L'osmo-Resistenza di<i>Dunaliella Salina</i>Ricerche Ultrastrutturali

Trezzi, F.; Galli, Maria Grazia; Bellini, E.

doi:10.1080/11263506509430829

Cited by 35 publications

(15 citation statements)

References 2 publications

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“…We interpret this as indicating that, upon addition of osmolytes, the lumenal space contracted, bringing the two thylakoid membranes closer together. Similar ultrastructural changes were reported for strong HOS to Dunaliella salina (Trezzi et al, 1965). The fact that the thylakoid structures observed under HOS were two separate membranes appressed against each other is demonstrated in many thin sections where the thick aggregate membrane pair is observed to split into two typically sized thylakoid membranes.…”

Section: Ultrastructural Changes Associated With Osmotic Stresssupporting

confidence: 58%

Inhibition of Plastocyanin to P700 +Electron Transfer inChlamydomonas reinhardtiiby Hyperosmotic Stress

et al. 2001

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Oxygen electrode and fluorescence studies demonstrate that linear electron transport in the freshwater alga Chlamydomonas reinhardtii can be completely abolished by abrupt hyperosmotic shock. We show that the most likely primary site of inhibition of electron transfer by hyperosmotic shock is a blockage of electron transfer between plastocyanin (PC) or cytochrome c 6 and P 700 . The effects on this reaction were reversible upon dilution of the osmolytes and the stability of plastocyanin or photosystem (PS) I was unaffected. Electron micrographs of osmotically shocked cells showed a significant decrease in the thylakoid lumen volume. Comparison of estimated lumenal width with the x-ray structures of plastocyanin and PS I suggest that lumenal space contracts during HOS so as to hinder the movement of docking to PS I of plastocyanin or cytochrome c 6 .The effects of high osmotic potentials on primary photosynthetic processes are of great interest because they are thought to influence the ability of plants to survive desiccation and salt stress. It has been known for some time that photosynthesis can be inhibited by hyperosmotic shock (HOS), and several studies have been made on the effects of such conditions on the primary processes of photosynthesis (for review, see Kirst, 1990). However, the nature of the primary lesions to photosynthesis caused by HOS has remained elusive. To date, the most intensive studies on the responses of green algae to HOS have been performed on marine species, in particular Duneliella salina (e.g. Wiltens et al., 1978; Satoh et al., 1983;Gilmour et al., 1984). Because such species are found in waters of variable salinity, they are expected to have robust osmoregulatory systems. On the other hand, freshwater algae are likely to respond differently to salt or osmotic stresses. Because of the detailed genetic information and its ability to be transformed, the fresh water Chlorophyte, Chlamydomonas reinhardtii, has become an important laboratory species, particularly in studies of photosynthesis; thus, understanding its ecophysiology has become critical. Considerable work has been done on the effects of HOS on cyanobacteria species, such as Anacystis nidulans and Synechococcus sp. PCC 7942 (Grodzinski and Colman, 1973;Fulda et al., 1999; Allakhverdiev et al., 2000a), which pointed to direct effects of HOS on the photosynthetic reaction centers, particularly photosystem (PS) II (Allakhverdiev et al., 2000b). However, direct comparisons of the effects with those in freshwater green algae may be difficult considering their evolutionary and physiological differences.Previous research has shown that overall photosynthetic capacity of C. reinhardtii is severely inhibited by HOS (Reynoso and Gamboa, 1982;Berkowitz et al., 1983;Gamboa et al., 1985; Neale and Melis, 1989; Kirst, 1990;Endo et al., 1995; Leó n and Galván, 1995). Furthermore, Neale and Melis (1989) have shown that the photosynthetic apparatus of C. reinhardtii cells is significantly more susceptible to photoinhibition or photodamage...

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Section: Ultrastructural Changes Associated With Osmotic Stresssupporting

confidence: 58%

Inhibition of Plastocyanin to P700 +Electron Transfer inChlamydomonas reinhardtiiby Hyperosmotic Stress

et al. 2001

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“…This is consistent with observations on another euryhaline alga, Dunaliella salina, exhibiting compressed thylakoid membranes after a hypertonic shock (Trezzi, Galli & Bellini, 1965) and maintaining this arrangement over a longer period when cultivated in highly saline media (Pfeifhofer & Belton, 1975).…”

Section: Resultssupporting

confidence: 87%

“…This explains the physiological observations of a severe inhibition of photosynthesis (Kirst, 1975) while respiration is stimulated (Kirst & Keller, 1976) at this stage. A swelling of the chloroplast resulting in disorientation of the thylakoid structure has also been described in Dunaliella salina (Trezzi et al, 1965) after a decrease in external osmolarity.…”

Section: Resultsmentioning

confidence: 91%

Cytological evidence for cytoplasmic volume control inPlatymonas subcordiformisafter osmotic stress

Kirst¹,

Kramer²

1981

Plant Cell & Environment

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Platymonas subcordiformis, a marine phytoplankton flagellate, shows partial control of cell volume in response to osmotic stress. Electron micrographs of samples taken at short intervals after application of a hypo-osmotic stress revealed that a large vacuolar system is formed by fusion of vesicles originating from the Golgi apparatus. The chloroplast is swollen and the thylakoid stacking is transiently disturbed for 1 to 5 min after the osmotic shock. It then regains the original size and stacked organization of the thylakoids, while the vacuoles remain permanently. It is assumed that mainly the cytoplasmic compartment is under volume control rather than the whole cell, as has been found in other wall-less micro-algae.

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“…In cells subjected to decreased molarity a large mass of heterochromatin was often accumulated at one side of the inner nuclear envelope. A change in the density of the nucleoplasm of os motically stressed cells reported by Trezzi, Galli & Bellini (1965) is not seen in D. tertioleeta.…”

Section: Resultsmentioning

confidence: 60%

Ultrastructure of the green flagellate Dunaliella tertiolecta (Chlorophyceae, Volvocales) with comparative notes on three other species

Hoshaw

Maluf

1981

Phycologia

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The ultrastructure of Dunaliella tertiolecta, a naked, halotolerant unicellular green alga, is described and compared with ultrastructural features reported previously for three other species: D. bioculata, D. primolecta and D. salina. Most internal cell features are chlamy domonad in structure and arrangement. Conspicuous changes occur in D. tertiolecta between logarithmic and stationary growth phases. Vacuoles are more abundant and vac uolar inclusions have a different appearance in stationary as opposed to logarithmic phase cells. Thylakoids of the chloroplast are densely stacked in eight to ten layers in stationary phase cells, but are in stacks of two to four in logarithmic phase. Cytoplasmic and chloroplastic lipids, including eyespot granules, appear to increase with age of the cell. During logarith mic phase the endoplasmic reticulum shows greater proliferation. In cells subjected to increasing osmotic stress, large masses of dense-staining, tubular material is seen protrud ing and sometimes separating from the plasmalemma. Thylakoid stacking is more pro nounced in cells introduced into high salt concentration than in normal cells.

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L'osmo-Resistenza diDunaliella SalinaRicerche Ultrastrutturali

Cited by 35 publications

References 2 publications

Inhibition of Plastocyanin to P700 +Electron Transfer inChlamydomonas reinhardtiiby Hyperosmotic Stress

Inhibition of Plastocyanin to P700 +Electron Transfer inChlamydomonas reinhardtiiby Hyperosmotic Stress

Cytological evidence for cytoplasmic volume control inPlatymonas subcordiformisafter osmotic stress

Ultrastructure of the green flagellate Dunaliella tertiolecta (Chlorophyceae, Volvocales) with comparative notes on three other species

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