New Research Reveals That Complex Green Organisms Emerged a Billion Years Ago

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A research team at Göttingen University is leading an investigation into the emergence of multicellularity.

Of all the organisms that photosynthesize, land plants have the most complex bodies. How did this morphology emerge? A team of scientists led by the University of Göttingen has taken a deep dive into the evolutionary history of morphological complexity in streptophytes, which include land plants and many green algae.

Their research allowed them to go back in time to investigate lineages that emerged long before land plants existed. Their results revise the understanding of the relationships of a group of filamentous algal land colonizers much older than land plants. Using modern gene sequencing data, researchers pinpoint the emergence of multicellularity to almost a billion years ago. The results were published in the journal Current BiologyCurrent Biology is a peer-reviewed scientific journal published biweekly by Cell Press. It is focused on all aspects of biology, from molecular biology and genetics to ecology and evolutionary biology. The journal covers a wide range of topics, including cellular biology, neuroscience, animal behavior, plant biology, and more. Current Biology is known for its high-impact research articles, as well as its insightful commentary, analysis, and reviews of the latest developments in the field. It is widely read by scientists and researchers in biology and related fields, and has a reputation for publishing groundbreaking research that advances our understanding of the natural world.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Current Biology.

The Diversity and Adaptability of Klebsormidiophyceae

The study focused on Klebsormidiophyceae, a class of green algae known for its ability to colonize diverse habitats worldwide. The team of researchers conducted extensive sampling, investigating habitats ranging from streams, rivers, and lake shores to bogs, soil, natural rocks, tree bark, acidic post-mining sites, sand dunes, urban walls, and building façades.

Microscope image of the filamentous alga Klebsormidium crenulatum, a land-dwelling alga that is very dessication resistant due to its thick cell wall. (scale is 10 µm, corresponding to 0.01 mm). Credit: Tatyana Darienko

“It’s really fascinating that these tiny robust little organisms have such a high diversity in their morphology and also are extremely well adapted to live in sometimes very harsh environments,” says Dr Tatyana Darienko, University of Göttingen’s Institute for Microbiology and Genetics. This comprehensive sampling aimed to create a global distribution map for Klebsormidiophyceae, emphasizing their adaptability, ecological significance, and hidden diversity. Based on genetic data calibrated by fossils, the researchers performed “molecular clock analyses”.

Overcoming Challenges with Phylogenomics

While delving into the complex evolutionary history of Klebsormidiophyceae, the researchers faced challenges in resolving phylogenetic relationships using traditional markers. To overcome this, they employed hundreds of genes obtained from the transcriptomes of 24 isolates from different continents and habitats.

“Our approach, known as phylogenomics, was to reconstruct the evolutionary history taking into account whole genomes or large fractions of genomes,” explains Dr Iker Irisarri, Leibniz Institute for the Analysis of Biodiversity Change. “This extremely powerful method can reconstruct evolutionary relationships with very high precision.”

Microscope image of the multicellular alga Streptosarcina arenaria, another terrestrial alga, which inhabits dry and tropical areas. (scale is 10 µm, corresponding to 0.01 mm). Credit: Tatyana Darienko

Discovering the Roots of Multicellularity in Streptophytes

Their research revealed a new phylogenomic tree of life for Klebsormidiophyceae which is divided into three orders. “This deep dive into the phylogenomic framework and our molecular clock unveiled Klebsormidiophyceae’s ancient ancestor – a multicellular entity thriving millions of years ago whose descendants began to split into three distinct branches over 800 million years ago,” says Maaike Bierenbroodspot, PhD researcher in Applied Bioinformatics, University of Göttingen.

These results were used to explore the evolutionary history of multicellularity within streptophytes. The study showed that an ancient common ancestor of land plants, other streptophyte algae, and Klebsormidiophyceae was already multicellular. Professor Jan de Vries, Göttingen University’s Institute for Microbiology and Genetics, concludes: “This finding sheds light on the genetic potential for multicellularity among streptophytes, indicating an ancient origin for this crucial trait almost a billion years ago.”

Reference: “Phylogenomic insights into the first multicellular streptophyte” by Maaike J. Bierenbroodspot, Tatyana Darienko, Sophie de Vries, Janine M.R. Fürst-Jansen, Henrik Buschmann, Thomas Pröschold, Iker Irisarri and Jan de Vries, 19 January 2024, Current Biology.
DOI: 10.1016/j.cub.2023.12.070