Abstract
Microalgae have emerged as a promising source for biofuel production. Massive oil and starch accumulation in microalgae is possible, but occurs mostly when biomass growth is impaired. The molecular networks underlying the negative correlation between growth and reserve formation are not known. Thus isolation of strains capable of accumulating carbon reserves during optimal growth would be highly desirable. To this end, we screened an insertional mutant library of Chlamydomonas reinhardtii for alterations in oil content. A mutant accumulating five times more oil and twice more starch than wild-type during optimal growth was isolated and named constitutive oil accumulator 1 (coa1). Growth in photobioreactors under highly controlled conditions revealed that the increase in oil and starch content in coa1 was dependent on light intensity. Genetic analysis and DNA hybridization pointed to a single insertional event responsible for the phenotype. Whole genome re-sequencing identified in coa1 a >200 kb deletion on chromosome 14 containing 41 genes. This study demonstrates that, 1), the generation of algal strains accumulating higher reserve amount without compromising biomass accumulation is feasible; 2), light is an important parameter in phenotypic analysis; and 3), a chromosomal region (Quantitative Trait Locus) acts as suppressor of carbon reserve accumulation during optimal growth.
Highlights
Promoter-binding protein domain transcription factor[13], a CXC domain-containing protein[17], and two members of the dual-specificity tyrosine phosphorylation-regulated kinase family, i.e. the triacylglycerol accumulation regulator[1] (TAR1)[18] and the starch degradation 1 (STD1)[19]
Higher Nile red fluorescence is generally used as a probe for increased cellular oil content, and TAG quantification confirmed that the mutant 6D8 made 5 times more oil than WT under nitrogen-replete conditions (Fig. 1A)
We observed that during the recovery phase following a period of nitrogen starvation, the mutant was impaired in oil remobilization (Supplemental Figure S2)
Summary
Hugh Douglas Goold1,2,3,4,*, Hoa Mai Nguyen1,2,3,*, Fantao Kong[1,2,3], Audrey BeylyAdriano[1,2,3], Bertrand Légeret[1,2,3], Emmanuelle Billon[1,2,3], Stéphan Cuiné[1,2,3], Fred Beisson[1,2,3], Gilles Peltier1,2,3 & Yonghua Li-Beisson[1,2,3]. With increasing world population and diminishing fossil fuels, alternative fuel sources that are renewable and do not compete with food production for fresh water and arable land are highly sought after[1,2] Due to their high growth rate and their intrinsic capacity (at least under certain growth conditions) to store large amounts of carbon rich compounds (i.e. starch and oils), microalgae have been investigated intensively as sources for biofuel production (bioethanol from starch; biodiesel from lipids)[1,2,3]. This mutant accumulated increased oil and starch relative to the wild-type strain in a light-dependent manner The isolation of this mutant should provide a molecular basis for our understanding of the control of TAG and starch accumulation during optimal growth
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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.
