Brown Algae Unveils Complex Development Patterns

Researchers at the Max Planck Institute for Biology in Germany have uncovered a conserved developmental framework known as the hourglass model in brown algae. This discovery suggests that the hourglass model could be a fundamental trait shared by complex multicellular organisms.

The development of complex multicellularity has arisen independently in various eukaryotic lineages, including animals, plants, fungi, and algae. This significant evolutionary step requires intricate developmental processes to effectively manage cell differentiation in new specialized tissues.

According to the hourglass model, both the early and late stages of development show a range of morphological and molecular diversity, while a mid-embryonic phase remains remarkably consistent across species. This conserved phase is essential for establishing the basic body structure of the organism.

In the research paper titled "A transcriptomic hourglass in brown algae," published in Nature, the team aimed to explore whether the hourglass pattern observed in other organisms is also present in brown algae, which developed multicellularity around 450 million years ago.

The study examined several brown algal species, including Fucus serratus, Fucus distichus, and Ectocarpus sp., as well as kelp species such as Laminaria digitata and Saccorhiza polyschides. Researchers employed RNA sequencing to investigate gene expression across various developmental stages.

More complex brown algae exhibited a clear hourglass pattern during embryonic development, characterized by notable changes in gene expression during the early and late stages, with a well-conserved mid-phase. The team utilized the transcriptome age index to assess the conservation and variation in gene expression throughout the life cycles of the species studied.

In contrast, simpler brown algae, like Ectocarpus, demonstrated a continuous transition from unicellular to multicellular forms, lacking the distinctive hourglass gene expression pattern. This research extends the application of the hourglass model to brown algae, enriching our understanding of the developmental mechanisms that underpin complex multicellularity in eukaryotic life.