Broad Phylogenomic Sampling and the Sister Lineage of Land Plants

Abstract

The tremendous diversity of land plants all descended from a single charophyte green alga that colonized the land somewhere between 430 and 470 million years ago. Six orders of charophyte green algae, in addition to embryophytes, comprise the Streptophyta s.l. Previous studies have focused on reconstructing the phylogeny of organisms tied to this key colonization event, but wildly conflicting results have sparked a contentious debate over which lineage gave rise to land plants. The dominant view has been that ‘stoneworts,’ or Charales, are the sister lineage, but an alternative hypothesis supports the Zygnematales (often referred to as “pond scum”) as the sister lineage. In this paper, we provide a well-supported, 160-nuclear-gene phylogenomic analysis supporting the Zygnematales as the closest living relative to land plants. Our study makes two key contributions to the field: 1) the use of an unbiased method to collect a large set of orthologs from deeply diverging species and 2) the use of these data in determining the sister lineage to land plants. We anticipate this updated phylogeny not only will hugely impact lesson plans in introductory biology courses, but also will provide a solid phylogenetic tree for future green-lineage research, whether it be related to plants or green algae.

Eukaryotic algal phytochromes span the visible spectrum

“…To date, photochemical properties have only been reported for algal phytochromes from charophytes (26)(27)(28), organisms associated with shallow freshwater ecosystems (29). These proteins exhibit red/far-red photocycles similar to those of land plant phytochromes, which are the closest extant relatives of charophytes…”

Characterization of the Heterotrimeric G-Protein Complex and Its Regulator from the Green Alga Chara braunii Expands the Evolutionary Breadth of Plant G-Protein Signaling

“…The charophyte green algae are especially interesting from an evolutionary perspective, since they are the closest living relatives of the ancestors of the embryophytes (Becker and Marin, 2009; Niklas and Kutschera, 2010;Wodniok et al, 2011;Laurin-Lemay et al, 2012;Timme et al, 2012;Raven, 2013;Zhong et al, 2013). Superficially, these algae (e.g.…”

Green Algae and the Origins of Multicellularity in the Plant Kingdom

“…This view has been corroborated and refined using molecular phylogenetics that have begun to clarify relationships within charophyte algae and with their sister clade, the land plants (embryophytes) (Turmel et al 2002;Finet et al 2010;Wodniok et al 2011;Laurin-Lemay et al 2012;Timme et al 2012;Zhong et al 2013).…”

“…It is important to note that the extant charophyte lineages are highly diverged from each other and have probably undergone secondary character losses that complicate comparisons and inferences about the progression to multicellularity in the embryophytes Timme et al 2012;Bowman 2013). Moreover, the fossil record of charophyte algae is incomplete and does not extend earlier than that of land plants, so is not a reliable source of information on timing for emergence of early embryophytes whose earliest fossils appear 500 million years ago ).…”

“…Moreover, the fossil record of charophyte algae is incomplete and does not extend earlier than that of land plants, so is not a reliable source of information on timing for emergence of early embryophytes whose earliest fossils appear 500 million years ago ). As noted above, the charophyte algal order that is most closely related to land plants is unresolved, but it is clear that the most developmentally complex order, Charophyceae (stoneworts), is probably not the closest relative of the embryophyte lineage (Wodniok et al 2011;Laurin-Lemay et al 2012;Timme et al 2012;Zhong et al 2013). Despite this ambiguity and the likelihood of both character loss and gain in the extant charophyte algal orders, some of the steps leading to multicellularity in the embryophytes can still be inferred.…”