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

Xiaocui Bai,Si Chen,Kun Zhu,Hanqi Ye,Haifeng Qian,Zhengwei Fu,Hao Song,Yiyuan Su,Michel Lavoie

doi:10.1038/srep25494

Abstract

Microalgae biosynthesize high amount of lipids and show high potential for renewable biodiesel production. However, the production cost of microalgae-derived biodiesel hampers large-scale biodiesel commercialization and new strategies for increasing lipid production efficiency from algae 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.

Highlights

Microalgae biosynthesize high amount of lipids and show high potential for renewable biodiesel production
The present study shows that total lipid cell quotas in P. tricornutum, one of the best strains for biodiesel production[5], can strongly increase after a darkness treatment
When photosynthesis was abolished in the dark and synthesis of the proteins involved in the biosynthesis of the photosynthetic machinery was decreased, we found that cellular C, N and energy were redirected toward lipid biosynthesis (Fig. 4)

Summary

Introduction

Microalgae biosynthesize high amount of lipids and show high potential for renewable biodiesel production. 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]. We submitted P. tricornutum to a long-term dark stress (4 d) and followed the cellular regulatory mechanisms leading to lipid accumulation in this species using a combination of physiological, proteomic (analysis of the algal proteome by isobaric tags for the relative and absolute quantitation, iTRAQ) and transcriptomic (qRT-PCR) approaches. An exposure for 1 to 4 days in the dark of algae at the end of exponential phase successfully increased lipid cell quotas relative to the light-exposed control cells

Methods

Results

Conclusion