Among organelles, lipid droplets (LDs) uniquely constitute a hydrophobic phase in the aqueous environment of the cytosol. Their hydrophobic core of neutral lipids stores metabolic energy and membrane components, making LDs hubs for lipid metabolism. In addition, LDs are implicated in a number of other cellular functions, ranging from protein storage and degradation to viral replication. These processes are functionally linked to many physiological and pathological conditions, including obesity and related metabolic diseases. Despite their important functions and nearly ubiquitous presence in cells, many aspects of LD biology are unknown. In the past few years, the pace of LD investigation has increased, providing new insights. Here, we review the current knowledge of LD cell biology and its translation to physiology.

Lipid Droplets and Cellular Lipid Metabolism

Acyl lipids in Arabidopsis and all other plants have a myriad of diverse functions. These include providing the core diffusion barrier of the membranes that separates cells and subcellular organelles. This function alone involves more than 10 membrane lipid classes, including the phospholipids, galactolipids, and sphingolipids, and within each class the variations in acyl chain composition expand the number of structures to several hundred possible molecular species. Acyl lipids in the form of triacylglycerol account for 35% of the weight of Arabidopsis seeds and represent their major form of carbon and energy storage. A layer of cutin and cuticular waxes that restricts the loss of water and provides protection from invasions by pathogens and other stresses covers the entire aerial surface of Arabidopsis. Similar functions are provided by suberin and its associated waxes that are localized in roots, seed coats, and abscission zones and are produced in response to wounding. This chapter focuses on the metabolic pathways that are associated with the biosynthesis and degradation of the acyl lipids mentioned above. These pathways, enzymes, and genes are also presented in detail in an associated website (ARALIP: http://aralip.plantbiology.msu.edu/). Protocols and methods used for analysis of Arabidopsis lipids are provided. Finally, a detailed summary of the composition of Arabidopsis lipids is provided in three figures and 15 tables.

/pdf/acyl-lipid-metabolism-2156uh7qdu.pdf

Acyl-Lipid Metabolism

https://digital.csic.es/bitstream/10261/170827/4/ProgLipResPostprint.pdf

A global perspective on carotenoids: Metabolism, biotechnology, and benefits for nutrition and health

https://www.cell.com/trends/plant-science/pdf/S1360-1385(09)00252-0.pdf

Plant-made vaccine antigens and biopharmaceuticals.

transformation, co-transformation, linked transgenes, marker gene excision, metabolic engineering, multigene manipulation, polyproteins, pyramiding, retransformation, stacking.

Gene stacking in transgenic plants--the challenge for 21st century plant biotechnology.

The ontogeny of seed structure and the accumulation of seed storage substances is the result of a determinant genetic program. Using RNA interference, the synthesis of soybean (Glycine max) glycinin and conglycinin storage proteins has been suppressed. The storage protein knockdown (SP−) seeds are overtly identical to the wild type, maturing to similar size and weight, and in developmental ontogeny. The SP− seeds rebalance the proteome, maintaining wild-type levels of protein and storage triglycerides. The SP− soybeans were evaluated with systems biology techniques of proteomics, metabolomics, and transcriptomics using both microarray and next-generation sequencing transcript sequencing (RNA-Seq). Proteomic analysis shows that rebalancing of protein content largely results from the selective increase in the accumulation of only a few proteins. The rebalancing of protein composition occurs with small alterations to the seed’s transcriptome and metabolome. The selectivity of the rebalancing was further tested by introgressing into the SP− line a green fluorescent protein (GFP) glycinin allele mimic and quantifying the resulting accumulation of GFP. The GFP accumulation was similar to the parental GFP-expressing line, showing that the GFP glycinin gene mimic does not participate in proteome rebalancing. The results show that soybeans make large adjustments to the proteome during seed filling and compensate for the shortage of major proteins with the increased selective accumulation of other proteins that maintains a normal protein content.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1334&context=bbmb_ag_pubs

Silencing of soybean seed storage proteins results in a rebalanced protein composition preserving seed protein content without major collateral changes in the metabolome and transcriptome

Production of Escherichia coli heat labile toxin (LT) B subunit in soybean seed and analysis of its immunogenicity as an oral vaccine.

Suppression of Soybean Oleosin Produces Micro-Oil Bodies that Aggregate into Oil Body/ER Complexes

In a number of disciplines including ecology, ecotoxicology, water quality management, water resource management, fishery biology etc., there is significant interest in the testing of new materials, environmental samples (of water or sediments) and specific sites, in terms of their effects on biota. In the first instance, we consider various sources of aquatic pollution, sources typically associated with developed areas of the world. Historically, much water quality assessment has been performed by researchers with a background in chemistry or engineering, thus chemical analysis was a dominant form of assessment. However, chemical analyses, particularly of such materials as organochlorines and polyaromatic hydrocarbons can be expensive, and local environmental factors may cause the actual exposure of an organism to be little correlated with chemical concentrations in the surrounding water or sediments. To a large extent toxicity testing has proceeded independently of environmental quality assessment in situ, and the work has been done by different, and differently-trained researchers. Here we attempt to bring together the various forms of biological assessment of aquatic pollution, because in our opinion it is worth developing a coherent framework for the application of this powerful tool. Biotic assessment in its most primitive form involves the simple tracking of mortality in exposed organisms. However, in most natural environments it is extended, chronic exposure to contaminants that has the most wide-ranging and irreversible repercussions--thus measures of sub-lethal impairment are favoured. From an ecological standpoint, it is most valuable to assess ecological effects by direct study of in situ contaminant body burdens and impairment of growth and reproduction compared with 'clean' sites. A distinction is made here between bioindication and biomonitoring, and a case is made for including aquatic macrophytes (angiosperms) in studies of contaminant levels and effects in the biota. It is apparent that there is a concurrent need for laboratory-based testing of new industrial by-products before any are released in the environment, and such studies should aid the investigation of mechanisms and modes of toxicity, but environmental assessment, and tracking of improvements in environmental quality are most effectively achieved by active biomonitoring experiments.

Biological assessment of aquatic pollution: a review, with emphasis on plants as biomonitors*

Seeds possess a high intrinsic capacity for protein production that makes them a desirable bioreactor platform for the manufacture of transgenic products. One strategy to enhance foreign protein production involves exchanging the capacity to produce intrinsic proteins for the capacity to produce a high level of foreign proteins. Suppression of the alpha/alpha' subunit of beta-conglycinin storage protein synthesis in soybean has been shown previously to result in an increase in the accumulation of the glycinin storage protein, some of which is sequestered as proglycinin into de novo endoplasmic reticulum (ER)-derived protein bodies. The exchange of glycinin for conglycinin is quantitative, with the remodelled soybeans possessing a normal protein content with an altered proteome. The green fluorescent protein (GFP)-kdel reporter was transferred in a construct using the glycinin promoter and terminator to mimic glycinin gene expression. When expressed in soybean seeds, GFP-kdel accreted to form ER-derived protein bodies. The introgression of GFP-kdel into the alpha/alpha' subunit of the beta-conglycinin suppression background resulted in a fourfold enhancement of GFP-kdel accumulation to > 7% (w/w) of the total protein in soybean seeds. The resulting seeds accumulated a single population of ER membrane-bound protein bodies that contained both GFP-kdel and glycinin. Thus, the collateral proteome rebalancing that occurs with the suppression of intrinsic proteins in soybean can be exploited to produce an enhanced level of foreign proteins.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1467-7652.2008.00364.x

Monica A. Schmidt

Papers

Silencing of soybean seed storage proteins results in a rebalanced protein composition preserving seed protein content without major collateral changes in the metabolome and transcriptome

Production of Escherichia coli heat labile toxin (LT) B subunit in soybean seed and analysis of its immunogenicity as an oral vaccine.

Suppression of Soybean Oleosin Produces Micro-Oil Bodies that Aggregate into Oil Body/ER Complexes

Biological assessment of aquatic pollution: a review, with emphasis on plants as biomonitors*

Proteome rebalancing in soybean seeds can be exploited to enhance foreign protein accumulation.