Acoels are unique marine worms that have the ability to regenerate their bodies after injury and form symbiotic relationships with photosynthetic algae that live inside them. These relationships create a holobiont, a collection of symbiotic organisms. Researchers, led by Bo Wang, have been studying Convolutriloba longifissura, a species of acoel that hosts the algae Tetraselmis. Their recent study, published in Nature Communications, found that a genetic factor involved in acoel regeneration also controls how the algae inside them reacts, suggesting a connection between the gene networks of the two species.
Acoels, which have no separation between their inner and outer organs, host symbiotic algae inside their organs, providing a safe zone for the algae and extra energy for the acoel through photosynthesis. The researchers found that there was uncertainty about communication between the acoels and the algae since the algae were not within the acoel’s cells but simply floating around them. When acoels reproduce asexually, they bisect themselves, with the head growing a tail to become a new acoel, and the tail growing two heads that eventually split into two separate animals.
The researchers were curious about how the algal colonies inside the acoels reacted during the regeneration process. They found that the algae continued to photosynthesize during the process, undergoing changes in their photosynthetic machinery controlled by a common transcription factor, runt, in the acoels. This factor, highly conserved and responsible for regeneration in many organisms, was found to control not only the acoel’s regenerative process but also the communication with the algae inside them.
Understanding how partners in symbiotic relationships communicate at the molecular level raises new questions about this field of research. Researchers are exploring whether there are rules of symbiosis that dictate these interactions and how different species interact to form holobionts. Wang believes that studying these interactions can provide insights into how symbiotic species couple with each other and how these connections may be affected by factors such as climate change, leading to the separation of symbiotic partners. The team’s research has sparked questions that can be applied to other organisms and symbiotic systems.
The study sheds light on the intricate communication between acoels and their symbiotic algae and how a common transcription factor controls both the regeneration process in acoels and the responses of the algae during this process. By studying how these symbiotic relationships function at the molecular level, researchers can gain a better understanding of the mechanisms that govern interactions between different species in holobionts. The research was made possible through funding from various sources, including a Bio-X Bowes Fellowship, the Stanford Interdisciplinary Graduate Fellowship, and the National Institutes of Health.