Location: Plant Physiology and Genetics ResearchTitle: Arabidopsis lipid droplet-associated protein (LDAP)–interacting protein (LDIP) influences lipid droplet size and neutral lipid homeostasis in both leaves and seeds
|PYC, MICHAL - University Of Guelph|
|CAI, YINGQI - University Of North Texas|
|GIDDA, SATINDER - University Of Guelph|
|PARK, SUNJUNG - Central Arizona College|
|KRETSCHMAR, FRANZISKA - Goettingen University|
|ISCHEBECK, TILL - Goettingen University|
|VALERIUS, OLIVER - Gottingen University|
|BRAUS, GERHARD - Goettingen University|
|CHAPMAN, KENT - University Of North Texas|
|MULLEN, ROBERT - University Of Guelph|
Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2017
Publication Date: 11/27/2017
Publication URL: http://handle.nal.usda.gov/10113/5872560
Citation: Pyc, M., Cai, Y., Gidda, S.K., Yurchenko, O., Park, S., Kretschmar, F., Ischebeck, T., Valerius, O., Braus, G.H., Chapman, K., Dyer, J.M., Mullen, R.T. 2017. Arabidopsis lipid droplet-associated protein (LDAP)–interacting protein (LDIP) influences lipid droplet size and neutral lipid homeostasis in both leaves and seeds. Plant Journal. 92:1182-1201.
Interpretive Summary: Oilseed crops synthesize and store large amounts of oil (up to 40% dry weight) in their seeds, which serve as a carbon and energy reserve for germinated seedlings and as an important nutritional resource for humans and animal feed. While the enzymes for oil synthesis in plants are generally well understood, the processes involved in the “packaging” of oil into subcellular organelles called “lipid droplets” are relatively unknown. In collaborative research between scientists at the ARS lab in Maricopa, Arizona, the University of North Texas, and the University of Guelph, a new protein was identified that plays a key role in the formation of lipid droplets in plant cells. Disruption of the gene encoding this protein resulted in much larger lipid droplets and higher amounts of oil in both leaves and seeds. While the protein itself has no known function in oil biosynthesis, changes in overall lipid metabolism resulted in increases of up to 20% oil content in seeds. These results open the door to the usage of mutational breeding strategies, which are considered non-transgenic, for identifying plant lines that harbor mutations in this gene, which holds promise for substantially increasing oil content of oilseed crops. The work will be of great interest to other scientists studying the basic mechanisms of oil formation in plants as well as scientists and breeders in private industry working to develop elite oilseed cultivars that have enhanced oil content.
Technical Abstract: Cytoplasmic lipid droplets (LDs) are found in all types of plant cells where they are derived from the endoplasmic reticulum and function as a repository for neutral lipids, as well as serving in lipid remodelling and signalling. However, the mechanisms underlying the formation and functioning of plant LDs, particularly in non-seed tissues, are relatively unknown. Previously, we showed that the LD-Associated Proteins (LDAPs) are a family of plant-specific, LD surface-associated coat proteins that are required for proper LD biogenesis and neutral lipid homeostasis in vegetative tissues. Here, we screened a yeast two-hybrid library using the Arabidopsis LDAP3 isoform as ‘bait’ in an effort to identify other novel LD protein constituents. One of the candidate LDAP3-interacting proteins was Arabidopsis At5g16550, which is a plant-specific protein of unknown function that we termed LDIP (LDAP-Interacting Protein). Using a combination of biochemical and cellular approaches, we show that LDIP targets specifically to the LD surface, contains a discrete amphipathic a-helical targeting sequence, and participates in both homotypic and heterotypic associations with itself and LDAP3, respectively. Analysis of LDIP T-DNA knockdown and knockout mutants showed a decrease in LD abundance and increase in variability of LD size in leaves, with concomitant increases in total neutral lipid content. Similar phenotypes were observed in plant seeds, which showed enlarged LDs and increases in total seed oil amounts. Collectively, these data identify LDIP as a new player in LD biogenesis in plants that modulates both LD size and cellular neutral lipid homeostasis.