A recent study published in the journal Molecular Plant has delved into the genetics of macroalgae, also known as seaweed, to uncover the genetic mechanisms that allowed these organisms to evolve multicellularity. It was discovered that three lineages of macroalgae independently developed multicellularity by acquiring genes for cell adhesion, extracellular matrix formation, and cell differentiation. Surprisingly, many of these genes had viral origins. The study, which increased the number of sequenced macroalgal genomes from 14 to 124, provides valuable insights into the evolution of macroalgae through genomics.
Macroalgae are complex multicellular organisms found in both fresh and seawater, with distinct organs and tissues, unlike microalgae, which are microscopic and unicellular. The three main groups of macroalgae – red, green, and brown – independently evolved multicellularity at different times and in different environments. Rhodophytes and Chlorophytes evolved multicellularity over a billion years ago, while Ochrophytes became multicellular more recently, about 200,000 years ago. This diversity in evolutionary timelines makes macroalgae an intriguing subject for genetic study.
To investigate the evolution of macroalgal multicellularity, researchers sequenced 110 new macroalgal genomes from 105 different species from diverse habitats around the world. They identified metabolic pathways unique to macroalgae that may be responsible for the success of invasive species. Many of these metabolic genes were acquired from algae-infecting viruses, with a higher prevalence in the more recent brown algae lineage. The study also found new genes acquired by macroalgae on their path to multicellularity, including those involved in cell adhesion, differentiation, communication, and inter-cellular transport.
One of the key findings of the study is the origin of genes associated with multicellular functions in brown algae, which had signatures similar to those found in viruses that infect them. This suggests that horizontally transferred genes from viruses played a critical role in the evolution of multicellularity in brown algae. The researchers also observed greater diversity between species of Rhodophyte, the first lineage to evolve multicellularity, and noted genomic similarities between Chlorophytes and land plants, hinting at shared ancestral genes.
Future research will focus on exploring environmental and habitat adaptations among macroalgae using the extensive genomic dataset generated in this study. The team plans to sequence and analyze more macroalgal genomes to further advance our understanding of the genetic mechanisms underlying the evolution of these fascinating organisms. This research, supported by NYUAD Faculty Research Funds and Tamkeen, lays the groundwork for future studies exploring the genetic diversity and evolutionary history of macroalgae.
