Basal Angiosperms Research Articles

Functional and Predictive Structural Characterization of WRINKLED2, A Unique Oil Biosynthesis Regulator in Avocado.

WRINKLED1 (WRI1), a member of the APETALA2 (AP2) class of transcription factors regulates fatty acid biosynthesis and triacylglycerol (TAG) accumulation in plants. Among the four known Arabidopsis WRI1 paralogs, only WRI2 was unable to complement and restore fatty acid content in wri1-1 mutant seeds. Avocado (Persea americana) mesocarp, which accumulates 60-70% dry weight oil content, showed high expression levels for orthologs of WRI2, along with WRI1 and WRI3, during fruit development. While the role of WRI1 as a master regulator of oil biosynthesis is well-established, the function of WRI1 paralogs is poorly understood. Comprehensive and comparative in silico analyses of WRI1 paralogs from avocado (a basal angiosperm) with higher angiosperms Arabidopsis (dicot), maize (monocot) revealed distinct features. Predictive structural analyses of the WRI orthologs from these three species revealed the presence of AP2 domains and other highly conserved features, such as intrinsically disordered regions associated with predicted PEST motifs and phosphorylation sites. Additionally, avocado WRI proteins also contained distinct features that were absent in the nonfunctional Arabidopsis ortholog AtWRI2. Through transient expression assays, we demonstrated that both avocado WRI1 and WRI2 are functional and drive TAG accumulation in Nicotiana benthamiana leaves. We predict that the unique features and activities of ancestral PaWRI2 were likely lost in orthologous genes such as AtWRI2 during evolution and speciation, leading to at least partial loss of function in some higher eudicots. This study provides us with new targets to enhance oil biosynthesis in plants.

Distribution of endemic angiosperm species in Brazil on a municipality level.

BackgroundHerbarium collections and the data they hold are the main sources of plant biodiversity information. These collections contain taxonomical and spatial data on living and extinct species; consequently, they are the fundamental basis for temporal and spatial biogeographical studies of plants. Mega projects focused on providing digital and free access to accurate biodiversity data have transformed plant science research, mainly in the past two decades. In this sense, researchers today are overwhelmed by the many different datasets in online repositories. There are also several challenges involved in using these data for biogeographical analyses. Analyses performed on the data available in the repositories show that 70-75% of the total amount of data have spatial deficiencies and a high number of records lack coordinates. This shortage of reliable primary biogeographical information creates serious impediments for biogeographical analyses and conservation assessments and taxonomic revisions consequently produces obstacles for evaluations of threats to biodiversity at global, regional and local levels. With the aim of contributing to botanical and biogeographical research, this paper provides georeferenced spatial data for angiosperm species endemic to Brazil. The information from two reliable online databases, i.e. the Flora do Brasil 2020 floristic database (BFG) and Plantas do Brasil: Resgate Histórico e Herbário Virtual para o Conhecimento e Conservação da Flora Brasileira (REFLORA), which are both based on records collected over the course of the last two centuries, is used to create this spatial dataset.New informationWe provide three taxonomically-edited and georeferenced datasets for basal angiosperms, monocots and eudicots, covering a total of 14,992 endemic species from Brazil. Producing this consolidated dataset involved several months of detailed revision of coordinates and nomenclaturally updating of the names in these datasets. The information provided in this geo-referenced dataset, covering two centuries of specimen collections, will contribute to several botanical and mainly biogeographical studies.

Searching for a nearest living equivalent for Bennettitales: a promising extinct plant group for stomatal proxy reconstructions of Mesozoic pCO2

ABSTRACT To understand Earth´s climate variability and improve predictions of future climate change, studying past climates is an important avenue to explore. A previously published record of pCO2, across the Triassic–Jurassic boundary (TJB, ~201 Ma) of East Greenland, showed that Bennettitales (Anamozamites and Pterophyllum) responded in parallel to the empirically proven pCO2-responders Ginkgoales, reducing their stomatal densities by half across the TJB, indicating a transient doubling of pCO2. The abundance of fossil Bennettitales in Mesozoic strata and natural history museum collections worldwide offers enormous potential for further stomatal proxy pCO2 reconstructions, but a suitable nearest living equivalent (NLE) should ideally first be identified for this extinct plant group. Using specimens from herbarium collections, three species of cycads, historically considered the best NLE, were tested for pCO2 response, as well as two species of tree ferns, grown in experimental growth chambers. None responded to changes in pCO2, and were consequently rejected as NLEs. Finally, two species of ferns were selected from the literature, and produced very similar pCO2 compared to Ginkgoales. However, these understory ferns are not appropriate NLEs for Bennettitales due to differences in habitat and a distant evolutionary relationship. Future work should test additional plant groups, in particular seed plants such as basal angiosperms and Gnetales, for suitability as NLE for Bennettitales in pCO2 reconstructions, for example through biogeochemical fingerprinting using infrared microspectroscopy. Until an appropriate NLE is identified, Bennettitales pCO2 can be reconstructed based on cross-calibration of stomatal densities with those of co-occurring pCO2 responders, such as Ginkgoales.

Understanding the Ethnobotany, Chemistry, Pharmacology, and Distribution of Genus Hydnora (Aristolochiaceae).

The genus Hydnora (Hydnoraceae) is one of the basal angiosperms in the order Piperales, found in the semi-arid regions of Africa, and the Southern Arabian Peninsula. Plants in this genus play essential roles in communities around the world as revealed by various studies. Currently, there are eight species of the genus Hydnora; seven in Africa and one in the Arabian Peninsula. Notably, Hydnora abyssinica A.Br. and Hydnora africana Thunb. are widely distributed compared to other species. They are widely used for their medicinal and nutritional values. The information on ethnobotany, chemistry, pharmacology, and distribution of genus Hydnora was gathered using phytochemical and ethnobotanical books, electronic sources, and published articles. Preliminary phytochemical screening shows that flavonoids, phenolics, proanthocyanidins, and tannins are the main compounds in H. abyssinica and H. africana. Furthermore, 11 compounds have been isolated from H. abyssinica. The biological activities of H. abyssinica and H. africana have been reported. They include antibacterial, antiproliferative, antioxidant, antidiarrhea, and antifungal potentials. Despite the Hydnora species being practiced in ancient folkloric medicine, their traditional uses and pharmacological value are poorly documented. Based on the available information on ethnobotany, phytochemistry, pharmacology, and distribution, we aim to provide research gaps and challenges for a better understanding of this genus. This may be resourceful in the development of effective phytomedicines, and aid in conservation. The available studies on this genus on some aspects such as phytochemistry, pharmacological activities, and distribution are under-reported hence the need for further research.

Searching for Novel Transcriptional Regulators of Lignin Deposition Within the PIRIN Family in the Model C4 Grass Setaria Viridis

PIRINs (PRNs) comprise a family of cupin domain-containing proteins that are conserved between prokaryotic and eukaryotic organisms, but whose functions remain largely elusive. A member of the PIRIN family has been recently characterized as a transcriptional co-regulator of lignin deposition in the eudicot Arabidopsis thaliana, consisting of another player in the complex regulatory mechanism controlling the timing, localization and final structure of the lignin polymer. However, a similar regulatory function for PRNs in other plant species remains to be determined. Here, we characterized the PIRIN gene family in the C4 model grass Setaria viridis and further identified members potentially involved in lignification. A total of 4 genes encoding PRNs (SvPRN1 to SvPRN4) were found in the genome of S. viridis, similar to the number found in other grasses. Phylogenetic analysis using 39 plant species depicted three groups of PRN proteins, not equally conserved across the plant kingdom. SvPRN2 clustered into Group 1 together with other PRNs from eudicots and grasses, whereas the other SvPRNs clustered into Group 3, consisting mainly of PRNs from grasses. Group 2 was exclusively composed of PRN proteins from eudicot species, together with PRN from the basal Angiosperm Amborella trichopoda. Predictive structural analysis suggests that PRN proteins belonging to Group 3 harbor distinct structural features potentially related to functional diversification. The identification of SvPRN genes potentially involved in lignification in S. viridis was based on the following criteria: i) similar expression pattern to lignin biosynthetic genes in a set of different S. viridis tissues; ii) similar expression pattern to lignin biosynthetic genes in the elongating internode of S. viridis; iii) co-expression with secondary cell wall- (SCW) and lignin-related genes in co-expression databases; iv) presence of SCW-related cis elements in its promoter region; v) high expression in S. viridis tissues undergoing active lignification. These analyses suggest that SvPRN2 is the strongest candidate to play a role in the regulation of lignin deposition in S. viridis, although other members of the family met some of these criteria and might also function in this biological process. Functional studies are necessary to confirm and further characterize the precise role of these SvPRN genes in S. viridis.

BHLH IRIDOID SYNTHESIS 3 is a member of a bHLH gene cluster regulating terpenoid indole alkaloid biosynthesis in Catharanthus roseus.

Basic helix‐loop‐helix (bHLH) transcription factors (TFs) are key regulators of plant specialized metabolites, including terpenoid indole alkaloids (TIAs) in Catharanthus roseus. Two previously characterized subgroup‐IVa bHLH TFs, BIS1 (bHLH Iridoid Synthesis 1) and BIS2 regulate iridoid biosynthesis in the TIA pathway. We reanalyzed the recently updated C. roseus genome sequence and discovered that BIS1 and BIS2 are clustered on the same genomic scaffold with a previously uncharacterized bHLH gene, designated as BIS3. Only a few bHLH gene clusters have been studied to date. Comparative analysis of 49 genome sequences from different plant lineages revealed the presence of analogous bHLH clusters in core angiosperms, including the medicinal plants Calotropis gigantea (giant milkweed) and Gelsemium sempervirens (yellow jessamine), but not in the analyzed basal angiosperm and lower plants. Similar to the iridoid pathway genes, BIS3 is highly expressed in roots and induced by methyl jasmonate. BIS3 activates the promoters of iridoid branch genes, geraniol synthase (GES), geraniol 10‐hydroxylase (G10H), 8‐hydroxygeraniol oxidoreductase (8HGO), iridoid synthase (IS), 7‐deoxyloganetic acid glucosyl transferase (7‐DLGT), and 7‐deoxyloganic acid hydroxylase (7DLH), but not iridoid oxidase (IO). Transactivation of the promoters was abolished when BIS3 is converted to a dominant repressor by fusing with the ERF‐associated amphiphilic repression (EAR) sequence. In addition, BIS3 acts synergistically with BIS1 and BIS2 to activate the G10H promoter in tobacco cells. Mutation of the known bHLH TF binding motif, G‐box (CACGTG) in the G10H promoter significantly reduced but did not abolish the transactivation by BIS3. Promoter deletion analysis of G10H suggests that the sequences adjacent to the G‐box are also involved in the regulation by BIS3. Overexpression of BIS3 in C. roseus flower petals significantly upregulated the expression of iridoid biosynthetic genes and increased loganic acid accumulation. BIS2 expression was significantly induced by BIS3 although BIS3 did not directly activate the BIS2 promoter. Our results advance our understanding of the regulation of plant specialized metabolites by bHLH TF clusters.

Two centuries of distribution data: detection of areas of endemism for the Brazilian angiosperms.

Brazil has high levels of biodiversity and has received strong criticism for the increasing country-wide deforestation that threatens it. Although a significant percentage of land area in Brazil is protected, the areas are insufficient and unevenly distributed. Many studies have contributed to the biogeographical knowledge of Brazilian flora, but no endemicity analysis (EA) has been conducted including all endemic angiosperms. We investigated the spatial component, drawing on a huge and taxonomically diverse dataset based on 827016 records collected over the last two centuries. We conducted an EA for 15034 species from 173 families using an optimality criterion with 2° and 3° grid sizes, in order to search for distributional concordance, to identify the biogeographical units and discuss the implications for conservation. Six analyses were run for basal angiosperms, monocots and eudicots. The EA recovered 66 consensus areas (CAs). The concordance of CAs enabled the identification of five best-supported areas of endemism--three in the Atlantic and Parana Forest and two areas in the Cerrado province--supported by species of 120 families. The age of divergence for some genera that contributed significantly to the identification of areas recovered in the Cerrado coincides with the recent, <10Ma, estimated age of that province. By contrast, the areas in the Atlantic and Parana Forest are supported by genera with earlier diversification >30Ma, supporting an ancient origin. Most areas in the Atlantic Forest are partially superimposed with the limits of the protected areas, however, big gaps were identified in the Cerrado. Protecting Brazilian biomes was at the heart of Brazil's environmental policy. Regrettably, this scenario has radically changed based on misleading divergences in conservation policy. Areas of endemism are pivotal for biodiversity conservation due to the common evolutionary history shared by their endemic taxa. Thus, we hope that these congruent patterns of endemism support the establishment of biodiversity priorities.

Comparative analyses of angiosperm secretomes identify apoplastic pollen tube functions and novel secreted peptides

Key messageAnalyses of secretomes of in vitro grown pollen tubes from Amborella, maize and tobacco identified many components of processes associated with the cell wall, signaling and metabolism as well as novel small secreted peptides.Flowering plants (angiosperms) generate pollen grains that germinate on the stigma and produce tubes to transport their sperm cells cargo deep into the maternal reproductive tissues toward the ovules for a double fertilization process. During their journey, pollen tubes secrete many proteins (secreted proteome or secretome) required, for example, for communication with the maternal reproductive tissues, to build a solid own cell wall that withstands their high turgor pressure while softening simultaneously maternal cell wall tissue. The composition and species specificity or family specificity of the pollen tube secretome is poorly understood. Here, we provide a suitable method to obtain the pollen tube secretome from in vitro grown pollen tubes of the basal angiosperm Amborella trichopoda (Amborella) and the Poaceae model maize. The previously published secretome of tobacco pollen tubes was used as an example of eudicotyledonous plants in this comparative study. The secretome of the three species is each strongly different compared to the respective protein composition of pollen grains and tubes. In Amborella and maize, about 40% proteins are secreted by the conventional “classic” pathway and 30% by unconventional pathways. The latter pathway is expanded in tobacco. Proteins enriched in the secretome are especially involved in functions associated with the cell wall, cell surface, energy and lipid metabolism, proteolysis and redox processes. Expansins, pectin methylesterase inhibitors and RALFs are enriched in maize, while tobacco secretes many proteins involved, for example, in proteolysis and signaling. While the majority of proteins detected in the secretome occur also in pollen grains and pollen tubes, and correlate in the number of mapped peptides with relative gene expression levels, some novel secreted small proteins were identified. Moreover, the identification of secreted proteins containing pro-peptides indicates that these are processed in the apoplast. In conclusion, we provide a proteome resource from three distinct angiosperm clades that can be utilized among others to study the localization, abundance and processing of known secreted proteins and help to identify novel pollen tube secreted proteins for functional studies.

Increasing axial parenchyma fraction in the Malagasy Magnoliids facilitated the co-optimisation of hydraulic efficiency and safety.

The evolution of angiosperms was accompanied by the segregation and specialisation of their xylem tissues. This study aimed to determine whether the fraction and arrangement of parenchyma tissue influence the hydraulic efficiency-safety trade-off in the basal angiosperms. We examined xylem anatomical structure and hydraulic functioning of 28 woody species of Magnoliids in a tropical rainforest of Madagascar and reported, for the first time, quantitative measurements that support the relationship between vessel-to-xylem parenchyma connectivity and the hydraulic efficiency-safety trade-off. We also introduced a new measurement - the distance of species from the trade-off limit - to quantify the co-optimisation of hydraulic efficiency and safety. Although the basal angiosperms in this study had low hydraulic conductivity and safety, species with higher axial parenchyma fraction (APf) had significantly higher hydraulic conductivity. Hydraulic efficiency-safety optimisation was accompanied by higher APf and vessel-to-axial parenchyma connectivity. Conversely, species exhibiting high ray parenchyma fraction and high vessel-to-ray connectivity had lower Ks and were further away from the hydraulic trade-off limit line. Our results provide evidence that axial parenchyma fraction and paratracheal arrangement are associated with both enhanced hydraulic efficiency and safety.

Revisiting the occurrence and evidence of endodermis in angiosperm shoots

A sampling of angiosperms across a broad spectrum of families and generas was done to determine if angiosperms from the ANA grade basal angiosperms to the Zingiberales of the monocots and Apiales of the eudicots had an endodermis with demonstrable Casparian bands in shoots because the literature has a paucity of demonstrable images, especially for key basal plants. In the Amborellales, Amborella had no stem endodermis, but the aquatic Trithuria of the Nymphaeales had a monostele in which a layer endodermis enclosed its stem axial vascular tissues. Cabomba, Brasenia, and Nuphar of the Nymphaeales had polysteles in which an endodermis of distinct Casparian bands encircled each axial vascular bundle; Nymphaea had either an atactostele or a reduced polystele with only a few axial vascular bundles surrounded by endodermis. Among the magnoliids, Saururus and Houttuynia had monosteles with distinct endodermis Casparian bands. In many monocots, from Acorus, Acorales, to Thalia, Zingiberales, there was a monostele with an endodermis of Casparian bands surrounding a central cylinder of scattered axial vascular bundles. At the base of the eudicots, Ceratophyllum had a vascular core without endodermis. Some members of the Ranunuculales had stem endodermis in a polystelic arrangement. Nelumbo, Proteales, had a monostele of Casparian bands only in stolons. Unusual endodermal and vascular patterns, siphonosteles, were found in Gunnera, Gunnerales. Most eudicots with stem endodermis usually had a monostele or one endodermal layer of Casparian bands only surrounding one ring of vascular bundles, e. g., Myriophyllum, Drosera, Hippuris, Alternanthera, Lysimachia, and Hydrocotyle, but a polystele was present in Justicia. Some leaf petioles and lamina, e. g., Gunnera, Myriophyllum, Hippuris, and Hydrocotyle, had endodermis around their individual vascular bundles. While a stem endodermis was a distinct feature of aquatic or wetland plants, derived from terrestrial ancestors, the presence of stem endodermis by plants at the bases of some major angiosperm lines suggests that it may have been present early in angiosperm evolution.

Catanthus, an Extinct Magnoliid Flower from the Early Cretaceous of Portugal

Premise of research. Early Cretaceous flowers recovered from Portugal and North America are some of the oldest and most informative angiosperm structures known. Analyses of this material provide a more direct basis for inferring floral structure and biology in early angiosperms than extrapolations based solely on extant taxa, and they have documented an unanticipated diversity of angiosperms, including the presence of many extinct forms, during the Early Cretaceous. The fossil flower described here from the Early Cretaceous of Portugal adds to the knowledge of this extinct diversity.Methodology. Coalified fossil flowers were extracted from unconsolidated sediments and cleaned with HF, HCl, and water. Details were studied using scanning electron microscopy and synchrotron radiation X-ray tomographic microscopy. Phylogenetic relationships were evaluated by adding the fossil to a phylogenetic analysis of extant basal angiosperms based on morphological characters but constrained according to a topology based on molecular data.Pivotal results. A new genus and species, Catanthus dolichostemon, are described on the basis of the fossil flowers. The perianth consists of three thick sepal-like tepals in an outer whorl and six thinner petallike tepals in two inner whorls. The androecium consists of several whorls of stamens with long, broad filaments and anthers with extrorse dehiscence. Pollen is trichotomocolpate and possibly monocolpate. The gynoecium is superior and apocarpous, consisting of six or, rarely, five carpels. Analysis of the phylogenetic position of Catanthus suggests a relationship to Canellales and Magnoliales.Conclusions. Catanthus is a new Early Cretaceous magnoliid angiosperm for which the relationship to the two major clades of extant magnoliids (Laurales + Magnoliales or Canellales + Piperales) is not resolved securely. Catanthus adds to the evidence of substantial extinct diversity among early angiosperms, including the presence of extinct forms related to extant magnoliids, and it is consistent with a general pattern that angiosperm assemblages from the middle Albian and earlier are dominated by noneudicots.

A theoretical morphological model for quantitative description of the three-dimensional floral morphology in water lily (Nymphaea).

Water lilies (Nymphaea spp.) have diverse floral morphologies. Water lilies are not only commonly used as ornamental plants, but they are also important for understanding the diversification of basal angiosperms. Although the diversity in floral morphology of water lily provides useful information for evolutionary biology, horticulture, and horticultural science, it is difficult to describe and analyze the three-dimensional morphology of flowers. In this study, we propose a method to describe the floral morphology of water lily using a three-dimensional theoretical morphological model. The theoretical model was constructed based on three components, i.e., (1) the gradual change in size of floral organs, (2) spiral phyllotaxis, and (3) the interpolation of elevation angles, which were integrated into the model. We generated three-dimensional representation of water lily flowers and visualized theoretical morphospaces by varying each morphological parameter. The theoretical morphospace is a mathematical space of morphological spectrum generated by a theoretical morphological model. These morphospaces seems to display the large part of morphological variations of water lily. We measured morphological parameters of real flowers based on our theoretical model and display the occupation pattern of morphological parameters. We also surveyed the relation between morphological parameters and flower shape descriptions found in a catalog. In some parameters, we found breeders' description can link to our morphological model. In addition, the relationship between the global features of floral morphology and the parameters of the theoretical model was calculated with flower silhouettes simulated with a range of parameter values and the global features of the silhouette. We used two simple indices to assess the global morphological features, which were calculated with the convex hull. The results indicated that our method can effectively provide an objective and quantitative overview of the diversity in the floral morphology of water lily.

Transcriptomic and Proteomic Insights into Amborella trichopoda Male Gametophyte Functions.

Flowering plants (angiosperms) are characterized by pollen tubes (PTs; male gametophytes) carrying two immobile sperm cells that grow over long distances through the carpel toward the ovules, where double fertilization is executed. It is not understood how these reproductive structures evolved, which genes occur de novo in male gametophytes of angiosperms, and to which extent PT functions are conserved among angiosperms. To contribute to a deeper understanding of the evolution of gametophyte functions, we generated RNA sequencing data from seven reproductive and two vegetative control tissues of the basal angiosperm Amborella trichopoda and complemented these with proteomic data of pollen grains (PGs) and PTs. The eudicot model plant Arabidopsis (Arabidopsis thaliana) served as a reference organism for data analysis, as more than 200 genes have been associated with male gametophyte functions in this species. We describe methods to collect bicellular A. trichopoda PGs, to induce their germination in vitro, and to monitor PT growth and germ cell division. Transcriptomic and proteomic analyses indicate that A. trichopoda PGs are prepared for germination requiring lipids, energy, but likely also reactive oxygen species, while PTs are especially characterized by catabolic/biosynthetic and transport processes including cell wall biosynthesis and gene regulation. Notably, a number of pollen-specific genes were lacking in Arabidopsis, and the number of genes involved in pollen signaling is significantly reduced in A. trichopoda In conclusion, we provide insight into male gametophyte functions of the most basal angiosperm and establish a valuable resource for future studies on the evolution of flowering plants.

Another building block in the plant cell wall: Barley xyloglucan xyloglucosyl transferases link covalently xyloglucan and anionic oligosaccharides derived from pectin.

We report on the homo- and hetero-transglycosylation activities of the HvXET3 and HvXET4 xyloglucan xyloglucosyl transferases (XET; EC 2.4.1.207) from barley (Hordeum vulgare L.), and the visualisation of these activities in young barley roots using Alexa Fluor 488-labelled oligosaccharides. We discover that these isozymes catalyse the transglycosylation reactions with the chemically defined donor and acceptor substrates, specifically with the xyloglucan donor and the penta-galacturonide [α(1-4)GalAp]5 acceptor - the homogalacturonan (pectin) fragment. This activity is supported by 3D molecular models of HvXET3 and HvXET4 with the docked XXXG donor and [α(1-4)GalAp]5 acceptor substrates at the -4 to +5 subsites in the active sites. Comparative sequence analyses of barley isoforms and seed-localised TmXET6.3 from nasturtium (Tropaeolum majus L.) permitted the engineering of mutants of TmXET6.3 that could catalyse the hetero-transglycosylation reaction with the xyloglucan/[α(1-4)GalAp]5 substrate pair, while wild-type TmXET6.3 lacked this activity. Expression data obtained by real-time quantitative polymerase chain reaction of HvXET transcripts and a clustered heatmap of expression profiles of the gene family revealed that HvXET3 and HvXET6 co-expressed but did not share the monophyletic origin. Conversely, HvXET3 and HvXET4 shared this relationship, when we examined the evolutionary history of 419 glycoside hydrolase 16 family members, spanning monocots, eudicots and a basal Angiosperm. The discovered hetero-transglycosylation activity in HvXET3 and HvXET4 with the xyloglucan/[α(1-4)GalAp]5 substrate pair is discussed against the background of roles of xyloglucan-pectin heteropolymers and how they may participate in spatial patterns of cell wall formation and re-modelling, and affect the structural features of walls.

A Reappraisal of the Evolutionary and Developmental Pathway of Apomixis and Its Genetic Control in Angiosperms.

Apomixis sensu stricto (agamospermy) is asexual reproduction by seed. In angiosperms it represents an easy byway of life cycle renewal through gamete-like cells that give rise to maternal embryos without ploidy reduction (meiosis) and ploidy restitution (syngamy). The origin of apomixis still represents an unsolved problem, as it may be either evolved from sex or the other way around. This review deals with a reappraisal of the origin of apomixis in order to deepen knowledge on such asexual mode of reproduction which seems mainly lacking in the most basal angiosperm orders (i.e., Amborellales, Nymphaeales and Austrobaileyales, also known as ANA-grade), while it clearly occurs in different forms and variants in many unrelated families of monocots and eudicots. Overall findings strengthen the hypothesis that apomixis as a whole may have evolved multiple times in angiosperm evolution following different developmental pathways deviating to different extents from sexuality. Recent developments on the genetic control of apomixis in model species are also presented and adequately discussed in order to shed additional light on the antagonist theories of gain- and loss-of-function over sexuality.

The complete chloroplast genome sequence of Acorus tatarinowii (Araceae) from Fujian, China

Acorus tatarinowii is a useful traditional Chinese medicine (TCM) and is officially documented in the Chinese Pharmacopeia with the name ‘Shi Chang Pu’. It belongs to the Araceae family and is used for the treatment of dementia, epilepsy, amnesia and insomnia. We resequenced complete chloroplast (cp) genome of A. tatarinowii from Fujian, China. The whole genome was 153,453 bp in length, consisting of a pair of inverted repeats (IR 25,795 bp), a large single-copy region (LSC 83,631 bp), and a small single-copy region (SSC 18,232 bp). The complete genome contained 132 genes, including 84 protein-coding genes, 38 tRNA, and 8 rRNA genes. The overall GC content of the whole genome was 38.7%. A maximum-likelihood phylogenetic analysis showed that A. tatarinowii is sister to A. tatarinowii which was collected in Yunnan, China. The complete chloroplast genome of A. tatarinowii will help improve and integrate the existing genome data of monocots and provide insights into the phylogenetic relationship among basal angiosperms, monocots and dicots.

The complete chloroplast genome sequence of Knema conferta (Myristicaceae)

Knema conferta is a member of Myristicaceae. The K. conferta chloroplast genome is found to be 155,744 bp in length and has a base composition of A (30.02%), G (19.30%), C (19.90%), and T (30.78%). The genome contained two short inverted repeat (IRa and IRb) regions (48,052 bp) which were separated by a large single copy (LSC) region (86,926 bp) and a small single copy (SSC) region (20,770 bp). The genome encoded a total of 128 unigenes, including 89 protein-coding genes, 31 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Further, complete chloroplast sequence of K. conferta was aligned together with 2 species of Knema and 5 basal angiosperms species which have reported the complete chloroplast sequence. This complete chloroplast genome will provide valuable information for the development of DNA markers for future species resource development and phylogenetic analysis of K. conferta.

The complete chloroplast genome sequence of Knema linifolia (Myristicaceae)

Knema linifolia is a member of Myristicaceae. The K. linifolia chloroplast genome is found to be 155,754 bp in length and has a base composition of A (30.02%), G (19.30%), C (19.89%), and T (30.79%). The genome contained two short inverted repeat (IRa and IRb) regions (48,080 bp) which were separated by a large single copy (LSC) region (86,991 bp) and a small single copy (SSC) region (20,683 bp). The chloroplast genome has 89 protein-coding genes, 31 transfer RNA (tRNA) genes, and 8 ribosomal RNA (rRNA) genes. Further, complete chloroplast sequence of K. linifolia was aligned together with 2 species of Knema and 5 basal angiosperms species which have reported the complete chloroplast sequence. This complete chloroplast genome will provide valuable information for the development of DNA markers for future species resource development and phylogenetic analysis of K. linifolia.

Diversity and Distribution of Vascular Epiphytic Flora in Sub-temperate Forests of Darjeeling Himalaya, India

Aims: This communication deals with the diversity and distribution including host species distribution of vascular epiphytes also reflecting its phenological observations.&#x0D; Study Design: Random field survey was carried out in the study site to identify and record the taxa. Host species was identified and vascular epiphytes were noted.&#x0D; Study Site and Duration: The study was conducted in the sub-temperate forests of Darjeeling Himalaya which is a part of the eastern Himalaya hotspot. The zone extends between 1200 to 1850 m amsl representing the amalgamation of both sub-tropical and temperate vegetation. The study was conducted during the year 2018-2019.&#x0D; Methodology: Process of random sampling collection was followed. Host trees with CBH &gt;30 cm were identified and percentage of distribution of epiphytes in the host tree was analyzed and divided into two zones depending on the abundance of epiphytes. Data for the epiphytic plant specimens were collected in the field. Exsiccates were made with the collected voucher specimens and were deposited at the Calcutta University Herbarium (CUH) following the conventional methodology. Study on the taxa are based on their host tree distribution, micro-habitat and phenological status. The location and altitude of the study sites were recorded by global positioning system.&#x0D; Results: A total number of 115 species under 70 genera and 31 families have been identified with 65% other vascular angiosperms (basal angiosperms and eudicots) and 16% monocots. Orchidaceae among the monocots represented 36% with 41 species and 18 genera. Ferns and lycophytes include 25% of the diversity with 29 taxa under 6 families. Most favorable host trees were Ficus auriculata Lour., Ficus neriifolia Sm., Saurauia nepalensis DC., Erythrina variegata L., Macaranga denticulata (Blume) Müll. Arg., Cryptomeria japonica (Thunb. ex L.f.) D. Don and Engelhardia spicata Lechen ex Blume.&#x0D; Conclusion: The other vascular angiosperms preferred wet monsoon for flowering whereas spring season was most favourable for Orchidaceae. Although a healthy number of vascular epiphytes have been identified, a number of threats are still prevailing in the regions which are mostly anthropogenic. Proper collaborative strategies have to be maintained for its conservation.

Evidence for an extinct lineage of angiosperms from the Early Cretaceous of Patagonia and implications for the early radiation of flowering plants.

The pinnately lobed Aptian leaf fossil Mesodescolea plicata was originally described as a cycad, but new evidence from cuticle structure suggests that it is an angiosperm. Here we document the morphology and cuticle anatomy of Mesodescolea and explore its significance for early angiosperm evolution. We observed macrofossils and cuticles of Mesodescolea with light, scanning electron and transmission electron microscopy, and used phylogenetic methods to test its relationships among extant angiosperms. Mesodescolea has chloranthoid teeth and tertiary veins forming elongate areoles. Its cuticular morphology and ultrastructure reject cycadalean affinities, whereas its guard cell shape and stomatal ledges are angiospermous. It shares variable stomatal complexes and epidermal oil cells with angiosperm leaves from the lower Potomac Group. Phylogenetic analyses and hypothesis testing support its placement within the basal ANITA grade, most likely in Austrobaileyales, but it diverges markedly in leaf form and venation. Although many Early Cretaceous angiosperms fall within the morphological range of extant taxa, Mesodescolea reveals unexpected early morphological and ecophysiological trends. Its similarity to other Early Cretaceous lobate leaves, many identified previously as eudicots but in some cases pre-dating the appearance of tricolpate pollen, may indicate that Mesodescolea is part of a larger extinct lineage of angiosperms.