Proteomics to reveal metabolic network shifts towards lipid accumulation following nitrogen deprivation in the diatom Phaeodactylum tricornutum

Abstract

The marine diatom Phaeodactylum tricornutum is attracting considerable interest as a candidate for biofuel production due to its fast growth and high lipid content. Nitrogen deficiency can increase the lipid content in certain microalgae species, including P. tricornutum. However, the molecular basis of such changes remains unclear without analyzing metabolism at the proteomic level. We attempted to systematically analyze protein expression level changes of P. tricornutum upon N deprivation. We observed translational level changes that could overall redirect the metabolic network from carbon flux towards lipid accumulation. N deprivation led to an increase in the expression of genes involved in nitrogen assimilation and fatty acid biosynthesis and a concomitant decrease in photosynthesis and lipid catabolism enzymes. These molecular level changes are consistent with the observed physiological changes, e.g., in photosynthesis rate and saturated lipid content. Our results provide information at the proteomic level of the key enzymes involved in carbon flux towards lipid accumulation in P. tricornutum and suggest candidates for genetic manipulation in microalgae breeding for biodiesel production.

Comprehensive metabolic reprograming in freshwater Nitzschia palea strains undergoing nitrogen starvation is likely associated with its ecological origin

“…2). In good agreement, it has been previously demonstrated that a decrease in photosynthesis due to N deprivation leads to changes in metabolic pathways involved in carbon and N assimilation and metabolism [18,27,33,71]. Moreover, N shortage also results in degradation of storage compounds in some diatoms [70,72].…”

“…Changes in lipid profile caused by deficiency of N in microalgae have already been reported [18,23,27,75,76]. In absence of N, a metabolic reprogramming of central carbon metabolism occurs, which diverts the carbon flow towards lipids synthesis [27,70].…”

“…In addition, deficiency of iron [17], phosphate [18], silicon [19,20] and nitrogen (N) [21][22][23] leads to metabolic changes in lipid biosynthesis. It has been also shown that the lipid content of Fragilaria capucina is altered according to either silicon or N concentration [20].…”

The Regulation of Photosynthetic Structure and Function during Nitrogen Deprivation in Chlamydomonas reinhardtii

“…Using the annotated C. reinhardtii genome (Merchant et al, 2007), the C. reinhardtii transcriptome was analyzed before and after N deprivation, which revealed multiple changes in gene expression that affect diverse parts of metabolism (Miller et al, 2010;Blaby et al, 2013;Goodenough et al, 2014;Schmollinger et al, 2014). In addition, proteomics have been used to profile the changes in protein expression during N deprivation in Phaeodactylum tricornutum (Yang et al, 2014), C. reinhardtii Longworth et al, 2012;Schmollinger et al, 2014), and Nannochloropsis oceanica (Dong et al, 2013), and metabolomics have been used to assess changes in metabolite pool sizes (Bölling and Fiehn, 2005;Lee et al, 2012). These and other studies point to wide-ranging changes in the structure and operation of the metabolic and other cellular networks.…”

Microalgal Systems Biology Through Genome-Scale Metabolic Reconstructions for Industrial Applications

“…Under these conditions, 15 proteins in carbohydrate metabolism, stress response and defense, amino acid biosynthesis, and secondary metabolite biosynthesis were downregulated (Li et al, 2013). P. tricornutum was shown to redirect the metabolic network from carbon flux toward lipid accumulation (Yang et al, 2014). Investigation of the Synechocystis sp.…”