The receptor-like kinase ARK controls symbiotic balance across land plants.

The mutualistic arbuscular mycorrhizal (AM) symbiosis arose in land plants more than 450 million years ago and is still widely found in all major land plant lineages. Despite its broad taxonomic distribution, little is known about the molecular components underpinning symbiosis outside of flowering plants. The ARBUSCULAR RECEPTOR-LIKE KINASE (ARK) is required for sustaining AM symbiosis in distantly related angiosperms. Here, we demonstrate that ARK has an equivalent role in symbiosis maintenance in the bryophyte Marchantia paleacea and is part of a broad AM genetic program conserved among land plants. In addition, our comparative transcriptome analysis identified evolutionarily conserved expression patterns for several genes in the core symbiotic program required for presymbiotic signaling, intracellular colonization, and nutrient exchange. This study provides insights into the molecular pathways that consistently associate with AM symbiosis across land plants and identifies an ancestral role for ARK in governing symbiotic balance.

Non-seed plants are emerging gene sources for agriculture and insect control proteins.

The non-seed plants (e.g., charophyte algae, bryophytes, and ferns) have multiple human uses, but their contributions to agriculture and research have lagged behind seed plants. While sharing broadly conserved biology with seed plants and the major crops, non-seed plants sometimes possess alternative molecular and physiological adaptations. These adaptations may guide crop improvements. One such area is the presence of multiple classes of insecticidal proteins found in non-seed plant genomes which are either absent or widely diverged in seed plants. There are documented uses of non-seed plants, and ferns for example have been used in human diets. Among the occasional identifiable toxins or antinutritive components present in non-seed plants, none include these insecticidal proteins. Apart from these discrete risk factors which can be addressed in the safety assessment, there should be no general safety concern about sourcing genes from non-seed plant species.

Molecular insights into MpAGO1 and its regulatory miRNA, miR11707, in the high-temperature acclimation of Marchantia polymorpha.

As a model plant for bryophytes, Marchantia polymorpha offers insights into the role of RNA silencing in aiding early land plants navigate the challenges posed by high-temperature environments. Genomic analysis revealed unique ARGONAUTE1 ortholog gene (MpAGO1) in M. polymorpha that is regulated by two species-specific microRNAs (miRNAs), miR11707.1 and miR11707.2. Comparative studies of small RNA profiles from M. polymorpha cellular and MpAGO1 immunoprecipitation (MpAGO1-IP) profiles at various temperatures, along with analyses of Arabidopsis AGO1 (AtAGO1), revealed that MpAGO1 has a low-selectivity for a diverse range of small RNA species than AtAGO1. Protein structural comparisons revealed no discernible differences in the MID domains of MpAGO1 and AtAGO1, suggesting the complexity of miRNA species specificity and necessitating further exploration. Small RNA profiling and size exclusion chromatography have pinpointed a subset of M. polymorpha miRNAs, notably miR11707, that remain in free form within the cell at 22°C but are loaded into MpAGO1 at 28°C to engage in RNA silencing. Investigations into the mir11707 gene editing (mir11707ge) mutants provided evidence of the regulation of miR11707 in MpAGO1. Notably, while MpAGO1 mRNA expression decreases at 28°C, the stability of the MpAGO1 protein and its associated miRNAs is essential for enhancing the RISC activity, revealing the importance of RNA silencing in enabling M. polymorpha to survive thermal stress. This study advances our understanding of RNA silencing in bryophytes and provides groundbreaking insights into the evolutionary resilience of land plants to climatic adversities.

Evolution of parental care in haploid-diploid plants.

In bryophytes that alternate between haploid gametophytes and diploid sporophytes through sexual reproduction, sporophytes are often attached to and nurtured on the female gametophyte. A similar phenomenon is seen in Florideophyceae (a group of red algae). These systems in which a gametophyte (mother) invests nutrients in sporophytes (offspring) are ideal for studying the evolution of 'parental care' in non-animal organisms. Here, we propose a model of a haploid-diploid life cycle and examine the evolution of maternal investment in sporophytes focusing on two effects: the degree of paternal or maternal control of investment and the number of sporophytes. We find that when the female dominantly controls the investment, the evolutionarily stable level of investment is that which maximizes the expected reproductive success of the female gametophyte. The genomic conflict between maternal and paternal alleles complicates the evolutionary outcome; however, a greater male allelic effect and a higher number of sporophytes favour a higher energy investment, which may lead to evolutionary branching or run-away escalation of the investment level. This suggests that the selfishness of the paternal gene is the evolutionary driver of parental care and that complex structures such as fusion cells in red algae may have evolved to suppress it.

Life under the snow: A year-round transcriptome analysis of Antarctic mosses in natural habitats provides insight into the molecular adaptation of plants under extreme environment.

Mosses are vital components of ecosystems, exhibiting remarkable adaptability across diverse habitats from deserts to polar ice caps. Sanionia uncinata (Hedw.) Loeske, a dominant Antarctic moss survives extreme environmental condition through perennial lifecycles involving growth and dormancy alternation. This study explores genetic controls and molecular mechanisms enabling S. uncinata to cope with seasonality of the Antarctic environment. We analysed the seasonal transcriptome dynamics of S. uncinata collected monthly from February 2015 to January 2016 in King George Island, Antarctica. Findings indicate that genes involved in plant growth were predominantly upregulated in Antarctic summer, while those associated with protein synthesis and cell cycle showed marked expression during the winter-to-summer transition. Genes implicated in cellular stress and abscisic acid signalling were highly expressed in winter. Further, validation included a comparison of the Antarctic field transcriptome data with controlled environment simulation of Antarctic summer and winter temperatures, which revealed consistent gene expression patterns in both datasets. This proposes a seasonal gene regulatory model of S. uncinate to understand moss adaptation to extreme environments. Additionally, this data set is a valuable resource for predicting genetic responses to climatic fluctuations, enhancing our knowledge of Antarctic flora's resilience to global climate change.

Biolistics-mediated transformation of hornworts and its application to study pyrenoid protein localization.

Hornworts are a deeply diverged lineage of bryophytes that are sister to mosses and liverworts. Hornworts have an array of unique features that can be leveraged to illuminate not only the early evolution of land plants, but also alternative paths for nitrogen and carbon assimilation via cyanobacterial symbiosis and a pyrenoid-based CO2-concentrating mechanism (CCM), respectively. Despite this, hornworts are one of the few plant lineages with limited available genetic tools. Here we report an efficient biolistics method for generating transient-expression and stable transgenic lines in the model hornwort, Anthoceros agrestis. An average of 569 (± 268) cells showed transient expression per bombardment, with green fluorescent protein expression observed within 48-72 hours. A total of 81 stably transformed lines were recovered across three separate experiments, averaging six lines per bombardment. We followed the same method to transiently transform nine additional hornwort species, and obtained stable transformants from one. This method was further used to verify the localization of Rubisco and Rubisco activase in pyrenoids, which are central proteins for CCM function. Together, our biolistics approach offers key advantages over existing methods as it enables rapid transient expression and can be applied to widely diverse hornwort species.

Biomonitoring of airborne microplastics and microrubbers in Shiraz, Iran, using lichens and moss.

HIGHLIGHTS: Microplastics (MPs) and microrubbers (MRs) determined in lichens and mosses around Shiraz. In lichens, MPs mainly thin fibres up to 1 MP g-1; MRs were < 0.1 MP g-1. In mosses, abundances were similar but with a greater fraction of larger, non-fibrous particles. Larger MPs and MRs decreased in abundance with distance and elevation from Shiraz. Around Shiraz, the common moss, Grimmia critina, would be the most suitable biomonitor. Lichens and mosses have been employed as biomonitors of atmospheric particulate pollutants, like metals and industrial solids, for many decades. Here, we evaluated the potential of nine species of crustose and foliose lichens and a widely distributed moss (Grimmia critina) to act as biomonitors of airborne microplastics (MPs) and microrubbers (MRs). About 200 lichens and 40 mosses were sampled across different altitudinal transects in the vicinity of Shiraz City, southwest Iran, and MPs and MRs were quantified and characterised after sample peroxidation. In most species of lichen, MP and MR abundance overall was < 1 g-1 and < 0.1 g-1, respectively, and the majority of plastics were fibres of < 10 µm in diameter and < 1000 µm in length. Respective weight normalised abundances of MPs and MRs were similar in G. critina, but there were greater proportions of both larger (> 1000 µm) and non-fibrous particles among the MPs. In both lichens and moss, there was a greater number of larger MPs and MRs at locations closest to and at the same elevation as Shiraz than at more distant and elevated locations, suggesting an inverse relationship between particle size and distance travelled. Among the lichens, members of the genus Acarospora, with their areolated form, appeared to act as the most suitable biomonitors for MPs and MRs. Overall, however, the wide distribution of the moss, G. crinita, and its ability to intercept and accumulate a broader range of sizes and shapes of MPs and MRs make this species a better choice, at least in the type of environment studied.

Species of associated bryophytes and their effects on the yield and quality of Dendrobium nobile.

BACKGROUND: Dendrobium nobile has unique growth environment requirements, and unstable yields and high management costs are the key factors restricting the development of its imitation wild cultivation industry. The present study explored the effects of different associated bryophyte species on the yield and quality of D. nobile to clarify the dominant bryophyte species associated with D. nobile and to provide a scientific basis for the rational cultivation and quality evaluation of D. nobile. RESULTS: The growth of D. nobile was closely related to the microenvironment of the Danxia stone, and the different associated bryophytes had different effects on D. nobile growth. There was a rich variety of bryophytes associated with D. nobile, with a total of 15 families, 24 genera and 31 species of bryophytes identified in the study area, including 13 families, 22 genera and 29 species of mosses and 2 families, 2 genera and 2 species of liverworts, and mosses predominated in the association with D. nobile. Usually, 3-9 species of bryophytes were growing in association with D. nobile, among which associations of 5-6 bryophytes species were more common, and the bryophytes associated with D. nobile were only related to the species to which they belonged. The dry matter accumulation, quality and mineral content of D. nobile differed significantly among different bryophyte species. The coefficients of variation of dry matter accumulation, dendrobine content and content of 11 mineral elements of D. nobile in the 35 sample quadrats were 25.00%, 21.08%, and 11.33-57.96%, respectively. The biomass, dendrobine content and mineral content of D. nobile were analysed by principal component analysis (PCA) and membership function. The results showed that each evaluation method initially screened Trachycystis microphylla and Leucobryum juniperoideum as the dominant associated bryophytes in the preliminary identification analysis, and the frequency of occurrence and coverage of the two bryophytes were significantly higher than those of the remaining bryophytes. It was determined that T. microphylla and L. juniperoideum were the dominant associated bryophytes. CONCLUSIONS: There is a rich variety of bryophytes associated with D. nobile. The yield and quality of D. nobile differed significantly among different bryophyte species. T. microphylla and L. juniperoideum were the dominant associated bryophytes, and were the two bryophytes associated with D. nobile through mixed growth.

Morphological and physiological adaptation characteristics of lithophytic bryophytes to karst high calcium environment.

BACKGROUND: Lithophytic bryophytes grow on the rock surface, change the habitat on the rock surface through biological karstification, and provide a material basis for the growth of other plants. However, the surface calcium content of bare rock is high. The lithophytic bryophytes may have a special mechanism to adapt to the karst high calcium environment. The present study aimed to explore the physiological regulation process of karst lithophytic bryophytes under high calcium environment, and to provide scientific basis for revealing the maintenance mechanism of karst biodiversity. RESULTS: With the increase of Ca2+ concentration, the contents of Pro, SP and MDA of lithophytic bryophytes showed a downward-upward-downward trend. However, when Ca2+ ≥ 400 mmol/L, the contents of Pro and SP changed significantly at 1d, 2d, 3d, 5d and 7d with the extension of culture time, and lithophytic bryophytes died after 2 months of culture. Under different Ca2+ concentrations, the maximum SOD activity of lithophytic bryophytes is 1758.00 (U/g FW), the minimum is 92.60 (U/g FW), the maximum POD activity is 120.88 (U/g FW), and the minimum is 4.80 (U/g FW). The antioxidative activity of of Hyophila involuta are higher than that of Didymodon constrictus and Eurohypnum leptothallum, and its enzyme activity changed significantly with the increase of calcium concentration and time.At the same time, the contents of TChl, Chla, and Chlb in lithophytic bryophytes decreased with the increase of Ca2+ concentration. When Ca2+ = 400 mmol/L, the contents of TChl and Chla were the lowest, but when Ca2+ > 400 mmol/L, they began to increase. In addition, ABA is negatively correlated with TChl and Chla, and positively correlated with ROS. It shows that ABA has a certain role in regulating the adaptation of lithophytic bryophytes to high calcium environment. CONCLUSIONS: Lithophytic bryophytes have strong calcium tolerance, and their physiological response to high calcium stress is different from vascular bundle plants. The general stress principle is not applicable to lithophytic bryophytes. The response of lithophytic bryophytes to the change of Ca2+concentration is slow, showing passive response or inert response.

A Physcomitrella PIN protein acts in spermatogenesis and sporophyte retention.

The auxin efflux PIN-FORMED (PIN) proteins are conserved in all land plants and important players in plant development. In the moss Physcomitrella (Physcomitrium patens), three canonical PINs (PpPINA-C) are expressed in the leafy shoot (gametophore). PpPINA and PpPINB show functional activity in vegetative growth and sporophyte development. Here, we examined the role of PpPINC in the life cycle of Physcomitrella. We established reporter and knockout lines for PpPINC and analysed vegetative and reproductive tissues using microscopy and transcriptomic sequencing of moss gametangia. PpPINC is expressed in immature leaves, mature gametangia and during sporophyte development. The sperm cells (spermatozoids) of pinC knockout mutants exhibit increased motility and an altered flagella phenotype. Furthermore, the pinC mutants have a higher portion of differentially expressed genes related to spermatogenesis, increased fertility and an increased abortion rate of premeiotic sporophytes. Here, we show that PpPINC is important for spermatogenesis and sporophyte retention. We propose an evolutionary conserved way of polar growth during early moss embryo development and sporophyte attachment to the gametophore while suggesting the mechanical function in sporophyte retention of a ring structure, the Lorch ring.

Dark-induced chloroplast relocation depends on actin filaments in the liverwort Apopellia endiviifolia along with the light- and cold-induced relocations.

Chloroplasts move to the periclinal walls of cells under weak light to harness light energy for photosynthesis and to anticlinal walls to avoid strong light. These responses involve the cytoskeleton components microtubules and/or actin filaments. In the dark, chloroplasts move to the anticlinal cell walls bordering neighbouring cells (dark-positioning response), but this response in various plants normally requires a prolonged dark incubation period, which has hampered analysis. However, we recently demonstrated the dark-positioning response that can be induced after a short period of dark incubation in the liverwort Apopellia endiviifolia. Here, we investigated whether the cytoskeleton components function in the dark-positioning response of A. endiviifolia cells. Microtubules and actin filaments were fluorescently visualised in A. endiviifolia cells and were disrupted following treatment with the microtubule and actin filament polymerisation inhibitors. The dark-positioning response was unaffected in the cells with disrupted microtubules. By contrast, the dark-positioning response was inhibited by the disruption of actin filaments. The disruption of actin filaments also restricted chloroplast mobility during light- and cold-dependent chloroplast movements in A. endiviifolia. Therefore, the dark-positioning response of A. endiviifolia depends solely on an actin filament-associated motility mechanism, as do the light- and cold-dependent chloroplast responses.

The phylogeny of Syntrichia: An ecologically diverse clade of mosses with an origin in South America.

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.

Long-term biocrust responses to wildfires in Washington, USA.

PREMISE: Dryland ecosystems in the western United States are affected by invasive species, wildfires, livestock grazing, and climate change in ways that are difficult to distinguish. Biocrusts perform important ecological roles in these systems and are sensitive to all of these pressures. METHODS: We revisited a Washington, USA, site sampled for biocrusts in 1999 to focus on effects of exotic annual grass invasion and wildfires in the absence of livestock grazing. We examined changes between 1999 and 2020 using a Bayesian directed acyclic graph (DAG) to interpret direct and indirect causal impacts of wildfire on perennial bunchgrasses, exotic annual grasses, and biocrusts. RESULTS: Between 1999 and 2020, exotic annual grass cover increased in all plots and in unburned plots by 16% and 18%, respectively, bunchgrass cover decreased by 21% and 25%, and biocrust cover decreased by 8.9% and 9.8%. Our DAG suggested that decreases in bunchgrass increased exotic annual grass, which reduced biocrust cover. Wildfires did not directly influence changes in bunchgrass, exotic annual grass, or biocrust cover. Areas dominated by exotic annual grass had less abundant and diverse biocrusts than areas with less exotic annual grass. CONCLUSIONS: Biocrust community changes were more strongly related to increasing exotic annual grasses than to wildfires. Changes may relate to other soil disturbances or broad-scale changes in climate or air quality. The minimal influence of wildfire on exotic annual grass and biocrusts suggests that apparent negative impacts of wildfire at other sites may be due to exacerbation by livestock grazing or other surface disturbance.

Moss and Liverwort Covers Structure Soil Bacterial and Fungal Communities Differently in the Icelandic Highlands.

Cryptogamic covers extend over vast polar tundra regions and their main components, e.g., bryophytes and lichens, are frequently the first visible colonizers of deglaciated areas. To understand their role in polar soil development, we analyzed how cryptogamic covers dominated by different bryophyte lineages (mosses and liverworts) influence the diversity and composition of edaphic bacterial and fungal communities as well as the abiotic attributes of underlying soils in the southern part of the Highlands of Iceland. For comparison, the same traits were examined in soils devoid of bryophyte covers. We measured an increase in soil C, N, and organic matter contents coupled with a lower pH in association with bryophyte cover establishment. However, liverwort covers showed noticeably higher C and N contents than moss covers. Significant changes in diversity and composition of bacterial and fungal communities were revealed between (a) bare and bryophyte-covered soils, (b) bryophyte covers and the underlying soils, and (c) moss and liverworts covers. These differences were more obvious for fungi than bacteria, and involved different lineages of saprotrophic and symbiotic fungi, which suggests a certain specificity of microbial taxa to particular bryophyte groups. In addition, differences observed in the spatial structure of the two bryophyte covers may be also responsible for the detected differences in microbial community diversity and composition. Altogether, our findings indicate that soil microbial communities and abiotic attributes are ultimately affected by the composition of the most conspicuous elements of cryptogamic covers in polar regions, which is of great value to predict the biotic responses of these ecosystems to future climate change.

Nitrogen fixation and nifH gene diversity in cyanobacteria living on feather mosses in a subalpine forest of Mt. Fuji.

In the boreal forests, feather mosses such as Hylocomium splendens and Pleurozium schreberi are colonized by cyanobacteria, which provide large amounts of nitrogen to forest ecosystems through nitrogen fixation. Although these feather mosses are also ubiquitous in subalpine forests of East Asia, little is known regarding their associated cyanobacteria and their ability to fix nitrogen. In this study, we investigated (1) whether cyanobacteria co-exist and fix nitrogen in the two species of feather mosses that cover the ground surface in a subalpine forest of Mt. Fuji, (2) whether cyanobacteria belonging to a common cluster with boreal forests are found in feather mosses in Mt. Fuji, and (3) whether moss-associated nitrogen fixation rates differed among moss growing substrates, canopy openness, and moss nitrogen concentrations in the same forest area. Our results showed that cyanobacteria colonized feather mosses in the subalpine forests of Mt. Fuji and acetylene reduction rates as an index of nitrogen fixation tended to be higher in H. splendens than in P. schreberi. Based on analysis of the nifH gene, 43 bacterial operational taxonomic units (OTUs) were identified, 28 of which represented cyanobacteria. Among the five clusters of cyanobacteria classified based on their nifH gene and identified in northern Europe, four (Nostoc cluster I, Nostoc cluster II, Stigonema cluster, and nifH2 cluster) were also found at Mt. Fuji. The acetylene reduction rate differed depending on the moss growing substrate and the total nitrogen concentration of moss shoots, and a strong negative correlation was observed with the total nitrogen concentration.

Diversity and assembly of lichens and bryophytes on tree trunks along a temperate to boreal elevation gradient.

Based on hypotheses related to environmental filtering vs. stochastic community assembly, we tested taxon-specific predictions regarding the relationships of alpha diversity, beta diversity and species composition of epiphytic macrolichens and bryophytes with elevation and the lateral gradient on trees (the different sides of the tree bole related to aspect and trunk inclination) at Parc national du Mont-Mégantic in Southeastern Québec, Canada. For lichens on firs, increasing elevation was associated with increasing alpha diversity, and a marked shift in community composition, at the scale of whole trees. In contrast, for bryophytes on maples, tree inclination and the lateral gradient had the strongest effects: more inclined trees had greater whole-tree alpha diversity and stronger within-tree contrasts in composition between the upper and lower bole surfaces. For lichens on maples, whole-tree alpha diversity showed a weak, negative relationship with inclination, and beta diversity increased slightly with elevation. Our results are consistent with theories predicting greater alpha diversity in more favorable environments (for lichens: high elevation with high relative air humidity and lower temperatures; for bryophytes: upper surfaces of tree boles with liquid water available), but support was weak for the prediction of greater beta diversity in more favorable environments. Overall, the important predictors of epiphytic cryptogam diversity vary more among the species of tree host (maple vs. fir) than focal taxa (lichens vs. bryophytes), with patterns likely related to different effects of water, temperature, and competition between lichens and bryophytes.

Study of the Biological Activity and Phenolic Content of the Ethanol Extract of Phyllogonium viride Brid. (Phyllogoniaceae, Bryophyta).

The present study aimed to examine the phenolic content and evaluate the antimicrobial and antioxidant potential of ethanol extracts from the moss species Phyllogonium viride Brid. on the pathogenic bacteria Salmonella enterica serovar enteritidis, Staphylococcus aureus, Listeria monocytogenes and Escherichia coli, and the pathogenic fungi Candida albicans and Cryptococcus neoformans. The antimicrobial activity was determined from Minimum Inhibitory Concentration (MIC) Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC). Antioxidant activity was determined by the DPPH method. Folin-Denis reagent was used for the content of total phenolics and flavonoids and HPLC-DAD for identification of phenolic compounds. The results showed that bacteriostatic and bactericidal activities occurred at concentrations ranging from 9.76 µg/mL-78.13 µg/mL among all evaluated microorganisms. These values, considering the criteria used, suggest the P. viride extract as a potent antimicrobial. For antioxidant activity, P. viride extract was considered weak. Analysis of the phenolic content showed a wide range of compounds, with Kaempferol (0.41 mg/g) being the major compound, followed by t-cinnamic acid and caffeic acid (0.17 mg/g). Although P. viride is a species of moss not yet referenced in scientific publications of biotechnological interest, it has shown promising potential for further studies and possible application as an antimicrobial of natural origin.

Non-Protein Thiol Compounds and Antioxidant Responses Involved in Bryophyte Heavy-Metal Tolerance.

Heavy-metal pollution represents a problem which has been widely discussed in recent years. The biological effects of heavy metals have been studied in both animals and plants, ranging from oxidative stress to genotoxicity. Plants, above all metal-tolerant species, have evolved a wide spectrum of strategies to counteract exposure to toxic metal concentrations. Among these strategies, the chelation and vacuolar sequestration of heavy metals are, after cell-wall immobilization, the first line of defence that prevent heavy metals from interacting with cell components. Furthermore, bryophytes activate a series of antioxidant non-enzymatic and enzymatic responses to counteract the effects of heavy metal in the cellular compartments. In this review, the role of non-protein thiol compounds and antioxidant molecules in bryophytes will be discussed.

To dry perchance to live: Insights from the genome of the desiccation-tolerant biocrust moss Syntrichia caninervis.

With global climate change, water scarcity threatens whole agro/ecosystems. The desert moss Syntrichia caninervis, an extremophile, offers novel insights into surviving desiccation and heat. The sequenced S. caninervis genome consists of 13 chromosomes containing 16 545 protein-coding genes and 2666 unplaced scaffolds. Syntenic relationships within the S. caninervis and Physcomitrella patens genomes indicate the S. caninervis genome has undergone a single whole genome duplication event (compared to two for P. patens) and evidence suggests chromosomal or segmental losses in the evolutionary history of S. caninervis. The genome contains a large sex chromosome composed primarily of repetitive sequences with a large number of Copia and Gypsy elements. Orthogroup analyses revealed an expansion of ELIP genes encoding proteins important in photoprotection. The transcriptomic response to desiccation identified four structural clusters of novel genes. The genomic resources established for this extremophile offer new perspectives for understanding the evolution of desiccation tolerance in plants.

MS1/MMD1 homologues in the moss Physcomitrium patens are required for male and female gametogenesis.

The Arabidopsis Plant HomeoDomain (PHD) proteins AtMS1 and AtMMD1 provide chromatin-mediated transcriptional regulation essential for tapetum-dependent pollen formation. This pollen-based male gametogenesis is a derived trait of seed plants. Male gametogenesis in the common ancestors of land plants is instead likely to have been reminiscent of that in extant bryophytes where flagellated sperms are produced by an elaborate gametophyte generation. Still, also bryophytes possess MS1/MMD1-related PHD proteins. We addressed the function of two MS1/MMD1-homologues in the bryophyte model moss Physcomitrium patens by the generation and analysis of reporter and loss-of-function lines. The two genes are together essential for both male and female fertility by providing functions in the gamete-producing inner cells of antheridia and archegonia. They are furthermore expressed in the diploid sporophyte generation suggesting a function during sporogenesis, a process proposed related by descent to pollen formation in angiosperms. We propose that the moss MS1/MMD1-related regulatory network required for completion of male and female gametogenesis, and possibly for sporogenesis, represent a heritage from ancestral land plants.