Comparative analysis of mycorrhizal communities associated with Struthiopteris spicant (L.) Weiss across Europe and North America.

Introduction: Ferns constitute the second largest group of vascular plants. Previous studies have shown that the diversity and composition of fern communities are influenced by resource availability and water stress, among other factors. However, little is known about the influence of these environmental factors on their biotic interactions, especially regarding the relationship between mycorrhizal fungi and ferns. The present study compares the mycorrhizal communities associated with 36 populations of Struthiopteris spicant L. Weiss across Europe and North America. This species exhibits a great tolerance to variations in light, nutrient, and pH conditions, and it can survive with and without mycorrhizae. Methods: With the aim of determining which environmental factors impact the composition and abundance of the root-associated fungal communities in this species, we used an ITS-focused metabarcoding approach to identify the mycorrhizal fungi present and analyzed the influence of climatic and edaphic variables at global and regional scales. Results and discussion: We encountered striking differences in the relative abundance of arbuscular mycorrhizal fungi (AMF) between S. spicant populations at both spatial levels. We recorded a total of 902 fungal ASVs, but only 2- 4% of the total fungal diversity was observed in each individual, revealing that each fern had a unique fungal community. Light availability and the interactive action of pH and soil nitrogen concentration showed a positive influence on AMF relative abundance, explaining 89% of the variance. However, environmental factors could only explain 4- 8% of the variability in AMF community composition, indicating that it might be determined by stochastic processes. These results support the hypothesis that ferns may be more independent of mycorrhization than other plant groups and interact with fungi in a more opportunistic manner.

Conservation applications of niche modeling: Native and naturalized ferns may compete for limited Hawaiian dryland habitat.

Premise: Competition from naturalized species and habitat loss are common threats to native biodiversity and may act synergistically to increase competition for decreasing habitat availability. We use Hawaiian dryland ferns as a model for the interactions between land-use change and competition from naturalized species in determining habitat availability. Methods: We used fine-resolution climatic variables and carefully curated occurrence data from herbaria and community science repositories to estimate the distributions of Hawaiian dryland ferns. We quantified the degree to which naturalized ferns tend to occupy areas suitable for native species and mapped the remaining available habitat given land-use change. Results: Of all native species, Doryopteris angelica had the lowest percentage of occurrences of naturalized species in its suitable area while D. decora had the highest. However, all Doryopteris spp. had a higher percentage overlap, while Pellaea ternifolia had a lower percentage overlap, than expected by chance. Doryopteris decora and D. decipiens had the lowest proportions (<20%) of suitable area covering native habitat. Discussion: Areas characterized by shared environmental preferences of native and naturalized ferns may decrease due to human development and fallowed agricultural lands. Our study demonstrates the value of place-based application of a recently developed correlative ecological niche modeling approach for conservation risk assessment in a rapidly changing and urbanized island ecosystem.

Transcriptomics and metabolomics analyses provide insights into resistance genes of tree ferns.

As ancient organisms, tree ferns play a crucial role as an evolutionary bridge between lower and higher plant species, providing various utilitarian benefits. However, they face challenges such as overexploitation, climate change, adverse environmental conditions, and insect pests, resulting in conservation concerns. In this study, we provide an overview of metabolic and transcriptomic resources of leaves in two typical tree ferns, A. spinulosa and A. metteniana, and explore the resistance genes for the first time. The landscape of metabolome showed that the compound skimmin may hold medicinal significance. A total of 111 differentially accumulated metabolites (DAMs) were detected, with pathway enrichment analysis highlighting 14 significantly enriched pathways, including 2-oxocarboxylic acid metabolism possibly associated with environmental adaptations. A total of 14,639 differentially expressed genes (DEGs) were found, among which 606 were resistance (R) genes. We identified BAM1 as a significantly differentially expressed R gene, which is one of the core genes within the R gene interaction network. Both the maximum-likelihood phylogenetic tree and the PPI network revealed a close relationship between BAM1, FLS2, and TMK. Moreover, BAM1 showed a significant positive correlation with neochlorogenic acid and kaempferol-7-O-glucoside. These metabolites, known for their antioxidant and anti-inflammatory properties, likely play a crucial role in the defense response of tree ferns. This research provides valuable insights into the metabolic and transcriptomic differences between A. spinulosa and A. metteniana, enhancing our understanding of resistance genes in tree ferns.

Angiopterisnodosipetiolata (Marattiaceae), a new fern species from Yunnan, China.

Angiopterisnodosipetiolata Ting Wang tris, H.F.Chen & Y.H.Yan, a new fern of Marattiaceae, is described and illustrated. Morphologically, A.nodosipetiolata is similar to A.chingii with more than one naked pulvinus on the stipe and numerous jointed hairs on the undersides of the mature pinnae. However, the pinnae of A.nodosipetiolata are lanceolate and can reach up to 4-6 pairs, whereas they are elliptic and occur in 2-3 pairs in A.chingii. Phylogenetic and genetic distance analysis, based on the plastid genomes, also indicates that A.nodosipetiolata is not closely related to A.chingii. Currently, there are ca. 500 mature individuals in Gulinqing Nature Reserve and we suggest A.nodosipetiolata should be categorised as an Endangered (EN) species according to the criteria of IUCN.

Box-Behnken Design-Based Optimization of Phytochemical Extraction from Diplazium esculentum (Retz.) Sw. Associated with Its Antioxidant and Anti-Alzheimer's Properties.

A previous study reported that the ethanolic extract of the edible fern, Diplazium esculentum (Retz.) Sw. (DE), obtained from a non-optimized extraction condition exhibited anti-Alzheimer's disease (AD) properties through the inhibition of a rate-limiting enzyme in amyloid peptide formation, ß-secretase-1 (BACE-1). Nevertheless, a non-optimized or suboptimal extraction may lead to several issues, such as a reduction in extraction efficiency and increased time and plant materials. In this study, extraction of the DE was optimized to obtain appropriate BACE-1 inhibition using a Box-Behnken design (BBD) and response surface methodology (RSM). Data revealed that the optimal extraction condition was 70% (v/v) aqueous ethanol, 50 min extraction time, 30 °C extraction temperature, and 1:30 g/mL solid/liquid ratio, giving BACE-1 inhibition at 56.33%. In addition, the extract also exhibited significant antioxidant activities compared to the non-optimized extraction. Metabolomic phytochemical profiles and targeted phytochemical analyses showed that kaempferol, quercetin, and their derivatives as well as rosmarinic acid were abundant in the extract. The optimized DE extract also acted synergistically with donepezil, an AD drug suppressing BACE-1 activities. Data received from Drosophila-expressing human amyloid precursor proteins (APPs) and BACE-1, representing the amyloid hypothesis, showed that the optimized DE extract penetrated the fly brains, suppressed BACE-1 activities, and improved locomotor functions. The extract quenched the expression of glutathione S transferase D1 (GSTD1), inositol-requiring enzyme (IRE-1), and molecular chaperone-binding immunoglobulin (Bip), while donepezil suppressed these genes and other genes involved in antioxidant and endoplasmic reticulum (ER) stress response, including superoxide dismutase type 1 (SOD1), activating transcription factor 6 (ATF-6), and protein kinase R-like endoplasmic reticulum kinase (PERK). To sum up, the optimized extraction condition reduced extraction time while resulting in higher phytochemicals, antioxidants, and BACE-1 inhibitors.

Effects of clonal fragmentation on Pyrrosia nuda depend on growth stages in a rubber plantation.

Introduction: Clonal fragmentation helps to assess clonal plants' growth resilience to human and environmental disturbance. Although clonal integration in epiphytes in tropical rubber plantations is important to understand their role in enhancing biodiversity and ecosystem services, research on this subject is limited. These plantations are typically monospecific economic forests that face increased anthropogenic disturbances. Methods: In this study, we selected the clonal fern Pyrrosia nuda to study its survival status, biomass, maximum quantum yield of photosystem II (Fv/Fm), and frond length in response to the level of clonal fragmentation in a tropical rubber plantation. Results and discussion: The results showed that (1) clonal fragmentation significantly negatively affected the survival rate, biomass, and frond length of clonal plants, but with minimal effects on Fv/Fm at different growth stages; (2) the performance of a ramet (e.g., biomass or frond length) increased with ramet developmental ages and decreased with the number of ramets in a clonal fragment. The age-dependent impacts of clonal fragmentation provide insights into the biodiversity conservation of epiphytes and forest management in man-made plantations. Therefore, to better conserve the biodiversity in tropical forests, especially in environment-friendly rubber plantations, there is a need to reduce anthropogenic disturbances and alleviate the level of fragmentation.

Fern mycorrhizae do not respond to fertilization in a tropical montane forest.

Ferns are known to have a lower incidence of mycorrhization than angiosperms. It has been suggested that this results from carbon being more limiting to fern growth than nutrient availability, but this assertion has not been tested yet. In the present study, we took advantage of a fertilization experiment with nitrogen and phosphorus on cloud forest plots of the Ecuadorean Andes for 15 years. A previous analysis revealed changes in the abundances of fern species in the fertilized plots compared to the control plots and hypothesized that this might be related to the responses of the mycorrhizal relationships to nutrient availability. We revisited the plots to assess the root-associated fungal communities of two epiphytic and two terrestrial fern species that showed shifts in abundance. We sampled and analyzed the roots of 125 individuals following a metabarcoding approach. We recovered 1382 fungal ASVs, with a dominance of members of Tremellales (Basidiomycota) and Heliotales (Ascomycota). The fungal diversity was highly partitioned with little overlap between individuals. We found marked differences between terrestrial and epiphytic species, with the latter fundamentally missing arbuscular mycorrhizal fungi (AMF). We found no effect of fertilization on the diversity or relative abundance of the fungal assemblages. Still, we observed a direct impact of phosphorus fertilization on its concentration in the fern leaves. We conclude that fern-fungi relationships in the study site are not restricted by nutrient availability and suggest the existence of little specificity on the fungal partners relative to the host fern species.

Control of leaf development in the water fern Ceratopteris richardii by the auxin efflux transporter CrPINMa in the CRISPR/Cas9 analysis.

BACKGROUND: PIN-FORMED genes (PINs) are crucial in plant development as they determine the directionality of auxin flow. They are present in almost all land plants and even in green algae. However, their role in fern development has not yet been determined. This study aims to investigate the function of CrPINMa in the quasi-model water fern Ceratopteris richardii. RESULTS: CrPINMa possessed a long central hydrophilic loop and characteristic motifs within it, which indicated that it belonged to the canonical rather than the non-canonical PINs. CrPINMa was positioned in the lineage leading to Arabidopsis PIN6 but not that to its PIN1, and it had undergone numerous gene duplications. CRISPR/Cas9 genome editing had been performed in ferns for the first time, producing diverse mutations including local frameshifts for CrPINMa. Plants possessing disrupted CrPINMa exhibited retarded leaf emergence and reduced leaf size though they could survive and reproduce at the same time. CrPINMa transcripts were distributed in the shoot apical meristem, leaf primordia and their vasculature. Finally, CrPINMa proteins were localized to the plasma membrane rather than other cell parts. CONCLUSIONS: CRISPR/Cas9 genome editing is feasible in ferns, and that PINs can play a role in fern leaf development.

Polyploid goldback and silverback ferns (Pentagramma) occupy a wider, colder, and wetter bioclimatic niche than diploid counterparts.

PREMISE: The western North American fern genus Pentagramma (Pteridaceae) is characterized by complex patterns of ploidy variation, an understanding of which is critical to comprehending both the evolutionary processes within the genus and its current diversity. METHODS: We undertook a cytogeographic study across the range of the genus, using a combination of chromosome counts and flow cytometry to infer ploidy level. Bioclimatic variables and elevation were used to compare niches. RESULTS: We found that diploids and tetraploids are common and widespread, and triploids are rare and sporadic; in contrast with genome size inferences in earlier studies, no hexaploids were found. Diploids and tetraploids show different geographic ranges: only tetraploids were found in the northernmost portion of the range (Washington, Oregon, and British Columbia) and only diploids were found in the Sierra Nevada of California. Diploid, triploid, and tetraploid cytotypes were found to co-occur in relatively few localities: in the southern (San Diego County, California) and desert Southwest (Arizona) parts of the range, and along the Pacific Coast of California. CONCLUSIONS: Tetraploids occupy a wider bioclimatic niche than diploids both within P. triangularis and at the genus-wide scale. It is unknown whether the wider niche of tetraploids is due to their expansion upon the diploid niche, if diploids have contracted their niche due to competition or changing abiotic conditions, or if this wider niche occupancy is due to multiple origins of tetraploids.

Incorporating fossils into the joint inference of phylogeny and biogeography of the tree fern order Cyatheales.

Present-day geographic and phylogenetic patterns often reflect the geological and climatic history of the planet. Neontological distribution data are often sufficient to unravel a lineage's biogeographic history, yet ancestral range inferences can be at odds with fossil evidence. Here, I use the fossilized birth-death process and the dispersal-extinction cladogenesis model to jointly infer the dated phylogeny and range evolution of the tree fern order Cyatheales. I use data for 101 fossil and 442 extant tree ferns to reconstruct the biogeographic history of the group over the last 220 million years. Fossil-aware reconstructions evince a prolonged occupancy of Laurasia over the Triassic-Cretaceous by Cyathealean tree ferns, which is evident in the fossil record but hidden from analyses relying on neontological data alone. Nonetheless, fossil-aware reconstructions are affected by uncertainty in fossils' phylogenetic placement, taphonomic biases, and specimen sampling and are sensitive to interpretation of paleodistributions and how these are scored. The present results highlight the need and challenges of incorporating fossils into joint inferences of phylogeny and biogeography to improve the reliability of ancestral geographic range estimation.

Foliar phenols and flavonoids level in pteridophytes: an insight to culturable fungal endophyte colonisation.

There are many available reports of secondary metabolites as bioactive molecules from culturable endophytes, nevertheless, there are scarce research pertaining to the levels of metabolites in plants with respect to the incidence and colonisation of fungal endophytes in the same foliar tissues. Therefore, the study was focussed to examine whether fungal endophyte colonisation and the accumulation of secondary metabolites, such as flavonoids and phenols, in the plants are related in any way. For this reason, the study aims to analyse phenols and flavonoids from the fronds of eleven pteridophytes along with the culture-dependent isolation of fungal endophytes from the host plants subsequently assigning them to morphological category and their quantitative analysis and further resolving its identities through molecular affiliation. The results revealed that nine morpho-categories of fungal endophytes were allotted based on culture attributes, hyphal patterns and reproductive structural characters. Highest numbers of species were isolated from Adiantum capillus-veneris and least was recorded from Pteris vittata and Dicranopteris linearis. Maximum phenol content was analysed from the fronds of P. vittata and lowest was recorded in A. capillus-veneris. Highest flavonoid content was measured in D. linearis and lowest was detected in Christella dentata. Significant negative correlation was observed between phenol content of ferns and species richness of fungi. Moreover, significant positive correlation was observed with the relative abundance of Chaetomium globosum and flavonoid content of ferns and negative significant relation was found between relative abundance of Pseudopestalotiopsis chinensis and phenol content of pteridophytes. The occurrence and the quantitative aspects of endophytes in ferns and their secondary metabolites are discussed.

Entrapment of atmospheric particle bound heavy metals by ferns as evidenced by lead (Pb) isotope and MixSIAR: Implications for improving air quality.

Plant metal uptake can occur through both soil-root and atmospheric transfer from leaves. The latter holds potential implications for development of biofiltration systems. To explore this potential, it is crucial to understand entrapment capacity and metal sources within plants. As ferns absorb materials from atmosphere, this study focuses on two abundant fern species growing in densely populated and highly polluted regions of Eastern India. Gravimetric quantification, elemental concentration and Pb isotopic analyses were performed by segregating the ferns into distinct components: foliage dusts (loose dust (LD) and wax-bound dust (WD)) and plant tissue (leaves and roots). To understand metal sources, the study analyzes soil, and atmospheric particulates (PM10 and dust fall (DF)). Results indicate that, while LDs have soil dust influence, wax entraps atmospheric particulates and translocates them inside the leaves. Furthermore, roots demonstrate dissimilar isotopic ratios from soil, while displaying close association with atmospheric particulates. Isotopic composition and subsequent mixing model reveal dominant contribution from DF in leaves (53-73%) and roots (33-86%). Apart from DF, leaf Pb is sourced from PM10 (21-38%) with minimal contribution from soil (6-10%). Conversely, in addition to dominance from DF, roots source Pb primarily from soil (12-62%) with a meagre 2-8% contribution from PM10.

Microsatellite Content in 397 Nuclear Exons and Their Flanking Regions in the Fern Family Ophioglossaceae.

Microsatellites or SSRs are small tandem repeats that are 1-6 bp long. They are usually highly polymorphic and form important portions of genomes. They have been extensively analyzed in humans, animals and model plants; however, information from non-flowering plants is generally lacking. Here, we examined 29 samples of Ophioglossaceae ferns, mainly from the genera Botrychium and Sceptridium. We analyzed the SSR distribution, density and composition in almost 400 nuclear exons and their flanking regions. We detected 45 SSRs in exons and 1475 SSRs in the flanking regions. In the exons, only di-, tri- and tetranucleotides were found, and all of them were 12 bp long. The annotation of the exons containing SSRs showed that they were related to various processes, such as metabolism, catalysis, transportation or plant growth. The flanking regions contained SSRs from all categories, with the most numerous being dinucleotides, followed by tetranucleotides. More than one-third of all the SSRs in the flanking regions were 12 bp long. The SSR densities in the exons were very low, ranging from 0 to 0.07 SSRs/kb, while those in the flanking regions ranged from 0.24 to 0.81 SSRs/kb; and those in the combined dataset ranged from 0.2 to 0.81 SSRs/kb. The majority of the detected SSRs in the flanking regions were polymorphic and present at the same loci across two or more samples but differing in the number of repeats. The SSRs detected here may serve as a basis for further population genetic, phylogenetic or evolutionary genetic studies, as well as for further studies focusing on SSRs in the genomes and their roles in adaptation, evolution and diseases.

Niche and phenotypic differentiation in fern hybrid speciation, a case study of Pteris fauriei (Pteridaceae).

BACKGROUND AND AIMS: Niche differentiation is a crucial issue in speciation. Although it has a well-known role in adaptive processes of hybrid angiosperms, it is less understood in hybrid ferns. Here, we investigate whether an intermediate ecological niche of a fern hybrid is a novel adaptation that provides insights into fern hybrid speciation. METHODS: Pteris fauriei (Pteridaceae) is a natural hybrid fern, occurring in environments between its parent species. The maternal Pteris minor is found in sunny areas, but the habitat of the paternal Pteris latipinna is shady. We combined data from morphology, leaf anatomy and photosynthetic traits to explore adaptation and differentiation, along with measuring the environmental features of their niches. We also performed experiments in a common garden to understand ecological plasticity. KEY RESULTS: The hybrid P. fauriei was intermediate between the parent species in stomatal density, leaf anatomical features and photosynthetic characteristics in both natural habitats and a common garden. Interestingly, the maternal P. minor showed significant environmental plasticity and was more similar to the hybrid P. fauriei in the common garden, suggesting that the maternal species experiences stress in its natural habitats but thrives in environments similar to those of the hybrid. CONCLUSIONS: Based on the similar niche preferences of the hybrid and parents, we propose hybrid superiority. Our results indicate that the hybrid P. fauriei exhibits greater fitness and can compete with and occupy the initial niches of the maternal P. minor. Consequently, we suggest that the maternal P. minor has experienced a niche shift, elucidating the pattern of niche differentiation in this hybrid group. These findings offer a potential explanation for the frequent occurrence of hybridization in ferns and provide new insights into fern hybrid speciation, enhancing our understanding of fern diversity.

Living jewels: iterative evolution of iridescent blue leaves from helicoidal cell walls.

BACKGROUND AND AIMS: Structural colour is responsible for the remarkable metallic blue colour seen in the leaves of several plants. Species belonging to only ten genera have been investigated to date, revealing four photonic structures responsible for structurally coloured leaves. One of these is the helicoidal cell wall, known to create structural colour in the leaf cells of five taxa. Here we investigate a broad selection of land plants to understand the phylogenetic distribution of this photonic structure in leaves. METHODS: We identified helicoidal structures in the leaf epidermal cells of 19 species using transmission electron microscopy. Pitch measurements of the helicoids were compared with the reflectance spectra of circularly polarized light from the cells to confirm the structure-colour relationship. RESULTS: By incorporating species examined with a polarizing filter, our results increase the number of taxa with photonic helicoidal cell walls to species belonging to at least 35 genera. These include 19 monocot genera, from the orders Asparagales (Orchidaceae) and Poales (Cyperaceae, Eriocaulaceae, Rapateaceae) and 16 fern genera, from the orders Marattiales (Marattiaceae), Schizaeales (Anemiaceae) and Polypodiales (Blechnaceae, Dryopteridaceae, Lomariopsidaceae, Polypodiaceae, Pteridaceae, Tectariaceae). CONCLUSIONS: Our investigation adds considerably to the recorded diversity of plants with structurally coloured leaves. The iterative evolution of photonic helicoidal walls has resulted in a broad phylogenetic distribution, centred on ferns and monocots. We speculate that the primary function of the helicoidal wall is to provide strength and support, so structural colour could have evolved as a potentially beneficial chance function of this structure.

The traditional utilization, biological activity and chemical composition of edible fern species.

ETHNOPHARMACOLOGICAL RELEVANCE: Ferns form an important part of the human diet. Young fern fiddleheads are mostly consumed as vegetables, while the rhizomes are often extracted for starch. These edible ferns are also often employed in traditional medicine, where all parts of the plant are used, mostly to prepare extracts. These extracts are applied either externally as lotions and baths or internally as potions, decoctions and teas. Ailments traditionally treated with ferns include coughs, colds, fevers, pain, burns and wounds, asthma, rheumatism, diarrhoea, or skin diseases (eczema, rashes, itching, leprosy). AIM OF THE REVIEW: This review aims to compile the worldwide knowledge on the traditional medicinal uses of edible fern species correlating to reported biological activities and isolated bioactive compounds. MATERIALS AND METHODS: The articles and books published on edible fern species were searched through the online databases Web of Science, Pubmed and Google Scholar, with critical evaluation of the hits. The time period up to the end of 2022 was included. RESULTS: First, the edible fern species were identified based on the literature data. A total of 90 fern species were identified that are eaten around the world and are also used in traditional medicine. Ailments treated are often associated with inflammation or bacterial infection. However, only the most common and well-known fern species, were investigated for their biological activity. The most studied species are Blechnum orientale L., Cibotium barometz (L.) J. Sm., Diplazium esculentum (Retz.) Sw., Marsilea minuta L., Osmunda japonica Thunb., Polypodium vulgare L., and Stenochlaena palustris (Burm.) Bedd. Most of the fern extracts have been studied for their antioxidant, anti-inflammatory and antimicrobial activities. Not surprisingly, antioxidant capacity has been the most studied, with results reported for 28 edible fern species. Ferns have been found to be very rich sources of flavonoids, polyphenols, polyunsaturated fatty acids, carotenoids, terpenoids and steroids and most of these compounds are remarkable free radical scavengers responsible for the outstanding antioxidant capacity of fern extracts. As far as clinical trials are concerned, extracts from only three edible fern species have been evaluated. CONCLUSIONS: The extracts of edible fern species exert antioxidant anti-inflammatory and related biological activities, which is consistent with their traditional medicinal use in the treatment of wounds, burns, colds, coughs, skin diseases and intestinal diseases. However, studies to prove pharmacological activities are scarce, and require chemical-biological standardization. Furthermore, correct botanical classification needs to be included in publications to simplify data acquisition. Finally, more in-depth phytochemical studies, allowing the linking of traditional use to pharmacological relevance are needed to be done in a standardized way.

Differential expression and co-localization of transcriptional factors during callus transition to differentiation for shoot organogenesis in the water fern Ceratopteris richardii.

BACKGROUND AND AIMS: In flowering plants, regeneration can be achieved by a variety of approaches, and different sets of transcriptional factors are involved in these processes. However, regeneration in taxa other than flowering plants remains a mystery. Ceratopteris richardii is a representative fern capable of both direct and indirect organogenesis, and we aimed to investigate the genetics underlying the transition from callus proliferation to differentiation. METHODS: Morphological and histological analyses were used to determine the type of regeneration involved. RNA sequencing and differential gene expression were used to investigate how the callus switches from proliferation to differentiation. Phylogenetic analysis and RNA in situ hybridization were used to understand whether transcriptional factors are involved in this transition. KEY RESULTS: The callus formed on nascent leaves and subsequently developed the shoot pro-meristem and shoot meristem, thus completing indirect de novo shoot organogenesis in C. richardii. Genes were differentially expressed during the callus transition from proliferation to differentiation, indicating a role for photosynthesis, stimulus response and transmembrane signalling in this transition and the involvement of almost all cell layers that make up the callus. Transcriptional factors were either downregulated or upregulated, which were generally in many-to-many orthology with genes known to be involved in callus development in flowering plants, suggesting that the genetics of fern callus development are both conserved and divergent. Among them, an STM-like, a PLT-like and an ethylene- and salt-inducible ERF gene3-like gene were expressed simultaneously in the vasculature but not in the other parts of the callus, indicating that the vasculature played a role in the callus transition from proliferation to differentiation. CONCLUSIONS: Indirect de novo shoot organogenesis could occur in ferns, and the callus transition from proliferation to differentiation required physiological changes, differential expression of transcriptional factors and involvement of the vasculature.

'Out of Africa' origin of the pantropical staghorn fern genus Platycerium (Polypodiaceae) supported by plastid phylogenomics and biogeographical analysis.

BACKGROUND AND AIMS: The staghorn fern genus Platycerium is one of the most commonly grown ornamental ferns, and it evolved to occupy a typical pantropical intercontinental disjunction. However, species-level relationships in the genus have not been well resolved, and the spatiotemporal evolutionary history of the genus also needs to be explored. METHODS: Plastomes of all the 18 Platycerium species were newly sequenced. Using plastome data, we reconstructed the phylogenetic relationships among Polypodiaceae members with a focus on Platycerium species, and further conducted molecular dating and biogeographical analyses of the genus. KEY RESULTS: The present analyses yielded a robustly supported phylogenetic hypothesis of Platycerium. Molecular dating results showed that Platycerium split from its sister genus Hovenkampia ~35.2 million years ago (Ma) near the Eocene-Oligocene boundary and began to diverge ~26.3 Ma during the late Oligocene, while multiple speciation events within Platycerium occurred during the middle to late Miocene. Biogeographical analysis suggested that Platycerium originated in tropical Africa and then dispersed eastward to southeast Asia-Australasia and westward to neotropical areas. CONCLUSIONS: Our analyses using a plastid phylogenomic approach improved our understanding of the species-level relationships within Platycerium. The global climate changes of both the Late Oligocene Warming and the cooling following the mid-Miocene Climate Optimum may have promoted the speciation of Platycerium, and transoceanic long-distance dispersal is the most plausible explanation for the pantropical distribution of the genus today. Our study investigating the biogeographical history of Platycerium provides a case study not only for the formation of the pantropical intercontinental disjunction of this fern genus but also the 'out of Africa' origin of plant lineages.

Chemical composition of soil carbon is governed by microbial diversity during understory fern removal in subtropical pine forests.

Understory vegetation has an important impact on soil organic carbon (SOC) accumulation. However, little is known about how understory vegetation alters soil microbial community composition and how microbial diversity contributes to SOC chemical composition and persistence during subtropical forest restoration. In this study, removal treatments of an understory fern (Dicranopteris dichotoma) were carried out within pine (Pinus massoniana) plantations restored in different years in subtropical China. Soil microbial community composition and microbial diversity were measured using phospholipid fatty acids (PLFAs) biomarkers and high-throughput sequencing, respectively. The chemical composition of SOC was also measured via solid-state 13C nuclear magnetic resonance (13C NMR). Our results showed that fern removal decreased alkyl C by 4.2 % but increased O-alkyl C by 15.6 % on average, leading to a decline of alkyl C/O-alkyl C ratio, suggesting altered chemical composition of SOC and lowered SOC recalcitrance without fern. Fern removal significantly lowered the fungi-to-bacteria ratio, and it also reduced fungal and bacterial diversity. Partial correlation analysis revealed that soil nitrogen availability was a key factor influencing microbial diversity. Bacterial diversity showed a close relationship with the Alkyl C/O-alkyl C ratio following fern removal. Furthermore, the microbial community structure and bacterial diversity were responsible for 18 % and 55 % of the explained variance in the chemical composition of SOC, respectively. Taken together, these analyses jointly suggest that bacterial diversity exerts a greater role than microbial community structure in supporting SOC persistence during understory fern removal. Our study emphasizes the significance of understory ferns in supporting microbial abundance and diversity as a means of altering SOC persistence during subtropical forest restoration.

Re-examining meristems through the lens of evo-devo.

The concept of the meristem was introduced in 1858 to characterize multicellular, formative, and proliferative tissues that give rise to the entire plant body, based on observations of vascular plants. Although its original definition did not encompass bryophytes, this concept has been used and continuously refined over the past 165 years to describe the diverse apices of all land plants. Here, we re-examine this matter in light of recent evo-devo research and show that, despite displaying high anatomical diversity, land plant meristems are unified by shared genetic control. We also propose a modular view of meristem function and highlight multiple evolutionary mechanisms that are likely to have contributed to the assembly and diversification of the varied meristems during the course of plant evolution.