Understanding desiccation tolerance and sex-specific responses in Bryum argenteum: insights from phenological phases and physiological analyses.

BACKGROUND AND AIMS: Desiccation tolerance (DT) is crucial for survival in arid environments, where organisms develop strategies in reproduction, maintenance and defence to cope with water scarcity. Therefore, investigating the relationship between reproduction and DT is essential to understand the ecology and adaptive strategies of species. This study explores the connection between the development of male and female gametangia in the moss Bryum argenteum and the decrease in DT during the progression of phenological phases in gametangia and protonema. METHODS: Samples collected from a dry tropical forest in Brazil were cultivated, cloned and subjected to desiccation. Subsequently, the physiological parameters of shoots and protonemata were analysed. Shoot and protonema regeneration were monitored for 28 d after the physiological analyses. Both phases were subjected to control and desiccation treatments. KEY RESULTS: Significant effects of desiccation and sex on the physiological parameters and regeneration capacity of shoots and protonemata were found. Male shoots generally exhibited lower values of Fv/Fm (quantum efficiency of photosystem II) and ϕPSII (effective quantum yield of photosystem II), while females demonstrated higher values and better recovery after desiccation. Protonemata also showed variation in Fv/Fm over time and with sex, with no significant differences in ϕPSII between them. Desiccated male shoots had higher mortality rates and produced fewer new shoots. For females, the regeneration patterns varied between the desiccation-exposed groups and the control, with decreased shoot production, and some protonemata growing into filaments without forming shoots. CONCLUSION: These findings improve our understanding of the ecological responses of bryophytes to desiccation stress and provide insights into their adaptive strategies in challenging environments, such as the possible rarity of males in dioicous moss populations.

The spatial arrangement of sexes is related to reproductive allocation in mosses: a comparative study of reproductive allocation in three different monoicous sexual systems.

BACKGROUND AND AIMS: We examined the relationship between reproductive allocation and vegetative growth in three monoicous sexual systems of bryophytes. The sexual systems show a gradient of increasing distance between the sexes, from gonioautoicous to cladautoicous to rhizautoicous. Here, we investigated the following two hypotheses: (1) reproductive allocation differs between sexes and sexual systems, and male reproductive allocation increases with increasing distance between male and female gametangia; and (2) reproductive allocation is negatively related to vegetative growth. METHODS: We sampled the three sexual systems, represented by three moss species of the genus Fissidens in the Atlantic Forest of Southeastern Brazil. Ramets were washed in the laboratory; the reproductive structures were detached from the vegetative ramets and sorted regarding sex and individual, dried at 70 °C for 72 h, and weighed in an ultramicrobalance. We calculated the mean reproductive and vegetative mass and reproductive allocation and used generalized linear models to test our predictions. KEY RESULTS: Reproductive allocation differed between species and sexes. It was higher in the rhizautoicous than in the cladautoicous and gonioautoicous species. Mean reproductive allocation was greater in males than in females of the rhizautoicous species, greater in females than males of the cladautoicous species, and did not differ between the sexes in the gonioautoicous species. Estimates of reproductive and vegetative mass were positively related in females of the rhizautoicous species. Vegetative mass was not related to reproductive allocation in the gonioautoicous species, but negatively related to reproductive allocation in the male and female branchlets of the cladautoicous species and in the female ramets of the rhizautoicous species. CONCLUSIONS: The reproductive allocation patterns differ between the rhizautoicous species and the 'truly' monoicous species, with shorter intersexual distances, which implies that our hypotheses were supported only in part. We suggest that the hypotheses should be reformulated and tested further by comparing 'truly' monoicous species with dioicous species and by including other genera.

N6 -Methyladenosine modification of mRNA contributes to the transition from 2D to 3D growth in the moss Physcomitrium patens.

Plants colonized the land approximately 470 million years ago, coinciding with the development of apical cells that divide in three planes. The molecular mechanisms that underly the development of the 3D growth pattern are poorly understood, mainly because 3D growth in seed plants starts during embryo development. In contrast, the transition from 2D to 3D growth in the moss Physcomitrium patens has been widely studied, and it involves a large turnover of the transcriptome to allow the establishment of stage-specific transcripts that facilitate this developmental transition. N6 -Methyladenosine (m6 A) is the most abundant, dynamic and conserved internal nucleotide modification present on eukaryotic mRNA and serves as a layer of post-transcriptional regulation directly affecting several cellular processes and developmental pathways in many organisms. In Arabidopsis, m6 A has been reported to be essential for organ growth and determination, embryo development and responses to environmental signals. In this study, we identified the main genes of the m6 A methyltransferase complex (MTC), MTA, MTB and FIP37, in P. patens and demonstrate that their inactivation leads to the loss of m6 A in mRNA, a delay in the formation of gametophore buds and defects in spore development. Genome-wide analysis revealed several transcripts affected in the Ppmta background. We demonstrate that the PpAPB1-PpAPB4 transcripts, encoding central factors orchestrating the transition from 2D to 3D growth in P. patens, are modified by m6 A, whereas in the Ppmta mutant the lack of the m6 A marker is associated with a corresponding decrease in transcript accumulation. Overall, we suggest that m6 A is essential to enable the proper accumulation of these and other bud-specific transcripts directing the turnover of stage-specific transcriptomes, and thus promoting the transition from protonema to gametophore buds in P. patens.

Metabolome of Ceratodon purpureus (Hedw.) Brid., a cosmopolitan moss: the influence of seasonality.

MAIN CONCLUSION: Ceratodon purpureus showed changes in disaccharides, flavonoids, and carotenoids throughout annual seasons. These changes indicate harsher environmental conditions during the dry period, directing metabolic precursors to enhance the antioxidant system. Bryophytes are a group of land plants comprising mosses (Bryophyta), liverworts (Marchantyophyta), and hornworts (Antocerotophyta). This study uses the molecular networking approach to investigate the influence of seasonality (dry and rainy seasons) on the metabolome and redox status of the moss Ceratodon purpureus (Hedw.) Brid., from Campos do Jordão, Brazil. Samples of C. purpureus were submitted to three extraction methods: 80% methanol producing the soluble fraction (intracellular compounds), followed by debris hydrolysis using sodium hydroxide producing the insoluble fraction (cell wall conjugated compounds), both analyzed by HPLC-MS; and extraction using pre-cooled methanol, separated into polar and non-polar fractions, being both analyzed by GC-MS. All fractions were processed using the Global Natural Product Social Molecular Network (GNPS). The redox status was assessed by the analysis of four enzyme activities combined with the analysis of the contents of ascorbate, glutathione, carotenoids, reactive oxygen species (ROS), and malondialdehyde acid (MDA). During the dry period, there was an increase of most biflavonoids, as well as phospholipids, disaccharides, long-chain fatty acids, carotenoids, antioxidant enzymes, ROS, and MDA. Results indicate that C. purpureus is under harsher environmental conditions during the dry period, mainly due to low temperature and less water availability (low rainfall).

Sex-specific differences in reproductive life-history traits of the moss Weissia jamaicensis.

PREMISE: We investigated sex-specific differences in the life-history traits of a metapopulation of the dioicous moss Weissia jamaicensis. Field observations revealed high rates of fertilization, which is uncommon for most dioicous bryophytes. We raised four hypotheses associated with the way the reproductive traits are related to the fertilization rate in this metapopulation. METHODS: We sampled 10 patches of the metapopulation and quantified sexual expression, sex ratio, reproductive success, and reproductive allocation. The ramets were classified as male, non-sporophytic female, sporophytic female, or non-sex-expressing. Thirty ramets from each of the categories expressing sex were placed for regeneration to test the effect of reproductive allocation on this trait. RESULTS: We found greater expression of the female function in all patches, implying a female bias in the metapopulation. The number of male ramets was variable in each patch and did not affect reproductive success. At the prezygotic level, the allocation of resources to the male function was higher. However, the large allocation of resources to sporophyte development in sporophytic females, which exceeded allocations at prezygotic levels, was related to the higher mortality rate of these ramets, suggesting reproductive cost. CONCLUSIONS: The prezygotic ramets that allocated the greatest amount of resources to reproduction expressed sex less frequently, biasing the sex ratio toward the sex that allocated the least amount of resources to reproduction. Overall, the ramets that allocated the greatest amount of resources to reproduction had the lowest regeneration rate, suggesting reproductive cost.

Moss transcription factors regulating development and defense responses to stress.

Transcription factors control gene expression, leading to regulation of biological processes that determine plant development and adaptation to the environment. Land colonization by plants occurred 450-470 million years ago and was accompanied by an increase in the complexity of transcriptional regulation associated to transcription factor gene expansions. AP2/ERF, bHLH, MYB, NAC, GRAS, and WRKY transcription factor families increased in land plants compared with algae. In angiosperms, they play crucial roles in regulating plant growth and responses to environmental stressors. However, less information is available in bryophytes and only in a few cases is the functional role of moss transcription factors in stress mechanisms known. In this review, we discuss current knowledge of the transcription factor families involved in development and defense responses to stress in mosses and other bryophytes. By exploring and analysing the Physcomitrium patens public database and published transcriptional profiles, we show that a high number of AP2/ERF, bHLH, MYB, NAC, GRAS, and WRKY genes are differentially expressed in response to abiotic stresses and during biotic interactions. Expression profiles together with a comprehensive analysis provide insights into relevant transcription factors involved in moss defenses, and hint at distinct and conserved biological roles between bryophytes and angiosperms.

Pseudocrossidium replicatum (Taylor) R.H. Zander is a fully desiccation-tolerant moss that expresses an inducible molecular mechanism in response to severe abiotic stress.

KEY MESSAGE: The moss Pseudocrossidium replicatum is a desiccation-tolerant species that uses an inducible system to withstand severe abiotic stress in both protonemal and gametophore tissues. Desiccation tolerance (DT) is the ability of cells to recover from an air-dried state. Here, the moss Pseudocrossidium replicatum was identified as a fully desiccation-tolerant (FDT) species. Its gametophores rapidly lost more than 90% of their water content when exposed to a low-humidity atmosphere [23% relative humidity (RH)], but abscisic acid (ABA) pretreatment diminished the final water loss after equilibrium was reached. P. replicatum gametophores maintained good maximum photosystem II (PSII) efficiency (Fv/Fm) for up to two hours during slow dehydration; however, ABA pretreatment induced a faster decrease in the Fv/Fm. ABA also induced a faster recovery of the Fv/Fm after rehydration. Protein synthesis inhibitor treatment before dehydration hampered the recovery of the Fv/Fm when the gametophores were rehydrated after desiccation, suggesting the presence of an inducible protective mechanism that is activated in response to abiotic stress. This observation was also supported by accumulation of soluble sugars in gametophores exposed to ABA or NaCl. Exogenous ABA treatment delayed the germination of P. replicatum spores and induced morphological changes in protonemal cells that resembled brachycytes. Transcriptome analyses revealed the presence of an inducible molecular mechanism in P. replicatum protonemata that was activated in response to dehydration. This study is the first RNA-Seq study of the protonemal tissues of an FDT moss. Our results suggest that P. replicatum is an FDT moss equipped with an inducible molecular response that prepares this species for severe abiotic stress and that ABA plays an important role in this response.

Transcriptional profiling reveals conserved and species-specific plant defense responses during the interaction of Physcomitrium patens with Botrytis cinerea.

KEY MESSAGE: Evolutionary conserved defense mechanisms present in extant bryophytes and angiosperms, as well as moss-specific defenses are part of the immune response of Physcomitrium patens. Bryophytes and tracheophytes are descendants of early land plants that evolved adaptation mechanisms to cope with different kinds of terrestrial stresses, including drought, variations in temperature and UV radiation, as well as defense mechanisms against microorganisms present in the air and soil. Although great advances have been made on pathogen perception and subsequent defense activation in angiosperms, limited information is available in bryophytes. In this study, a transcriptomic approach uncovered the molecular mechanisms underlying the defense response of the bryophyte Physcomitrium patens (previously Physcomitrella patens) against the important plant pathogen Botrytis cinerea. A total of 3.072 differentially expressed genes were significantly affected during B. cinerea infection, including genes encoding proteins with known functions in angiosperm immunity and involved in pathogen perception, signaling, transcription, hormonal signaling, metabolic pathways such as shikimate and phenylpropanoid, and proteins with diverse role in defense against biotic stress. Similarly as in other plants, B. cinerea infection leads to downregulation of genes involved in photosynthesis and cell cycle progression. These results highlight the existence of evolutionary conserved defense responses to pathogens throughout the green plant lineage, suggesting that they were probably present in the common ancestors of land plants. Moreover, several genes acquired by horizontal transfer from prokaryotes and fungi, and a high number of P. patens-specific orphan genes were differentially expressed during B. cinerea infection, suggesting that they are important players in the moss immune response.

How do sexual expression, reproductive phenology and reproductive success relate to sexual systems in Fissidens Hedw. (Fissidentaceae)? A case study comparing two different sexual systems in mosses.

Reproductive performance is known to differ between co-sexual and non-co-sexual species. Thus, our aim was to determine whether: (i) the distance between sex structures is negatively associated with sex expression; (ii) male gametangia take longer to mature in rhizautoicous species than in gonioautoicous species; and (iii) the gonioautoicous sexual system has greater reproductive success (i.e. percentage of ramets with sporophyte) than the rhizautoicous sexual system. One population each of the mosses Fissidens scariosus and F. submarginatus, rhizautoicous and gonioautoicous, respectively, in a remnant of Atlantic Forest in Brazil were sampled monthly from September 2016 until August 2017. The number and phenophases of antheridia, archegonia and sporophytes were analysed for each species. Sexual expression and reproductive success were calculated, and reproductive phenology compared across environmental variables. As expected, sexual expression was significantly higher for the gonioautoicous species, which produced antheridia throughout the year and archegonia over many months, while gametangia production by the rhizautoicous species occurred only during the rainy season. Mean number of gametangia per perigonium and perichaetium were slightly higher for the rhizautoicous species (6.84 antheridia; 11.38 archegonia) than for the gonioautoicous species (4.39; 7.62). Gametangia and sporophyte production in the rhizautoicous species were markedly seasonal compared to that of the gonioautoicous species, although reproductive success did not differ. Therefore, we infer that the rhizautoicy (i.e. a functional dioicy) promotes lower expression of gametangia compared to gonioautoicy but is more efficient and so obtains the same reproductive success.

Evaluation of the acute toxicity, phototoxicity and embryotoxicity of a residual aqueous fraction from extract of the Antarctic moss Sanionia uncinata.

BACKGROUND: Ultraviolet (UV) radiation is the main exogenous inductor of skin damage and so photoprotection is important to control skin disorders. The Antarctic moss Sanionia uncinata is an important source of antioxidants and the photoprotective activity of its organic extracts has been investigated. This study aimed to evaluate the potential photoprotection, cytotoxicity and embryotoxicity of residual aqueous fraction (AF) from the moss S. uncinata. METHODS: UV-visible spectrum and SPF (sun protection factor) were determined by spectrophotometry. Embryotoxicity potential was evaluated by Fish embryo-larval toxicity test using zebrafish (Danio rerio) as organism model. Cell death assays by water-soluble tetrazolium salt (WST-1) and lactate dehydrogenase (LDH) were investigated using HaCaT keratinocyte cell line cultured in monolayers and three dimensions (3D). Phototoxicity and association with UV-filters were performed by 3T3 neutral red uptake test. RESULTS: The AF showed sharp absorption bands in the UV region and less pronounced in the visible region. The SPF was low (2.5 ± 0.3), but the SPF values of benzophenone-3 and octyl-methoxycinnamate increased ~ 3 and 4 times more, respectively, in association with AF. The AF did not induce significant lethal and sublethal effects on zebrafish early-life stages. In monolayers, the HaCaT cell viability, evaluated by WST-1, was above 70% by ≤0.4 mg AF/mL after 48 and 72-h exposure, whereas ≤1 mg AF/mL after 24-h exposure. The LDH assay showed that the cell viability was above 70% by ≤0.4 mg AF/mL even after 72-h exposure, but ≤1 mg/mL after 24 and 48-h exposure. In 3D cell culture, an increased cell resistance to toxicity was observed, because cell viability of HaCaT cell by WST-1 and LDH was above ~ 90% when using ≤1 and 4 mg AF/mL, respectively. The AF demonstrated values of photo irritation factor < 2 and of photo effect < 0.1, even though in association with UV-filters. CONCLUSIONS: The residual AF absorbs UV-vis spectrum, increased SPF values of BP-3 and OMC and does not induce embryotoxicity to zebrafish early life-stage. The cell death assays allowed establishing non-toxic doses of AF and phototoxicity was not detected. AF of S. uncinata presents a good potential for skin photoprotection against UV-radiation.

Desiccation tolerance in the Antarctic moss Sanionia uncinata.

BACKGROUND: One of the most extreme environments on our planet is the Maritime Antarctic territory, due to its low-water availability, which restricts the development of plants. Sanionia uncinata Hedw. (Amblystegiaceae), the main colonizer of the Maritime Antarctic, has effective mechanisms to tolerate this environment. It has been described that the tolerance to desiccation is mediated by the hormone abscisic acid (ABA), antioxidants systems, accumulation of compatible solutes and proteins of the late embryogenesis abundant (LEA). However, to date, these mechanisms have not been described in S. uncinata. Therefore, in this work, we postulate that the tolerance to desiccation in the Antarctic moss S. uncinata is mediated by the accumulation of ABA, the osmolytes proline and glycine betaine, and dehydrins (an LEA class 11 proteins). To demonstrate our hypothesis, S. uncinata was subjected to desiccation for 24 h (loss in 95% of water content), and the effects on its physiological, photosynthetic, antioxidant and biochemical parameters were determined. RESULTS: Our results showed an accumulation of ABA in response to water loss, and the activation of protective responses that involves an increment in levels of proline and glycine betaine, an increment in the activity of antioxidant enzymes such as SOD, CAT, APX and POD, and the accumulation of dehydrins proteins. CONCLUSION: The results showed, suggest that S. uncinata is a  desiccation-tolerant moss, property mediated by high cellular plasticity regulated by ABA.

Desiccation tolerance in the Antarctic moss Sanionia uncinata

BACKGROUND: One of the most extreme environments on our planet is the Maritime Antarctic territory, due to its low-water availability, which restricts the development of plants. Sanionia uncinata Hedw. (Amblystegiaceae), the main colonizer of the Maritime Antarctic, has effective mechanisms to tolerate this environment. It has been described that the tolerance to desiccation is mediated by the hormone abscisic acid (ABA), antioxidants systems, accumulation of compatible solutes and proteins of the late embryogenesis abundant (LEA). However, to date, these mechanisms have not been described in S. uncinata. Therefore, in this work, we postulate that the tolerance to desiccation in the Antarctic moss S. uncinata is mediated by the accumulation of ABA, the osmolytes proline and glycine betaine, and dehydrins (an LEA class 11 proteins). To demonstrate our hypothesis, S. uncinata was subjected to desiccation for 24 h (loss in 95% of water content), and the effects on its physiological, photosynthetic, antioxidant and biochemical parameters were determined. RESULTS: Our results showed an accumulation of ABA in response to water loss, and the activation of protective responses that involves an increment in levels of proline and glycine betaine, an increment in the activity of antioxidant enzymes such as SOD, CAT, APX and POD, and the accumulation of dehydrins proteins. CONCLUSION: The results showed, suggest that S. uncinata is a desiccation-tolerant moss, property mediated by high cellular plasticity regulated by ABA.

Heterologous protein production in the moss Physcomitrella patens

Over the last decades plants have been used for the heterologous production of pharmaceuticals, industrial enzymes and edible vaccines. The moss Physcomitrella patens is considered as an experimental model of choice for basic molecular, cytological and developmental questions in plant biology, as well as an outstanding plant model system for heterologous protein production. Here we use P. patens to produce osmotin, a tobacco protein with fungicidal properties. We have generated a transgenic plant able to synthesize and secrete a biologically active osmotin protein(AU)

Durante las últimas décadas las plantas han sido utilizadas para la producción heteróloga de farmacéuticos, enzimas de uso industrial y vacunas. El musgo Physcomitrella patens es considerado como un modelo de experimentación de elección para abordar preguntas en las áreas de biología molecular, citología y de biología del desarrollo en plantas; así como un excelente sistema modelo para la producción de proteínas heterólogas. En este trabajo se utilizó P. patens para la producción de osmotina, una proteína de tabaco con propiedades fungicidas. Se generó una planta transgénica capaz de sintetizar y secretar osmotina biológicamente activa(AU)

Genome-wide identification and characterization of tRNA-derived RNA fragments in land plants.

KEY MESSAGE: The manuscript by Alves et al. entitled "Genome-wide identification and characterization of tRNA-derived RNA fragments in land plants" describes the identification and characterization of tRNAderived sRNA fragments in plants. By combining bioinformatic analysis and genetic and molecular approaches, we show that tRF biogenesis does not rely on canonical microRNA/siRNA processing machinery (i.e., independent of DICER-LIKE proteins). Moreover, we provide evidences that the Arabidopsis S-like Ribonuclease 1 (RNS1) might be involved in the biogenesis of tRFs. Detailed analyses showed that plant tRFs are sorted into different types of ARGONAUTE proteins and that they have potential target candidate genes. Our work advances the understanding of the tRF biology in plants by providing evidences that plant and animal tRFs shared common features and raising the hypothesis that an interplay between tRFs and other sRNAs might be important to fine-tune gene expression and protein biosynthesis in plant cells. Small RNA (sRNA) fragments derived from tRNAs (3'-loop, 5'-loop, anti-codon loop), named tRFs, have been reported in several organisms, including humans and plants. Although they may interfere with gene expression, their biogenesis and biological functions in plants remain poorly understood. Here, we capitalized on small RNA sequencing data from distinct species such as Arabidopsis thaliana, Oryza sativa, and Physcomitrella patens to examine the diversity of plant tRFs and provide insight into their properties. In silico analyzes of 19 to 25-nt tRFs derived from 5' (tRF-5s) and 3'CCA (tRF-3s) tRNA loops in these three evolutionary distant species showed that they are conserved and their abundance did not correlate with the number of genomic copies of the parental tRNAs. Moreover, tRF-5 is the most abundant variant in all three species. In silico and in vivo expression analyses unraveled differential accumulation of tRFs in Arabidopsis tissues/organs, suggesting that they are not byproducts of tRNA degradation. We also verified that the biogenesis of most Arabidopsis 19-25 nt tRF-5s and tRF-3s is not primarily dependent on DICER-LIKE proteins, though they seem to be associated with ARGONAUTE proteins and have few potential targets. Finally, we provide evidence that Arabidopsis ribonuclease RNS1 might be involved in the processing and/or degradation of tRFs. Our data support the notion that an interplay between tRFs and other sRNAs might be important to fine tune gene expression and protein biosynthesis in plant cells.

Origin and function of stomata in the moss Physcomitrella patens.

Stomata are microscopic valves on plant surfaces that originated over 400 million years (Myr) ago and facilitated the greening of Earth's continents by permitting efficient shoot-atmosphere gas exchange and plant hydration1. However, the core genetic machinery regulating stomatal development in non-vascular land plants is poorly understood2-4 and their function has remained a matter of debate for a century5. Here, we show that genes encoding the two basic helix-loop-helix proteins PpSMF1 (SPEECH, MUTE and FAMA-like) and PpSCREAM1 (SCRM1) in the moss Physcomitrella patens are orthologous to transcriptional regulators of stomatal development in the flowering plant Arabidopsis thaliana and essential for stomata formation in moss. Targeted P. patens knockout mutants lacking either PpSMF1 or PpSCRM1 develop gametophytes indistinguishable from wild-type plants but mutant sporophytes lack stomata. Protein-protein interaction assays reveal heterodimerization between PpSMF1 and PpSCRM1, which, together with moss-angiosperm gene complementations6, suggests deep functional conservation of the heterodimeric SMF1 and SCRM1 unit is required to activate transcription for moss stomatal development, as in A. thaliana7. Moreover, stomata-less sporophytes of ΔPpSMF1 and ΔPpSCRM1 mutants exhibited delayed dehiscence, implying stomata might have promoted dehiscence in the first complex land-plant sporophytes.

Prezygotic resource-allocation dynamics and reproductive trade-offs in Calymperaceae (Bryophyta).

PREMISE OF THE STUDY: Resource allocation is difficult to characterize in plants because of the challenges of quantifying gametes and propagules. We surveyed six sympatric, unisexual species in the family Calymperaceae (Bryophyta) to test for trade-offs in prezygotic sexual and asexual expression and density-dependent survivorship of female gametangia. METHODS: We tallied gametangial and asexual propagule output for 1820 shoots from 17 populations of six species at monthly intervals during one year (2010-2011) in a central Amazonian forest. Generalized linear mixed models were used to test for trade-offs in sexual and asexual expression and density-dependent senescence probability of gametangia. Precipitation and microsite variables were also included in the model. KEY RESULTS: For all species, sexual and asexual expression were positively correlated with mean monthly precipitation. Asexually expressing shoots produced significantly fewer gametangia than nonexpressing ones, and the probability of senescence increased with shoot density. Archegonium density per shoot was also consistently lower than the modeled optimum to maximize the number of receptive archegonia. CONCLUSIONS: Trade-offs among reproductive strategies and positive density-dependent senescence of female gametangia suggest that prezygotic sexual and asexual expression come at a tangible investment. However, the apparently inefficient resource-allocation dynamics in the production of female gametangia makes the possible advantages of squandering such investments unclear. One possibility is that the study populations, like those of many dioicous mosses, are skewed toward expressing females with low sporophyte production, which would suggest that asexual reproduction predominates and upstages efficient resource allocation in prezygotic investment.

Soluble carbohydrate content variation in Sanionia uncinata and Polytrichastrum alpinum, two Antarctic mosses with contrasting desiccation capacities.

BACKGROUND: Cryptogamic vegetation dominates the ice-free areas along the Antarctic Peninsula. The two mosses Sanionia uncinata and Polytrichastrum alpinum inhabit soils with contrasting water availability. Sanionia uncinata grows in soil with continuous water supply, while P. alpinum grows in sandy, non-flooded soils. Desiccation and rehydration experiments were carried out to test for differences in the rate of water loss and uptake, with non-structural carbohydrates analysed to test their role in these processes. RESULTS: Individual plants of S. uncinata lost water 60 % faster than P. alpinum; however, clumps of S. uncinata took longer to dry than those of P. alpinum (11 vs. 5 h, respectively). In contrast, rehydration took less than 10 min for both mosses. Total non-structural carbohydrate content was higher in P. alpinum than in S. uncinata, but sugar levels changed more in P. alpinum during desiccation and rehydration (60-50 %) when compared to S. uncinata. We report the presence of galactinol (a precursor of the raffinose family) for the first time in P. alpinum. Galactinol was present at higher amounts than all other non-structural sugars. CONCLUSIONS: Individual plants of S. uncinata were not able to retain water for long periods but by growing and forming carpets, this species can retain water the longest. In contrast individual P. alpinum plants required more time to lose water than S. uncinata, but as moss cushions they suffered desiccation faster than the later. On the other hand, both species rehydrated very quickly. We found that when both mosses lost 50 % of their water, carbohydrates content remained stable and the plants did not accumulate non-structural carbohydrates during the desiccation prosses as usually occurs in vascular plants. The raffinose family oligosaccarides decreased during desiccation, and increased during rehydration, suggesting they function as osmoprotectors.

Soluble carbohydrate content variation in Sanionia uncinata and Polytrichastrum alpinum, two Antarctic mosses with contrasting desiccation capacities

BACKGROUND: Cryptogamic vegetation dominates the ice-free areas along the Antarctic Peninsula. The two mosses Sanionia uncinata and Polytrichastrum alpinum inhabit soils with contrasting water availability. Sanionia uncinata grows in soil with continuous water supply, while P. alpinum grows in sandy, non-flooded soils. Desiccation and rehydration experiments were carried out to test for differences in the rate of water loss and uptake, with non-structural carbohydrates analysed to test their role in these processes. RESULTS: Individual plants of S. uncinata lost water 60 % faster than P. alpinum; however, clumps of S. uncinata took longer to dry than those of P. alpinum (11 vs. 5 h, respectively). In contrast, rehydration took less than 10 min for both mosses. Total non-structural carbohydrate content was higher in P. alpinum than in S. uncinata, but sugar levels changed more in P. alpinum during desiccation and rehydration (60-50 %) when compared to S. uncinata. We report the presence of galactinol (a precursor of the raffinose family) for the first time in P. alpinum. Galactinol was present at higher amounts than all other non-structural sugars. CONCLUSIONS: Individual plants of S. uncinata were not able to retain water for long periods but by growing and forming carpets, this species can retain water the longest. In contrast individual P. alpinum plants required more time to lose water than S. uncinata, but as moss cushions they suffered desiccation faster than the later. On the other hand, both species rehydrated very quickly. We found that when both mosses lost 50 % of their water, carbohydrates content remained stable and the plants did not accumulate non-structural carbohydrates during the desiccation prosses as usually occurs in vascular plants. The raffinose family oligosaccarides decreased during desiccation, and increased during rehydration, suggesting they function as osmoprotectors.

Chemical structure and anticoagulant activity of highly pyruvylated sulfated galactans from tropical green seaweeds of the order Bryopsidales.

Sulfated and pyruvylated galactans were isolated from three tropical species of the Bryopsidales, Penicillus capitatus, Udotea flabellum, and Halimeda opuntia. They represent the only important sulfated polysaccharides present in the cell walls of these highly calcified seaweeds of the suborder Halimedineae. Their structural features were studied by chemical analyses and NMR spectroscopy. Their backbone comprises 3-, 6-, and 3,6-linkages, constituted by major amounts of 3-linked 4,6-O-(1'-carboxy)ethylidene-d-galactopyranose units in part sulfated on C-2. Sulfation on C-2 was not found in galactans from other seaweeds of this order. In addition, a complex sulfation pattern, comprising also 4-, 6-, and 4,6-disulfated galactose units was found. A fraction from P. capitatus, F1, showed a moderate anticoagulant activity, evaluated by general coagulation tests and also kinetics of fibrin formation was assayed. Besides, preliminary results suggest that one of the possible mechanisms involved is direct thrombin inhibition.

A primary assessment of the endophytic bacterial community in a xerophilous moss (Grimmia montana) using molecular method and cultivated isolates.

Investigating the endophytic bacterial community in special moss species is fundamental to understanding the microbial-plant interactions and discovering the bacteria with stresses tolerance. Thus, the community structure of endophytic bacteria in the xerophilous moss Grimmia montana were estimated using a 16S rDNA library and traditional cultivation methods. In total, 212 sequences derived from the 16S rDNA library were used to assess the bacterial diversity. Sequence alignment showed that the endophytes were assigned to 54 genera in 4 phyla (Proteobacteria, Firmicutes, Actinobacteria and Cytophaga/Flexibacter/Bacteroids). Of them, the dominant phyla were Proteobacteria (45.9%) and Firmicutes (27.6%), the most abundant genera included Acinetobacter, Aeromonas, Enterobacter, Leclercia, Microvirga, Pseudomonas, Rhizobium, Planococcus, Paenisporosarcina and Planomicrobium. In addition, a total of 14 species belonging to 8 genera in 3 phyla (Proteobacteria, Firmicutes, Actinobacteria) were isolated, Curtobacterium, Massilia, Pseudomonas and Sphingomonas were the dominant genera. Although some of the genera isolated were inconsistent with those detected by molecular method, both of two methods proved that many different endophytic bacteria coexist in G. montana. According to the potential functional analyses of these bacteria, some species are known to have possible beneficial effects on hosts, but whether this is the case in G. montana needs to be confirmed.