Uncovering The Origins Of Oily Organelles

By closely examining liverwort cells, scientists from Japan have shed light on how diverse organelles like oil bodies were first formed.

AsianScientist (Feb. 9, 2021) – Small and often mistaken for moss, liverwort plants coat soil surfaces almost everywhere in the world. Despite their unobtrusive nature, these plants hold the key to a long-standing evolutionary mystery: how distinct parts of the cells called organelles came to be.

By closely examining liverwort cells, researchers from Japan have discovered that similar evolutionary pathways gave rise to two markedly different organelles—namely the cell plate and oil body. Their findings, published in Nature Communications, highlight a common strategy for plant cells to acquire organelles.

As cells are the basic unit of life, studying their structure and function is a staple in introductory biology. Within each cell are organelles, each with a specific function. The mitochondria is popularly known as the powerhouse of the cell, whereas the nucleus contains genetic material. In addition to these, liverwort cells also house the cell plate, which forms during cell division, and the oil body, which stores various chemical substances.

Given the diversity of these organelles, scientists have long tried to uncover the murky origins of such structures. One clue may come from membrane trafficking proteins, which play a pivotal role in shuffling important biomolecules between organelles.

Focusing on a group of membrane trafficking proteins called SYP1 in the liverwort Marchantia polymorpha, a team from Japan’s National Institute for Basic Biology found that SYP1 proteins were required for the formation of both the cell plate and oil body. Specifically, MpSYP12A was required for cell plate formation, while MpSYP12B was functional only in liverwort cells containing oil bodies.

The team also showed that oil body formation occurs when the pathway responsible for carrying biomolecules to the cell surface membrane is instead redirected inward. This causes lipid membranes called vesicles to fuse together, eventually becoming the oil body.

Aside from MpSYP12B, the researchers also discovered that the MpERF13 gene served as the ‘master regulator’ for oil body formation. For instance, knocking out MpERF13 resulted in the complete loss of the oil body, while enhancing MpERF13’s function caused the overgeneration of the oil body throughout the plant.

Going a step further, the team also probed the biological significance of the oil body by exposing hungry pill bugs to liverworts with and without oil bodies. The liverworts without the oil body were readily eaten by the pill bugs, while the liverworts with an excess of oil bodies were not. This indicates that oil bodies protect liverworts and similar plants from herbivores like the pill bug.

“I had eaten some liverwort when I started my research on this plant. It tasted really horrible,” shared first author Dr. Takehiko Kanazawa. “This extreme experience helped me come up with the idea of the pill bug assay in exploring the biological function of the oil body.”

Studying the mechanism of the genes involved in oil body formation could help improve the production of the compounds stored within the oil bodies. Moving forward, Kanazawa and his collaborators will also explore the unique bioactivities of these compounds—many of which potentially have antibacterial, anticancer and antiviral applications.

The article can be found at: Kanazawa et al. (2020) The Liverwort Oil Body Is Formed by Redirection of the Secretory Pathway.


Source: National Institutes of Natural Sciences; Photo: Shutterstock.
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