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Plant Evolution: When Arabidopsis Is More Ancestral Than Marchantia
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International audience. The quest for determining how looked like the plants that first lived on lands 450 million years ago is among the most exciting challenges in evolutionary biology. Recent works indicate that they displayed angiosperm-like stomata. Text: The ancestor of extant land plants diverged from the lineage leading to the Zygnematophyceae algae and gradually adapted to the terrestrial environment. Fossils of 450-475 million years old spore dyads and tetrads, which are structures associated only with land plant, are the first evidence of the changes in this branch of the green lineage [1]. Well-preserved fossil specimens tell us that less than 50 million years later the plant lineage had already diversified, with plants displaying subaerial and underground axes, and vasculature [2]. Between these two milestones: a gap of 50 million years devoid of known macrofossils, leaving a gap even wider in our understanding of plant evolution. The morphology, physiology and overall biology of the first land plants remain an absolute mystery. Although the hunt for fossils of the first land plants is ongoing, an alternative approach would be to infer, to predict, their morphology and physiology based on extant land plant species. For such an inference, an accurate understanding of the plant phylogeny and the precise description of the traits of interest across this phylogeny are needed [3]. In this issue of Current Biology Harris et al. (XXX) combined a consolidated plant phylogeny with the phylogenetic analysis of genes linked to stomata development to determine whether stomata were present in the most recent common ancestor (MRCA) of land plants. The monophyly of Bryophytes supported once again Resolving the deep nodes of the land-plant phylogeny, the ones close to their origin more than 450 million years ago, has been a major goal in evolutionary biology for decades. Over the last five years, the availability of newly sequenced genomes and transcriptomes combined with a wide array of molecular phylogenetic methods allowed two hypotheses to
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