Ecophysiology of the hypotonic response in the salt‐tolerant charophyte alga <i>Lamprothamnium papulosum</i>

Shepherd, Virginia A.; Beilby, Mary J.; Heslop, David

doi:10.1046/j.1365-3040.1999.00414.x

Cited by 38 publications

(29 citation statements)

References 42 publications

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“…The occurrence of the stretch-activated channel (which was at least partly selective for Cl − and voltageindependent) can apparently be taken as a hint that turgor-dependent transport elements contribute to the membrane conductance of turgescent cells both under steadystate conditions and during turgor pressure regulation (Cosgrove & Hedrich, 1991;Garill, Tyerman & Findlay, 1994;Shepherd, Beilby & Heslop, 1999).…”

Section: Discussionmentioning

confidence: 99%

A Patch-Clamp Study of Ion Channels in Protoplasts Prepared from the Marine Alga Valonia utricularis

Heidecker

Wegner

Zimmermann

1999

Journal of Membrane Biology

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The giant marine alga Valonia utricularis is a classical model system for studying the electrophysiology and water relations of plant cells by using microelectrode and pressure probe techniques. The recent finding that protoplasts can be prepared from the giant "mother cells" (Wang, J., Sukhorukov, V.L., Djuzenova, C.S., Zimmermann, U., Müller, T., Fuhr, G., 1997, Protoplasma 196:123-134) allowed the use of the patch-clamp technique to examine ion channel activity in the plasmalemma of this species. Outside-out and cell-attached experiments displayed three different types of voltage-gated Cl(-) channels (VAC1, VAC2, VAC3, Valonia Anion Channel 1,2,3), one voltage-gated K(+) channel (VKC1, Valonia K(+) Channel 1) as well as stretch-activated channels. In symmetrical 150 mm Cl(-) media, VAC1 was most frequently observed and had a single channel conductance of 36 +/- 7 pS (n = 4) in the outside-out and 33 +/- 5 pS (n = 10) in the cell-attached configuration. The reversal potential of the corresponding current-voltage curves was within 0 +/- 4 mV (n = 4, outside-out) and 9 +/- 7 mV (n = 10, cell-attached) close to the Nernst potential of Cl(-) and shifted towards more negative values when cell-attached experiments were performed in asymmetrical 50:150 mm Cl(-) media (bath/pipette; E(Cl(-)) -20 +/- 7 mV (n = 4); Nernst potential -28 mV). Consistent with a selectivity for Cl(-), VAC1 was inhibited by 100 micronM DIDS (4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid). VAC1 was activated by a hyperpolarization of the patch. Boltzmann fits of the channel activity under symmetrical 150 mm Cl(-) conditions yielded a midpoint potential of -12 +/- 5 mV (n = 4, outside-out) and -3 +/- 6 mV (n = 9, cell-attached) and corresponding apparent minimum gating charges of 15 +/- 3 (n = 4) and 18 +/- 5 (n = 9). The midpoint potential shifted to more negative values in the presence of a Cl(-) gradient. VAC2 was activated by voltages more negative than E(Cl(-)) and was always observed together with VAC1, but less frequently. It showed a "flickering" gating. The single channel conductance was 99 +/- 10 pS (n = 6). VAC3 was activated by membrane depolarization and frequently exhibited several subconductance states. The single channel conductance of the main conductance state was 36 +/- 5 pS (n = 5). VKC1 was also activated by positive clamped voltages. Up to three conductance states occurred whereby the main conductance state had a single channel conductance of 124 +/- 27 pS (n = 6). In the light of the above results it seems to be likely that VAC1 contributes mainly to the Cl(-) conductance of the plasmalemma of the turgescent "mother cells" and that this channel (as well as VAC2) can operate in the physiological membrane potential range. The physiological significance of VAC3 and VKC1 is unknown, but may be related (as the stretch-activated channels) to processes involved in turgor regulation.

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Section: Discussionmentioning

confidence: 99%

A Patch-Clamp Study of Ion Channels in Protoplasts Prepared from the Marine Alga Valonia utricularis

Heidecker

Wegner

Zimmermann

1999

Journal of Membrane Biology

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“…Light microscopy (LM): To determine changes in some aspects of the biochemical composition of N. salina, including starch and crude mucilage, two separate samples of the algal cells were centrifuged and stained individually using iodine solution (KI/I 2 , 15%, w/v) to detect starch (Lobban et al, 1988) and Toluidine blue dye to detect crude mucilage (0.5% (w/v), Shepherd et al, 1999).…”

Section: Microscopic Examinationsmentioning

confidence: 99%

“…Other alterations may be detected by specific histological staining (Lobban et al, 1988). Observations of optical properties (Gitelson et al, 2000), growth (Ansari et al, 1997), pigment composition (Gentile & Blanch, 2001), production of exopolysaccharides (Shepherd et al, 1999) and microscopic examination of cells (Soto et al, 1979a,b) will also reveal stress induced alterations. Some recent studies have also attempted to discriminate between controlled and stressed algal cells by spectrometric tools such as resonance Raman spectroscopy (Wu et al, 1998) and fluorescence spectroscopy (Henrion et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Temporal alterations of Nannochloropsis salina (Eustigmatophyceae) grown under aqueous diesel fuel stress

et al. 2005

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The influence of an aqueous extract of diesel fuel was tested on growth of the marine eustigmatophyte Nannochloropsis (Monallantus) salina Hibberd. An increase in the concentration of the pollutant led to a decrease in growth rate as measured by optical density, with maximum effect observed (33% of control) at 100% aqueous pollutant. Spectrophotometric examination of cell viability (using Evan's blue dye) showed a significant negative effect of the diesel extract ( p ≤ 0.05, r = −0.92). Infrared spectra showed a slight change in the absorbance of contaminated compared with controlled cells. Proteome analysis (sodium dodecyl sulfate polyacrylamide gel electrophoresis -"SDS-PAGE") indicated that cell protein profiles depended on the pollutant concentration. Some of the resultant bands were characteristic to the pollutant concentration applied, indicating a distinct effect of the pollutant on the proteome structure. Iodine and toluidine blue dyes were applied using light microscopy to detect starch and mucilage, respectively. This indicated the presence of starch during all treatments, while the mucilage has been reduced. Transmission electron microscopy showed alterations to cell walls and membranes with different degrees of plasmolysis leading to a gradual increase in cell volume. However, the nucleus, the nucleolus and the pyrenoid remained unaffected. Similar results were obtained when the alga was cultured for 25 days in the 100% aqueous diesel extract indicating that long-term culture does not affect the degree of pollutant stress. Further, these cells recovered their normal appearance and characteristics within two days of being transferred to culture medium free of extract, indicating that N. salina shows a high tolerance to aqueous diesel fuel pollution.

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“…Sulfate bridges could clearly contribute to wound plug integrity as displayed in the bridging of sulfated galactans as reported by Rees (1969). Additionally, sulfated polysaccharides provide a negatively charged barrier that reduces the opening of Ca 2+ channels in response to hypotonic shock and contribute to the steady‐state turgor pressure by reducing the activity of water (Shepard and Beilby 1999, Shepard and Heslop 1999, Shepard et al 2004).…”

Section: Discussionmentioning

confidence: 95%

RAPID ASSEMBLY OF A WOUND PLUG: STAGE ONE OF A TWO‐STAGE WOUND REPAIR MECHANISM IN THE GIANT UNICELLULAR CHLOROPHYTE DASYCLADUS VERMICULARIS (CHLOROPHYCEAE)¹

Ross

Vreeland

Waite

et al. 2005

Journal of Phycology

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Upon injury, selected coenocytic algae are capable of forming temporary wound plugs to prevent detrimental cytoplasmic loss. Wound plugs of Dasycladus vermicularis ([Scropoli] Krasser) were harvested 5 min post-injury and dried. The plug material contained 94% water and can be considered a hydrogel. The gel plug extended several millimeters from the cut end and filled the space inside the cell wall, which resulted from cytoplasmic retraction. Total organic carbon included 55% sugars, 5%-15% protein, and 0.18% lipids. The major sugars were glucose, galactose, mannose, and galacturonic acid. Fluorescein isothiocyanate-lectins specific for these sugars were localized around the plug matrix. Sulfur content calculated as sulfate corresponded to 17% of the carbohydrate by weight, and sulfated material was detected in plugs by Alcian Blue staining. Formation of the initial plug occurred within 1 min of injury and was not significantly perturbed by the addition of ionic, antioxidant, or chelating agents to the seawater medium. However, addition of exogenous D( þ )-galactose and D( þ )-glucose prevented formation of the nascent gel plug. Wound plugs that were allowed to form from 10 min up until 24 h post-injury were isolated and incubated with selected biochemical probes to identify the biochemical processes involved in plug formation. The operative strategy in Dasycladus to prevent ''cytoplasmic hemorrhage'' required availability of sequestered carbohydrate and lectin precursor components throughout the thallus for plug assembly. Once the initial assembly had commenced, additional biochemical interactions were initiated (as a function of time) to promote structural integrity.

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Ecophysiology of the hypotonic response in the salt‐tolerant charophyte alga Lamprothamnium papulosum

Abstract: The ecophysiology of the hypotonic response was studied in the charophyte alga, Lamprothamnium papulosum, which was grown in a marine (SW; 1072 mosmol kg -1 ) and a brackish (

Cited by 38 publications

References 42 publications

A Patch-Clamp Study of Ion Channels in Protoplasts Prepared from the Marine Alga Valonia utricularis

A Patch-Clamp Study of Ion Channels in Protoplasts Prepared from the Marine Alga Valonia utricularis

Temporal alterations of Nannochloropsis salina (Eustigmatophyceae) grown under aqueous diesel fuel stress

RAPID ASSEMBLY OF A WOUND PLUG: STAGE ONE OF A TWO‐STAGE WOUND REPAIR MECHANISM IN THE GIANT UNICELLULAR CHLOROPHYTE DASYCLADUS VERMICULARIS (CHLOROPHYCEAE)¹

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Ecophysiology of the hypotonic response in the salt‐tolerant charophyte alga Lamprothamnium papulosum

Abstract: The ecophysiology of the hypotonic response was studied in the charophyte alga, Lamprothamnium papulosum, which was grown in a marine (SW; 1072 mosmol kg -1 ) and a brackish (

Cited by 38 publications

References 42 publications

A Patch-Clamp Study of Ion Channels in Protoplasts Prepared from the Marine Alga Valonia utricularis

A Patch-Clamp Study of Ion Channels in Protoplasts Prepared from the Marine Alga Valonia utricularis

Temporal alterations of Nannochloropsis salina (Eustigmatophyceae) grown under aqueous diesel fuel stress

RAPID ASSEMBLY OF A WOUND PLUG: STAGE ONE OF A TWO‐STAGE WOUND REPAIR MECHANISM IN THE GIANT UNICELLULAR CHLOROPHYTE DASYCLADUS VERMICULARIS (CHLOROPHYCEAE)1

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RAPID ASSEMBLY OF A WOUND PLUG: STAGE ONE OF A TWO‐STAGE WOUND REPAIR MECHANISM IN THE GIANT UNICELLULAR CHLOROPHYTE DASYCLADUS VERMICULARIS (CHLOROPHYCEAE)¹