Location: Plant Physiology and Genetics ResearchTitle: Mouse fat storage-inducing transmembrane protein 2 (FIT2) promotes lipid droplet accumulation in plants
|CAI, YINGQI - University Of North Texas|
|MCCLINCHIE, ELIZABETH - University Of North Texas|
|PRICE, ANN - University Of North Texas|
|NGUYEN, THUY - University Of Guelph|
|GIDDA, SATINDER - University Of Guelph|
|WATT, SAMANTHA - University Of Guelph|
|PARK, SUNJUNG - Central Arizona College|
|STURTEVANT, DREW - University Of North Texas|
|MULLEN, ROBERT - University Of Guelph|
|CHAPMAN, KENT - University Of North Texas|
Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2016
Publication Date: 12/17/2016
Citation: Cai, Y., McClinchie, E., Price, A., Nguyen, T.N., Gidda, S.K., Watt, S.C., Yurchenko, O., Park, S., Sturtevant, D., Mullen, R.T., Dyer, J.M., Chapman, K.D. 2016. Mouse fat storage-inducing transmembrane protein 2 (FIT2) promotes lipid droplet accumulation in plants. Plant Biotechnology Journal. 15(7):824-836. https://doi.org/10.1111/pbi.12678.
Interpretive Summary: Plant oils are high value commodities that are used for food, cooking, and feedstocks for production of biofuels and bio-products. Given their diversified end-uses, there is significant interest in understanding the molecular mechanisms of oil production in plants, which provides opportunities for increasing oil content in crops through molecular breeding approaches. While much is known about the various enzymatic steps involved in oil biosynthesis, significantly less is known about the cellular processes by which oil is packaged and stored in subcellular organelles called lipid droplets. In an effort to increase our understanding of lipid droplet formation in plant cells, scientists at the ARS lab in Maricopa, Arizona, the University of North Texas, and the University of Guelph collaborated to study the expression of a mammalian protein called “Fat storage-inducing transmembrane protein 2” (FIT2) in plant cells. FIT2 was previously shown to play a key role in one of the earliest steps of lipid droplet formation in a variety of eukaryotic cell types, but interestingly, there are no FIT2-like proteins detected in plants. Expression of mammalian FIT2 in a variety of plant cell types resulted in a significant increase in lipid droplet abundance, similar to results observed when the protein is over-expressed in mammalian cells. Further, the lipid droplets were much larger in size, leading to accumulation of higher amounts of oil in both leaf and seed tissues. Taken together, the results demonstrate that FIT2 functions properly in a plant cell context to modulate lipid droplet abundance and increase oil content. The results also suggest that FIT2 might serve as a useful tool for further characterizing the relationships of oil synthesis and packaging in plants, and could be used in biotechnology approaches for enhancing oil content in dedicated, non-food bioenergy crop crops. These findings will be of greatest interest to other scientists interested in both basic and applied aspects of oil production in plants.
Technical Abstract: Fat Storage-Inducing Transmembrane protein 2 (FIT2) is an endoplasmic reticulum (ER)-localized protein that plays an important role in lipid droplet (LD) formation in animal cells. However, no obvious homologue of FIT2 is found in plants. Here, we tested the function of FIT2 in plant cells by ectopically expressing mouse (Mus musculus) FIT2 in Nicotiana tabacum suspension-cultured cells, N. benthamiana leaves, and Arabidopsis thaliana plants. Confocal microscopy indicated that the expression of FIT2 dramatically increased the number and size of LDs in leaves of N. benthamiana and Arabidopsis, and lipidomics analysis and mass spectrometry imaging confirmed the accumulation of neutral lipids in leaves. FIT2 also increased seed oil content by ~13% in some stable, overexpressing lines of Arabidopsis. When expressed transiently in leaves of N. benthamiana or suspension cells of N. tabacum, FIT2 localized specifically to the ER, and was often concentrated at certain regions of the ER that resembled ER-LD junction sites. FIT2 also co-localized at the ER with other proteins known to be involved in triacylglycerol biosynthesis or LD formation in plants, but not with ER resident proteins involved in electron transfer or ER-vesicle exit sites. Collectively, these results demonstrate that mouse FIT2 promotes LD accumulation in plants, a surprising functional conservation in the context of a plant cell given the apparent lack of FIT2 homologues in higher plants. These results suggest also that FIT2 expression represents an effective synthetic biology strategy for elaborating neutral lipid compartments in plant tissues for potential biofuel or bio-products purposes.