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A gelatinous blob on top of a wet stone has led to the discovery that bacteria likely helped plants conquer land. In 2006, on a plant collecting trip about 50 kilometers from the University of Cologne in Germany where he worked, phycologist Michael Melkonian came upon an unusual alga, known until then only from a 19th century French natural historian’s description. Now, Melkonian and his colleagues have analyzed its genome—and that of a close relative—to track down genes important for life’s emergence from water. At least two of those genes come from soil bacteria and were likely transferred into an ancestor shared by these algae and land plants.
Sequencing these two algae, Spirogloea muscicola and Mesotaenium endlicherianum, “is a milestone for the field of early plant evolution,” says Jan de Vries, an evolutionary plant biologist at the Georg August University of Göttingen in Germany. And the link to soil bacteria is an added bonus. “That horizontal gene transfer may have contributed to the colonization of land is pretty exciting,” says Pamela Soltis, a plant evolutionary biologist at the University of Florida in Gainesville who was not involved in the work. Although it’s well accepted that bacteria exchange genes, examples of gene transfer to more complex organisms are still controversial. If this case holds up, it demonstrates how important the process can be for evolution, she adds.
Others - Decades - Plants - Landfall - Genomes
She and others have puzzled for decades about how plants made landfall. Comparing genomes of close relatives is one way to track down when landlubber traits evolved, but only since 2012 have researchers considered these algae, part of the class Zygnematophyceae, to be the closest to land plants. Most Zygnematophyceae are aquatic and have huge, complicated genomes, but not S. muscicola or M. endlicherianum. Their genomes are less than one-tenth the size of the human...
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