Proteomic analyses bring new insights into the effect of a dark stress on lipid biosynthesis in Phaeodactylum tricornutum

Abstract

are urgently needed. Here we submitted the marine algae Phaeodactylum tricornutum to a 4-day dark stress, a condition increasing by 2.3-fold the total lipid cell quotas, and studied the cellular mechanisms leading to lipid accumulation using a combination of physiological, proteomic (iTRAQ) and genomic (qRT-PCR) approaches. Our results show that the expression of proteins in the biochemical pathways of glycolysis and the synthesis of fatty acids were induced in the dark, potentially using excess carbon and nitrogen produced from protein breakdown. Treatment of algae in the dark, which increased algal lipid cell quotas at low cost, combined with optimal growth treatment could help optimizing biodiesel production.As the world demand of fossil fuels increases and the greenhouse gas carbon dioxide levels continues to rise, the development of cost-effective biofuels is of high importance and should be a priority 1 . Microalgae are considered as one of the most promising biodiesel sources because of their rapid growth rates and high lipid cell content 2,3 , i.e. more than 50% of dry weight in some nutrient-limited microalgal species 4,5 . Microalgae-derived biodiesel is currently viewed as an appealing alternative for fossil fuels since the scale-up of algal biofuel production could be sufficient to meet at least 5% of U.S. demand for transportation fuels 6 . In addition, domestic production of renewable fuels including algal biofuels has the potential to meet the dual goals of improving energy security and decreasing greenhouse gas emissions from the transportation sector 3 . However, the production cost of biodiesel is still too high hampering large-scale commercialization of algae-derived biodiesel and new efficient strategies are urgently needed to increase economic viability of biodiesel production.Many studies have looked at the ecological and physiological factors regulating the production of lipids in autotrophic microalgae 1,3,7 . It is known that several environmental stressors (temperature, pH, salinity, and nutrient starvation) increase lipid cell quotas 8,9 . Nutrient starvation, nitrogen (N) especially proved to be one of the most successful approaches for enhancing lipid cell content in various microalgae species, such as Chlorella emersonii 10 (Trebouxiophyceae), Parietochloris incise 11 (chlorophyceae), Nannochloropsis spp 12 (Eustigmatophyceae), and Phaeodactylum tricornutum 7,13,14 (Bacillariophyceae). Although N starvation and other environmental stressors decrease algal growth rate and total lipid production, it has been suggested that a combination of optimal growth conditions and growth-limited conditions could help improve biodiesel production 3 . Another strategy that has the potential to improve the cost-effectiveness of biofuel production would be to overexpress key genes of fatty acid synthesis via genetic engineering 14 . Even though the study of Niu et al. 15 have shown that the overexpression of a type-2 diacylglycerol acyltransferase in a genetically engineered strain of a marine diato...

ppGpp influences protein protection, growth and photosynthesis inPhaeodactylum tricornutum

“…Reduction of photosynthesis and growth arrest is a common response to most stresses in diatoms suggesting that ppGpp may play an important role in stress acclimation (Litchman et al , 2003; Allen et al , 2011; Brembu et al , 2017). Other cell responses to ppGpp, such as the dramatic increase in HSP20, are similar to those found in response to dark stress (Bai et al , 2016). However, despite these similarities, the effect of ppGpp accumulation is clearly different from those reported for nutrient stress.…”

Transcriptome Profiling of Bigelowiella natans in Response to Light Stress

“…), and in a different diatom, P. tricornutum , ribosomal proteins were downregulated in the dark (Bai et al. ). In plants, one ribosomal protein (L10) responded specifically to UV‐B exposure (Ferreyra et al.…”

Dark metabolism: a molecular insight into how the Antarctic sea‐ice diatom Fragilariopsis cylindrus survives long‐term darkness

“…Several studies have described the effect of darkness on the survivability of Antarctic phytoplankton and sea‐ice algae (Bunt & Lee, ; Palmisano & Sullivan, ; Peters & Thomas, ; Baldisserotto et al ., ; Reeves et al ., ), but most research has focused on physiological adaptation rather than the biochemical and molecular drivers behind dark‐induced metabolism. Recent advances in functional genomics has made it possible to examine the molecular processes enabling dark survival (Nymark et al ., ; Bai et al ., ; Mock et al ., ). In this study we aim to gain a comprehensive insight into how F. cylindrus can survive extended periods of darkness by examining the expression profile of the proteome.…”