Comparative Lipidomics and Proteomics of Lipid Droplets in the Mesocarp and Seed Tissues of Chinese Tallow (Triadica sebifera)

Abstract

Lipid droplets (LDs) are composed of a monolayer of phospholipids (PLs), surrounding a core of non-polar lipids that consist mostly of triacylglycerols (TAGs) and to a lesser extent diacylglycerols. In this study, lipidome analysis illustrated striking differences in non-polar lipids and PL species between LDs derived from Triadica sebifera seed kernels and mesocarp. In mesocarp LDs, the most abundant species of TAG contained one C18:1 and two C16:0 and fatty acids, while TAGs containing three C18 fatty acids with higher level of unsaturation were dominant in the seed kernel LDs. This reflects the distinct differences in fatty acid composition of mesocarp (palmitate-rich) and seed-derived oil (α-linoleneate-rich) in T. sebifera. Major PLs in seed LDs were found to be rich in polyunsaturated fatty acids, in contrast to those with relatively shorter carbon chain and lower level of unsaturation in mesocarp LDs. The LD proteome analysis in T. sebifera identified 207 proteins from mesocarp, and 54 proteins from seed kernel, which belong to various functional classes including lipid metabolism, transcription and translation, trafficking and transport, cytoskeleton, chaperones, and signal transduction. Oleosin and lipid droplets associated proteins (LDAP) were found to be the predominant proteins associated with LDs in seed and mesocarp tissues, respectively. We also show that LDs appear to be in close proximity to a number of organelles including the endoplasmic reticulum, mitochondria, peroxisomes, and Golgi apparatus. This comparative study between seed and mesocarp LDs may shed some light on the structure of plant LDs and improve our understanding of their functionality and cellular metabolic networks in oleaginous plant tissues.

PUX10 Is a Lipid Droplet-Localized Scaffold Protein That Interacts with CELL DIVISION CYCLE48 and Is Involved in the Degradation of Lipid Droplet Proteins

“…Therefore, the first goal in this study was to investigate the proteome of LDs to extend the number of known LD-bound proteins. Tobacco pollen tubes were chosen, as LDs of this tissue have not been previously investigated by proteomics, in contrast to other studies that focused on LDs in seeds (Jolivet et al, 2004;Liu et al, 2015), seedlings (Pyc et al, 2017b), mesocarp of avocado (Persea americana) (Horn et al, 2013), and chinese tallow (Triadica sebifera; Zhi et al, 2017). In addition, tobacco pollen tubes can be easily transformed to verify the association of candidate proteins with the LDs (Müller et al, 2017), eliminating the need to switch systems from identification to verification.…”

SEIPIN Isoforms Interact with the Membrane-Tethering Protein VAP27-1 for Lipid Droplet Formation

“…Several plant LD proteomics studies have identified VAPs, clathrins, dynamins, and other vesicle-trafficking-related proteins in purified LD fractions (Brocard et al, 2017;Zhi et al, 2017;Kretzschmar et al, 2018). If recruitment of scission-related proteins by AtVAP27-1 to the ER-LD junction is indeed important for formation of LDs in plants, the loss of AtVAP27-1 might result in production of aberrant, large-sized LDs, due to an inability to terminate the process of LD expansion.…”

“…Both strategies converged on the vesicleassociated membrane protein (VAMP)-associated proteins (VAPs), particularly the Arabidopsis VAP isoform AtVAP27-1. The presence of VAPs in plant LD proteomes (Brocard et al, 2017;Zhi et al, 2017;Kretzschmar et al, 2018) further attracted our attention. Here, we show that the N termini of both AtSEIPIN2 and AtSEIPIN3 interact specifically and directly with AtVAP27-1 in yeast two-hybrid (Y2H) assays and in plant cells using colocalization and bimolecular fluorescence complementation (BiFC) analysis.…”

Comprehensive and quantitative analysis of white and brown adipose tissue by shotgun lipidomics

“…Obtaining detailed lipidomic profiles from patients at various stages of a disease will be crucial for investigating the aetiology of obesity-related pathologies. Samples rich in lipid droplets are another example [40][41][42].…”