Microorganism lipid droplets and biofuel development
Microorganism lipid droplets and biofuel development
BMB Reports. 2013. Dec, 46(12): 575-581
Copyright © 2013, Korean Society for Biochemistry and Molecular Biology
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
  • Received : December 02, 2013
  • Published : December 30, 2013
Export by style
Cited by
About the Authors
Yingmei Liu
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
Congyan Zhang
University of Chinese Academy of Sciences, Beijing 100049, China
Xipeng Shen
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
Xuelin Zhang
Capital University of Physical Education and Sports, Beijing 100191, China
Simon Cichello
School of Life Sciences, La Trobe University, Melbourne, Victoria 3086, Australia
Hongbin Guan
Marine College, Shandong University at Weihai, 180 Wenhua Xilu, Weihai, Shandong 264209, China, Hongbin Guan
Pingsheng Liu
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China, Hongbin Guan

Lipid droplet (LD) is a cellular organelle that stores neutral lipids as a source of energy and carbon. However, recent research has emerged that the organelle is involved in lipid synthesis, transportation, and metabolism, as well as mediating cellular protein storage and degradation. With the exception of multi-cellular organisms, some unicellular microorganisms have been observed to contain LDs. The organelle has been isolated and characterized from numerous organisms. Triacylglycerol (TAG) accumulation in LDs can be in excess of 50% of the dry weight in some microorganisms, and a maximum of 87% in some instances. These microorganisms include eukaryotes such as yeast and green algae as well as prokaryotes such as bacteria. Some organisms obtain carbon from CO2 via photosynthesis, while the majority utilizes carbon from various types of biomass. Therefore, high TAG content generated by utilizing waste or cheap biomass, coupled with an efficient conversion rate, present these organisms as bio-tech ‘factories’ to produce biodiesel. This review summarizes LD research in these organisms and provides useful information for further LD biological research and microorganism biodiesel development. [BMB Reports 2013; 46(12): 575-581]
Lipid droplets (LDs) are a spherical cellular structure that consists of a neutral lipid core, a monolayer phospholipid membrane, and numerous proteins (1 - 4) . LDs have been found in almost all organisms, from mammals to bacteria (1 , 5) . LD biology research in mammals has developed rapidly due to the drastic development of human metabolic syndromes, such as obesity, fatty liver, atherosclerosis, and type 2 diabetes. Since perilipin was identified in adipocytes in 1991 (6) , another four LD proteins that are expressed in other tissues have also been uncovered. These LD proteins, including perilipin, adipocyte differentiation related protein (ADRP) (7 , 8) , tail interacting protein (Tip47) (9) , S3-12 (10) , and OXPAT (11) contain a PAT (Perilipin, ADRP and Tip47) domain, thus termed PAT family proteins initially (12) and later the name changed to perilipin family proteins, with a recent simplification as PLIN 1-5 (13) . Unfortunately, PLINs are only expressed in mammals and Drosophila (12) . Recent proteomic analyses of isolated LDs identified several groups of functional proteins, including LD resident proteins, lipid synthetic enzymes, membrane trafficking proteins, signaling proteins, and lipases (5) . Based on current studies, LDs are proposed to be generated on endoplasmic reticulum (ER) and found to migrate onto microtubules (14) , and also are observed to interact with other cellular organelles via Rab proteins (15 - 18) , and fuse each other using SNAREs (19) and Fsp27 (20) . At least three types of neutral lipids, such as triacylglycerol, ether lipids, and cholesterol ester, were identified as major components of LDs using lipidomic analysis (21) . In culmination, these findings lead to a conclusion that LDs are a cellular organelle (15) .
LDs are also observed in plant seeds and some plant cells, and often termed lipid bodies within this field. Plant LDs have also been successfully isolated and analyzed (22 - 25) . Their LD resident proteins were identified, including oleosins (26) and caleosins (27) . Interestingly, both types of plant LD resident proteins do not contain PAT domain that are common with all 5 mammalian PLINs. Further, a neutral lipid insertion sequence plays an important role in the targeting of oleosin to LDs, which is also different with PLINs. Early works also found that oleosins can be recognized by anti-apolipoprotein antibodies (28) . An apolipoprotein motif has recently been found to be common in most LD resident proteins (5) .
Moreover, LDs in microorganisms have also been studied, although in similarity to plants and seed embryos, that they do not contain PLINs either (29) . At least LDs present in three types of microorganisms, such as yeast (30 - 32) , green algae (33 , 34) , and bacteria (35 - 37) , have been well analyzed and characterized. This is primarily due to their importance as useful models to study cellular organelle biology as well as of biofuel development. Many LD-associated proteins have been identified, especially several LD resident proteins, which have been found to be involved in LD dynamic regulation. Among these LD proteins, lipid synthetic enzymes have also drawn attention because of their ability for triacylglycerol (TAG) production.
The accepted consensus is that fossil oil deposits are limited and non-renewable. The extensive use of fossil fuels has lead to climatic and subsequent social problems such as the “greenhouse” effect and the air pollution (38) in addition to potential energy exhaustion. Therefore, it is imperative to develop renewable biomass that can quickly accumulated carbon source such as crops, grass, and microorganisms (39 , 40) . Due to the lower sulphur and nitrogen pollution, the rapid accumulation and the high applicability, biofuel especially biodiesel is becoming more and more popular as a potential replacement for fossil fuel derived diesel (41) .
TAG stored in the LDs of plants and microorganisms can be converted to biodiesel. Using oil crops (i.e. canola) to produce biodiesel not only in some cases competes human food requirement but also has very low efficiency of TAG production when compared with microorganisms. For example, green algae can produce nearly 100 fold more TAG than what the best oil plant, soybean can make (42) . In addition, one type of bacteria, Rhodococcus opacus PD630 is able to store TAG in LDs nearly 87% of its dry weight, making it potentially the ideal microorganism for biodiesel development (43 , 44) . Interestingly, this bacterium can also be used as a model organism to study LD biology since it does not contain any other cellular organelles (45) .
Therefore, it is necessary to review existing researches that have been done on these organisms so far, in particular to review proteins that have been identified by proteomics using isolated LDs from these organisms. The information accumulated will not only facilitate these organisms as LD biology model systems but also promote biofuel development using these organisms.
As a good genetic model organism, yeast has been utilized in biological research field well and many important molecular mechanisms of biological processes have been discovered using the organism. Since nearly all yeasts contain LDs, yeast is a useful organism for LD research and in fact, many studies have been done and some important pathways that govern LD biogenesis and dynamics have been revealed. Yeast is also a good organism to convert biomass to neutral lipids such as TAG in LDs that can be used produce biodiesel.
Using Saccharomyces cerevisiae ( S. cerevisiae ), Dr. Daum’s research group has gained many progresses in LD biology of the organism, especially in the understanding of LD lipids and proteins. LDs had been designated as lipid particles in S. cerevisiae until recently (46) . To study LDs in detail, LDs were isolated from S. cerevisiae (47) . Lipid composition of the isolated LDs was determined, with more than 90% of lipids comprising as TAG and steryl esters (47) . In 1999, the same group isolated LDs again and conducted a proteomic analysis on LD proteins (48) . Among these proteins, lipid synthetic enzymes were identified on LDs for the first time, such as Erg1p, Erg6p, and Erg7p that are involved in ergosterol biosynthesis, and Faa1p and Faa4p that are involved in long-chain fatty acid acyl-CoA synthesis. Moreover, detailed lipidomics and proteomics were carried out recently on isolated LDs from S. cerevisiae (46) . The comparative studies of LDs from cells cultured in glucose and oleate uncovered dynamic changes of LD lipids and proteins. Based on these findings, it is proposed that LDs are a cellular organelle that is not only involved in lipid metabolism but also contributes to lipid synthesis.
In S. cerevisiae , LDs/lipid bodies are found to be in contact with peroxisomes and also a part of peroxisome is often observed in LDs, which may accumulate free fatty acids. It is termed “gnarl”, indicating that this physical contact between LDs and peroxisome facilitates lipolysis within LDs and fatty acid oxidation in peroxisomes (49) . The paper also identifies many other proteins in isolated LDs, further verifying previous finding, suggesting the interaction between LDs and other cellular organelles, such as endoplasmic reticulum (ER) and mitochondria (49) . Moreover, the lipid synthetic enzymes identified by Dr. Daum are also verified by this study.
In an applied field, S. cerevisiae has also been utilized as a biological model to study metabolic disorders. For example, a lipodystrophy protein seipin was found to alter LD morphology by two research groups, Drs. Goodman and Yang, respectively (32 , 50) . By screening S. cerevisiae mutants, 59 genes were revealed to be associated with LD morphological alternation, with seipin being one of those identified (50) . Another mutant screening of S. cerevisiae identified that the dysfunction of seipin, which regulates LD morphology and often results in super-sized LD formation (31) . Although S. cerevisiae is a good model to study LD biology and related metabolic disorders, it may not be a suitable organism to use for biodiesel production due to the high steryl esters (SE) content and low neutral lipid storage capacity. So, genetic engineering optimization of S. cerevisiae is required to utilize it for biodiesel development.
Other types of yeast species have also been studied and manipulated for neutral lipid storage and biodiesel development, i.e. Yarrowia lipolytica ( Y. lipolytica ) (51) . Y. lipolytica is considered as an oleaginous yeast, and has a pronounced ability to digest hydrophobic substances, and also convert the metabolites to lipids, and further store the lipids in LDs. Further, LDs/lipid particles of Y. lipolytica were isolated and their proteins and lipids analyzed (52) . In comparison with S. cerevisiae , Y. lipolytica yeast contains a much higher ratio of TAG/SE, such as 1.2 in S. cerevisiae (47) as opposed to 10.8 in Y. lipolytica (52) , suggesting that Y. lipolytica is suitable for biodiesel production. Moreover, another yeast, Pichia pastoris ( P. pastoris ) has also been found to have higher ratio of TAG/SE as recently by analyzing isolated LDs using lipidomics (53) . The proteomic study of isolated LDs determined that LD-associated proteins of P. pastoris are less than the LD proteins of S. cerevisiae . Together, these finding suggests that yeasts Y. lipolytica and P. pastoris are better utilized than S. cerevisiae for TAG production and TAG accumulation, therefore more suitable for biodiesel development.
Lastly, another oleaginous yeast Rhodosporidium toruloides ( R. toruloides ) has also been established by Dr. Zhao’s group recently. The whole genome and transcriptome of the organism are sequenced and characterized (54) . Furthermore, the genes involved in lipid synthesis and metabolism are identified, providing a useful database for further developing the organism for biodiesel production.
The growing crisis of world energy and food shortages initiates the use of green algae to produce vegetable oil, essential fatty acids, as well as biofuel. As a photosynthetic microorganism, algae convert CO 2 and H 2 O to TAG using sunlight. Usage of CO 2 from the atmosphere reduces greenhouse gas accumulation and slows down global warming. As opposed with agricultural oil crops, algaculture can produce oil 10 to 100 fold more per unit of land (42) . Using urban building design such as skyscrapers for algaculture, this yield can be multiplied as a function of level number and utilize the vertical aspect of the building which would be perpendicular to the sun’s angle throughout the day and thus energy needed for growth and biodiesel production. In addition, genetic engineering algaculture can produce high value vegetable oil such as omega-3 oil and food supplemental oil such as arachidonic acid containing TAG. Furthermore, genetic engineering can modify algae to synthesize many other types of biofuels. Therefore, alga LD biology is rapidly gained more attention.
Similar as plants, LDs are not only found in the cytoplasm of green algae but also in chloroplast (55) . Based on lipid analysis of isolated chloroplasts from Chlamydomonas reinhardtii ( C. reinhardtii ), it appears to be that TAG synthesis is located in chloroplasts, with LDs being distributed to both cytosol and chloroplasts (56) . This is in agreement with the hypothesis of LD biogenesis in mammals in which LDs are proposed to be formed on surface of endoplasmic reticulum (2) .
Proteomic studies have been performed using isolated LDs from several alga species and alga LD protein databases generated, which promote the development of utilization of green algae in lipid storage for biodiesel. In common with LD proteomes, alga LD-associated proteins contain lipid synthetic enzymes and membrane trafficking proteins. The difference between mammalian LDs and green alga LDs is the perilipin family proteins, with alga LDs lacking of these proteins. Therefore, the important discovery of alga LD proteomic studies is the identification of a 28 kDa alga LD protein that has been named major lipid droplet protein (MLDP) in C. reinhardtii (57) . Reduction of MLDP expression has been found to increase the size of LDs without changing TAG content, suggesting its function to regulate LD morphology (57) . MLDP has also been found in other green algae by sharing a conserved motif with 21 identical amino acids (58) . No homology of the MLDP protein sequence has been observed in other organisms, which indicates that MLDP is a unique protein in the green algal lineage of photosynthetic organisms (57 , 58) . These characteristics of MLDP make it an alga LD resident/structural protein, analogous to the perilipin 1 and ADRP for LDs in mammals.
In extreme conditions, for instance, nitrogen deprivation or highlight exposure, the growth of many green algae can be limited, and in addition neutral lipids will be accumulated in LDs. Using this treatment, several studies of LD isolation from C. reinhardtii have been conducted recently (33 , 57 , 59) . Wang et al . obtained relative pure LDs that are absence of chloroplast specific neutral lipids (galactolipids) (60) . They analyzed the lipid compositions of the LDs but did not examine the proteome. Since perilipin family proteins are only expressed in mammals and Drosophila, to identify alga LD resident proteins, Moellering and Benning isolated LDs from C. reinhardtii and conducted the proteomic studies (57) . 259 proteins were found to be associated with the isolated LDs, including proteins involved in lipid metabolism, vesicular trafficking, translation, mitochondrial activity, and photosynthesis (57) . Many of these proteins have been identified previously in the isolated LDs of other organisms, particularly in mammals, such as acyl-CoA synthetases, acyl-CoA transferases, Rab proteins, and ARF-related GTPase. A primary protein band about 28 kDa was identified to be MLDP. James et al . then isolated LDs from C. reinhardtii and conducted another proteomic analysis (61) . 28 kDa MLDP is also the most abundant band in LDs proteins. Nguyen et al . further verified the proteomic study of LDs that was carried out by Moellering and Benning, and analyzed LD proteins in detail for lipid metabolism (33) .
More proteomic studies of isolated LDs from green algae have been conducted recently, including LDs from Dunaliella salina ( D. salina ) and Haematococcus pluvialis ( H. pluvialis ). The protein profile of LDs isolated from H. pluvialis significantly differs when compared with other LD proteins. A protein that shares partial homology with C. reinhardtii MLDP is observed in isolated LDs with a molecular weight 33 kDa (34) . The protein is then termed the Haematococcus Oil Globule Protein (HOGP) (34) . In isolated LDs from D. salina , MLDP is identified as the most abundant LD protein with molecular weight of approximately 28 kDa (58) . Based on a sequence alignment, MLDP was found in six species of green algae including C. reinhardtii , D. salina , D. bardawil , D. parva , H. pluvialis , Volvox carteri ( V. carteri ) (58) . This analysis also identified a 21 amino acids conserved domain in all six species and a 4-proline signature near the C-terminus of the protein (58) . In addition, expression of MLDP is positively associated with TAG accumulation in nitrogen deficient culture condition (58) . Moreover, by reducing MLDP expression using RNAi, the LD size is observed to be increased without altering TAG content and metabolism rate (58) . MLDP is also localized on alga LDs by immunogold labeling (59) .
The accumulated data from proteomic and lipidomic studies of isolated LDs have facilitated LD biology of green algae, which stimulates the development of green algae to become a better model organism to photosynthesize TAG for biodiesel production.
Except almost all eukaryotic organisms contain LDs, with some prokaryotic cells have also been observed to accumulate large amount of lipids (62) . The LD studies in bacteria have recently been motivated by the search to understand the factors that govern infective bacterial action in humans as well as by developing prokaryotic organisms to produce biodiesel more efficiently. The actual size of bacterial LDs is relative small, which presents difficulty in their isolation and also analysis. Several studies of isolated LDs from bacteria have been conducted using an infective bacterium named Mycobacterium bovis bacillus Calmette-Guérin ( M. bovis BCG) (63) and also in two oleaginous bacteria, Rhodococcus opacus PD630 (PD630) (45 , 64) and Rhodococcus sp . RHA1 (RHA1) (37) .
LDs isolated from the infective bacterium M. bovis BCG were analyzed by Dr. Wenk’s group (63) . The LD-associated protein composition significantly differs with the total cell lysate, encouraging the group further to subject these unique protein bands to MS analysis. Their discoveries are similar to Yeast in terms of identification of proteins on the isolated LDs that are involved in lipid synthetic and hydrolysis (63) .
The genome of RHA1 was obtained in 2006, which allows the researchers to study this organism in many aspects (65) . For biodiesel development, Dr. Liu’s research group isolated LDs from RHA1 and also conducted comprehensive proteomic analyses (37) . They identified a LD-associated protein and determined its LD targeting sequence. Deletion of this gene in RHA1 causes larger LD formation without increasing cellular TAG, suggesting that it functions to protect LD fusion (37) . They designated the protein as the microorganism lipid droplet small (MLDS) in order to distinguish it from MLDP in green algae (37) .
Strikingly, PD630 is able to accumulate 87% TAG of the bacterial dry weight (43 , 44) , which proposes it as an ideal organism for the study of the regulation of lipid biosynthesis and storage of the organism. Dr. Steinbüchel’s research group has investigated this bacterium since 1995 and generated many useful data that are the basis of recent studies (44) . His laboratory isolated lipid inclusions from both PD630 and Rhodococcus ruber for the first time and identified a series of granule-associated (GA) proteins (64) . The genes that may govern lipid metabolism in PD630 were then analyzed and the genome was partially sequenced (66) . In order to obtain a complete genomic regulation roadmap that controls lipid metabolism as well as storage in PD630, Dr. Liu’s group has conducted a whole genome sequencing, comparative transcriptomes, and LD isolation and proteomic study since 2009, and eventually published them this year (45) . Together, these works established not only a model organism for LD biology but also developed a good microorganism for applied biodiesel production.
We herein summarized three microorganisms that have been well established in LD biology including isolation of their LDs as well as the proteomic studies of the isolated LDs ( Table 1 ). Commonality of these findings is that the lipid synthetic pathway is conserved throughout these organisms. The studies on LDs from the bacteria RHA1 and PD630 develop a new path for micro-diesel production using waste biomass.
Lipid droplets of microorganisms
PPT Slide
Lager Image
Lipid droplets of microorganisms
This work was supported by grant 2011CBA00906 and grant 2011CBA00907 from the Ministry of Science and Technology of China and grant 31100854 from National Natural Science Foundation of China.
Murphy D. J. (2001) The biogenesis and functions of lipid bodies in animals, plants and microorganisms. Prog. Lipid. Res. 40 325 - 438    DOI : 10.1016/S0163-7827(01)00013-3
Martin S. , Parton R. G. (2006) Lipid droplets: a unified view of a dynamic organelle. Nat. Rev. Mol. Cell. Biol. 7 373 - 378    DOI : 10.1038/nrm1912
Thiam A. R. , Farese R. V. Jr. , Walther T. C. (2013) The biophysics and cell biology of lipid droplets. Nat. Rev. Mol. Cell. Biol. 14 775 - 786    DOI : 10.1038/nrm3699
Farese R. V. Jr. , Walther T. C. (2009) Lipid droplets finally get a little R-E-S-P-E-C-T. Cell 139 855 - 860    DOI : 10.1016/j.cell.2009.11.005
Yang L. , Ding Y. , Chen Y. , Zhang S. , Huo C. , Wang Y. , Yu J. , Zhang P. , Na H. , Zhang H. , Ma Y. , Liu P. (2012) The proteomics of lipid droplets: structure, dynamics, and functions of the organelle conserved from bacteria to humans. J. Lipid. Res. 53 1245 - 1253    DOI : 10.1194/jlr.R024117
Greenberg A. S. , Egan J. J. , Wek S. A. , Garty N. B. , Blanchette-Mackie E. J. , Londos C. (1991) Perilipin, a major hormonally regulated adipocyte-specific phosphoprotein associated with the periphery of lipid storage droplets. J. Biol. Chem. 266 11341 - 11346
Jiang H. P. , Serrero G. (1992) Isolation and characterization of a full-length cDNA coding for an adipose differentiation-related protein. Proc. Natl. Acad. Sci. U. S. A. 89 7856 - 7860    DOI : 10.1073/pnas.89.17.7856
Brasaemle D. L. , Barber T. , Wolins N. E. , Serrero G. , Blanchette-Mackie E. J. , Londos C. (1997) Adipose differentiation-related protein is an ubiquitously expressed lipid storage droplet-associated protein. J. Lipid. Res. 38 2249 - 2263
Wolins N. E. , Rubin B. , Brasaemle D. L. (2001) TIP47 associates with lipid droplets. J. Biol. Chem. 276 5101 - 5108    DOI : 10.1074/jbc.M006775200
Wolins N. E. , Skinner J. R. , Schoenfish M. J. , Tzekov A. , Bensch K. G. , Bickel P. E. (2003) Adipocyte protein S3-12 coats nascent lipid droplets. J. Biol. Chem. 278 37713 - 37721    DOI : 10.1074/jbc.M304025200
Wolins N. E. , Quaynor B. K. , Skinner J. R. , Tzekov A. , Croce M. A. , Gropler M. C. , Varma V. , Yao-Borengasser A. , Rasouli N. , Kern P. A. , Finck B. N. , Bickel P. E. (2006) OXPAT/PAT-1 is a PPAR-induced lipid droplet protein that promotes fatty acid utilization. Diabetes 55 3418 - 3428    DOI : 10.2337/db06-0399
Miura S. , Gan J. W. , Brzostowski J. , Parisi M. J. , Schultz C. J. , Londos C. , Oliver B. , Kimmel A. R. (2002) Functional conservation for lipid storage droplet association among Perilipin, ADRP, and TIP47 (PAT)-related proteins in mammals, Drosophila, and Dictyostelium. J. Biol. Chem. 277 32253 - 32257    DOI : 10.1074/jbc.M204410200
Kimmel A. R. , Brasaemle D. L. , McAndrews-Hill M. , Sztalryd C. , Londos C. (2010) Adoption of PERILIPIN as a unifying nomenclature for the mammalian PAT-family of intracellular lipid storage droplet proteins. J. Lipid. Res. 51 468 - 471    DOI : 10.1194/jlr.R000034
Welte M. A. , Gross S. P. , Postner M. , Block S. M. , Wieschaus E. F. (1998) Developmental regulation of vesicle transport in Drosophila embryos: forces and kinetics. Cell 92 547 - 557    DOI : 10.1016/S0092-8674(00)80947-2
Liu P. , Ying Y. , Zhao Y. , Mundy D. I. , Zhu M. , Anderson R. G. (2004) Chinese hamster ovary K2 cell lipid droplets appear to be metabolic organelles involved in membrane traffic. J. Biol. Chem. 279 3787 - 3792    DOI : 10.1074/jbc.M311945200
Liu P. , Bartz R. , Zehmer J. K. , Ying Y. S. , Zhu M. , Serrero G. , Anderson R. G. (2007) Rab-regulated interaction of early endosomes with lipid droplets. Bba-Mol. Cell. Res. 1773 784 - 793    DOI : 10.1016/j.bbamcr.2007.02.004
Martin S. , Driessen K. , Nixon S. J. , Zerial M. , Parton R. G. (2005) Regulated localization of Rab18 to lipid droplets: effects of lipolytic stimulation and inhibition of lipid droplet catabolism. J. Biol. Chem. 280 42325 - 42335    DOI : 10.1074/jbc.M506651200
Ozeki S. , Cheng J. , Tauchi-Sato K. , Hatano N. , Taniguchi H. , Fujimoto T. (2005) Rab18 localizes to lipid droplets and induces their close apposition to the endoplasmic reticulum-derived membrane. J. Cell. Sci. 118 2601 - 2611    DOI : 10.1242/jcs.02401
Boström P. , Andersson L. , Rutberg M. , Perman J. , Lidberg U. , Johansson B. R. , Fernandez-Rodriguez J. , Ericson J. , Nilsson T. , Borén J. , Olofsson S. O. (2007) SNARE proteins mediate fusion between cytosolic lipid droplets and are implicated in insulin sensitivity. Nat. Cell. Biol. 9 1286 - 1293    DOI : 10.1038/ncb1648
Gong J. , Sun Z. , Wu L. , Xu W. , Schieber N. , Xu D. , Shui G. , Yang H. , Parton R. G. , Li P. (2011) Fsp27 promotes lipid droplet growth by lipid exchange and transfer at lipid droplet contact sites. J. Cell. Biol. 195 953 - 963    DOI : 10.1083/jcb.201104142
Bartz R. , Li W. H. , Venables B. , Zehmer J. K. , Roth M. R. , Welti R. , Anderson R. G. , Liu P. , Chapman K. D. (2007) Lipidomics reveals that adiposomes store ether lipids and mediate phospholipid traffic. J. Lipid. Res. 48 837 - 847    DOI : 10.1194/jlr.M600413-JLR200
Yatsu L. Y. , Jacks T. J. , Hensarling T. P. (1971) Isolation of spherosomes (oleosomes) from onion, cabbage, and cottonseed tissues. Plant. Physiol. 48 675 - 682    DOI : 10.1104/pp.48.6.675
Jacks T. J. , Yatsu L. Y. , Altschul A. M. (1967) Isolation and characterization of peanut spherosomes. Plant. Physiol. 42 585 - 597    DOI : 10.1104/pp.42.4.585
Jolivet P. , Boulard C. , Bellamy A. , Larre C. , Barre M. , Rogniaux H. , d'Andrea S. , Chardot T. , Nesi N. (2009) Protein composition of oil bodies from mature Brassica napus seeds. Proteomics 9 3268 - 3284    DOI : 10.1002/pmic.200800449
Katavic V. , Agrawal G. K. , Hajduch M. , Harris S. L. , Thelen J. J. (2006) Protein and lipid composition analysis of oil bodies from two Brassica napus cultivars. Proteomics 6 4586 - 4598    DOI : 10.1002/pmic.200600020
Qu R. D. , Huang A. H. (1990) Oleosin KD 18 on the surface of oil bodies in maize. Genomic and cDNA sequences and the deduced protein structure. J. Biol. Chem. 265 2238 - 2243
Chen J. C. , Tsai C. C. , Tzen J. T. (1999) Cloning and secondary structure analysis of caleosin, a unique calcium-binding protein in oil bodies of plant seeds. Plant. Cell. Physiol. 40 1079 - 1086    DOI : 10.1093/oxfordjournals.pcp.a029490
Au D. M. , Kang A. S. , Murphy D. J. (1989) An immunologically related family of apolipoproteins associated with triacylglycerol storage in the Cruciferae. Arch. Biochem. Biophys. 273 516 - 526    DOI : 10.1016/0003-9861(89)90511-0
Murphy D. J. (2012) The dynamic roles of intracellular lipid droplets: from archaea to mammals. Protoplasma 249 541 - 585    DOI : 10.1007/s00709-011-0329-7
Binns D. , Januszewski T. , Chen Y. , Hill J. , Markin V. S. , Zhao Y. , Gilpin C. , Chapman K. D. , Anderson R. G. , Goodman J. M. (2006) An intimate collaboration between peroxisomes and lipid bodies. J. Cell. Biol. 173 719 - 731    DOI : 10.1083/jcb.200511125
Fei W. , Shui G. , Gaeta B. , Du X. , Kuerschner L. , Li P. , Brown A. J. , Wenk M. R. , Parton R. G. , Yang H. (2008) Fld1p, a functional homologue of human seipin, regulates the size of lipid droplets in yeast. J. Cell. Biol. 180 473 - 482    DOI : 10.1083/jcb.200711136
Grillitsch K. , Connerth M. , Kofeler H. , Arrey T. N. , Rietschel B. , Wagner B. , Karas M. , Daum G. (2011) Lipid particles/droplets of the yeast Saccharomyces cerevisiae revisited: lipidome meets proteome. Biochim. Biophys. Acta. 12 26 -
Nguyen H. M. , Baudet M. , Cuiné S. , Adriano J. M. , Barthe D. , Billon E. , Bruley C. , Beisson F. , Peltier G. , Ferro M. , Li-Beisson Y. (2011) Proteomic profiling of oil bodies isolated from the unicellular green microalga Chlamydomonas reinhardtii: with focus on proteins involved in lipid metabolism. Proteomics 11 4266 - 4273    DOI : 10.1002/pmic.201100114
Peled E. , Leu S. , Zarka A. , Weiss M. , Pick U. , Khozin-Goldberg I. , Boussiba S. (2011) Isolation of a novel oil globule protein from the green alga Haematococcus pluvialis (Chlorophyceae). Lipids 46 851 - 861    DOI : 10.1007/s11745-011-3579-4
Low K. L. , Shui G. , Natter K. , Yeo W. K. , Kohlwein S. D. , Dick T. , Rao S. P. , Wenk M. R. (2010) Lipid droplet-associated proteins are involved in the biosynthesis and hydrolysis of triacylglycerol in Mycobacterium bovis bacillus Calmette-Guerin. J. Biol. Chem. 285 21662 - 21670    DOI : 10.1074/jbc.M110.135731
Kalscheuer R. , Waltermann M. , Alvarez M. , Steinbuchel A. (2001) Preparative isolation of lipid inclusions from Rhodococcus opacus and Rhodococcus ruber and identification of granule-associated proteins. Arch. Microbiol. 177 20 - 28    DOI : 10.1007/s00203-001-0355-5
Ding Y. , Yang L. , Zhang S. , Wang Y. , Du Y. , Pu J. , Peng G. , Chen Y. , Zhang H. , Yu J. , Hang H. , Wu P. , Yang F. , Yang H. , Steinbüchel A. , Liu P. (2012) Identification of the major functional proteins of prokaryotic lipid droplets. J. Lipid. Res. 53 399 - 411    DOI : 10.1194/jlr.M021899
Miao X. , Wu Q. (2004) High yield bio-oil production from fast pyrolysis by metabolic controlling of Chlorella protothecoides. J. Biotechnol. 110 85 - 93    DOI : 10.1016/j.jbiotec.2004.01.013
McLaughlin S. B. , Adams Kszos L. (2005) Development of switchgrass (Panicum virgatum) as a bioenergy feedstock in the United States. Biomass and Bioenergy 28 515 - 535    DOI : 10.1016/j.biombioe.2004.05.006
McKendry P. (2002) Energy production from biomass (part 1): overview of biomass. Bioresour. Technol. 83 37 - 46    DOI : 10.1016/S0960-8524(01)00118-3
Fargione J. , Hill J. , Tilman D. , Polasky S. , Hawthorne P. (2008) Land Clearing and the Biofuel Carbon Debt. Science 319 1235 - 1238    DOI : 10.1126/science.1152747
Greenwell H. C. , Laurens L. M. , Shields R. J. , Lovitt R. W. , Flynn K. J. (2010) Placing microalgae on the biofuels priority list: a review of the technological challenges. J. R. Soc. Interface 7 703 - 726    DOI : 10.1098/rsif.2009.0322
Alvarez H. M. , Steinbuchel A. (2002) Triacylglycerols in prokaryotic microorganisms. Appl. Microbiol. Biotechnol. 60 367 - 376    DOI : 10.1007/s00253-002-1135-0
Alvarez H. M. , Mayer F. , Fabritius D. , Steinbuchel A. (1996) Formation of intracytoplasmic lipid inclusions by Rhodococcus opacus strain PD630. Arch. Microbiol. 165 377 - 386    DOI : 10.1007/s002030050341
Chen Y. , Ding Y. , Yang L. , Yu J. , Liu G. , Wang X. , Zhang S. , Yu D. , Song L. , Zhang H. , Zhang C. , Huo L. , Huo C. , Wang Y. , Du Y. , Zhang H. , Zhang P. , Na H. , Xu S. , Zhu Y. , Xie Z. , He T. , Zhang Y. , Wang G. , Fan Z. , Yang F. , Liu H. , Wang X. , Zhang X. , Zhang M. Q. , Li Y. , Steinbüchel A. , Fujimoto T. , Cichello S. , Yu J. , Liu P. (2013) Integrated omics study delineates the dynamics of lipid droplets in Rhodococcus opacus PD630. Nucleic Acids Res. [Epub ahead of print] 22
Grillitsch K. , Connerth M. , Kofeler H. , Arrey T. N. , Rietschel B. , Wagner B. , Karas M. , Daum G. (2011) Lipid particles/droplets of the yeast Saccharomyces cerevisiae revisited: lipidome meets proteome. Biochim. Biophys. Acta. 1811 1165 - 1176    DOI : 10.1016/j.bbalip.2011.07.015
Leber R. , Zinser E. , Zellnig G. , Paltauf F. , Daum G. (1994) Characterization of lipid particles of the yeast, Saccharomyces cerevisiae. Yeast 10 1421 - 1428    DOI : 10.1002/yea.320101105
Athenstaedt K. , Zweytick D. , Jandrositz A. , Kohlwein S. D. , Daum G. (1999) Identification and characterization of major lipid particle proteins of the yeast Saccharomyces cerevisiae. J. Bacteriol. 181 6441 - 6448
Binns D. , Januszewski T. , Chen Y. , Hill J. , Markin V. S. , Zhao Y. , Gilpin C. , Chapman K. D. , Anderson R. G. , Goodman J. M. (2006) An intimate collaboration between peroxisomes and lipid bodies. J. Cell. Biol. 173 719 - 731    DOI : 10.1083/jcb.200511125
Szymanski K. M. , Binns D. , Bartz R. , Grishin N. V. , Li W. P. , Agarwal A. K. , Garg A. , Anderson R. G. , Goodman J. M. (2007) The lipodystrophy protein seipin is found at endoplasmic reticulum lipid droplet junctions and is important for droplet morphology. Proc. Natl. Acad. Sci. U. S. A. 104 20890 - 20895    DOI : 10.1073/pnas.0704154104
Beopoulos A. , Cescut J. , Haddouche R. , Uribelarrea J. L. , Molina-Jouve C. , Nicaud J. M. (2009) Yarrowia lipolytica as a model for bio-oil production. Prog. Lipid Res. 48 375 - 387    DOI : 10.1016/j.plipres.2009.08.005
Athenstaedt K. , Jolivet P. , Boulard C. , Zivy M. , Negroni L. , Nicaud J. M. , Chardot T. (2006) Lipid particle composition of the yeast Yarrowia lipolytica depends on the carbon source. Proteomics. 6 1450 - 1459    DOI : 10.1002/pmic.200500339
Ivashov V. A. , Grillitsch K. , Koefeler H. , Leitner E. , Baeumlisberger D. , Karas M. , Daum G. (2013) Lipidome and proteome of lipid droplets from the methylotrophic yeast Pichia pastoris. Biochim. Biophys. Acta. 1831 282 - 290    DOI : 10.1016/j.bbalip.2012.09.017
Liu H. , Zhao X. , Wang F. , Li Y. , Jiang X. , Ye M. , Zhao Z. K. , Zou H. (2009) Comparative proteomic analysis of Rhodosporidium toruloides during lipid accumulation. Yeast. 26 553 - 566    DOI : 10.1002/yea.1706
Ytterberg A. J. , Peltier J. B. , van Wijk K. J. (2006) Protein profiling of plastoglobules in chloroplasts and chromoplasts. A surprising site for differential accumulation of metabolic enzymes. Plant. Physiol. 140 984 - 997    DOI : 10.1104/pp.105.076083
Ramanan R. , Kim B.-H. , Cho D.-H. , Ko S.-R. , Oh H.-M. , Kim H.-S. (2013) Lipid droplet synthesis is limited by acetate availability in starchless mutant of Chlamydomonas reinhardtii. FEBS Lett. 587 370 - 377    DOI : 10.1016/j.febslet.2012.12.020
Moellering E. R. , Benning C. (2010) RNA interference silencing of a major lipid droplet protein affects lipid droplet size in Chlamydomonas reinhardtii. Eukaryot. Cell 9 97 - 106    DOI : 10.1128/EC.00203-09
Davidi L. , Katz A. , Pick U. (2012) Characterization of major lipid droplet proteins from Dunaliella. Planta 236 19 - 33    DOI : 10.1007/s00425-011-1585-7
Huang N. L. , Huang M. D. , Chen T. L. , Huang A. H. (2013) Oleosin of subcellular lipid droplets evolved in green algae. Plant. Physiol. 161 1862 - 1874    DOI : 10.1104/pp.112.212514
Wang Z. T. , Ullrich N. , Joo S. , Waffenschmidt S. , Goodenough U. (2009) Algal lipid bodies: stress induction, purification, and biochemical characterization in wild-type and starchless Chlamydomonas reinhardtii. Eukaryot. Cell 8 1856 - 1868    DOI : 10.1128/EC.00272-09
James G. O. , Hocart C. H. , Hillier W. , Chen H. , Kordbacheh F. , Price G. D. , Djordjevic M. A. (2011) Fatty acid profiling of Chlamydomonas reinhardtii under nitrogen deprivation. Bioresour. Technol. 102 3343 - 3351    DOI : 10.1016/j.biortech.2010.11.051
Waltermann M. , Steinbuchel A. (2005) Neutral lipid bodies in prokaryotes: recent insights into structure, formation, and relationship to eukaryotic lipid depots. J. Bacteriol. 187 3607 - 3619    DOI : 10.1128/JB.187.11.3607-3619.2005
Low K. L. , Shui G. , Natter K. , Yeo W. K. , Kohlwein S. D. , Dick T. , Rao S. P. , Wenk M. R. (2010) Lipid droplet-associated proteins are involved in the biosynthesis and hydrolysis of triacylglycerol in Mycobacterium bovis bacillus Calmette-Guerin. J. Biol. Chem. 285 21662 - 21670    DOI : 10.1074/jbc.M110.135731
Kalscheuer R. , Waltermann M. , Alvarez M. , Steinbuchel A. (2001) Preparative isolation of lipid inclusions from Rhodococcus opacus and Rhodococcus ruber and identification of granule-associated proteins. Arch. Microbiol. 177 20 - 28    DOI : 10.1007/s00203-001-0355-5
McLeod M. P. , Warren R. L. , Hsiao W. W. , Araki N. , Myhre M. , Fernandes C. , Miyazawa D. , Wong W. , Lillquist A. L. , Wang D. , Dosanjh M. , Hara H. , Petrescu A. , Morin R. D. , Yang G. , Stott J. M. , Schein J. E. , Shin H. , Smailus D. , Siddiqui A. S. , Marra M. A. , Jones S. J. , Holt R. , Brinkman F. S. , Miyauchi K. , Fukuda M. , Davies J. E. , Mohn W. W. , Eltis L. D. (2006) The complete genome of Rhodococcus sp. RHA1 provides insights into a catabolic powerhouse. Proc. Natl. Acad. Sci. U. S. A. 103 15582 - 15587    DOI : 10.1073/pnas.0607048103
Holder J. W. , Ulrich J. C. , DeBono A. C. , Godfrey P. A. , Desjardins C. A. , Zucker J. , Zeng Q. , Leach A. L. , Ghiviriga I. , Dancel C. , Abeel T. , Gevers D. , Kodira C. D. , Desany B. , Affourtit J. P. , Birren B. W. , Sinskey A. J. (2011) Comparative and functional genomics of Rhodococcus opacus PD630 for biofuels development. PLoS Genet. 7 8 -    DOI : 10.1371/journal.pgen.1002219
Hoiczyk E. , Ring M. W. , McHugh C. A. , Schwar G. , Bode E. , Krug D. , Altmeyer M. O. , Lu J. Z. , Bode H. B. (2009) Lipid body formation plays a central role in cell fate determination during developmental differentiation of Myxococcus xanthus. Mol. Microbiol. 74 497 - 517    DOI : 10.1111/j.1365-2958.2009.06879.x
Nojima D. , Yoshino T. , Maeda Y. , Tanaka M. , Nemoto M. , Tanaka T. (2013) Proteomics analysis of oil body-associated proteins in the oleaginous diatom. J. Proteome. Res. 12 5293 - 5301    DOI : 10.1021/pr4004085
Vieler A. , Brubaker S. B. , Vick B. , Benning C. (2012) A lipid droplet protein of Nannochloropsis with functions partially analogous to plant oleosins. Plant. physiol. 158 1562 - 1569    DOI : 10.1104/pp.111.193029
Guarnieri M. T. , Nag A. , Smolinski S. L. , Darzins A. , Seibert M. , Pienkos P. T. (2011) Examination of triacylglycerol biosynthetic pathways via de novo transcriptomic and proteomic analyses in an unsequenced microalga. PloS One. 6 e25851 -    DOI : 10.1371/journal.pone.0025851
Guarnieri M. T. , Nag A. , Yang S. , Pienkos P. T. (2013) Proteomic analysis of Chlorella vulgaris: Potential targets for enhanced lipid accumulation. J. Proteomics. 93 245 - 253    DOI : 10.1016/j.jprot.2013.05.025
Fei W. , Zhong L. , Ta M. T. , Shui G. , Wenk M. R. , Yang H. (2011) The size and phospholipid composition of lipid droplets can influence their proteome. Biochem. Biophys. Res. Commun. 415 455 - 462    DOI : 10.1016/j.bbrc.2011.10.091
Leber R. , Landl K. , Zinser E. , Ahorn H. , Spok A. , Kohlwein S. D. , Turnowsky F. , Daum G. (1998) Dual localization of squalene epoxidase, Erg1p, in yeast reflects a relationship between the endoplasmic reticulum and lipid particles. Mol. Biol. Cell. 9 375 - 386    DOI : 10.1091/mbc.9.2.375
Natter K. , Leitner P. , Faschinger A. , Wolinski H. , McCraith S. , Fields S. , Kohlwein S. D. (2005) The spatial organization of lipid synthesis in the yeast Saccharomyces cerevisiae derived from large scale green fluorescent protein tagging and high resolution microscopy. Mol. Cell. Proteomics. 4 662 - 672    DOI : 10.1074/mcp.M400123-MCP200
Noothalapati Venkata H. N. , Shigeto S. (2012) Stable isotope-labeled Raman imaging reveals dynamic proteome localization to lipid droplets in single fission yeast cells. Chem. Biol. 19 1373 - 1380    DOI : 10.1016/j.chembiol.2012.08.020