Provision of carbon skeleton for lipid synthesis from the breakdown of intracellular protein and soluble sugar in Phaeodactylum tricornutum under high CO2

Aiyou Huang,Songcui Wu,Guangce Wang,Wenhui Gu,Yuanxiang Li,Xiujun Xie

doi:10.1186/s12896-019-0544-4

Abstract

BackgroundIncreasing CO2 emissions have resulted in ocean acidification, affecting marine plant photosynthesis and changing the nutrient composition of marine ecosystems. The physiological and biochemical processes of marine phytoplankton in response to ocean acidification have been reported, but have been mainly focused on growth and photosynthetic physiology. To acquire a thorough knowledge of the molecular regulation mechanisms, model species with clear genetic background should be selected for systematic study. Phaeodactylum tricornutum is a pennate diatom with the characteristics of small genome size, short generation cycle, and easy to transform. Furthermore, the genome of P. tricornutum has been completely sequenced.Results and discussionIn this study, P. tricornutum was cultured at high and normal CO2 concentrations. Cell composition changes during culture time were investigated. The 13C isotope tracing technique was used to determine fractional labeling enrichments for the main cellular components. The results suggested that when lipid content increased significantly under high CO2 conditions, total protein and soluble sugar contents decreased. The 13C labeling experiment indicated that the C skeleton needed for fatty acid C chain elongation in lipid synthesis under high CO2 conditions is not mainly derived from NaHCO3 (carbon fixed by photosynthesis).ConclusionThis study indicated that breakdown of intracellular protein and soluble sugar provide C skeleton for lipid synthesis under high CO2 concentration.

Highlights

Increasing CO2 emissions have resulted in ocean acidification, affecting marine plant photosynthesis and changing the nutrient composition of marine ecosystems
This study indicated that breakdown of intracellular protein and soluble sugar provide C skeleton for lipid synthesis under high CO2 concentration
Li et al (2012) found that high CO2 had no effect on the growth of P. tricornutum [14]. These inconsistent results might be caused by different light intensities.Besides, stress such as C-limitation might trigger modifications of the carbon flow in P. triconutom [15, 16]. These results suggest that factors such as culture time, light intensity, and nutritional status can affect the response of P. tricornutum to high CO2, which are important for revealing the physiological and ecological processes of marine diatoms under high CO2

Summary

Introduction

Increasing CO2 emissions have resulted in ocean acidification, affecting marine plant photosynthesis and changing the nutrient composition of marine ecosystems. Increased CO2 emissions have caused ocean acidification, which has greatly affected the photosynthesis process of marine plants. Ocean acidification has increased photosynthetic and respiration rates [1], and down regulated the carbon concentration mechanism [2], and influenced nutrition uptake, and altered the C/N ratio and cell composition in marine phytoplankton [3, 4]. Since marine phytoplankton are the main primary producers in the ocean, changes in their. As the main components of marine phytoplankton, marine diatoms produce approximately 20% of global primary productivity and play an important role in inorganic C fixation and material cycles [5, 6]. The study of the C flow distribution mechanism in P. tricornutum under high CO2 has fundamental research significance and important application value

Methods

Results

Conclusion