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Fatty acids from membrane lipids become incorporated into lipid bodies during Myxococcus xanthus differentiation.

Bhat S, Boynton TO, Pham D, Shimkets LJ - PLoS ONE (2014)

Bottom Line: Third, peripheral rods, developing cells that do not produce lipid bodies, fail to shorten.The lipid body regulon involves many developmental genes that are not specifically involved in fatty acid synthesis or degradation.MazF RNA interferase and its target, enhancer-binding protein Nla6, appear to negatively regulate cell shortening and TAG accumulation whereas most cell-cell signals activate these processes.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Georgia, Athens, Georgia, United States of America.

ABSTRACT
Myxococcus xanthus responds to amino acid limitation by producing fruiting bodies containing dormant spores. During development, cells produce triacylglycerides in lipid bodies that become consumed during spore maturation. As the cells are starved to induce development, the production of triglycerides represents a counterintuitive metabolic switch. In this paper, lipid bodies were quantified in wild-type strain DK1622 and 33 developmental mutants at the cellular level by measuring the cross sectional area of the cell stained with the lipophilic dye Nile red. We provide five lines of evidence that triacylglycerides are derived from membrane phospholipids as cells shorten in length and then differentiate into myxospores. First, in wild type cells, lipid bodies appear early in development and their size increases concurrent with an 87% decline in membrane surface area. Second, developmental mutants blocked at different stages of shortening and differentiation accumulated lipid bodies proportionate with their cell length with a Pearson's correlation coefficient of 0.76. Third, peripheral rods, developing cells that do not produce lipid bodies, fail to shorten. Fourth, genes for fatty acid synthesis are down-regulated while genes for fatty acid degradation are up regulated. Finally, direct movement of fatty acids from membrane lipids in growing cells to lipid bodies in developing cells was observed by pulse labeling cells with palmitate. Recycling of lipids released by Programmed Cell Death appears not to be necessary for lipid body production as a fadL mutant was defective in fatty acid uptake but proficient in lipid body production. The lipid body regulon involves many developmental genes that are not specifically involved in fatty acid synthesis or degradation. MazF RNA interferase and its target, enhancer-binding protein Nla6, appear to negatively regulate cell shortening and TAG accumulation whereas most cell-cell signals activate these processes.

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Lipid body production in WT cells during development.(A) DK1622 cells stained with the lipophilic dye Nile red at times indicated during development. Phase (Left), fluorescence (Right). Bar is 10 µm. (B) Lipid bodies were quantified by measuring the average cross sectional area stained with Nile red using at least 30 cells (grey bars). Cell length was measured using phase contrast images of 30 randomly chosen cells (filled diamonds). At 48 h, the cells are a nearly equal mixture of long, peripheral rods and spherical myxospores.
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pone-0099622-g001: Lipid body production in WT cells during development.(A) DK1622 cells stained with the lipophilic dye Nile red at times indicated during development. Phase (Left), fluorescence (Right). Bar is 10 µm. (B) Lipid bodies were quantified by measuring the average cross sectional area stained with Nile red using at least 30 cells (grey bars). Cell length was measured using phase contrast images of 30 randomly chosen cells (filled diamonds). At 48 h, the cells are a nearly equal mixture of long, peripheral rods and spherical myxospores.

Mentions: Lipid body size was quantified using Nile red stained wild type DK1622 cells [4]. Vegetative cells grown in a rich medium (0 h) have no lipid bodies (Figure 1A). 6 h after starvation initiates development, several small lipid bodies appear close to the membrane. Over the next 12 h, lipid bodies increase in size and number. By 18 h, the peak of lipid body production, the area of the cell stained with Nile red is roughly 20% the cross-sectional area of the cell. Cell shortening begins soon after initiation of development in WT cells and coincides temporally with the appearance of lipid bodies. By 18 h, a few cells have become spherical while the cylindrical cells are about 40% shorter (Figure 1B). Lipid bodies then decline in size and number after 18 h (Figure 1B) before finally disappearing completely in mature spores. The coupling of diminishing cell length with lipid body accumulation suggests the use of internal carbon sources as a reservoir for TAG building blocks. Another possibility is the recycling of lipids released by cells undergoing PCD. A small amount of lysis occurs by 18 h [9].


Fatty acids from membrane lipids become incorporated into lipid bodies during Myxococcus xanthus differentiation.

Bhat S, Boynton TO, Pham D, Shimkets LJ - PLoS ONE (2014)

Lipid body production in WT cells during development.(A) DK1622 cells stained with the lipophilic dye Nile red at times indicated during development. Phase (Left), fluorescence (Right). Bar is 10 µm. (B) Lipid bodies were quantified by measuring the average cross sectional area stained with Nile red using at least 30 cells (grey bars). Cell length was measured using phase contrast images of 30 randomly chosen cells (filled diamonds). At 48 h, the cells are a nearly equal mixture of long, peripheral rods and spherical myxospores.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4048283&req=5

pone-0099622-g001: Lipid body production in WT cells during development.(A) DK1622 cells stained with the lipophilic dye Nile red at times indicated during development. Phase (Left), fluorescence (Right). Bar is 10 µm. (B) Lipid bodies were quantified by measuring the average cross sectional area stained with Nile red using at least 30 cells (grey bars). Cell length was measured using phase contrast images of 30 randomly chosen cells (filled diamonds). At 48 h, the cells are a nearly equal mixture of long, peripheral rods and spherical myxospores.
Mentions: Lipid body size was quantified using Nile red stained wild type DK1622 cells [4]. Vegetative cells grown in a rich medium (0 h) have no lipid bodies (Figure 1A). 6 h after starvation initiates development, several small lipid bodies appear close to the membrane. Over the next 12 h, lipid bodies increase in size and number. By 18 h, the peak of lipid body production, the area of the cell stained with Nile red is roughly 20% the cross-sectional area of the cell. Cell shortening begins soon after initiation of development in WT cells and coincides temporally with the appearance of lipid bodies. By 18 h, a few cells have become spherical while the cylindrical cells are about 40% shorter (Figure 1B). Lipid bodies then decline in size and number after 18 h (Figure 1B) before finally disappearing completely in mature spores. The coupling of diminishing cell length with lipid body accumulation suggests the use of internal carbon sources as a reservoir for TAG building blocks. Another possibility is the recycling of lipids released by cells undergoing PCD. A small amount of lysis occurs by 18 h [9].

Bottom Line: Third, peripheral rods, developing cells that do not produce lipid bodies, fail to shorten.The lipid body regulon involves many developmental genes that are not specifically involved in fatty acid synthesis or degradation.MazF RNA interferase and its target, enhancer-binding protein Nla6, appear to negatively regulate cell shortening and TAG accumulation whereas most cell-cell signals activate these processes.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Georgia, Athens, Georgia, United States of America.

ABSTRACT
Myxococcus xanthus responds to amino acid limitation by producing fruiting bodies containing dormant spores. During development, cells produce triacylglycerides in lipid bodies that become consumed during spore maturation. As the cells are starved to induce development, the production of triglycerides represents a counterintuitive metabolic switch. In this paper, lipid bodies were quantified in wild-type strain DK1622 and 33 developmental mutants at the cellular level by measuring the cross sectional area of the cell stained with the lipophilic dye Nile red. We provide five lines of evidence that triacylglycerides are derived from membrane phospholipids as cells shorten in length and then differentiate into myxospores. First, in wild type cells, lipid bodies appear early in development and their size increases concurrent with an 87% decline in membrane surface area. Second, developmental mutants blocked at different stages of shortening and differentiation accumulated lipid bodies proportionate with their cell length with a Pearson's correlation coefficient of 0.76. Third, peripheral rods, developing cells that do not produce lipid bodies, fail to shorten. Fourth, genes for fatty acid synthesis are down-regulated while genes for fatty acid degradation are up regulated. Finally, direct movement of fatty acids from membrane lipids in growing cells to lipid bodies in developing cells was observed by pulse labeling cells with palmitate. Recycling of lipids released by Programmed Cell Death appears not to be necessary for lipid body production as a fadL mutant was defective in fatty acid uptake but proficient in lipid body production. The lipid body regulon involves many developmental genes that are not specifically involved in fatty acid synthesis or degradation. MazF RNA interferase and its target, enhancer-binding protein Nla6, appear to negatively regulate cell shortening and TAG accumulation whereas most cell-cell signals activate these processes.

Show MeSH
Related in: MedlinePlus