Olivier De Clerck at Ghent University in Belgium led this international study, and doctoral student Fatima Foflonker and I coauthored it. The outcome was exciting and opened up new avenues in sea lettuce research.
We found that the genome is comprised of about 98.5 million bases (i.e., A, C, G, T; ours is 3 billion bases) and contains 12,994 protein coding genes. Despite being multicellular, the genome did not show the typical footprints of gene family expansion associated with this increase in complexity, suggesting Ulva has made the transition in a novel way that needs to be investigated.
Ulva is fascinating because it relies on bacterial help to gain its typical blade-like form and cannot develop normally in a bacterium-free axenic culture. This observation led the research team to search for instances of bacterial gene transfer to the Ulva genome that may contribute to its biology. It is now well understood that, like the human gut microbiome, many other species also need microbes to grow and develop normally. This bioinformatic search turned up only 13 strong candidates of bacterial gene transfer, but most were expanded by gene duplication after their introduction, suggesting they play key roles in sea lettuce biology. An exceptional case is haem peroxidase, an enzyme that occurs in 36 copies and is involved in scavenging hydrogen peroxide that can result from high-light stress. The enzyme also plays a role in cell wall modification. The intertidal zone is bathed in full sunlight at low tide; therefore, the haem peroxidase gene family derived from a bacterial gene may help Ulva survive this hostile environment. The researchers also described the sulfur metabolic pathways in Ulva and the role of this seaweed in the global sulfur cycle.
Read the full article at National Fisherman