THE SIGNAUX-BIONRJ project aimed at investingating how manipulating energy signaling could improve biofuel production in photosynthetic eukaryotes, iparticularly microalgae
The development of renewable energy is a major issue at a time when access to fossil fuels is limited and environmental problems related to climate change are worsening. Microalgae are particularly interesting because they convert solar energy into chemical energy during photosynthesis, a process that captures atmospheric CO2. Algae do not compete with agriculture and produce reserve lipids that can be converted into biofuels. However, the highest concentrations of reserve lipids are obtained during nutrient starvation, a condition that blocks growth and limits microalgae productivity. The ANR SIGAUX-BIONRJ project involved the study of two systems controlling growth and metabolism (signaling pathways), operating within two different cellular compartments: cytosol and chloroplast where photosynthesis takes place. The study of these two distinct mechanisms and their potential interactions could provide a global view of how microalgae regulate the balance between lipid accumulation and growth in order to improve their productivity for biotechnology.
We have shown that manipulating the TOR kinase activity can lead to improved TAG productivity in a microalgae, compared to nitrogen deficiency, which was the main objective of the project. This move towards a biotech application will no doubt require further productivity improvement by playing on specific sub-elements of this signalling pathway. We observed a more complex situation for ppGpp where its accumulation leads to a transient accumulation of TAG within lipid droplets in a diatom and then a decrease in TAG accumulation.
We have identified conditions of partial TOR inhibition leading to an increased TAG productivity in a diatom. We also characterize the role of ppGpp in diatoms and moss.
The characterisation of conditions allowing TAG accumulation without compromising growth could help resolve a major problem for the industrial development of third generation biofuels.
Following this project, experiments in large scale incubators could be proposed.
Harchouni, S., England, S., Vieu, J., Aouane, A., Citerne, S., Legeret, B., Li-Beisson, Y., Menand, B.#, Field, B.# (2021) Guanosine tetraphosphate (ppGpp) accumulation inhibits chloroplast gene expression and promotes super grana formation in the moss Physcomitrium (Physcomitrella) patens. BioRxv doi.org/10.1101/2021.01.06.425534
Avilan, L., Lebrun, R., Puppo, C., Citerne, S., Cuine, S., Li-Beisson, Y., Menand, B., Field, B.#, Gontero, B.# (2021) ppGpp influences protein protection, growth and photosynthesis in Phaeodactylum tricornutum (2021) New Phytologist. doi: 10.1111/nph.17286.
Prioretti, L., Carriere, F., Field, B., Avilan, L., Montané M.-H., Menand, B.#, Gontero, B.# (2020) Minireview: Targeting TOR signaling for enhanced lipid productivity in algae. Biochimie 169, 12-17.
Avilan, L., Puppo, C., Villain, A., Bouveret, E., Menand, B. Field, B.#, Gontero, B.#. (2019) RSH enzyme diversity for (p)ppGpp metabolism in Phaeodactylum tricornutum and other diatoms. Scientific Reports 9, 17682.
Prioretti, L., Avilan, L., Carriere, F., Montané, M.-H., Field, B., Gregori, G., Menand, B.#, Gontero, B.#. (2017). The inhibition of TOR in the model diatom Phaeodactylum tricornutum promotes a get-fat growth regime. Algal Research 26, 265–274.7.
Montané, MH#, Menand, B.# (2019) TOR inhibitors: from mammalian outcomes to pharmacogenetics in plants and algae, Journal of Experimental Botany 70, 2297-2312, erz053.
Harchouni, S., Field, B.#, & Menand, B.# (2018). AC-202, a highly effective fluorophore for the visualization of lipid droplets in green algae and diatoms. Biotechnology for biofuels, 11, 120.
Field (2018) Green magic: regulation of the chloroplast stress response by (p)ppGpp in plants and algae. Journal of Experimental Botany. (2018) May 19;69(11):2797-2807. doi: 10.1093/jxb/erx48
One of the most promising alternative energy solutions is the use of microalgae like diatoms to produce biofuels, particularly lipids, by converting solar energy. However, the highest concentrations of lipids (triacylglycerol: TAG) are obtained during starvation, but this results in growth arrest and limits overall yield. The rationale of SIGNAUX_BIONRJ is that the manipulation of stress and energy signaling pathways could increase TAG content without compromising growth. We aim to generate fundamental knowledge on how two major stress and energy signaling pathways integrate signals from the chloroplast and the cytosol in order to regulate the balance between growth and TAG accumulation. Specific and conserved features of this regulation will be determined by studying the model photosynthetic eukaryote Physcomitrella patens, where we have proof-of-concept data, and two evolutionary distant diatoms; the marine diatom, Phaeodactylum tricornutum and the freshwater diatom Asterionella formosa. The three partners of this project will combine expertise on signaling, microalgae, lipid metabolism, enzymology and transcriptomic. The project will have a global impact in the fields of biotechnology, academic research, education and training of young scientists and will raise awareness of important societal issues with the public.
Monsieur Benoit Menand (Laboratoire de Gébétique et Biophysique des Plantes, UMR7265)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
CNRS DR12 _UMR7281 Centre National de la Recherche Scientifique délégation Provence et Corse_Laboratoire de Bioénergétique et Ingénierie des protéines
LB3M Laboratoire de Bioénergétique et Biotechnologie des Bactéries et des Microalgues, UMR7265
LGBP Laboratoire de Gébétique et Biophysique des Plantes, UMR7265
Help of the ANR 512,850 euros
Beginning and duration of the scientific project: September 2015 - 48 Months