Location: Plant Physiology and Genetics ResearchTitle: Lipid droplet-associated proteins (LDAPs) are involved in the compartmentalization of lipophilic compounds in plant cells Author
Submitted to: Plant Signaling and Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2013
Publication Date: 12/4/2013
Citation: Gidda, S.K., Watt, S.C., Collins-Silva, J., Kilaru, A., Arondel, V., Yurchenko, O., Horn, P., James, C.N., Shintani, D., Ohlrogge, J.B., Chapman, K.D., Mullen, R.T., Dyer, J.M. 2013. Lipid droplet-associated proteins (LDAPs) are involved in the compartmentalization of lipophilic compounds in plant cells. Plant Signaling and Behavior. 8(11):e27141. Interpretive Summary: Vegetable oils are important for human nutritionand there is increasing demand for these oils as feedstocks for the biofuel industry. As such, the demand for plant oils is far higher than what agriculture can typically deliver, and novel ways of dramatically increasing oil content of plants are widely sought. One avenue of research being pursued by academic, government, and private industry scientists is to engineer plants to produce oil in their vegetative biomass, such as leaves and stems, in addition to seeds. The rationale for this approach is that the biomass of a plant is dominated by leaves and stems, and production of even modest amounts of oil in these tissues could significantly increase the overall amount of oil recovered from a given area of land. Rational engineering of oil content in plant leaves, however, requires a better understanding of the molecular mechanisms involved in production, storage, and degradation of oil in these tissues. In a large collaborative effort between scientists at the USDA-ARS lab in Maricopa Arizona, University of Guelph, East Tennessee State University, Michigan State University, University of Nevada Reno, University of North Texas, and the University of Bordeaux, a new class of proteins associated with oil production in plant leaves was identified. Somewhat surprisingly, these proteins were similar to proteins known to be important for the production of rubber in certain rubber-accumulating plants such as Heveabrasiliensis and guayule. In this manuscript, the scientists showed that the rubber proteins could associate with oil-containing lipid droplets in non-rubber-accumulating plants. These and other results define a larger class of proteins that are important for the proper partitioning of lipophilic compounds in plants cells, including oil and rubber, and opens new avenues of research for exploring the production of high amounts of oil in the leaves of plants.
Technical Abstract: While lipid droplets have traditionally been considered as inert sites for the storage of triacylglycerols and sterol esters, they are now recognized as dynamic and functionally diverse organelles involved in energy homeostasis, lipid signaling, and stress responses. Unlike most other organelles, lipid droplets are delineated by a half-unit membrane whose protein constituents are poorly understood, except in the specialized case of oleosins, which are associated with seed lipid droplets. Recently, we identified a new class of lipid-droplet associated proteins called LDAPs that localize specifically to the lipid droplet surface within plant cells and share extensive sequence similarity with the small rubber particle proteins (SRPPs) found in rubber-accumulating plants. Here, we provide additional evidence for a role of LDAPs in lipid accumulation in oil-rich fruit tissues, and further explore the functional relationships between LDAPs and SRPPs. In addition, we propose that the larger LDAP/SRPP protein family plays important roles in the compartmentalization of lipophilic compounds, including triacylglycerols and polyisoprenoids, into lipid droplets within