Short read.
Biochemists at the U.S. Department of Energy’s Brookhaven National Laboratory have discovered two ways that autophagy, or self-eating, controls the levels of oils in plant cells. The study, published in The Plant Cell on April 29, 2019, describes how this cannibalistic-sounding process actually helps plants survive. It also provides mechanistic details scientists might leverage to get plants to accumulate more oil.
As we know plants store oil in seeds, if more oil were stored in the vegetative tissues of some plants it would make for a more useful way of producing bioenergy crops. These crops could be processed into biodiesel fuel, or burned to produce electricity, to heat buildings as explained by Chengcheng Xu research lead.
“Our study shows that autophagy plays two major roles in oil balance: First, it’s important for the biosynthesis of lipid droplets, the form in which oil is stored in vegetative and other tissues. It also plays a role in breaking down those droplets when plants need to use the oil to produce energy.”
Autophagy or "self eating" is a universal process occuring during normal growth in mammalian cells, yeast, and plants, it is inducable by stressful events (these include starvation or stressful events). Cellular scale autophagy is a form of recycling by the plant according to Xu. The study revealed that some of the biochemical building blocks set free by this normal autophagic recycling process are the fatty acids that make up oil droplets.
To produce a level of starvation in the plant cells the plants were then placed in the dark where no photosynthesis could occur. For this part of the study, the scientists used two fluorescent markers to label the lipid droplets (green) and the membrane surrounding the vacuole (red).
The images on the main header were taken using a confocal microscope at Brookhaven Lab's Center for Functional Nanomaterials, show lipid droplets (green) enclosed within plant cell vacuoles (red-labeled membranes). The plants had been in the dark and were in the process of "eating" their own lipid droplets to provide the cells with energy in the absence of sunlight/photosynthesis.
“Lipids are a major component of cellular membranes, including the membranes that surround every organelle,” Xu said. “Our study shows that autophagy delivers the old organelles with their lipid-rich membranes to the vacuole to be degraded, and then the labeled fatty acids released from the membranes end up in the oil stored in lipid droplets.”
Xu explains that, “There are a lot more details to discover about how this process happens. But if we can discover the signals that are involved, we may be able to manipulate the process to get plants to make and store more fatty acids, the major components of biodiesel. This knowledge could also be used to make oil droplets more stable, or plants that are more resistant to stress. It’s a whole new exciting research field!”
Are biofuels carbon neutral? This is the great controversy, in some cases it has been found that processing the biofuels can have a bigger carbon impact than using other fuels. There is also the question of biodiversity, the amount of land clearing needed could lead to the destruction of a dense population of natural habitat for both animals and plants. Forced growing in darkness could make use of abandoned underground areas if suitable for farming. The important theme seems to be to make this an ethical and sustainable way of producing a carbon neutral fuel, this is new research and so we await further progress.
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