This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: What did the algae that gave rise to the first land plants look like? A research team led by the University of Göttingen and including the universities of Maastricht and Innsbruck and Museo Nacional de Ciencias Naturales has now taken a detailed look at one of the most important groups for answering this question: the Zygnematophyceae, the closest living algal relatives of land plants.
These include familiar-looking filamentous algae such as Spirogyra, as well as many that just consist of single cells. Despite their relatively simple appearance, they are particularly important for understanding plant evolution due to their close relationship with land plants. Researchers analyzed a dataset covering more than 100 species and 2,000 genes to shed light on the evolution of multicellularity.
Their results were published in PLOS Biology. Previous studies have established that the Zygnematophyceae algae are the closest living algal relatives of land plants, but the evolutionary connections remained difficult to resolve because genomic data were available for only a small number of species. To address this, the researchers generated 43 new transcriptomes—collections of the genes that are active in cells—from strains representing a broad range of zygnematophyte diversity.
These data were combined with publicly available sequences to produce a dataset covering more than 100 species and 2,000 genes. The researchers' analysis indicates that the common ancestor of all Zygnematophyceae was probably a single-celled alga. Filamentous growth subsequently evolved several times independently.
This suggests that multicellular growth in these algae did not arise through a single evolutionary transition, but emerged repeatedly from simpler ancestral forms. "Many zygnematophytes look deceptively simple, but their genomes reveal a remarkably deep and complex evolutionary history and diversity. We can begin to see evolutionary events that remain invisible when we study only a handful of model species," says Dr.
Maaike Bierenbroodspot, who carried out this research for her Ph.D. at Göttingen University and is now a postdoc at the University of Maastricht. "These algae have genes that are part of what we call the 'land plant heritage,'" explains Cäcilia Kunz, University of Göttingen. "They show that some of the molecular components associated with important plant functions have much deeper evolutionary histories than the land plants themselves.
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