Identification and characterization of lipid droplet-associated 2 protein (LDAP) isoforms from tung tree (Vernicia fordii)

Authors: CLEWS, AYLSSA - University Of Guelph; WHITEHEAD, PAYTON - University Of North Texas; ZHANG, LINGLING - Wuhan Botanical Garden; LU, SHIYOU - Wuhan Botanical Garden; Shockey, Jay; CHAPMAN, KENT - University Of North Texas; Dyer, John; XU, YANG - University Of Guelph; MULLEN, REBORT - University Of Guelph

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2025
Publication Date: 3/6/2025
Citation: Clews, A.T., Whitehead, P.S., Zhang, L., Lu, S., Shockey, J.M., Chapman, K.D., Dyer, J.M., Xu, Y., Mullen, R.T. 2025. Identification and characterization of lipid droplet-associated 2 protein (LDAP) isoforms from tung tree (Vernicia fordii). Plants. 14(5): 814. https://doi.org/10.3390/plants14050814.
DOI: https://doi.org/10.3390/plants14050814

Interpretive Summary: The genetics and biochemistry of vegetable oil production in plant cells remains poorly understood. Many of the core enzymes that construct the oil molecules have been identified, which initially led many researchers in this field to believe that existing low-value oil crops could easily be engineered to produce high-value oils with just a few genes from an exotic plant. This has turned out not to be true; much more info regarding the synthesis and packaging of oils in seeds is necessary before rational engineering strategies can be conceived. Here our laboratories test the efficiency of certain packaging proteins that help to form oil droplets in developing seeds. These packaging proteins were only recently discovered and very little is known about them. The results show that these proteins increase the amount of oil plant cells expressing them can produce, and help to enrich these oils with higher amounts of high-value fatty acids, compared to negative control samples. These findings strongly suggest these packaging proteins have evolved to assist in this process and should be included in future engineering strategies.

Technical Abstract: Lipid droplets (LDs) are cytoplasmic organelles responsible primarily for the storage of neutral lipids, such as triacyclglycerols (TAGs). Derived from the endoplasmic reticulum bilayer, LDs are composed of a hydrophobic lipid core encased by a phospholipid monolayer and surface-associated proteins. To date, only a relatively few LD ‘coat’ proteins in plants have been identified and characterized, most of which having come from studies of the model plant Arabidopsis thaliana. To expand our knowledge of the plant LD proteome, the LD-associated protein (LDAP) family from the tung tree (Vernicia fordii), whose seeds are rich in a commercially valuable TAG containing the conjugated fatty acid a-eleostearic acid (C18:3'9cis,11trans,13trans [ESA]), was identified and characterized. Based on the tung tree transcriptome, three LDAP isoforms (VfLDAP1-3) were elucidated and the encoded proteins distinctly clustered into three clades along with their respective isoforms from other angiosperm species. Ectopic expression of the VfLDAPs in Nicotiana benthamiana leaves revealed that they localized specifically to LDs and influenced LD numbers and sizes, as well increasing TAG content and altering TAG fatty acid composition. Interestingly, in a partially reconstructed TAG-ESA biosynthetic pathway, co-expression of VfLDAP3 and, to a lesser degree, VfLDAP2, modestly increased the content of ESA stored within LDs. These results suggest that the VfLDAPs can influence the steady-state content and composition of TAG in plant cells and that certain LDAP isoforms may have evolved to more efficiently package TAGs containing unusual fatty acids, such as ESA.