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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: 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.Finally, reallocation of membrane lipids and induction of de novo triacylglycerol biosynthesis directed cells to accumulation of neutral lipids.

View Article: PubMed Central - PubMed

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

No MeSH data available.


Related in: MedlinePlus

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
Show All Figures
getmorefigures.php?uid=PMC4588885&req=5

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: 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.Finally, reallocation of membrane lipids and induction of de novo triacylglycerol biosynthesis directed cells to accumulation of neutral lipids.

View Article: PubMed Central - PubMed

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

No MeSH data available.


Related in: MedlinePlus