Establishment of Anthoceros agrestis as a model species for studying the biology of hornworts

Abstract

BackgroundPlants colonized terrestrial environments approximately 480 million years ago and have contributed significantly to the diversification of life on Earth. Phylogenetic analyses position a subset of charophyte algae as the sister group to land plants, and distinguish two land plant groups that diverged around 450 million years ago – the bryophytes and the vascular plants. Relationships between liverworts, mosses hornworts and vascular plants have proven difficult to resolve, and as such it is not clear which bryophyte lineage is the sister group to all other land plants and which is the sister to vascular plants. The lack of comparative molecular studies in representatives of all three lineages exacerbates this uncertainty. Such comparisons can be made between mosses and liverworts because representative model organisms are well established in these two bryophyte lineages. To date, however, a model hornwort species has not been available.ResultsHere we report the establishment of Anthoceros agrestis as a model hornwort species for laboratory experiments. Axenic culture conditions for maintenance and vegetative propagation have been determined, and treatments for the induction of sexual reproduction and sporophyte development have been established. In addition, protocols have been developed for the extraction of DNA and RNA that is of a quality suitable for molecular analyses. Analysis of haploid-derived genome sequence data of two A. agrestis isolates revealed single nucleotide polymorphisms at multiple loci, and thus these two strains are suitable starting material for classical genetic and mapping experiments.ConclusionsMethods and resources have been developed to enable A. agrestis to be used as a model species for developmental, molecular, genomic, and genetic studies. This advance provides an unprecedented opportunity to investigate the biology of hornworts.

Origins and Evolution of Stomatal Development

“…The development of molecular genetic techniques for the liverwort Marchantia (Ishizaki et al, 2008) and the hornwort Anthoceros (Szövényi et al, 2015) will permit a greater understanding of the relationships between ancestral clades and the acquisition of those traits that permitted the colonization of the land. With the identification of new genes that potentially act on stomatal development, we now have an updated roadmap with which to interrogate some of the unanswered questions relating to the evolution of stomata.…”

“…For simplicity, non-stomata-associated EPFs from vascular land plants have been omitted from the tree. The A. punctatus ApEPF1 partial sequence is based on Szövényi et al (2015). Alignment and phylogenetic trees were prepared as described for Figure 2.…”

“…Using the hornwort Anthoceros punctatus and pseudostomate Sphagnum fallax genomes (Szövényi et al, 2015;Shaw et al, 2016) and the prerelease of the liverwort Marchantia polymorpha genome on Phytozome V11 (Goodstein et al, 2012), we can begin to identify whether genes required for stomatal development are present in unexplored taxa and plant groups that lack stomata. Strikingly, our analyses indicate that the stomatous hornwort A. punctatus possesses genes closely related to both PpSMF1 and PpSCRM1 (Fig.…”

Field Guide to Plant Model Systems

“…Anthoceros agrestis (83 Mb) has been proposed as a model hornwort system—culture conditions and preliminary genome sequences have been produced (Szövényi et al, 2015a). As with the other bryophyte systems, the establishment of a transformation system perhaps based on that of M. polymorpha would facilitate functional genetic studies.…”

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