Study reveals the hidden genomic evolution of brown algae - and how bacteria and viruses helped

Covering over 70% of Earth’s surface, the oceans are home to countless life forms that maintain ecological balance and support human well-being. Among these, brown algae (Phaeophyceae) play a crucial role in sustaining coastal habitats, supporting marine biodiversity, and combating climate change through carbon capture. While they have long captured the interest of the scientific world, the genomic and evolutionary history of these organisms have remained largely unexplored.

A groundbreaking study by researchers from Sungkyunkwan University has unveiled the evolutionary journey of brown algae through a comprehensive genomic analysis of 44 species. The study was available online on November 20, 2024 and published on November 27, 2024 in Volume 187, Issue 24 of Cell. It created the Phaeoexplorer database, a valuable tool for comparative genomics. The researchers explored key evolutionary milestones, including the transition from unicellular to multicellular forms and the integration of viral sequences into brown algae genomes—an area previously unexplored.

The study revealed two major evolutionary milestones in the history of brown algae. Lead author Professor Hwan Su Yoon explains, ”Approximately 450 million years ago, brown algae transitioned from unicellular organisms to simple multicellular forms. This shift was driven by horizontal gene transfer from bacteria, enabling the synthesis of vital cell wall components like alginate and phlorotannin. These adaptations the algae aggregate, improved cell-to-cell communication, and defend against predators, marking a crucial step in their evolution.”

Break-up of Pangaea

Around 200 million years ago, following the breakup of the supercontinent Pangaea, brown algae underwent significant species diversification. Prof. Yoon explains, ”This diversification led to the development of complex life cycles, structural innovations, and specialized metabolic pathways, shaping the ecological roles of various species. The study also revealed widespread viral integration in brown algal genomes, with Phaeovirus sequences found in 67 out of 69 genomes analyzed.” These viral integrations likely played a key role in shaping the evolution and diversity of brown algae.

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The study offers valuable insights into practical applications of brown algae. In aquaculture, it supports selective breeding programs of commercially important species like Undaria pinnatifida and Saccharina japonica, boosting productivity and disease resistance. In biotechnology, the biosynthesis of compounds like alginate opens doors to health supplements, bioactive substances, and sustainable biomaterials. The study also highlights brown algae’s potential in climate change mitigation, particularly in carbon capture and ecosystem restoration, highlighting their ecological and economic benefits.

Climate insights

This study also offers valuable insights on how climate change could impact marine ecosystems. Prof. Yoon states, “By analyzing how past environmental changes shaped the evolution of brown algae, we can better predict how future climate shifts might affect marine biodiversity. The genomic resources established from this research help identify traits that enhance ecological resilience, guiding efforts to develop brown algae resistant to climate stresses such as rising temperatures and sea-level changes.” Additionally, promoting kelp forests as “blue carbon” reservoirs offers a natural solution to sequester carbon, mitigating climate change effects while fostering ecological sustainability in marine environments.

By decoding the genetic makeup of brown algae, this study enhances our understanding of marine ecosystems and provides insights into how we can use their ecological and economic potential for a more sustainable future.