We are very grateful to Human Frontier Science Program for supporting our ambitious project on symbiosis, in collaboration with Daniel Ducat (Michigan State University, US) and Dietrich Kohlheyer (Research Center Jülich, Germany). Our interdisciplinary team, covering expertise in biology, microfabrication of culture systems, reverse genetics, microscopy, and physiology will allow us to investigate some fundamental mechanistic steps of the integration of photosynthetic cells inside a host, and their metabolic responses to the engulfment.

Link to the list of 2025 Awardees: https://www.hfsp.org/bookletRG2025#undefined/

Abstract:

Life evolved by multiple symbiotic interactions between merging single-celled organisms that led to acquisition of genes, organelles, and new functionalities. For instance, a symbiosis between a host and intracellular photosynthetic cells (microalgae), called photosymbiosis, occurred several times in the evolution and led to the origin of all the photosynthetic organisms on earth, such as plants, trees and algae. In this process, engulfed photosynthetic cells were gradually transformed into an organelle, called the chloroplast, which produces oxygen and energy with light and feeds earth food webs. Photosymbiosis is still a widespread life strategy in aquatic and terrestrial ecosystems, such as lichens, corals and in the ocean plankton, and plays fundamental ecological roles with economic values. Despite the importance of photosymbiosis in the evolution of life and in ecosystems, we know very little on how the two organisms (host and photosynthetic partners) interact with each other, mainly because they are difficult to maintain and study in the laboratory and there is a lack of high-resolution imaging and genetic tools. How 2 cells become 1 cell (1+1=1) is one of the most intriguing mysteries in life we want to tackle in this project. We propose to create a new photosymbiosis with bioengineered cyanobacteria and a host cell with an interdisciplinary team covering expertise in biology, microfabrication of culture systems, microscopy, and physiology. This will allow us to investigate the fundamental steps of the integration of photosynthetic cells inside a host, and their metabolic responses to the engulfment. At relevant temporal and spatial scales, we will co-culture and scrutinize the two partners in different conditions using genetically-modified cyanobacteria that can perform different functions (excretion of sugars). This ambitious project will address fundamental questions in biology and will provide new knowledge on one of the most important events in the evolution of life.