Correction: Genome, Functional Gene Annotation, and Nuclear Transformation of the Heterokont Oleaginous Alga Nannochloropsis oceanica CCMP1779.

[This corrects the article DOI: 10.1371/journal.pgen.1003064.].

An Energy-Independent Pro-longevity Function of Triacylglycerol in Yeast.

Intracellular triacylglycerol (TAG) is a ubiquitous energy storage lipid also involved in lipid homeostasis and signaling. Comparatively, little is known about TAG's role in other cellular functions. Here we show a pro-longevity function of TAG in the budding yeast Saccharomyces cerevisiae. In yeast strains derived from natural and laboratory environments a correlation between high levels of TAG and longer chronological lifespan was observed. Increased TAG abundance through the deletion of TAG lipases prolonged chronological lifespan of laboratory strains, while diminishing TAG biosynthesis shortened lifespan without apparently affecting vegetative growth. TAG-mediated lifespan extension was independent of several other known stress response factors involved in chronological aging. Because both lifespan regulation and TAG metabolism are conserved, this cellular pro-longevity function of TAG may extend to other organisms.

The slim, the fat, and the obese: guess who lives the longest?

In a modern society that is increasingly older and "heavier," it is understandable that the majority favors a slimmer body that helps to sail smoothly into the dusk of life. Given the association between obesity and many metabolic and cardiovascular disorders, there are stern criticisms over such a thought of "good fat". Ironically, a phenomenon called "obesity paradox", that is, the overweight population purportedly enjoys the lowest all-cause mortality, and baffles open-minded clinicians and scientists. Lipids are essential to all life forms. Fat, in particular, triacylglycerol, also exists in different forms and in different locations in the human body, making any simple statement that vilifies all fat invalid. Whether the phenomenon of obesity paradox, indeed, has its root in a hitherto unrealized pro-survival function of fat deserves a serious look. Indeed, a recent publication using yeast as the model showed that elevation in the cellular storage of triacylglycerol extends lifespan in an energy expenditure independent fashion. In stark contrast, lean cells devoid of triacylglycerol biosynthetic capability die upon entering the senescence phase. Together, a new cytoprotective function of fat emerges. This mini-review aims to discuss potential mechanisms for the observed lifespan preservation function of triacylglycerol.

Genome, functional gene annotation, and nuclear transformation of the heterokont oleaginous alga Nannochloropsis oceanica CCMP1779.

Unicellular marine algae have promise for providing sustainable and scalable biofuel feedstocks, although no single species has emerged as a preferred organism. Moreover, adequate molecular and genetic resources prerequisite for the rational engineering of marine algal feedstocks are lacking for most candidate species. Heterokonts of the genus Nannochloropsis naturally have high cellular oil content and are already in use for industrial production of high-value lipid products. First success in applying reverse genetics by targeted gene replacement makes Nannochloropsis oceanica an attractive model to investigate the cell and molecular biology and biochemistry of this fascinating organism group. Here we present the assembly of the 28.7 Mb genome of N. oceanica CCMP1779. RNA sequencing data from nitrogen-replete and nitrogen-depleted growth conditions support a total of 11,973 genes, of which in addition to automatic annotation some were manually inspected to predict the biochemical repertoire for this organism. Among others, more than 100 genes putatively related to lipid metabolism, 114 predicted transcription factors, and 109 transcriptional regulators were annotated. Comparison of the N. oceanica CCMP1779 gene repertoire with the recently published N. gaditana genome identified 2,649 genes likely specific to N. oceanica CCMP1779. Many of these N. oceanica-specific genes have putative orthologs in other species or are supported by transcriptional evidence. However, because similarity-based annotations are limited, functions of most of these species-specific genes remain unknown. Aside from the genome sequence and its analysis, protocols for the transformation of N. oceanica CCMP1779 are provided. The availability of genomic and transcriptomic data for Nannochloropsis oceanica CCMP1779, along with efficient transformation protocols, provides a blueprint for future detailed gene functional analysis and genetic engineering of Nannochloropsis species by a growing academic community focused on this genus.