Affiliation:
1. Department of Biology, Washington University, St. Louis, Missouri 63130
2. Department of Cell Biology, Washington University School of Medicine, St. Louis, Missouri 63110
Abstract
ABSTRACT
Light microscopy and deep-etch electron microscopy were used to visualize triacylglyceride (TAG)-filled lipid bodies (LBs) of the green eukaryotic soil alga
Chlamydomonas reinhardtii
, a model organism for biodiesel production. Cells growing in nitrogen-replete media contain small cytoplasmic lipid bodies (α-cyto-LBs) and small chloroplast plastoglobules. When starved for N, β-cyto-LB formation is massively stimulated. β-Cyto-LBs are intimately associated with both the endoplasmic reticulum membrane and the outer membrane of the chloroplast envelope, suggesting a model for the active participation of both organelles in β-cyto-LB biosynthesis and packaging. When
sta6
mutant cells, blocked in starch biosynthesis, are N starved, they produce β-cyto-LBs and also chloroplast LBs (cpst-LBs) that are at least 10 times larger than plastoglobules and eventually engorge the chloroplast stroma. Production of β-cyto-LBs and cpst-LBs under the conditions we used is dependent on exogenous 20 mM acetate. We propose that the greater TAG yields reported for N-starved
sta6
cells can be attributed to the strain's ability to produce cpst-LBs, a capacity that is lost when the mutant is complemented by a
STA6
transgene. Provision of a 20 mM acetate “boost” during N starvation generates
sta6
cells that become so engorged with LBs—at the expense of cytoplasm and most organelles—that they float on water even when centrifuged. This property could be a desirable feature for algal harvesting during biodiesel production.
Publisher
American Society for Microbiology
Subject
Molecular Biology,General Medicine,Microbiology
Cited by
223 articles.
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