Disorganization Of Thylakoids Research Articles

An Argon-Ion-Induced Pale Green Mutant of Arabidopsis Exhibiting Rapid Disassembly of Mesophyll Chloroplast Grana.

Argon-ion beam is an effective mutagen capable of inducing a variety of mutation types. In this study, an argon ion-induced pale green mutant of Arabidopsis thaliana was isolated and characterized. The mutant, designated Ar50-33-pg1, exhibited moderate defects of growth and greening and exhibited rapid chlorosis in photosynthetic tissues. Fluorescence microscopy confirmed that mesophyll chloroplasts underwent substantial shrinkage during the chlorotic process. Genetic and whole-genome resequencing analyses revealed that Ar50-33-pg1 contained a large 940 kb deletion in chromosome V that encompassed more than 100 annotated genes, including 41 protein-coding genes such as TYRAAt1/TyrA1, EGY1, and MBD12. One of the deleted genes, EGY1, for a thylakoid membrane-localized metalloprotease, was the major contributory gene responsible for the pale mutant phenotype. Both an egy1 mutant and F1 progeny of an Ar50-33-pg1 × egy1 cross-exhibited chlorotic phenotypes similar to those of Ar50-33-pg1. Furthermore, ultrastructural analysis of mesophyll cells revealed that Ar50-33-pg1 and egy1 initially developed wild type-like chloroplasts, but these were rapidly disassembled, resulting in thylakoid disorganization and fragmentation, as well as plastoglobule accumulation, as terminal phenotypes. Together, these data support the utility of heavy-ion mutagenesis for plant genetic analysis and highlight the importance of EGY1 in the structural maintenance of grana in mesophyll chloroplasts.

Carfentrazone‐ethyl and glyphosate drift inhibits uredinial formation of Austropuccinia psidii on Eucalyptus grandis leaves

The response to infection of Austropuccinia psidii in resistant (CLR-383) and susceptible (CLR-384) Eucalyptus grandis clones, exposed to herbicide drift of carfentrazone-ethyl, glyphosate and a mixture of these two herbicides, was evaluated at microscopic and physiological levels. Plants of the two clones showed symptoms of phytotoxicity caused by herbicide drift. However, net CO2 assimilation rate, height and shoot dry matter were lower in CLR-384 than in CLR-383. At the ultrastructure level, the leaves of both clones exposed to the herbicides showed thylakoid disorganization and accumulation of starch grains in the chloroplasts. Only plants of CLR-384 were infected by A. psidii, but when exposed to herbicide drift, rust severity was lower than in control plants. Six days after inoculation (dai), plants of this clone exposed to the herbicides had smaller uredinia than control plants. At 12 dai, non-herbicide treated plants showed normal uredinia, containing abundant urediniospores. By contrast, plants exposed to the herbicides were less colonized by the fungus, and the uredinia were smaller with reduced production of urediniospores, which were sometimes not even detected. Glyphosate and carfentrazone-ethyl herbicide drift reduce infection and uredinial formation of A. psidii and to some extent induce basal resistance in a susceptible clone of E. grandis. © 2018 Society of Chemical Industry.

Morphology, photosynthesis, and internal structure alterations in field apple leaves under hidden and acute zinc deficiency

In the field, apple trees (Malus domestica L.) do not exhibit visible deficient symptoms when affected by hidden zinc (Zn) deficiency, while internal injury in the leaves may prior occurred. We named the leaves on Zn deficient trees without and with visible rosette symptoms as ‘hidden rosette leaves’ and ‘rosette leaves’, respectively. The healthy leaves of normal trees were named ‘normal leaves’ and selected as the control. The changes in leaf photosynthesis, physiology and internal structure were analyzed to elucidate the damage mechanism of Zn deficiency in apple leaves. We found that the reduction in photosynthesis under Zn deficiency was primarily due to non-stomatal limitation, in particular the changes in photosystem II (PS II). Zinc deficiency significantly reduced chlorophyll content in the hidden rosette leaves without obvious changes to chloroplasts and grana number. The intrinsic efficiency of PS II (Fv′/Fm′), actual photochemical efficiency of PS II (ϕPS II) and electron transport rate (ETR) were all significantly decreased in both hidden rosette leaves and rosette leaves, while a further significant increase in the minimal fluorescence (Fo) along with reductions in maximum photochemical efficiency of PSII (Fv/Fm) and photochemical quenching (qP) occurred in rosette leaves. These results indicate that the decrease in chlorophyll content and inhibition of PS II light-harvesting activity may account for the photosynthesis reduction during the initial stage of Zn deficiency. As Zn deficiency aggravated, cellular deficient characteristics like abnormal cell arrangements and disorganization of thylakoids became more exaggerated; visible external symptoms of Zn deficiency appeared with internal alterations, including photosynthetic apparatus damage accompanied by subsequent chloroplast and grana disintegration. We concluded that the PS II activity was relatively sensitive to Zn deficiency, hence the chlorophyll fluorescence parameters like Fv′/Fm′ and ϕPS II may be used as predictive indictors for hidden Zn deficiency on apple trees.

Effects of lead on anatomy, ultrastructure and concentration of nutrients in plants Oxycaryum cubense (Poep. & Kunth) Palla: a species with phytoremediator potential in contaminated watersheds

Lead (Pb) has been highlighted as a major pollutant of both terrestrial and aquatic ecosystems, causing negative impacts to these environments. The concentration of Pb in plants has increased in recent decades, mainly due to anthropogenic activities. This study has as a hypothesis that the species Oxycaryum cubense (Poep. & Kunth) Palla, abundant in aquatic environments, has the potential to be used a phytoremediator. The plants were grown in a hydroponic system with Pb in increasing concentrations (0, 4, 8, 16 and 32 mg l(-1)) for 15 days. Inductively coupled mass spectrometer (ICP OES) was used to determine the concentration of mineral nutrients and lead. Optical and transmission electron microscopy were used for the analysis of cellular damage induced by lead in roots and leaves. Ultrastructural alterations were observed as disorganization of thylakoids in the chloroplast and disruption of mitochondrial membranes in cells of leaf tissues of plants subjected to increasing Pb concentrations. There was accumulation of Pb, especially in the root system, affecting the absorption and translocation of some mineral nutrients analysed. In roots, there was reduction in the thickness of the epidermis in plants treated with Pb. This species was shown to be tolerant to the Pb concentrations evaluated, compartmentalizing and accumulating Pb mainly in roots. Due to these results, it may be considered a species with phytoremediation capacity for Pb, with potential rizofiltration of this metallic element in contaminated watersheds.

Inhibition of Microcystis aeruginosa by the Extracellular Substances from an Aeromonas sp.

Growth of Microcystis aeruginosa could be inhibited significantly within 24 h by the extracellular substances prepared from Aeromonas sp. strain FM. During the treatment, the concentration of extracellular soluble carbohydrates increased significantly in algal culture. Morphological and ultrastructural changes in M. aeruginosa cells, including breakage of the cell surface, secretion of mucilage, and intracellular disorganization of thylakoids, were observed. HPLC-MS analysis showed that the extracellular substances of Aeromonas sp. strain FM were a mixture of free amino acids, tripeptides, and clavulanate. Among these, the algae-lysis effects of lysine and clavulanate were confirmed.

Ultrastructure and X-ray microanalysis of Euglena gracilis (Euglenophyta) under chromium stress

I. Rocchetta, P.I. Leonardi, G.M. Amado Filho, M. del Carmen Ríos de Molina and V. Conforti. 2007. Ultrastructure and X-ray microanalysis of Euglena gracilis (Euglenophyta) under chromium stress. Phycologia 46: 300–306. DOI: 10.2216/06-49.1The effect of chromium on the biology of Euglena gracilis was studied. The ultrastructural modifications caused by this metal and its location within the cell were analyzed by TEM and EDXA, respectively. The effects of chromium on protein, pigment, and lipid contents were also studied in order to evaluate the metabolic responses to metal exposure. Two strains of Euglena gracilis, UTEX 753 (from the Culture Collection of Texas University) and MAT (isolated from the Matanza River), were used in this research. Both were grown in photoauxotrophic and photoheterotrophic conditions and exposed to different metal concentrations. In all treated cells, increases in total protein and lipid contents, changes in chlorophyll amount, and alterations in fine structure were observed, especially with the higher concentration tested. In photosynthetic treated cells, assays showed chloroplast thylakoid disorganization, the presence of cytoplasm lipid globules, and several vacuoles with electron-dense inclusions and remnants of membranes inside. Nuclei presented lobulations, and eventually total fragmentation in some cells treated with the highest chromium concentration was seen, suggesting that chromium cytotoxicity leads to cellular death. The EDXA spectrum showed well-defined Cr and S peaks in the vacuoles containing electron-dense inclusions and remnants of membranes from autotrophic MAT samples. These results indicate that the different defense mechanisms against chromium depend on strain type and culture conditions. The S peak detected in MAT would suggest that sulfur-rich proteins groups play an important role in the detoxification system inducing metal-complex accumulation into vacuoles.

Is fusaproliferin associated with disease symptoms in maize plants?

The possible role of fusariotoxin-fusaproliferin in Fusarium disease was investigated with respect to ultrastructure responses in the cells of maize leaves. The seedlings of resistant (Lucia) and susceptible (Pavla) maize cultivars were grown on two fusaproliferin concentrations (5 and 35 µg/mL −1 ). Only the higher concentration caused appearance of visible symptoms on the leaves. Structural changes of chloroplasts such as dilatation of grana thylakoids in the mesophyll chloroplasts, thylakoid disorganization, and an increased number of osmiophilic globules (plastoglobuli) in the stroma were observed in mesophyll and bundle sheath chloroplasts of both cultivars. The higher toxin concentration sporadically induced severe damage to the outer chloroplast membrane. The extent of ultrastructure disturbances depended on toxin concentration and it was greater in the susceptible cultivar Pavla. Fusaproliferin may be involved in Fusarium pathogenesis as a virulence factor or, by enhancing activity of some other t...

Effect of chromium on the fatty acid composition of two strains of Euglena gracilis

The effect of hexavalent chromium on fatty acid composition was studied in two strains of Euglena gracilis; UTEX 753 (from the Culture Collection of Algae of Texas University, USA) and MAT (isolated from a highly polluted River). Both were grown in photoauxotrophic and photoheterotrophic conditions and exposed to two metal concentrations, one below and one above IC 50. The high malondialdehyde (MDA) levels (3 to 7-fold) obtained with chromium concentration above IC 50, suggested the existence of metal-induced lipid peroxidation. Total lipid content increased only with concentration below IC 50, whereas it was inhibited by higher metal concentration. Photoheterotrophic control strains exhibited a significantly higher proportion of saturated and polyunsaturated fatty acids. Polyunsaturated acids were most affected by chromium, especially those related to chloroplast structures. Ultra-structure studies showed clear thylakoid disorganization in all treated cells. The results indicate that hexavalent chromium affects levels of fatty acids, especially those related to photosynthetic activity.

Relative Efficacy of Fusamotoxins on Young Maize Plants

Impact of fusariotoxins mixture (moniliformin, fiimonisin B1, fusaproliferin, zearalenone, zearalenol and deoxynivalenol, each at concentration 35 μg·mL−1) on maize plants of resistant (Lucia) and susceptible (Pavla) cultivars was studied. After 72 hours of root exposure to the fiisariotoxins the biomass production with both cultivars was approximately 6% lower than in the respective controls. In the resistant cultivar, chlorophyll content was higher comparing to control, with greater increase in chlorophyll b. In the susceptible cultivar, chlorophyll content was slightly decreased, particularly with chlorophyll b. In toxins treated plants, the young root cells were more vacuolated and plasmolysis occurred in the cells of outer cortex. The cells contained numerous osmiophilic globules in periplasmic space associated with plasmodesmata and plasma membrane, and within cytoplasm associated with membranes of ER, plastids, and tonoplast. In the leaves of the susceptible cultivar also disorganization of thylakoids in some chloroplasts was observed when treated by fiisariotoxins mixture.

Fine structural study of the red seaweed Gymnogongrus torulosus (Phyllophoraceae, Rhodophyta)

The present study analyzed several characters of the red seaweed Gymnogongrus torulosus, such as cellular structure of the thallus, cuticle, pit plug and cell wall ultrastructure, and morphology of some organelles like plastids, Golgi bodies and mitochondria. Also, anomalous chloroplasts with thylakoid disorganization were found in medullary cells. The significance of this thylakoid disposition is still unclear. This is one of the first studies focused on the fine structure of a red alga recorded in Argentina.

Toxicity of Fusarium mycotoxins on maize plants

Synergistic effects of Fusarium - toxins mixture (moniliformin, fumonisin B1, fusaproliferin, zearalenone, zearalenol and deoxynivalenol, each at concentration 3.5 μg mL-1) on maize plants of resistant and susceptible cultivars were studied. After 72-hour treatment the biomass production with both cultivars was approximately 6% lower than in the respective controls. In the resistant cultivar chlorophyll content was increased comparing to control, with higher increase in chlorophyll b. In susceptible cultivar chlorophyll content was slightly decreased, particularly with chlorophyll b.No significant differences between treated and non-treated plants were found in the cell ultrastructure. In susceptible plants the young root cells were more vacuolated and plasmolysis occurred in the cells of outer cortex. In leaves of this cultivar also disorganization of thylakoids in some chloroplasts was observed.

9,10-Anthraquinone Reduces the Photosynthetic Efficiency of Oscillatoria perornata and Modifies Cellular Inclusions.

The natural compound 9,10-anthraquinone was found to inhibit the growth of the musty odor-producing cyanobacterium Oscillatoria perornata at a low concentration (1 µM) in previous laboratory studies. In this study, the mode of action of 9,10-anthraquinone was investigated by observing ultrastructural changes in O. perornata and by monitoring chlorophyll fluorescence as an indicator of photosynthetic efficiency. Results indicate that 9,10-anthraquinone inhibits photosynthetic electron transport, probably at PSII, and thereby affects growth. Moreover, 9,10-anthraquinone treatment caused thylakoid disorganization and reduced the number of ribosomes in O. perornata. The thylakoid disorganization is identical to reported modification in a cyanobacterium treated with simazine, a PSII inhibitor.

Ultrastructural Changes Induced by Selected Cadmium Concentrations in the Cyanobacterium Nostoc UAM208

Summary The effects of cadmium on the fine structure of the nitrogen-fixing cyanobacterium Nostoc UAM208 have been studied. Cells were treated with final free ion Cd 2+ concentrations of 4.89 and 6.36 μM. Posible cell damage was examined at 6, 24, 48 and 96 h of heavy metal exposure. The main alterations induced by cadmium included the development of large areas of intrathylakoidal spaces, thylakoid disorganization and degradation, increase in the number and size of polyphosphate bodies, appearance of large cyanophycin granules and, eventually, cell lysis, leaving a much larger proportion of heterocysts. Finally, the physiological relevance of these observations is discused.

Effect of copper deficiency on photosynthetic electron transport in wheat plants

Copper deficiency in wheat (Triticum aestivum L. cv. Nazareno Stramppeli) markedly affects photosynthetic activity. Flag leaves of copper‐deficient plants showed a 50% reduction of the photosynthetic rate expressed as mg CO2 dm−2h−1. The activities of PSI and PSII, determined for isolated chloroplasts, as well as fluorescence measurements on intact leaves of copper‐deficient plants, indicated a low activity of photosynthetic electron transport. Ribulose bisphosphate carboxylase/oxygenase (Rubisco) activity was not affected by copper deficiency but copper deficiency affected the chloroplast ultrastructure, especially at the level of grana, where a disorganization of thylakoids is evident.

Algicidal properties of the pesticide cosolvent Aerotex 3470: growth, ATP synthesis, and ultrastructure

The algicidal properties of Aerotex 3470, a pesticide cosolvent in several fenitrothion formulations, have been investigated under controlled laboratory conditions. Aerotex (1–100 ppm) inhibited the growth of three unicellular freshwater algae (Chlamydomonas reinhardii, Chlorella pyrenoidosa, and Scenedesmus obtusiusculus) on agar plates and in liquid culture. Prolongation of the lag phase was directly related to Aerotex concentration. Algal cultures exposed for 1 h to Aerotex (1–10 ppm) had significantly reduced ATP levels. In all cases (agar, liquid culture, and ATP bioassays), Chlamydomonas and Chlorella were more sensitive to Aerotex than Scenedesmus.Electron microscopy demonstrated gross ultrastructural changes in Chlamydomonas treated for 1 h with Aerotex (5 ppm), including swollen mitochondria, disorganization of thylakoids, and crenulation of the cell membrane. Similar membrane damage was caused by 1-methylnaphthalene (5 ppm), a constituent of Aerotex.

Effect of mal secco toxin on lemon leaf cells

Leaves of Rough lemon (Citrus jambhiri) were inoculated withPhoma tracheiphila or treated with mal secco toxin. The ultrastructural changes in toxin-treated leaves resembled closely those infected by the pathogen, being characterized by separation of the plasmalemma from the cell wall, vesiculation of plasmalemma, disruption of the chloroplast membrane, disorganization of thylakoids, and increase in size and number of osmiophilic droplets in the chloroplasts. The rate of photo-synthetic CO2 fixation by mesophyll protoplasts was reduced in the presence of the toxin. The toxin induced agglutination of mesophyll protoplasts of lemon only in the presence of an antiserum to the toxin. Agglutination of protoplasts was independent of the biological activity of the toxin and was inhibited by Dmannose or after mild base hydrolysis of the toxin.