The size diversity of the Pteridaceae family chloroplast genome is caused by overlong intergenic spacers.

BACKGROUND: While the size of chloroplast genomes (cpDNAs) is often influenced by the expansion and contraction of inverted repeat regions and the enrichment of repeats, it is the intergenic spacers (IGSs) that appear to play a pivotal role in determining the size of Pteridaceae cpDNAs. This provides an opportunity to delve into the evolution of chloroplast genomic structures of the Pteridaceae family. This study added five Pteridaceae species, comparing them with 36 published counterparts. RESULTS: Poor alignment in the non-coding regions of the Pteridaceae family was observed, and this was attributed to the widespread presence of overlong IGSs in Pteridaceae cpDNAs. These overlong IGSs were identified as a major factor influencing variations in cpDNA size. In comparison to non-expanded IGSs, overlong IGSs exhibited significantly higher GC content and were rich in repetitive sequences. Species divergence time estimations suggest that these overlong IGSs may have already existed during the early radiation of the Pteridaceae family. CONCLUSIONS: This study reveals new insights into the genetic variation, evolutionary history, and dynamic changes in the cpDNA structure of the Pteridaceae family, providing a fundamental resource for further exploring its evolutionary research.

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.

Areas of endemism of Pteridaceae (Polypodiopsida) in Brazil: a first approach.

Areas of endemism (AoE) comprise regions host to two or more endemic taxa, whose distributional limits are congruent and not random. These areas are important for two reasons: they comprise the smallest geographic units for biogeographic analyses and they are priority targets for conservation actions. Ferns are a monophyletic group that despite having a wide geographic distribution, concentrates great species richness and endemism in some regions (centres). The southern and southeastern regions of Brazil comprise one of these centres for the Neotropics. This study aims to verify the AoE of Pteridaceae in Brazil and examine whether the results obtained here are congruent with areas already delimited for other groups and whether there is spatial correspondence between the AoE and Conservation Units. To this end, a database was created with collection records of the 205 Pteridaceae species occurring in Brazil based on a review of herbaria. We analysed 23 815 records for 205 Pteridaceae species using Endemicity Analysis (NDM-VNDM), selecting the fill and assumed parameters, and 1°, 2° and 3° grid-cells. The consensus of 158 AoE, using different grid sizes, was calculated, and subsequently, generalized AoE were established. The Guiana Shield, southern Brazil, southeastern Brazil, and southeastern Bahia were considered generalized AoE. These areas correspond to those found for animals and angiosperms, and in previous studies with ferns. Furthermore, two areas, Acre and Mato Grosso do Sul, were recovered only on grids with 2° and 3°. It will be essential to conduct more research to confirm the persistence of both AoE (Acre and Mato Grosso do Sul), especially after expanding sampling. Most endemic species distribution points occur outside protected areas, demonstrating an alarming situation regarding the conservation of these taxa. In addition, fern distribution data could (and should) be used in conservation practices, programmes and policies, given that they are good ecological indicators and that the distribution of ferns may not reflect that of angiosperms and animals.

Adaptive evolution and co-evolution of chloroplast genomes in Pteridaceae species occupying different habitats: overlapping residues are always highly mutated.

BACKGROUND: The evolution of protein residues depends on the mutation rates of their encoding nucleotides, but it may also be affected by co-evolution with other residues. Chloroplasts function as environmental sensors, transforming fluctuating environmental signals into different physiological responses. We reasoned that habitat diversity may affect their rate and mode of evolution, which might be evidenced in the chloroplast genome. The Pteridaceae family of ferns occupy an unusually broad range of ecological niches, which provides an ideal system for analysis. RESULTS: We conducted adaptive evolution and intra-molecular co-evolution analyses of Pteridaceae chloroplast DNAs (cpDNAs). The results indicate that the residues undergoing adaptive evolution and co-evolution were mostly independent, with only a few residues being simultaneously involved in both processes, and these overlapping residues tend to exhibit high mutations. Additionally, our data showed that Pteridaceae chloroplast genes are under purifying selection. Regardless of whether we grouped species by lineage (which corresponded with ecological niches), we determined that positively selected residues mainly target photosynthetic genes. CONCLUSIONS: Our work provides evidence for the adaptive evolution of Pteridaceae cpDNAs, especially photosynthetic genes, to different habitats and sheds light on the adaptive evolution and co-evolution of proteins.

Systematics and biogeography of the Old World fern genus Antrophyum.

Antrophyum is one of the largest genera of vittarioid ferns (Pteridaceae) and is most diverse in tropical Asia and the Pacific Islands, but also occurs in temperate Asia, Australia, tropical Africa and the Malagasy region. The only monographic study of Antrophyum was published more than a century ago and a modern assessment of its diversity is lacking. Here, we reconstructed a comprehensively sampled and robustly supported phylogeny for the genus based on four chloroplast markers using Bayesian inference, maximum likelihood and maximum parsimony analyses. We then explored the evolution of the genus from the perspectives of morphology, systematics and historical biogeography. We investigated nine critical morphological characters using a morphometric approach and reconstructed their evolution on the phylogeny. We describe four new species and provide new insight into species delimitation. We currently recognize 34 species for the genus and provide a key to identify them. The results of biogeographical analysis suggest that the distribution of extant species is largely shaped by both ancient and recent dispersal events.

Insights into the evolutionary history and taxonomic status of Sinopteris (Pteridaceae).

As an endemic Chinese genus, Sinopteris C. Chr. & Ching was once considered an early diverged taxon of cheilanthoid ferns, and its taxonomic status has long been controversial. In this study, eight datasets spanning the complete chloroplast genomes and three nuclear genes were used to reconstruct the phylogeny of Sinopteris and its relatives. In addition, combining morphological analyses, divergence time estimation, and ancestral trait reconstruction, the origin and evolutionary history of Sinopteris were comprehensively discussed. Based on the complete chloroplast genome dataset, our analyses yielded a phylogram with all clades strongly supported (ML-BS = 100, BI-PP = 1.0), and the topology was almost identical to that based on the concatenated sequences of nrDNA, CRY2, and IBR3. Two species of Sinopteris were united and sister to Aleuritopteris niphobola (C. Chr.) Ching. They constituted a stable monophyletic group embedded in Aleuritopteris Fée. This was also consistent with the results of morphological analyses. Divergence time estimation indicated that the clade of Aleuritopteris and Sinopteris originated in the early Miocene (ca. 16.80 Ma) and experienced two rapid diversifications, which could coincide with environmental heterogeneity caused by the progressive uplift of the Himalayas and the intense uplift of the Hengduan Mountains. Sinopteris originated in the late Miocene (ca. 6.96 Ma), accompanied by the sharp intensifications of Asian Monsoon, and began to diversify at 2.34 Ma, following the intense uplift of the Hengduan Mountains. Ancestral character reconstruction showed that monangial sori and subsessile sporangia were clearly late derived states rather than early diverged states. Both the molecular phylogenetic and morphological analyses support the inclusion of Sinopteris in Aleuritopteris.

A Large Intergenic Spacer Leads to the Increase in Genome Size and Sequential Gene Movement around IR/SC Boundaries in the Chloroplast Genome of Adiantum malesianum (Pteridaceae).

Expansion and contraction (ebb and flow events) of inverted repeat (IR) boundaries occur and are generally considered to be major factors affecting chloroplast (cp) genome size changes. Nonetheless, the Adiantum malesianum cp genome does not seem to follow this pattern. We sequenced, assembled and corrected the A. flabellulatum and A. malesianum cp genomes using the Illumina NovaSeq6000 platform, and we performed a comparative genome analysis of six Adiantum species. The results revealed differences in the IR/SC boundaries of A. malesianum caused by a 6876 bp long rpoB-trnD-GUC intergenic spacer (IGS) in the LSC. This IGS may create topological tension towards the LSC/IRb boundary in the cp genome, resulting in a sequential movement of the LSC genes. Consequently, this leads to changes of the IR/SC boundaries and may even destroy the integrity of trnT-UGU, which is located in IRs. This study provides evidence showing that it is the large rpoB-trnD-GUC IGS that leads to A. malesianum cp genome size change, rather than ebb and flow events. Then, the study provides a model to explain how the rpoB-trnD-GUC IGS in LSC affects A. malesianum IR/SC boundaries. Moreover, this study also provides useful data for dissecting the evolution of cp genomes of Adiantum. In future research, we can expand the sample to Pteridaceae to test whether this phenomenon is universal in Pteridaceae.

Reticulate evolution in the Pteris fauriei group (Pteridaceae).

The Pteris fauriei group (Pteridaceae) has a wide distribution in Eastern Asia and includes 18 species with similar but varied morphology. We collected more than 300 specimens of the P. fauriei group and determined ploidy by flow cytometry and inferred phylogenies by molecular analyses of chloroplast and nuclear DNA markers. Our results reveal a complicated reticulate evolution, consisting of seven parental taxa and 58 hybrids. The large number of hybrid taxa have added significant morphological complexity to the group leading to difficult taxonomic issues. The hybrids generally had broader ranges and more populations than their parental taxa. Genetic combination of different pairs of parental species created divergent phenotypes of hybrids, exhibited by both morphological characteristics and ecological fidelities. Niche novelty could facilitate hybrid speciation. Apogamy is common in this group and potentially contributes to the sustainability of the whole group. We propose that frequent hybridizations among members of the P. fauriei group generate and maintain genetic diversity, via novel genetic combinations, niche differentiation, and apogamy.

Once more unto the breach, dear friends: Resolving the origins and relationships of the Pellaea wrightiana hybrid complex.

PREMISE: The taxonomic status of Wright's cliff brake fern, Pellaea wrightiana, has been in dispute ever since it was first described by Hooker in 1858. Previously published evidence suggested that this "taxon" may represent a polyploid complex rather than a single discrete species, a hypothesis tested here using a multifaceted analytical approach. METHODS: Data derived from cytogenetics, spore analyses, leaf morphometrics, enzyme electrophoresis, and phylogenetic analyses of plastid and nuclear DNA sequences are used to elucidate the origin, relationships, and taxonomic circumscription of P. wrightiana. RESULTS: Plants traditionally assigned to this taxon represent three distinct polyploids. The most widespread, P. wrightiana, is a fertile allotetraploid that arose through hybridization between two divergent diploid species, P. truncata and P. ternifolia. Sterile triploids commonly identified as P. wrightiana, were found to be backcross hybrids between this fertile tetraploid and diploid P. truncata. Relatively common across Arizona and New Mexico, they are here assigned to P. ×wagneri hyb. nov. In addition, occasional sterile tetraploid plants assigned to P. wrightiana are shown here to be hybrids between the fertile allotetraploid and the tetraploid P. ternifolia subsp. arizonica. These tetraploid hybrids originated independently in two regions of parental sympatry (southern Arizona and west Texas) and are here assigned to P. ×gooddingii hyb. nov. CONCLUSIONS: Weaving together data from a diversity of taxonomic approaches, we show that plants identified as P. wrightiana represent three morphologically distinguishable polyploids that have arisen through repeated hybridization events involving the divergent sexual taxa P. ternifolia and P. truncata.

The biology of C. richardii as a tool to understand plant evolution.

The fern Ceratopteris richardii has been studied as a model organism for over 50 years because it is easy to grow and has a short life cycle. In particular, as the first homosporous vascular plant for which genomic resources were developed, C. richardii has been an important system for studying plant evolution. However, we know relatively little about the natural history of C. richardii. In this article, we summarize what is known about this aspect of C. richardii, and discuss how learning more about its natural history could greatly increase our understanding of the evolution of land plants.

Estudio fitoquímico de Argyrochosma Nivea (poir) Windham (cuti cuti) / Phytochemical study of argyrochosma nivea (poir.) windham (poir.) desv. (cuti cuti)

Nuestro país presenta un gran potencial de plantas medicinales en todo su territorio, por ser megadiverso, con muchas regiones agroecologicas y formaciones vegetales, pese a ello es incipiente la atención al desarrollo de las cadenas de valor del potencial de plantas medicinales, constituyendo un desafío el registro adecuado, con calidad y seguridad porque previenen y solucionan dificultades de salud por sus principios activos. Argyrochosma nivea (Poir.) Windham, "cuti cuti" conocido también como Notholaena nivea. Objetivos: Determinar los grupos metabólicos del extracto alcohólico al 20% de Argyrochosma nivea (Poir.) Windham, administrado a pacientes de diabetes del programa de medicina complementaria, EsSALUD Huancayo. Materiales y métodos: Estudios descriptivo, comparativo. La recolección de información relevante de aspectos botánicos, etnobotánicos, etnofarmacológicos y fitoquímicos sobre Argyrochosma nivea se realizó mediante la búsqueda en las bases de datos Scopus, ScienceDirect, PubMed y la biblioteca virtual del CONCYTEC (servicio de esa institución que reúne revistas de SciELO-Perú y la producción científica y tecnológica del Perú); además, se utilizó el buscador Google-Académico con el fin de agotar la búsqueda. Los términos de búsqueda fueron "Argyrochosma nivea", "Notholaena nivea" o "cuti cuti". Resultados: La Tintura de Argyrochosma nivea al 20% preparado con alcohol etílico al 50% en el analisis fitoquimico realizado se encontro compuestos de Flavanoides totales 0.111 mg de Catequina/ml, Flavonoides totales 0.133 mg de Quercitina /ml, Polifenoles totales 5.189 mg de ácido gálico/ml, Capacidad Antioxidante* 424.701 µ mol trolox/ml, Rutina 0.00579 mg de Rutina/ml, Quercitina 0.105mg/ml y Cumarinas 0.170 mg /ml. Ausencia de antocianinas totales, estos valores aportan la capacidad antioxidante de "cuti cuti", y el contenido de flavonoides (quercetina), permite la prevalencia en el tratamiento de la diabetes. Conclusión: El Estudio fitoquimico de Argyrochosma nivea (Poir.) Windham (Cuti cuti) mediante el análisis por espectrofotometría y análisis por HPLC verifico la existencia de 7 compuestos Flavanoides totales 0.111 mg de Catequina/ml, Flavonoides totales 0.133 mg de Quercitina /ml, Polifenoles totales 5.189 mg de ácido gálico/ml, Capacidad Antioxidante* 424.701 µ mol trolox/ml, Rutina 0.00579 mg de Rutina/ml, Quercitina 0.105mg de Qu ercitina/ml y Cumarinas 0.170 mg de Cumarina/ml(AU)

Our country has a great potential for medicinal plants throughout its territory, as it is megadiverse, with many agroecological regions and plant formations, despite this, attention to the development of value chains for the potential of medicinal plants is incipient, constituting a I challenge the proper registration, with quality and safety because they prevent and solve health difficulties due to their active ingredients. Argyrochosma nivea (Poir.) Windham, "cuti cuti" also known as Notholaena nivea. Objectives: To determine the metabolic groups of the 20% alcoholic extract of Argyrochosma nivea (Poir.) Windham, administered to diabetes patients of the complementary medicine program, EsSALUD Huancayo. Methods: Descriptive, comparative studies. The collection of relevant information on botanical, ethnobotanical, ethnopharmacological and phytochemical aspects of Argyrochosma nivea was carried out by searching the Scopus, ScienceDirect, PubMed databases and the virtual library of CONCYTEC (a service of that institution that brings together SciELO-Peru journals). and the scientific and technological production of Peru); In addition, the Google-Academic search engine was used in order to exhaust the search. The search terms were "Argyrochosma nivea", "Notholaena nivea" or "cuti cuti". Results: The Argyrochosma nivea tincture at 20% prepared with 50% ethyl alcohol in the phytochemical analysis carried out found compounds of total Flavanoids 0.111 mg of Catechin / ml, total Flavonoids 0.133 mg of Quercetin / ml, total Polyphenols 5.189 mg of acid gallic/ml, Antioxidant Capacity* 424.701 µmol trolox/ml, Rutin 0.00579 mg Rutin/ml, Quercetin 0.105mg/ml and Coumarins 0.170 mg/ml. Absence of total anthocyanins, these values provide the antioxidant capacity of "cuti cuti", and the content of flavonoids (quercetin), allows prevalence in the treatment of diabetes. Conclusion: The phytochemical study of Argyrochosma nivea (Poir.) Windham (Cuti cuti) through spectrophotometric analysis and HPLC analysis verified the existence of 7 total Flavanoid compounds 0.111 mg of Catechin/ml, total Flavonoids 0.133 mg of Quercetin /ml, Total polyphenols 5.189 mg of gallic acid/ml, Antioxidant Capacity* 424.701 µ mol trolox/ml, Rutin 0.00579 mg of Rutin/ml, Quercetin 0.105mg of Quercetin/ml and Coumarins 0.170 mg of Coumarin/ml(AU)

Phylogenetic comparative morphological analysis of fern spores in subfamily Pteridoideae (Pteridaceae, Pteridophyta).

Scanning electron microscopy (SEM) was used to characterize spore morphology of 24 taxa of the subfamily Pteridoideae C. Chr. ex Crabbe, Jermy & Mickel of the family Pteridaceae E.D.M. Kirchn. The family is considered to be one of the most taxonomically confusing families due to its high level of polymorphism. The standardized data on spore morphology of the subfamily Pteridoideae were projected onto the final phylogenetic tree in the Mesquite program. This approach made it possible to carry out a comprehensive interdisciplinary analysis of the evolution of spore morphology characters of the subfamily Pteridoideae, as well as to assess the relationships in the family Pteridaceae. The equatorial ridge (cingulum, "flange") has been proven as one of the key spore morphology features, which confirms the close relationship of "Onychium clade" with Pteris. The species-specific characters of the subfamily are fold and tubercle along laesura, equatorial ridge on proximal and distal side, tubercle, and folds on proximal and distal side. The knowledge will help to solve the problems of taxonomy in the family Preridaceae and to supplement the information on the natural classification of the subfamily Pteridoideae.

Spores morphology of the family Pteridaceae from Shandong Province, China.

In this article, we explored systematically the spore morphology of Pteridaceae by observation of the species distributed in Shandong Province using scanning electron microscopy (SEM). The results showed that the spore morphology of all the species in the family is tetrahedral and trilete. The characters of spore ornamentation are intraspecies stable, but significantly different among species and genera. Spore morphology is significant in exploring the phylogenetic relationships of Pteridaceae as well as in generic and specific delimitations.

Evaluation of Gravitropism in Non-seed Plants.

Tropisms are among the most important growth responses for plant adaptation to the surrounding environment. One of the most common tropisms is root gravitropism. Root gravitropism enables the plant to anchor securely to the soil enabling the absorption of water and nutrients. Most of the knowledge related to the plant gravitropism has been acquired from the flowering plants, due to limited research in non-seed plants. Limited research on non-seed plants is due in large part to the lack of standard research methods. Here, we describe the experimental methods to evaluate gravitropism in representative non-seed plant species, including the non-vascular plant moss Physcomitrium patens, the early diverging extant vascular plant lycophyte Selaginella moellendorffii and fern Ceratopteris richardii. In addition, we introduce the methods used for statistical analysis of the root gravitropism in non-seed plant species.

Spore Preparation and Protoplast Isolation to Study Gravity Perception and Response in Ceratopteris richardii.

Early studies revealed a highly predictable pattern of gravity-directed growth and development in Ceratopteris richardii spores. This makes the spore a valuable model system for the study of how a single-cell senses and responds to the force of gravity. Gravity regulates both the direction and magnitude of a trans-cell calcium current in germinating spores, and the orientation of this current predicts the polarization of spore development. In order to make Ceratopteris richardii cells easier to transform and image during this developmental process, a procedure for isolating protoplasts from Ceratopteris richardii gametophytes has been developed and optimized. These protoplasts follow the same developmental pattern as Ceratopteris richardii spores and can be used to monitor the molecular and developmental processes during single-cell polarization. Here, we describe this optimized procedure, along with protocols for sterilizing the spores, sowing them in solid or liquid growth media, and evaluating germination and polarization.

Taxonomy and spore morphology of selected taxa of Cheilanthoideae and Pteridoideae (Pteridaceae) from Pakistan.

Taxonomy and spore morphology of 12 taxa of Cheilanthoideae and Pteridoideae (Pteridaceae, Polypodiales) from Pakistan is illustrated with scanning electron microscopy images based upon the specimens collected from various localities. A total of six genera belong to 12 taxa viz. Actiniopteris radiata, Aleuritopteris albomarginata, A. ancepes, Notholaena himalaica, Oeosporangium nitidulum, O. pteridioides subsp. acrosticum, Onychium cryptogrammoides subsp. cryptogrammoides, O. vermae, Pteris cretica subsp. cretica, P. cretica subsp. laeta, P. vittata subsp. emodi, and P. vittata subsp. vittata were reported. Spore morphology of the taxa was trilete, triangular in proximal and distal view, ellipsoidal and hemicircular in equatorial view, polar proximal and distal surface with cristate, granulose, reticulate, perforate and tuberculate ornamentation.

Timing of meristem initiation and maintenance determines the morphology of fern gametophytes.

The alternation of generations in land plants occurs between the sporophyte phase and the gametophyte phase. The sporophytes of seed plants develop self-maintained, multicellular meristems, and these meristems determine plant architecture. The gametophytes of seed plants lack meristems and are heterotrophic. In contrast, the gametophytes of seed-free vascular plants, including ferns, are autotrophic and free-living, developing meristems to sustain their independent growth and proliferation. Compared with meristems in the sporophytes of seed plants, the cellular mechanisms underlying meristem development in fern gametophytes remain largely unknown. Here, using confocal time-lapse live imaging and computational segmentation and quantification, we determined different patterns of cell divisions associated with the initiation and proliferation of two distinct types of meristems in gametophytes of two closely related Pteridaceae ferns, Pteris vittata and Ceratopteris richardii. Our results reveal how the simple timing of a switch between two meristems has considerable consequences for the divergent gametophyte morphologies of the two ferns. They further provide evolutionary insight into the function and regulation of gametophyte meristems in seed-free vascular plants.

N-terminal region is required for functions of the HAM family member.

Shoot meristems contain stem cells, and they sustain growth and development of the above-ground tissues in land plants. The HAIRY MERISTEM (HAM) family genes, encoding GRAS-domain transcriptional regulators, play essential roles in the control of shoot meristem development and stem cell homeostasis in several flowering plants. Similar to other GRAS proteins, the C-terminal regions of HAM family proteins across land plants are conserved, containing signature motifs that define the GRAS domain. In contrast, the N-terminal regions of HAM family proteins display substantial divergence in sequence and length. Whether the variable and divergent N-termini are required for the conserved functions of HAM proteins is unknown. Our recent work showed that CrHAM - the HAM homolog in the fern Ceratopteris richardii was able to replace the role of type-II HAM genes in Arabidopsis, maintaining established shoot apical meristems and promoting the initiation of new stem cell niches. Here, we provide additional information and show that CrHAM contains a much longer N-terminal region compared to Arabidopsis HAM proteins, which is conserved among different fern HAM homologs. The deletion of this region largely compromises the ability of CrHAM to replace the function of Arabidopsis HAM proteins in shoot meristems. These new data together with previous results suggest that, although lacking the sequence conservation among HAM homologs from different plant lineages, the N-termini are important for the conserved functions of HAM family proteins.

Taxonomy and spore morphology of genus Adiantum (Vittarioideae; Pteridaceae) from Pakistan.

Taxonomy and spore morphology of genus Adiantum (Vittarioideae; Pteridaceae) from Pakistan is illustrated with scanning electron microscopy images based upon the specimens examined in herbaria of Pakistan, United Kingdom, and United States. A total of five species viz. Adiantum capillus-veneris, A. incisum subsp. incisum, A. pedatum subsp. pedatum, A. tibeticum, and A. venustum were reported with the habitat ecology of the species from Pakistan. Spore morphology of the taxa was trilete, triangular in proximal and distal view, ellipsoidal and hemicircular in equatorial view, polar proximal and distal surface was with tuberculate and granulose ornamentation.