Molecular circumscription of the hornworts (Anthocerotophyta) based on the chloroplast DNA trnL?trnF region

Abstract

In phylogenetic trees generated from partial trnL(UAA) intron sequences, the hornworts (represented by nine species from the genera Anthoceros, Dendroceros, Megaceros, Notothylas and Phaeoceros) are resolved as a monophyletic group and are separated from the clades of mosses, liverworts and tracheophytes. A secondary structure of the trnL(UAA) intron of Anthoceros agrestis is presented, displaying the arrangement of the stem-loop regions P1-P9. Compensatory base-pair changes (coevolutionary sites) are detected in regions P4/5 and P9 within the hornwort sequences. The original homology of the most variable region, P8, cannot be detected anymore due to the extremely fast divergent evolution of this segment in the major land plant groups. Similarly, a high sequence divergence occurs in the trnL-trnF intergenic spacer. Apart from synapomorphic substitutions in the trnL(UAA) intron, the hornworts are characterised by a large P6 region consisting of many repetitive elements. The molecular data therefore support the hornworts as representing an independent land plant lineage (Anthocerotophyta). Although relationships between hornworts and the other land plant groups remain unresolved in the trnL(UAA) intron trees, it is rather unlikely that bryophytes are monophyletic in their traditional circumscription, i.e. comprising hornworts, mosses and liverworts.

Systematic position of Habrodon (Habrodontaceae, Musci) as inferred from nuclear ITS1 and ITS2 and chloroplast trnL intron and trnL–trnF spacer sequence data

“…The region of the internal transcribed spacers of nrDNA conventionally includes the entire ITS1, 5,8S gene and ITS2 portion of the nrDNA cistron and is one of the most informative molecular markers for phylogenetic analyses at the genus and species levels (Coleman, 2003). Whereas, the chloroplast trnL-trnF region, especially the trnL intron, is used widely for inferring phylogenetic relationships among families and genera of angiosperms (Taberlet & al.,1991), of bryophytes (Stech & al., 2003) and therefore provide another independent marker for phylogenetic reconstruction in our study.…”

20,000 species and five key markers: The status of molecular bryophyte phylogenetics

“…Stech et al 2003a;Quandt & Stech 2005;Hernández-Maqueda et al 2008b). As the trnL intron represents one of the first widely used phylogenetic markers and can be sequenced easily, extensive sequence data is available for all three bryophyte lineages (see Stech et al 2003a;Quandt & Stech 2005). Considerable differences exist concerning the variability of the intron in the three bryophyte lineages.…”

“…In most bryological studies, however, the trnL intron is co-amplified with the rather short trnL-F spacer (see below), an approach mostly followed in seed plants as well (see Borsch & Quandt 2009). As with all other G1 introns, the trnL intron can be characterized by a mosaic structure of highly conserved elements called P, Q, R, and S, which are essential for correct splicing (Davies et al 1982;Cech 1990) and alternate with less constrained stem-loop regions P1−P9 of variable size (see Borsch et al 2003;Stech et al 2003aQuandt & Stech 2005;Borsch & Quandt 2009). Length variability is mostly confined to P6 and P8, which display a high degree of microstructural changes including inversions or deletions (e.g.…”

Sporoderm ultrastructure in Anthoceros agrestis Paton

“…Latest molecular data suggest that hornworts are sister group to vascular plants (Beckert et al, 1999, Samigullin et al, 2002Shaw & Renzaglia, 2004, Qui et al, 2006Troitsky et al, 2007;Stech et al, 2003), and that has aroused considerable interest to their morphology. Data on the spore morphology and ultrastructure are particularly pertinent because they allow comparisons with fossil material, including even the earliest land plants (Taylor, 2003;Taylor et al, 2011).…”