabidopsis. In situ hybridization results revealed that FAE1 transcripts were found exclusively in the embryo. RNA blot analysis and histochemical analysis of GUS activity in pFAE1::GUS transgenic Arabidopsis lines demonstrated that the FAE1 gene was already transcribed in the early torpedo stage embryos 4-5 days after flowering, with transcription reaching its peak 9-11 days after flowering. VLCFA deposition closely paralleled FAE1 transcript accumulation. FAE1 promoter was highly active and embryo-specific. Because its timing coincides with the period of major storage lipid accumulation, and because its in vivo activity in Arabidopsis is superior to the napin promoter, FAE1 promoter may be ideal for genetic engineering of seed oil composition. Abbreviations: X:Y, a fatty acyl group containing X carbons with Y double bond

Elektronsko-mikroskopska istraživanja plastida tijekom njihove diferencijacije i dediferencijacije

A survey of fine structural characteristics of various plastid types, their variability and interconvertibility, based on the authors’ experience is given. In this article the. fine structure and development of the main plastid types — chloroplasts, etioplasts, chromoplasts and leucoplasts — are described in several plant systems. The differentiation of chloroplasts proceeds either directly from proplastids or through the etioplast stage. Various environmental factors are shown to influence this process. The adaptability of chloroplasts to environmental changes is shown in aurea mutants. These plants promptly adapt their structure and function to the surrounding light conditions. The development of the photosynthetic activity in the thylakoids during chloroplast differentiation can be demonstrated by a cytochemical method. The fine structure of various chromoplast types is described. The evolution of their pigment containing structures can be successfully studied by applying specific inhibitors which block or alter their normal differentiation. The plastid dedifferentiation is demonstrated by several examples. These include changes from leucoplasts to chloroplasts and several types of chromoplasts to chloroplasts transformations. The significance of these transformations is discussed.Prikazani su razni tipovi plastida, njihova varijabilnost i interkonvertibilnost, na temelju višegodišnjih istraživanja autora. Na većem broju objekata opisani su ultrastruktura i razvoj glavnih tipova plastida (kloroplasta, etioplasta, kromoplasta i leukoplasta). Studirana je diferencijacija kloroplasta i istražen utjecaj različitih vanjskih čimbenika na taj proces. Razvoj fotosintetske aktivnosti u tilakoidima tijekom diferencijacije kloroplasta praćen je primjenom odgovarajuće citokemijske metode. Na primjeru mutanata tipa aurea prikazana je sposobnost prilagodbe kloroplasta na promjene okoliša (uvjete osvjetljenja). Opisana je ultrastruktura različitih tipova kromoplasta, a primjenom specifičnih inhibitora istražena je njihova diferencijacija. Dediferencijacija plastida prikazana je na nekoliko primjera. Opisana je prijetvorba leukoplasta u kloroplaste i prijetvorbe više tipova kromoplasta u kloroplaste. Raspravljeno je značenje tih prijetvorbi

Functional Characterization of the Arabidopsis β-Ketoacyl-Coenzyme A Reductase Candidates of the Fatty Acid Elongase

In plants, very-long-chain fatty acids (VLCFAs; \u3e18 carbon) are precursors of sphingolipids, triacylglycerols, cuticular waxes, and suberin. VLCFAs are synthesized by a multiprotein membrane-bound fatty acid elongation system that catalyzes four successive enzymatic reactions: condensation, reduction, dehydration, and a second reduction. A bioinformatics survey of the Arabidopsis (Arabidopsis thaliana) genome has revealed two sequences homologous to YBR159w encoding a Saccharomyces cerevisiae β-ketoacyl reductase (KCR), which catalyzes the first reduction during VLCFA elongation. Expression analyses showed that both AtKCR1 and AtKCR2 genes were transcribed in siliques, flowers, inflorescence stems, leaves, as well as developing embryos, but only AtKCR1 transcript was detected in roots. Fluorescent protein-tagged AtKCR1 and AtKCR2 were localized to the endoplasmic reticulum, the site of fatty acid elongation. Complementation of the yeast ybr159Δ mutant demonstrated that the two KCR proteins are divergent and that only AtKCR1 can restore heterologous elongase activity similar to the native yeast KCR gene. Analyses of insertional mutants in AtKCR1 and AtKCR2 revealed that loss of AtKCR1 function results in embryo lethality, which cannot be rescued by AtKCR2 expression using the AtKCR1 promoter. In contrast, a disruption of the AtKCR2 gene had no obvious phenotypic effect. Taken together, these results indicate that only AtKCR1 is a functional KCR isoform involved in microsomal fatty acid elongation. To investigate the roles of AtKCR1 in postembryonic development, transgenic lines expressing RNA interference and overexpression constructs targeted against AtKCR1 were generated. Morphological and biochemical characterization of these lines confirmed that suppressed KCR activity results in a reduction of cuticular wax load and affects VLCFA composition of sphingolipids, seed triacylglycerols, and root glycerolipids, demonstrating in planta that KCR is involved in elongation reactions supplying VLCFA for all these diverse classes of lipids

Characterization of Arabidopsis ABCG11/WBC11, an ATP binding cassette (ABC) transporter that is required for cuticular lipid secretion

Summary ABCG11/WBC11, an ATP binding cassette (ABC) transporter from Arabidopsis thaliana, is a key component of the export pathway for cuticular lipids. Arabidopsis wbc11 T-DNA insertional knock-out mutants exhibited lipidic inclusions inside epidermal cells similar to the previously characterized wax transporter mutant cer5, with a similar strong reduction in the alkanes of surface waxes. Moreover, the wbc11 knock-out mutants also showed defects not present in cer5, including post-genital organ fusions, stunted growth and a reduction in cutin load on the plant surface. A mutant line previously isolated in a forward genetics screen, called permeable leaves 1 (pel1), was identified as an allele of ABCG11/WBC11. The double knock-out wbc11 cer5 exhibited the same morphological and biochemical phenotypes as the wbc11 knock-out. A YFP-WBC11 fusion protein rescued a T-DNA knock-out mutant and was localized to the plasma membrane. These results show that WBC11 functions in secretion of surface waxes, possibly by interacting with CER5. However, unlike ABCG12/ CER5, ABCG11/WBC11 is important to the normal process of cutin formation