Mosses are a highly diverse lineage of land plants, whose diversification, spanning at least 400 million years, remains phylogenetically ambiguous due to the lack of fossils, massive early ...extinctions, late radiations, limited morphological variation, and conflicting signal among previously used markers. Here, we present phylogenetic reconstructions based on complete organellar exomes and a comparable set of nuclear genes for this major lineage of land plants. Our analysis of 142 species representing 29 of the 30 moss orders reveals that relative average rates of non-synonymous substitutions in nuclear versus plastid genes are much higher in mosses than in seed plants, consistent with the emerging concept of evolutionary dynamism in mosses. Our results highlight the evolutionary significance of taxa with reduced morphologies, shed light on the relative tempo and mechanisms underlying major cladogenic events, and suggest hypotheses for the relationships and delineation of moss orders.
Plant body plans arise by the activity of meristematic growing tips during development and radiated independently in the gametophyte (n) and sporophyte (2n) stages of the life cycle during evolution. ...Although auxin and its intercellular transport by PIN family efflux carriers are primary regulators of sporophytic shoot development in flowering plants, the extent of conservation in PIN function within the land plants and the mechanisms regulating bryophyte gametophytic shoot development are largely unknown.
We have found that treating gametophytic shoots of the moss Physcomitrella patens with exogenous auxins and auxin transport inhibitors disrupts apical function and leaf development. Two plasma membrane-targeted PIN proteins are expressed in leafy shoots, and pin mutants resemble plants treated with auxins or auxin transport inhibitors. PIN-mediated auxin transport regulates apical cell function, leaf initiation, leaf shape, and shoot tropisms in moss gametophytes. pin mutant sporophytes are sometimes branched, reproducing a phenotype only previously seen in the fossil record and in rare natural moss variants.
Our results show that PIN-mediated auxin transport is an ancient, conserved regulator of shoot development.
•PIN proteins have polar plasma membrane localizations in the moss Physcomitrella•PIN-mediated auxin transport drives gametophytic shoot development in Physcomitrella•PIN-mediated auxin transport suppresses branching in Physcomitrella sporophytes
Shooting systems have undergone 450 million years of independent evolution in flowering plant sporophytes and bryophyte gametophytes. Bennett et al. show that PIN-mediated auxin transport regulates shoot development in both life cycle stages in a moss and identify potential roles for PIN proteins in the evolution of plant body plans.
Premise
To address the biodiversity crisis, we need to understand the evolution of all organisms and how they fill geographic and ecological space. Syntrichia is one of the most diverse and dominant ...genera of mosses, ranging from alpine habitats to desert biocrusts, yet its evolutionary history remains unclear.
Methods
We present a comprehensive phylogenetic analysis of Syntrichia, based on both molecular and morphological data, with most of the named species and closest outgroups represented. In addition, we provide ancestral‐state reconstructions of water‐related traits and a global biogeographic analysis.
Results
We found 10 major well‐resolved subclades of Syntrichia that possess geographical or morphological coherence, in some cases representing previously accepted genera. We infer that the extant species diversity of Syntrichia likely originated in South America in the early Eocene (56.5–43.8 million years ago Mya), subsequently expanded its distribution to the neotropics, and finally dispersed to the northern hemisphere. There, the clade experienced a recent diversification (15–12 Mya) into a broad set of ecological niches (e.g., the S. caninervis and S. ruralis complexes). The transition from terricolous to either saxicolous or epiphytic habitats occurred more than once and was associated with changes in water‐related traits.
Conclusions
Our study provides a framework for understanding the evolutionary history of Syntrichia through the combination of morphological and molecular characters, revealing that migration events that shaped the current distribution of the clade have implications for morphological character evolution in relation to niche diversity.
Key message
Most known phytohormones regulate moss development. We present a comprehensive view of the synthesis and signaling pathways for the most investigated of these compounds in mosses, ...focusing on the model
Physcomitrium patens.
The last 50 years of research have shown that most of the known phytohormones are synthesized by the model moss
Physcomitrium patens
(formerly
Physcomitrella patens
) and regulate its development, in interaction with responses to biotic and abiotic stresses. Biosynthesis and signaling pathways are best described in
P. patens
for the three classical hormones auxins, cytokinins and abscisic acid. Furthermore, their roles in almost all steps of development, from early filament growth to gametophore development and sexual reproduction, have been the focus of much research effort over the years. Evidence of hormonal roles exist for ethylene and for CLE signaling peptides, as well as for salicylic acid, although their possible effects on development remain unclear. Production of brassinosteroids by
P. patens
is still debated, and modes of action for these compounds are even less known. Gibberellin biosynthesis and signaling may have been lost in
P. patens
, while gibberellin precursors such as
ent
-kaurene derivatives could be used as signals in a yet to discover pathway. As for jasmonic acid, it is not used per se as a hormone in
P. patens
, but its precursor OPDA appears to play a corresponding role in defense against abiotic stress. We have tried to gather a comprehensive view of the biosynthesis and signaling pathways for all these compounds in mosses, without forgetting strigolactones, the last class of plant hormones to be reported. Study of the strigolactone response in
P. patens
points to a novel signaling compound, the KAI2-ligand, which was likely employed as a hormone prior to land plant emergence.
Mosses were proved as an ideal and reliable biomonitor as well as an indicator of atmospheric trace metal pollution. They are used as model indicator species of air pollution since long back due to ...their simple structure, genetic diversity, totipotency, rapid colony-forming ability, and high metal resistance behavior. Bryomonitoring technique is gradually being popularized as an economically viable procedure for estimating the degrees of environmental health and evaluating the toxic pollutants in biosphere. Thus, in the present scenario, many parts of the world use these organisms for monitoring the air pollution. This article describes an overview of the relationship of terrestrial mosses with trace metals with respect to their uptake, accumulation, and toxification as well as detoxification and tolerance mechanisms. The review article explicitly expresses the caliber of the cryptogamic mosses in establishing the pristine environment around the world. It also highlights the underpinning mechanisms and potential for future research directions. We have referred more than 250 articles, which deals with the assessment and impact of different heavy metals on 52 numbers of different moss species belongs to different climatic zones. The present review covers the research work in this area carried out worldwide since 1965.
In karst rocky desertification areas, bryophytes coexist with algae, bacteria, and fungi on exposed calcareous rocks to form a bryophyte crust, which plays an irreplaceable role in the restoration of ...karst degraded ecosystems. We investigated the biodiversity of crust bryophytes in karst rocky desertification areas from Guizhou Province, China. A total of 145 species in 22 families and 56 genera were identified. According to frequency and coverage, seven candidate dominant mosses were screened out, and five drought-resistant indexes of them were measured.
Hypnum leptothallum
,
Racopilum cuspidigerum
, and
Hyophila involuta
have high drought adaptability. We explored the interactions between two dominant mosses (
H. leptothallum
,
H. involuta
) and the structure of microbial communities in three karst rocky desertification types. Microbial diversity and function analysis showed that both moss species and karst rocky desertification types affect microbial communities. Moss species much more strongly affected the diversity and changed the community composition of these microbial groups. Bacteria were more sensitive in the microbiome as their communities changed strongly between mosses and drought resistance factors. Moreover, several species of fungi and bacteria could be significantly associated with three drought-resistant indexes: Pro (free proline content), SOD (superoxide dismutase activity), and POD (peroxidase activity), which were closely related to the drought adaptability of mosses. Our results enforced the potential role of moss-associated microbes that are important components involved in the related biological processes when bryophytes adapted to arid habitats, or as one kind of promoters in the distribution pattern of early mosses succession in karst rocky desertification areas.
The "bryophytes" comprise three phyla of plants united by a similar haploid-dominant life cycle and unbranched sporophytes bearing one sporangium: the liverworts (Marchantiophyta), mosses ...(Bryophyta), and hornworts (Anthocerophyta). Combined, these groups include some 20000 species. As descendents of embryophytes that diverged before tracheophytes appeared, bryophytes offer unique windows into the early evolution of land plants. We review insights into the evolution of plant life cycles, in particular the elaboration of the sporophyte generation, the major lineages within bryophyte phyla, and reproductive processes that shape patterns of bryophyte evolution. Recent transcriptomic work suggests extensive overlap in gene expression in bryophyte sporophytes vs. gametophytes, but also novel patterns in the sporophyte, supporting Bower's antithetic hypothesis for origin of alternation of generations. Major lineages of liverworts, mosses, and hornworts have been resolved and general patterns of morphological evolution can now be inferred. The life cycles of bryophytes, arguably more similar to those of early embryophytes than are those in any other living plant group, provide unique insights into gametophyte mating patterns, sexual conflicts, and the efficacy and effects of spore dispersal during early land plant evolution.
Across the Canadian Arctic Archipelago, widespread ice retreat during the 20th century has sharply accelerated since 2004. In Sverdrup Pass, central Ellesmere Island, rapid glacier retreat is ...exposing intact plant communities whose radiocarbon dates demonstrate entombment during the Little Ice Age (1550–1850 AD). The exhumed bryophyte assemblages have exceptional structural integrity (i.e., setae, stem structures, leaf hair points) and have remarkable species richness (60 of 144 extant taxa in Sverdrup Pass). Although the populations are often discolored (blackened), some have developed green stem apices or lateral branches suggesting in vivo regrowth. To test their biological viability, Little Ice Age populations emerging from the ice margin were collected for in vitro growth experiments. Our results include a unique successful regeneration of subglacial bryophytes following 400 y of ice entombment. This finding demonstrates the totipotent capacity of bryophytes, the ability of a cell to dedifferentiate into a meristematic state (analogous to stem cells) and develop a new plant. In polar ecosystems, regrowth of bryophyte tissue buried by ice for 400 y significantly expands our understanding of their role in recolonization of polar landscapes (past or present). Regeneration of subglacial bryophytes broadens the concept of Ice Age refugia, traditionally confined to survival of land plants to sites above and beyond glacier margins. Our results emphasize the unrecognized resilience of bryophytes, which are commonly overlooked vis-a-vis their contribution to the establishment, colonization, and maintenance of polar terrestrial ecosystems.
Bryophytes, including liverworts, mosses, and hornworts, are gametophyte-dominant land plants that are derived from a common ancestor and underwent independent evolution from the sporophyte-dominant ...vascular plants since their divergence. The plant hormone auxin has been shown to play pleiotropic roles in the haploid bodies of bryophytes. Pharmacological and chemical studies identified conserved auxin molecules, their inactivated forms, and auxin transport in bryophyte tissues. Recent genomic and molecular biological studies show deep conservation of components and their functions in auxin biosynthesis, inactivation, transport, and signaling in land plants. Low genetic redundancy in model bryophytes enable unique assays, which are elucidating the design principles of the auxin signaling pathway. In this article, the physiological roles of auxin and regulatory mechanisms of gene expression and development by auxin in Bryophyta are reviewed.
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