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The ubiquitin-proteasome pathway protects Chlamydomonas reinhardtii against selenite toxicity, but is impaired as reactive oxygen species accumulate.

Vallentine P, Hung CY, Xie J, Van Hoewyk D - AoB Plants (2014)

Bottom Line: Additionally, proteasomal inhibition decreased the concentration of chlorophyll in cultures challenged with Se.Therefore, although the UPP protects Chlamydomonas against Se stress, severe oxidative stress induced by selenite toxicity likely hinders the UPP's capacity to mediate a stress response.The possibility that stress tolerance in plants is dependent upon optimal UPP activity and maintenance is discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Coastal Carolina University, Conway, SC 29526, USA.

No MeSH data available.


Related in: MedlinePlus

Proteasome activity in Chlamydomonas treated with selenite. (A) Values for proteasome activity represent fold change in activity of selenite-treated cells relative to untreated cells at each time interval. (B) Percentage of viable cells in cultures with the indicated treatments. Data are the mean of three biological replicates and standard deviation. Lowercase letters represent a significant difference in relative activity at each time point (P < 0.05). Standard errors were too small to plot.
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PLU062F1: Proteasome activity in Chlamydomonas treated with selenite. (A) Values for proteasome activity represent fold change in activity of selenite-treated cells relative to untreated cells at each time interval. (B) Percentage of viable cells in cultures with the indicated treatments. Data are the mean of three biological replicates and standard deviation. Lowercase letters represent a significant difference in relative activity at each time point (P < 0.05). Standard errors were too small to plot.

Mentions: To determine whether or not moderate and severe selenite stress induces the UPP, Chlamydomonas cells were grown to an OD0.5 and treated with or without 50 and 200 μM selenite. Compared with untreated cells, 50 μM selenite increased proteasome activity after 3, 8 and 28 h (Fig. 1A). Proteasome activity peaked in cells treated with selenite after 8 h, at which point activity was 1.8-fold higher compared with untreated cells. Curiously, however, the proteasome activity in 50 μM selenite-treated cells decreased at 28 h compared with 8 h, but activity was still 1.3-fold higher compared with untreated cells at the same time point. Severe Se stress caused by 200 μM selenite also increased proteasome activity after 3 h, but decreased 1.5- and 3-fold after 8 and 28 h, respectively, compared with untreated cells at the same time point. Cell viability was investigated to determine if the decreased proteasome activity caused by 200 μM selenite was a consequence of cell death. There was no difference in cell viability among the different treatments at 3 and 8 h (Fig. 1B). Compared with untreated cells at 28 h, viability decreased from 92 to 76% in cultures treated with 200 μM selenite. However, this decrease in viability does not coincide with the 3-fold decrease in proteasome activity after 28 h.Figure 1.


The ubiquitin-proteasome pathway protects Chlamydomonas reinhardtii against selenite toxicity, but is impaired as reactive oxygen species accumulate.

Vallentine P, Hung CY, Xie J, Van Hoewyk D - AoB Plants (2014)

Proteasome activity in Chlamydomonas treated with selenite. (A) Values for proteasome activity represent fold change in activity of selenite-treated cells relative to untreated cells at each time interval. (B) Percentage of viable cells in cultures with the indicated treatments. Data are the mean of three biological replicates and standard deviation. Lowercase letters represent a significant difference in relative activity at each time point (P < 0.05). Standard errors were too small to plot.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4231294&req=5

PLU062F1: Proteasome activity in Chlamydomonas treated with selenite. (A) Values for proteasome activity represent fold change in activity of selenite-treated cells relative to untreated cells at each time interval. (B) Percentage of viable cells in cultures with the indicated treatments. Data are the mean of three biological replicates and standard deviation. Lowercase letters represent a significant difference in relative activity at each time point (P < 0.05). Standard errors were too small to plot.
Mentions: To determine whether or not moderate and severe selenite stress induces the UPP, Chlamydomonas cells were grown to an OD0.5 and treated with or without 50 and 200 μM selenite. Compared with untreated cells, 50 μM selenite increased proteasome activity after 3, 8 and 28 h (Fig. 1A). Proteasome activity peaked in cells treated with selenite after 8 h, at which point activity was 1.8-fold higher compared with untreated cells. Curiously, however, the proteasome activity in 50 μM selenite-treated cells decreased at 28 h compared with 8 h, but activity was still 1.3-fold higher compared with untreated cells at the same time point. Severe Se stress caused by 200 μM selenite also increased proteasome activity after 3 h, but decreased 1.5- and 3-fold after 8 and 28 h, respectively, compared with untreated cells at the same time point. Cell viability was investigated to determine if the decreased proteasome activity caused by 200 μM selenite was a consequence of cell death. There was no difference in cell viability among the different treatments at 3 and 8 h (Fig. 1B). Compared with untreated cells at 28 h, viability decreased from 92 to 76% in cultures treated with 200 μM selenite. However, this decrease in viability does not coincide with the 3-fold decrease in proteasome activity after 28 h.Figure 1.

Bottom Line: Additionally, proteasomal inhibition decreased the concentration of chlorophyll in cultures challenged with Se.Therefore, although the UPP protects Chlamydomonas against Se stress, severe oxidative stress induced by selenite toxicity likely hinders the UPP's capacity to mediate a stress response.The possibility that stress tolerance in plants is dependent upon optimal UPP activity and maintenance is discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Coastal Carolina University, Conway, SC 29526, USA.

No MeSH data available.


Related in: MedlinePlus