The evolutionary emergence of land plants

Abstract

There can be no doubt that early land plant evolution transformed the planet but, until recently, how and when this was achieved was unclear. Coincidence in the first appearance of land plant fossils and formative shifts in atmospheric oxygen and CO 2 are an artefact of the paucity of earlier terrestrial rocks. Disentangling the timing of land plant bodyplan assembly and its impact on global biogeochemical cycles has been precluded by uncertainty concerning the relationships of bryophytes to one another and to the tracheophytes, as well as the timescale over which these events unfolded. New genome and transcriptome sequencing projects, combined with the application of sophisticated phylogenomic modelling methods, have yielded increasing support for the Setaphyta clade of liverworts and mosses, within monophyletic bryophytes. We consider the evolution of anatomy, genes, genomes and of development within this phylogenetic context, concluding that many vascular plant (tracheophytes) novelties were already present in a comparatively complex last common ancestor of living land plants (embryophytes). Molecular clock analyses indicate that embryophytes emerged in a mid-Cambrian to early Ordovician interval, compatible with hypotheses on their role as geoengineers, precipitating early Palaeozoic glaciations.

Divergent evolutionary trajectories of bryophytes and tracheophytes from a complex common ancestor of land plants

“…These analyses of individual gene families corroborated the pattern of loss along the branch leading to bryophytes. The loss of these orthologous gene families strengthens the hypothesis that ancestral embryophyte had a more complex vasculature system than that of extant bryophytes (Donoghue et al, 2021). Overall, the loss of gene families (Fig.…”

“…Likewise, interpretations of the early land plant fossil record have been contingent on the first land plants appearing more like extant bryophytes than tracheophytes. That the ancestral embryophyte may have been more complex than living bryophytes is in keeping with many early macrofossils being both more complex than bryophytes and possessing a mosaic of tracheophyte and bryophyte traits (Edwards et al, 2014;Donoghue et al, 2021). Supplementary Figure 11.…”

“…Embryophytes form a monophyletic group nested within fresh water streptophyte algae (de Vries and Archibald, 2018) and their move to land, while providing a new ecological niche, presented new challenges that required adaptation to water loss and growth against gravity (Raven, 2002). Early innovations that evolved in response to these challenges include a thick waxy cuticle, stomata, and means of transporting water from the roots up vertically growing stems (Pires and Dolan, 2012; de Vries and Archibald, 2018; Harrison and Morris, 2018;Donoghue et al, 2021). Modern land plants comprise two main lineages, vascular plants (tracheophytes) and non-vascular plants (bryophytes), that have responded to these evolutionary challenges in different ways.…”

Origin and evolution of green plants in the light of key evolutionary events

“…Early cladistic studies using morphological and biochemical characters, as well as the mitochondrial multigene data, strongly supported the paraphyly hypothesis of bryophytes (Mishler and Churchill, 1985; Qiu et al, 2006; Qiu, 2008). The availability of large‐scale nuclear genes and application of more complex evolutionary models have shown that bryophytes formed a monophyletic group, sister to the vascular plants (Figure 2; Puttick et al, 2018; de Sousa et al, 2019; Su et al, 2021; Donoghue et al, 2021). The inconsistent relationships within bryophytes phylogeny is likely caused by lineage‐specific differences of rate variation and deviating amino acid/nucleotide composition.…”

Evolutionary Analysis and Functional Identification of Ancient Brassinosteroid Receptors in Ceratopteris richardii

“…These adaptions to the environment primarily rely on a regulatory system of phytohormones [ 1 , 2 ]. From the terrestrial colonization by plants in the Paleozoic to the eventual dominance of angiosperms, the phytohormone regulation systems have continuously evolved, forming various regulation networks [ 3 , 4 ].…”