Natural Genetic Engineering Allowed Plants to Move from Water to Land

Horizontal gene transfer from soil bacteria to algae allowed early life to move to land, according to new research.

Cheng et al report genome sequences and analyses of two early diverging Zygnematophyceae species, Spirogloea muscicola and Mesotaenium endlicherianum, that share the same subaerial/terrestrial habitat with the earliest-diverging embryophytes, the bryophytes. Image credit: Cheng et al, doi: 10.1016/j.cell.2019.10.019.

Cheng et al report genome sequences and analyses of two early diverging Zygnematophyceae species, Spirogloea muscicola and Mesotaenium endlicherianum, that share the same subaerial/terrestrial habitat with the earliest-diverging embryophytes, the bryophytes. Image credit: Cheng et al, doi: 10.1016/j.cell.2019.10.019.

“The movement of life from water to land — called terrestrialization — began with plants and was followed by animals,” said University of Alberta’s Professor Gane Ka-Shu Wong.

“This study establishes how that first step took place.”

Professor Wong and colleagues made the discovery when they examined DNA of two species of the algae family Zygnematophyceae: Spirogloea muscicola and Mesotaenium endlicherianum.

They found genes that increase resistance to biotic and abiotic stresses in land plants (embryophytes) originated or expanded in the common ancestor of Zygnematophyceae and land plants, and were gained by horizontal gene transfer from soil bacteria.

“The movement of plants from water to land was made possible when genes from soil bacteria were transferred to algae through a process called horizontal gene transfer,” they explained.

“Unlike vertical gene transfer, such as the transfer of DNA from parent to child, horizontal gene transfer occurs between different species.”

“For hundreds of millions of years, green algae lived in freshwater environments that periodically fell dry, such as small puddles, river beds, and trickling rocks,” said Professor Michael Melkonian, from the University of Duisburg-Essen.

“These algae mingled with and received key genes from soil bacteria that helped them and their descendants to cope with the harsh terrestrial environment and eventually evolve into the land plant flora that we see today.”

“The approach that we used, phylogenomics, is a powerful method to pinpoint the underlying molecular mechanism of evolutionary novelty,” said Dr. Shifeng Cheng, from the Agricultural Genome Institute, the Chinese Academy of Agricultural Sciences.

The study was published in the journal Cell.

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Shifeng Cheng et al. 2019. Genomes of Subaerial Zygnematophyceae Provide Insights into Land Plant Evolution. Cell 179 (5): 1057-1067; doi: 10.1016/j.cell.2019.10.019

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