Michigan State University researchers are experimenting with harvesting seed oil to make biofuels. In a recent study published in the journal The Plant Cell, the researchers show that the chloroplast, where plant photosynthesis occurs, also participates in new ways to provide seed oil precursors.
Seed oil is made out of lipids—small molecules found in fats, oils, waxes and membranes that make up the boundaries of all living cell components. They also store a lot of energy. The scientists identified a new enzyme, named PLIP1, or Plastid Lipade 1, that interacts with lipids inside the chloroplast.
The enzyme breaks down lipids that make up the chloroplast’s internal membranes, the thylakoids, to be precise. The use and recycling of lipids keeps chloroplast membranes adjusted to developmental or environmental changes.—Kun Wang, lead author
|PLIP1 degrades internal chloroplast membranes surrounding the thylakoids. The left-over lipid products are transported to the endoplasmic reticulum, where they eventually turn into seed oil. Photo courtesy of MSU. Click to enlarge.
Leftover lipid products are transported to the endoplasmic reticulum where they become building blocks for seed oil. Previously, it was thought that seed oil production is largely based in the endoplasmic reticulum.
Now, we are finding that the chloroplast is responsible for 10% of seed oil precursors. That might seem like a low number. However, seed oil comes from many sources, and the main one is responsible for 20 to 40% of final product. So, 10% is significant.—Kun Wang
Wang wants to increase the level of PLIP1 in biofuel-targeted plants, so they produce more seed oil. PLIP1 is that it is found in most land plants, which makes it easy to experiment on different species, Wang added.
Initial testing has unexpectedly led to a smaller plant with more oil per seed but fewer seeds, and higher defense activity.
It seems oil production and plant defense functions don’t coexist well. We have a few ideas to bypass this limitation, and we’ve already filled out a patent application to try a new strategy to increase seed oil yield, using PLIP1.—Kun Wang
Kun Wang, John E. Froehlich, Agnieszka Zienkiewicz, Hope Lynn Hersh, Christoph Benning (2017) “A Plastid Phosphatidylglycerol Lipase Contributes to the Export of Acyl Groups from Plastids for Seed Oil Biosynthesis” The Plant Cell doi: 10.1105/tpc.17.00397