Surviving Starvation: Proteomic and Lipidomic Profiling of Nutrient Deprivation in the Smallest Known Free-Living Eukaryote.

Sarah F Martin,Eliane Salvo-Chirnside,Seshu R Tammireddy,Phillip D Whitfield,Mary K Doherty,Thierry Le Bihan,Jiaxiuyu Liu

doi:10.3390/metabo10070273

Sarah F Martin, Eliane Salvo-Chirnside + Show 5 more

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https://doi.org/10.3390/metabo10070273

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Abstract

Marine phytoplankton, comprising cyanobacteria, micro- and pico-algae are key to photosynthesis, oxygen production and carbon assimilation on Earth. The unicellular green picoalga Ostreococcus tauri holds a key position at the base of the green lineage of plants, which makes it an interesting model organism. O. tauri has adapted to survive in low levels of nitrogen and phosphorus in the open ocean and also during rapid changes in the levels of these nutrients in coastal waters. In this study, we have employed untargeted proteomic and lipidomic strategies to investigate the molecular responses of O. tauri to low-nitrogen and low-phosphorus environments. In the absence of external nitrogen, there was an elevation in the expression of ammonia and urea transporter proteins together with an accumulation of triglycerides. In phosphate-limiting conditions, the expression levels of phosphokinases and phosphate transporters were increased, indicating an attempt to maximise scavenging opportunities as opposed to energy conservation conditions. The production of betaine lipids was also elevated, highlighting a shift away from phospholipid metabolism. This finding was supported by the putative identification of betaine synthase in O. tauri. This work offers additional perspectives on the complex strategies that underpin the adaptive processes of the smallest known free-living eukaryote to alterations in environmental conditions.

Highlights

Marine phytoplankton, comprising cyanobacteria, micro- and pico-algae are responsible for approximately 50% of photosynthesis, oxygen production and carbon assimilation on Earth while making up less than 1% of global biomass [1]
From the isoelectric focusing (IEF) fractionated data sets, we examined the proteome of O. tauri for the enzymes involved in TG biosynthesis
Depriving O. tauri of nitrogen and/or phosphorus resulted in several specific adaptations, demonstrating that the limitation of nutrients is sensed and compensated for as a survival strategy

Summary

Introduction

Marine phytoplankton, comprising cyanobacteria, micro- and pico-algae are responsible for approximately 50% of photosynthesis, oxygen production and carbon assimilation on Earth while making up less than 1% of global biomass [1]. Vast areas of open ocean show little or no chlorophyll presence, as primary productivity is concentrated in nutrient-rich coastal areas and oxygen-rich polar oceans supported by upwelling of deeper water [2,3]. The unicellular pico-alga, Ostreococcus tauri, is the smallest known free-living eukaryote and holds a key position at the base of the green lineage of plants, which makes it an interesting and increasingly well-described model organism. Discovered in 1994 in the Thau lagoon in France [4], O. tauri has been isolated in oceans and coastal regions across the globe. Its genome is very compact with 8200 genes across 12.6 MB [6]

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