Project PI: Dr. Pablo Leivar

A circular bioeconomy demands the use of renewable resources to produce high value chemicals and pharmaceuticals. Metabolic engineering and synthetic biology may satisfy this demand through the construction of synthetic cells whose metabolism has been redesigned towards the production of complex biomolecules of interest. Unicellular microalgae are emerging as important hosts for sustainable industrial biotechnology, as they can use photosynthetic light to efficiently transform CO2 into added-value bioproducts. We are applying optogenetics and metabolic engineering for the construction of a synthetic green cell platform based on the microalgae Chlamydomonas reinhardtii, aimed at producing added-value glycolipids. The main topics include:

a) Genetic and metabolic engineering of green microalgae for the sustainable production of added-value glycolipids.

Glycolipids are a complex and diverse group of biomolecules, mostly produced by plants and microbes, with multiple applications in pharmaceutical, cosmeceutical, food, agriculture, petroleum, and bioremediation industries. Among the different glycolipids, rhamnolipids are preferred biosurfactants thanks to their excellent physicochemical properties, biological activities, and enhanced environmental biodegradability. Despite their interest, the use of glycolipids and rhamnolipids in industry is limited due to their challenging and costly production. Based on the extraordinary capacity of photosynthetic microalgae to produce, accumulate, and exchange glycolipids between different organelles, we propose to develop a novel cellular platform for the sustainable production of added-value glycolipids in different cellular compartments of the green microalgae Chlamydomonas reinhardtii.
(i) Production of glycoglycerolipids targeting novel subcellular compartments.
(ii) Engineering chloroplast metabolism for the biosynthesis of rhamnolipid biosurfactants.

Metabolic redesign of Chlamydomonas reinhardtii cells for the production of cytosolic glycoglycerolipids (left) and plastidial rhamnolipids (right).

b) Building an optogenetic module for the light control of gene expression in synthetic microalgae.

Synthetic biology is a multidisciplinary area of research that aims to design, construct, and modify biological parts and modules, including genes, enzymes, pathways, and organisms. A synthetic biology approach often consists on constructing artificial biological pathways, where an input signal is perceived by a sensor and transmitted through the genetic circuit to an actuator, which eventually implements the biological output. The precise control of the genetic circuits and system actuators requires the introduction of synthetic cell signaling modules that integrate and transmit the information of an input signal.
Optogenetics is an emerging discipline that uses light to modulate molecular events in a targeted manner in living cells. An optogenetic signaling module can be constructed with a light sensor, which perceives the light information, and an effector, which transduces the light signal to the downstream actuators. Light-switchable control of gene expression typically uses two genetically-encoded proteins (bimolecular switches) that are able to sense the light and transport this signal into target promoters. A red/far-red modulated system based on plant phytochrome B (phyB) photoreceptor and phytochrome-interacting factors (PIFs) was originally developed in yeast. Given the scarcity of tools to control the transcription of endogenous or recombinant proteins in microalgae, we are constructing a novel synthetic optogenetic module to control the genetic circuits of the system using light.

Construction of an optogenetic signaling module for the control of gene expression in synthetic microalgae.

Selected publications: 

Phytochrome-imposed inhibition of PIF7 activity shapes photoperiodic growth in Arabidopsis together with PIF1, 3, 4 and 5.
P. Leivar, G. Martín, J. Soy, J. Dalton-Roesler, P.H. Quail, E. Monte.
Physiologia Plantarum 169, 452-466 (2020). Abstract.

PIFs: systems integrators in plant development.
P. Leivar, E. Monte.
The Plant Cell 26, 56–78 (2014).