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Whole-cell response to nitrogen deprivation in the diatom Phaeodactylum tricornutum.

Alipanah L, Rohloff J, Winge P, Bones AM, Brembu T - J. Exp. Bot. (2015)

Bottom Line: Physiological and metabolite measurements indicated that the photosynthetic capacity and chlorophyll content of the cells decreased, while neutral lipids increased in N-deprived cultures.Following N deprivation, reduced biosynthesis and increased recycling of N compounds like amino acids, proteins, and nucleic acids was observed at the transcript level.The majority of the genes associated with photosynthesis and chlorophyll biosynthesis were also repressed.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.

No MeSH data available.


Accumulation of neutral lipids during nitrate deprivation. (A) Fluorescence intensity in P. tricornutum cells stained with BODIPY 505/515 at 48 and 72h after N deprivation. The level of lipid fluorescence was measured in 20–30 randomly selected cells using confocal microscopy. Statistical differences (*P<0.01) between nitrate-replete (N+) and nitrate deprived (N–) cultures are indicated. au, Arbitrary units. (B) Z-stack projections of P. tricornutum in N+ and N– cultures at 48 and 72h after N deprivation. Bar, 5 μm. (This figure is available in colour at JXB online.)
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Figure 2: Accumulation of neutral lipids during nitrate deprivation. (A) Fluorescence intensity in P. tricornutum cells stained with BODIPY 505/515 at 48 and 72h after N deprivation. The level of lipid fluorescence was measured in 20–30 randomly selected cells using confocal microscopy. Statistical differences (*P<0.01) between nitrate-replete (N+) and nitrate deprived (N–) cultures are indicated. au, Arbitrary units. (B) Z-stack projections of P. tricornutum in N+ and N– cultures at 48 and 72h after N deprivation. Bar, 5 μm. (This figure is available in colour at JXB online.)

Mentions: Measurements of chlorophyll a and fucoxanthin (the major carotenoid in diatoms) levels per cell showed that the content of these pigments declined progressively in N-deprived cells at both time points, while both pigments were stable in control cells (Table 2). In contrast, the ratio between chlorophyll a and fucoxanthin did not change. We also monitored the effect of N deprivation on the activity of PSII. Maximum quantum yield of PSII (Fv/Fm), applied as a proxy measure of photosynthesis, was similar in N-replete and N-deprived cultures after 24h. A clear drop in Fv/Fm was observed in N-deprived cells (Fv/Fm=0.33) after 72h, while the ratio remained unchanged (Fv/Fm=0.68) in the control cultures (Fig. 1B). Quantification of neutral lipids by confocal laser scanning microscopy and BODIPY 505/515 showed that the neutral lipid content increased significantly at 72h (t-test: P=1.87 E–06) and was 29.3% higher in N-deprived cells compared with N-replete cells (Fig. 2A). Representative images from the analysis showed that the lipid droplets were larger and more strongly stained by the BODIPY marker in N-deprived cells than in replete cells, implying higher lipid accumulation (Fig. 2B).


Whole-cell response to nitrogen deprivation in the diatom Phaeodactylum tricornutum.

Alipanah L, Rohloff J, Winge P, Bones AM, Brembu T - J. Exp. Bot. (2015)

Accumulation of neutral lipids during nitrate deprivation. (A) Fluorescence intensity in P. tricornutum cells stained with BODIPY 505/515 at 48 and 72h after N deprivation. The level of lipid fluorescence was measured in 20–30 randomly selected cells using confocal microscopy. Statistical differences (*P<0.01) between nitrate-replete (N+) and nitrate deprived (N–) cultures are indicated. au, Arbitrary units. (B) Z-stack projections of P. tricornutum in N+ and N– cultures at 48 and 72h after N deprivation. Bar, 5 μm. (This figure is available in colour at JXB online.)
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
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Figure 2: Accumulation of neutral lipids during nitrate deprivation. (A) Fluorescence intensity in P. tricornutum cells stained with BODIPY 505/515 at 48 and 72h after N deprivation. The level of lipid fluorescence was measured in 20–30 randomly selected cells using confocal microscopy. Statistical differences (*P<0.01) between nitrate-replete (N+) and nitrate deprived (N–) cultures are indicated. au, Arbitrary units. (B) Z-stack projections of P. tricornutum in N+ and N– cultures at 48 and 72h after N deprivation. Bar, 5 μm. (This figure is available in colour at JXB online.)
Mentions: Measurements of chlorophyll a and fucoxanthin (the major carotenoid in diatoms) levels per cell showed that the content of these pigments declined progressively in N-deprived cells at both time points, while both pigments were stable in control cells (Table 2). In contrast, the ratio between chlorophyll a and fucoxanthin did not change. We also monitored the effect of N deprivation on the activity of PSII. Maximum quantum yield of PSII (Fv/Fm), applied as a proxy measure of photosynthesis, was similar in N-replete and N-deprived cultures after 24h. A clear drop in Fv/Fm was observed in N-deprived cells (Fv/Fm=0.33) after 72h, while the ratio remained unchanged (Fv/Fm=0.68) in the control cultures (Fig. 1B). Quantification of neutral lipids by confocal laser scanning microscopy and BODIPY 505/515 showed that the neutral lipid content increased significantly at 72h (t-test: P=1.87 E–06) and was 29.3% higher in N-deprived cells compared with N-replete cells (Fig. 2A). Representative images from the analysis showed that the lipid droplets were larger and more strongly stained by the BODIPY marker in N-deprived cells than in replete cells, implying higher lipid accumulation (Fig. 2B).

Bottom Line: Physiological and metabolite measurements indicated that the photosynthetic capacity and chlorophyll content of the cells decreased, while neutral lipids increased in N-deprived cultures.Following N deprivation, reduced biosynthesis and increased recycling of N compounds like amino acids, proteins, and nucleic acids was observed at the transcript level.The majority of the genes associated with photosynthesis and chlorophyll biosynthesis were also repressed.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.

No MeSH data available.