Abstract
Chromochloris zofingiensis represents an industrially relevant and unique green alga, given its capability of synthesizing triacylglycerol (TAG) and astaxanthin simultaneously for storage in lipid droplets (LDs). To further decipher lipid metabolism, the nitrogen deprivation (ND)-induced LDs from C. zofingiensis were isolated, purified, and subjected to proteomic analysis. Intriguingly, many C. zofingiensis LD proteins had no orthologs present in LD proteome of the model alga Chlamydomonas reinhardtii. Seven novel LD proteins (i.e., two functionally unknown proteins, two caleosins, two lipases, and one l-gulonolactone oxidase) and the major LD protein (MLDP), which were all transcriptionally up-regulated by ND, were selected for further investigation. Heterologous expression in yeast demonstrated that all tested LD proteins were localized to LDs and all except the two functionally unknown proteins enabled yeast to produce more TAG. MLDP could restore the phenotype of mldp mutant strain and enhance TAG synthesis in wild-type strain of C. reinhardtii. Although MLDP and caleosins had a comparable abundance in LDs, they responded distinctly to ND at the transcriptional level. The two lipases, instead of functioning as TAG lipases, likely recycled polar lipids to support TAG synthesis. For the first time, we reported that l-gulonolactone oxidase was abundant in LDs and facilitated TAG accumulation. Moreover, we also proposed a novel working model for C. zofingiensis LDs. Taken together, our work unravels the unique characteristics of C. zofingiensis LDs and provides insights into algal LD biogenesis and TAG synthesis, which would facilitate genetic engineering of this alga for TAG improvement.
Highlights
Algae-derived lipids, which are believed to be superior to plant oils for biofuel production, have been considered as the nextgeneration biodiesel feedstock and are receiving increasing interest [1,2,3,4]
In order to evaluate TAG synthesis and lipid droplets (LDs) accumulation in C. zofingiensis, a time course analysis was performed with respect to TAG, total fatty acids (TFAs), TAG/TFAs ratio, and LD formation in response to nitrogen deprivation (ND)
We examined the localization of a type I diacylglycerol acyltransferase 1A (DGAT1A) and a type II diacylglycerol acyltransferase 5 (DGTT5) [45], which were not detected in our LD proteome (Dataset S1), to exclude the possibility of false positive observation introduced by green fluorescence protein (GFP) fusion
Summary
Algae-derived lipids, which are believed to be superior to plant oils for biofuel production, have been considered as the nextgeneration biodiesel feedstock and are receiving increasing interest [1,2,3,4]. To improve the content and yield of lipids, efforts other than optimizing culture conditions such as genetic engineering are needed for algae. This makes it imperative to better understand the biology and metabolism mechanism of triacylglycerol (TAG), the most energy-dense lipid class. The profiles of LD proteins, which help us understand LD biology and TAG metabolism, have been well documented by proteomic analysis for yeast [10,11,12], higher plant seeds [13,14,15], and mammalian adipose tissues [16,17,18]. These studies mainly focused on protein profiles with a rare touch of functional characterization
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
