title: SLDP: a novel protein related to caleosin is associated with the endosymbiotic Symbiodinium lipid droplets from Euphyllia glabrescens.
abstract: Intracellular lipid droplets (LDs) have been proposed to play a key role in the mutualistic endosymbiosis between reef-building corals and the dinoflagellate endosymbiont Symbiodinium spp. This study investigates and identifies LD proteins in Symbiodinium from Euphyllia glabrescens. Discontinuous Percoll gradient centrifugation was used to separate Symbiodinium cells from E. glabrescens tentacles. Furthermore, staining with a fluorescent probe, Nile red, indicated that lipids accumulated in that freshly isolated Symbiodinium cells and lipid analyses further showed polyunsaturated fatty acids (PUFA) was abundant. The stable LDs were purified from endosymbiotic Symbiodinium cells. The structural integrity of the Symbiodinium LDs was maintained via electronegative repulsion and steric hindrance possibly provided by their surface proteins. Protein extracts from the purified LDs revealed a major protein band with a molecular weight of 20 kDa, which was termed Symbiodinium lipid droplet protein (SLDP). Interestingly, immunological cross-recognition analysis revealed that SLDP was detected strongly by the anti-sesame and anti-cycad caleosin antibodies. It was suggested that the stable Symbiodinium LDs were sheltered by this unique structural protein and was suggested that SLDP might be homologous to caleosin to a certain extent.
authors.affiliation: Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung, 402, Taiwan.
authors.forename: Buntora
authors.initials: B
authors.lastname: Pasaribu
authors.forename: I-Ping
authors.initials: IP
authors.lastname: Lin
authors.forename: Jason T C
authors.initials: JT
authors.lastname: Tzen
authors.forename: Guang-Yuh
authors.initials: GY
authors.lastname: Jauh
authors.forename: Tung-Yung
authors.initials: TY
authors.lastname: Fan
authors.forename: Yu-Min
authors.initials: YM
authors.lastname: Ju
authors.forename: Jing-O
authors.initials: JO
authors.lastname: Cheng
authors.forename: Chii-Shiarng
authors.initials: CS
authors.lastname: Chen
authors.forename: Pei-Luen
authors.initials: PL
authors.lastname: Jiang
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000382:microbiology*; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004141:Dinoflagellida / Q000235:genetics* / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D007091:Image Processing, Computer-Assisted; D066292:Lipid Droplets / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D013559:Symbiosis; D013624:Taiwan
chemical_list: D002135:Calcium-Binding Proteins; D010940:Plant Proteins; C402836:caleosin protein, Sesamum indicum