Basal Eudicot Research Articles

The evolution of plant microRNAs: insights from a basal eudicot sacred lotus.

microRNAs (miRNAs) are important noncoding small RNAs that regulate mRNAs in eukaryotes. However, under which circumstances different miRNAs/miRNA families exhibit different evolutionary trajectories in plants remains unclear. In this study, we sequenced the small RNAs and degradome from a basal eudicot, sacred lotus (Nelumbo nucifera or lotus), to identify miRNAs and their targets. Combining with public miRNAs, we predicted 57 pre-eudicot miRNA families from different evolutionary stages. We found that miRNA families featuring older age, higher copy and target number tend to show lower propensity for miRNA family loss (PGL) and stronger signature of purifying selection during divergence of temperate and tropical lotus. Further analyses of lotus genome revealed that there is an association between loss of miRNA families in descendent plants and in duplicated genomes. Gene dosage balance is crucial in maintaining those preferentially retained MIRNA duplicates by imposing stronger purifying selection. However, these factors and selection influencing miRNA family evolution are not applicable to the putative MIRNA-likes. Additionally, the MIRNAs participating in lotus pollen-pistil interaction, a conserved process in angiosperms, also have a strong signature of purifying selection. Functionally, sequence divergence in MIRNAs escalates expression divergence of their target genes between temperate and tropical lotus during rhizome and leaf growth. Overall, our study unravels several important factors and selection that determine the miRNA family distribution in plants and duplicated genomes, and provides evidence for functional impact of MIRNA sequence evolution.

Genetics of flower development in Ranunculales - a new, basal eudicot model order for studying flower evolution.

Contents 361 I. 361 II. 362 III. 363 IV. 364 V. 364 Acknowledgements 365 References 365 SUMMARY: Ranunculales, the sister group to all other eudicots, encompasses species with a remarkable floral diversity, which are currently emerging as new model organisms to address questions relating to the genetic architecture of flower morphology and its evolution. These questions concern either traits only found in members of the Ranunculales or traits that have convergently evolved in other large clades of flowering plants. We present recent results obtained on floral organ identity and number, symmetry evolution and spur formation in Ranunculales species. We discuss benefits and future prospects of evo-devo studies in Ranunculales, which can provide the opportunity to decipher the genetic architecture of novel floral traits and also to appraise the degree of conservation of genetic mechanisms involved in homoplasious traits.

Inflorescence and floral development in Trochodendron aralioides (Trochodendraceae)

In the early development of Trochodendron aralioides (Trochodendraceae) inflorescences lateral flowers are initiated after the appearance of the floral pherophylls (subtending bracts). The terminal flower is preceded by metaxyphylls and is initiated earlier than the uppermost lateral flowers of the botryoid inflorescence. Small scales (interpreted as rudimentary perianth organs) precede the stamens. These scales are more distinct in the terminal flower than in the lateral flowers. In the radially symmetrical terminal flower, small scales (or metaxyphylls) and stamens are initiated in a spiral during early development. At anthesis, stamen phyllotaxis appears irregular or approximately whorled as a result of the rapid elongation and irregular slight curvature of the stamen filaments which distorts the originally regular pattern. Finally, the numerous carpels arise simultaneously in a single whorl. It takes about 9 months for flowers to develop and the 2-year reproductive cycle of T. aralioides is typical of many trees. The floral development of T. aralioides is compared with that of other basal eudicots. The bottle-shaped, unicellular stigmatic papillae and long, decurrent stigma of basally united carpels are similar to those of the Buxales¸ suggesting a close relationship.

Characterization ofCYCLOIDEA-like genes in Proteaceae, a basal eudicot family with multiple shifts in floral symmetry

The basal eudicot family Proteaceae (approx. 1700 species) shows considerable variation in floral symmetry but has received little attention in studies of evolutionary development at the genetic level. A framework for understanding the shifts in floral symmetry in Proteaceae is provided by reconstructing ancestral states on an upated phylogeny of the family, and homologues of CYCLOIDEA (CYC), a key gene for the control of floral symmetry in both monocots and eudicots, are characterized. Perianth symmetry transitions were reconstructed on a new species-level tree using parsimony and maximum likelihood. CYC-like genes in 35 species (31 genera) of Proteaceae were sequenced and their phylogeny was reconstructed. Shifts in selection pressure following gene duplication were investigated using nested branch-site models of sequence evolution. Expression patterns of CYC homologues were characterized in three species of Grevillea with different types of floral symmetry. Zygomorphy has evolved 10-18 times independently in Proteaceae from actinomorphic ancestors, with at least four reversals to actinomorphy. A single duplication of CYC-like genes occurred prior to the diversification of Proteaceae, with putative loss or divergence of the ProtCYC1 paralogue in more than half of the species sampled. No shifts in selection pressure were detected in the branches subtending the two ProtCYC paralogues. However, the amino acid sequence preceding the TCP domain is strongly divergent in Grevillea ProtCYC1 compared with other species. ProtCYC genes were expressed in developing flowers of both actinomorphic and zygomorphic Grevillea species, with late asymmetric expression in the perianth of the latter. Proteaceae is a remarkable family in terms of the number of transitions in floral symmetry. Furthermore, although CYC-like genes in Grevillea have unusual sequence characteristics, they display patterns of expression that make them good candidates for playing a role in the establishment of floral symmetry.

Genome and transcriptome sequencing characterises the gene space of Macadamia integrifolia (Proteaceae).

BackgroundThe large Gondwanan plant family Proteaceae is an early-diverging eudicot lineage renowned for its morphological, taxonomic and ecological diversity. Macadamia is the most economically important Proteaceae crop and represents an ancient rainforest-restricted lineage. The family is a focus for studies of adaptive radiation due to remarkable species diversification in Mediterranean-climate biodiversity hotspots, and numerous evolutionary transitions between biomes. Despite a long history of research, comparative analyses in the Proteaceae and macadamia breeding programs are restricted by a paucity of genetic information. To address this, we sequenced the genome and transcriptome of the widely grown Macadamia integrifolia cultivar 741.ResultsOver 95 gigabases of DNA and RNA-seq sequence data were de novo assembled and annotated. The draft assembly has a total length of 518 Mb and spans approximately 79% of the estimated genome size. Following annotation, 35,337 protein-coding genes were predicted of which over 90% were expressed in at least one of the leaf, shoot or flower tissues examined. Gene family comparisons with five other eudicot species revealed 13,689 clusters containing macadamia genes and 1005 macadamia-specific clusters, and provides evidence for linage-specific expansion of gene families involved in pathogen recognition, plant defense and monoterpene synthesis. Cyanogenesis is an important defense strategy in the Proteaceae, and a detailed analysis of macadamia gene homologues potentially involved in cyanogenic glycoside biosynthesis revealed several highly expressed candidate genes.ConclusionsThe gene space of macadamia provides a foundation for comparative genomics, gene discovery and the acceleration of molecular-assisted breeding. This study presents the first available genomic resources for the large basal eudicot family Proteaceae, access to most macadamia genes and opportunities to uncover the genetic basis of traits of importance for adaptation and crop improvement.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3272-3) contains supplementary material, which is available to authorized users.

Functional conservation and divergence of five SEPALLATA-like genes from a basal eudicot tree, Platanus acerifolia.

Five SEP -like genes were cloned and identified from Platanus acerifolia through the analysis of expression profiles, protein-protein interaction patterns, and transgenic phenotypes, which suggested that they play conservative and diverse functions in floral initiation and development, fruit development, bud growth, and dormancy. SEPALLATA (SEP) genes have been well characterized in core eudicots and some monocots, and they play important and diverse roles in plant development, including flower meristem initiation, floral organ identity, and fruit development and ripening. However, the knowledge on the function and evolution of SEP-like genes in basal eudicot species is very limited. Here, we cloned and identified five SEP-like genes from London plane (Platanus acerifolia), a basal eudicot tree that is widely used for landscaping in cities. Sequence alignment and phylogenetic analysis indicated that three genes (PlacSEP1.1, PlacSEP1.2, and PlacSEP1.3) belong to the SEP1/2/4 clade, while the other two genes (PlacSEP3.1 and PlacSEP3.2) are grouped into the SEP3 clade. Quantitative real-time PCR (qRT-PCR) analysis showed that all PlacSEPs, except PlacSEP1.1 and PlacSEP1.2, were expressed during the male and female inflorescence initiation, and throughout the flower and fruit development process. PlacSEP1.2 gene expression was only detected clearly in female inflorescence at April. PlacSEP1.3 and PlacSEP3.1 were also expressed, although relatively weak, in vegetative buds of adult trees. No evident PlacSEPs transcripts were detected in various organs of juvenile trees. Overexpression of PlacSEPs in Arabidopsis and tobacco plants resulted in different phenotypic alterations. 35S:PlacSEP1.1, 35S:PlacSEP1.3, and 35S:PlacSEP3.2 transgenic Arabidopsis plants showed evident early flowering, with less rosette leaves but more cauline leaves, while 35S:PlacSEP1.2 and PlacSEP3.1 transgenic plants showed no visible phenotypic changes. 35S:PlacSEP1.1 and 35S:PlacSEP3.2 transgenic Arabidopsis plants also produced smaller and curled leaves. Overexpression of PlacSEP1.1 and PlacSEP3.1 in tobacco resulted in the early flowering and producing more lateral branches. Yeast two-hybrid analysis indicated that PlacSEPs proteins can form homo- or hetero-dimers with the Platanus APETALA1 (AP1)/FRUITFULL (FUL), B-, C-, and D-class MADS-box proteins in different interacting patterns and intensities. Our results suggest that the five PlacSEP genes may play important and divergent roles during floral initiation and development, as well as fruit development, by collaborating with FUL, B-, C-, and D-class MADS-box genes in London plane; PlacSEP1.3 and PlacSEP3.1 genes might also involve in vegetative bud growth and dormancy. The results provide valuable data for us to understand the functional evolution of SEP-like genes in basal eudicot species.

Perianth symmetry changed at least 199 times in angiosperm evolution

AbstractPerianth bilateral symmetry (zygomorphy) has evolved repeatedly from radial symmetry (actinomorphy) throughout angiosperms. Zygomorphy has previously been linked with plant‐pollinator specialization and higher species diversification. However, the exact number of transitions to and from zygomorphy has remained so far unknown. We recorded perianth symmetry from 761 species, selected to represent all 61 orders and 426 currently accepted families of angiosperms and to include all presumed origins of perianth zygomorphy. We then reconstructed the evolution of perianth symmetry on a consensus backbone tree, using parsimony. We found perianth zygomorphy in 32 orders and 110 families. There was a minimum of 130 origins, almost double of what was previously estimated, and 69 reversals to actinomorphy. Among the origins, 2 were in magnoliids, 29 in monocots, 17 in basal eudicots, 35 in superrosids and 47 in superasterids. Among the reversals, 8 were in monocots, 4 in basal eudicots, 18 in superrosids and 39 in superasterids. This study shows that there has been many more origins of perianth zygomorphy and reversals to actinomorphy than previously shown. We then use this new framework to review the developmental evidence of changes in floral symmetry, showing convergence in the early stages of zygomorphy across angiosperms at the developmental level. We also review the evidence on the genetic control of floral symmetry, suggesting that a restricted number of genes has been recruited multiple times independently to achieve zygomorphy. In contrast to its relative homogeneity at the early developmental and molecular level, zygomorphy appears to be highly variable in its morphological expression at anthesis, involving various processes such as perianth part displacement and differentiation. We then review recent hypotheses on the relationship between floral symmetry, floral orientation, and pollination mode in terms of selective advantages and constraints. Our comprehensive angiosperm‐wide reconstruction of floral symmetry evolution provides a new context for future studies on the developmental, functional, and macroevolutionary aspects of floral symmetry.

Leaf-Like Sepals Induced by Ectopic Expression of a SHORT VEGETATIVE PHASE (SVP)-Like MADS-Box Gene from the Basal Eudicot Epimedium sagittatum.

Epimedium L. (Berberidaceae, Ranales), a perennial traditional Chinese medicinal herb, has become a new popular landscape plant for ground cover and pot culture in many countries based on its excellent ornamental characteristics and, distinctive and diverse floral morphology. However, little is known about the molecular genetics of flower development in Epimedium sagittatum. Here, we describe the characterization of EsSVP that encodes a protein sharing 68, 54, and 35% similarity with SVP, AGAMOUS-like 24 (AGL24) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) in Arabidopsis, respectively. Quantitative RT-PCR (qRT-PCR) indicated that EsSVP transcripts were principally found in petiole and leaf tissues, with little expression in roots and flowers and no in fruits. The highest EsSVP expression was observed in leaves. The flowering time of 35S::EsSVP in most Arabidopsis thaliana and in all petunia plants was not affected in both photoperiod conditions, but 35S::EsSVP 5# and 35S::EsSVP 1# Arabidopsis lines induced late and early flowering under long day (LD, 14 h light/10 h dark) and short day (SD, 10 h light/14 h dark) conditions, respectively. The 35S::EsSVP Arabidopsis produced extra secondary inflorescence or floral meristems in the axils of the leaf-like sepals with excrescent trichomes, and leaf-like sepals not able to enclose the inner three whorls completely. Moreover, almost all transgenic Arabidopsis plants showed persistent sepals around the completely matured fruits. Upon ectopic expression of 35S::EsSVP in Petunia W115, sepals were enlarged, sometimes to the size of leaves; corollas were greenish and did not fully open. These results suggest that EsSVP is involved in inflorescence meristem identity and flowering time regulation in some conditions. Although, the SVP homologs might have suffered functional diversification among diverse species between core and basal eudicots, the protein functions are conserved between Arabidopsis/Petunia and Epimedium.

The NnCenH3 protein and centromeric DNA sequence profiles of Nelumbo nucifera Gaertn. (sacred lotus) reveal the DNA structures and dynamics of centromeres in basal eudicots

Centromeres on eukaryotic chromosomes consist of large arrays of DNA repeats that undergo very rapid evolution. Nelumbo nucifera Gaertn. (sacred lotus) is a phylogenetic relict and an aquatic perennial basal eudicot. Studies concerning the centromeres of this basal eudicot species could provide ancient evolutionary perspectives. In this study, we characterized the centromeric marker protein NnCenH3 (sacred lotus centromere-specific histone H3 variant), and used a chromatin immunoprecipitation (ChIP)-based technique to recover the NnCenH3 nucleosome-associated sequences of sacred lotus. The properties of the centromere-binding protein and DNA sequences revealed notable divergence between sacred lotus and other flowering plants, including the following factors: (i) an NnCenH3 alternative splicing variant comprising only a partial centromere-targeting domain, (ii) active genes with low transcription levels in the NnCenH3 nucleosomal regions, and (iii) the prevalence of the Ty1/copia class of long terminal repeat (LTR) retrotransposons in the centromeres of sacred lotus chromosomes. In addition, the dynamic natures of the centromeric region showed that some of the centromeric repeat DNA sequences originated from telomeric repeats, and a pair of centromeres on the dicentric chromosome1 was inactive in the metaphase cells of sacred lotus. Our characterization of the properties of centromeric DNA structure within the sacred lotus genome describes a centromeric profile in ancient basal eudicots and might provide evidence of the origins and evolution of centromeres. Furthermore, the identification of centromeric DNA sequences is of great significance for the assembly of the sacred lotus genome.

Verneda hermaphroditicagen. & sp. nov.: A new flower head from the early Late Cretaceous (middle Cenomanian) of southeastern France

AbstractSpherical flower heads have often been reported from the late Early and Late Cretaceous of Asia and North America, but are rare in Europe. Palaeobotanists have included them in Altingiaceae and Hamamelidaceae (Saxifragales, basal core eudicots), and Platanaceae (Proteales, basal eudicots). We report newly collected flower heads from the Cenomanian of southeastern France. They are examined using scanning electron microscopy and propagation phase‐contrast X‐ray synchrotron microtomography with a voxel size down to 0.7 μm. They are described and compared with 95 living angiosperms, which include basal eudicots, basal rosids and basal asterids, based on a cladistic analysis of 64 characters.Verneda hermaphroditicagen. & sp. nov. consists of flower heads with around one hundred actinomorphic, pentamerous, bisexual flowers. The androecium has united filaments but free tetrasporangiate anthers. Pollen grains are tricolpate and reticulate. The gynoecium is eusyncarpous and pentalocular. Each of the five carpels contains a single ovule/seed. Cladistic analysis suggests thatVerneda hermaphroditicais sister to Platanaceae. It cannot, however, be included in this family because characters such as basally fused stamen filaments and eusyncarpous gynoecium are absent in living Platanaceae.

The mitochondrial genome map of Nelumbo nucifera reveals ancient evolutionary features.

Nelumbo nucifera is an evolutionary relic from the Late Cretaceous period. Sequencing the N. nucifera mitochondrial genome is important for elucidating the evolutionary characteristics of basal eudicots. Here, the N. nucifera mitochondrial genome was sequenced using single molecule real-time sequencing technology (SMRT), and the mitochondrial genome map was constructed after de novo assembly and annotation. The results showed that the 524,797-bp N. nucifera mitochondrial genome has a total of 63 genes, including 40 protein-coding genes, three rRNA genes and 20 tRNA genes. Fifteen collinear gene clusters were conserved across different plant species. Approximately 700 RNA editing sites in the protein-coding genes were identified. Positively selected genes were identified with selection pressure analysis. Nineteen chloroplast-derived fragments were identified, and seven tRNAs were derived from the chloroplast. These results suggest that the N. nucifera mitochondrial genome retains evolutionarily conserved characteristics, including ancient gene content and gene clusters, high levels of RNA editing, and low levels of chloroplast-derived fragment insertions. As the first publicly available basal eudicot mitochondrial genome, the N. nucifera mitochondrial genome facilitates further analysis of the characteristics of basal eudicots and provides clues of the evolutionary trajectory from basal angiosperms to advanced eudicots.

The Tree of Life: China project

The Tree of Life: China project

Evolving Ideas on the Origin and Evolution of Flowers: New Perspectives in the Genomic Era.

The origin of the flower was a key innovation in the history of complex organisms, dramatically altering Earth’s biota. Advances in phylogenetics, developmental genetics, and genomics during the past 25 years have substantially advanced our understanding of the evolution of flowers, yet crucial aspects of floral evolution remain, such as the series of genetic and morphological changes that gave rise to the first flowers; the factors enabling the origin of the pentamerous eudicot flower, which characterizes ∼70% of all extant angiosperm species; and the role of gene and genome duplications in facilitating floral innovations. A key early concept was the ABC model of floral organ specification, developed by Elliott Meyerowitz and Enrico Coen and based on two model systems, Arabidopsis thaliana and Antirrhinum majus. Yet it is now clear that these model systems are highly derived species, whose molecular genetic-developmental organization must be very different from that of ancestral, as well as early, angiosperms. In this article, we will discuss how new research approaches are illuminating the early events in floral evolution and the prospects for further progress. In particular, advancing the next generation of research in floral evolution will require the development of one or more functional model systems from among the basal angiosperms and basal eudicots. More broadly, we urge the development of “model clades” for genomic and evolutionary-developmental analyses, instead of the primary use of single “model organisms.” We predict that new evolutionary models will soon emerge as genetic/genomic models, providing unprecedented new insights into floral evolution.

Four SQUAMOSA PROMOTER BINDING PROTEIN-LIKE homologs from a basal eudicot tree (Platanus acerifolia) show diverse expression pattern and ability of inducing early flowering in Arabidopsis

Four SPL3/4/5 orthologous genes from Platanus acerifolia were identified, and their structure, expression patterns, role in controlling phase change and ability of inducing early flowering in Arabidopsis were analyzed. Plant flowering behavior is controlled by multiple pathways. The Arabidopsis thaliana SQUAMOSA PROMOTER BINDING PROTEIN-LIKE3/4/5 (AtSPL3/4/5) genes are involved in regulating vegetative phase change. Recent studies have shown that AtSPL3/4/5 genes are directly involved in inducing expression of three flowering integrator genes namely, LEAFY (LFY), FRUITFULL (FUL) and APETALA1 (AP1), thereby triggering flowering. This regulatory integration reveals a commonality of the flowering response with various other plant developmental pathways. We have isolated four SPL3/4/5 orthologous genes (PaSPL3a/b/c/d) from a basal eudicot London plane tree (Platanus acerifolia Wild), a woody species with a long juvenile phase. We investigated the role of these Platanus genes in flowering and detected expression levels between trees in vegetative and reproductive phase. Real-time PCR analysis demonstrated diverse expression patterns for the four PaSPL3 genes throughout the various P. acerifolia tissues, but all four were highly expressed in developing flower bud tissues. Expression of PaSPL3a/b/c in leaves changed according to the season and was regulated by temperature. Furthermore, three of the orthologous were found to induce an early flowering phenotype when overexpressed in Arabidopsis. The findings of this study indicate that PaSPL3 genes may participate in early stage inflorescence development in London Plane. However, there appears to be some divergence in the function of these genes in the control of phase change in London plane as compared to that within Arabidopsis.

Evidence for an ancient association between leaf mining flies and herbaceous eudicot angiosperms

We describe an early angiosperm and a leaf mine ichnofossil from the Lower Cretaceous Potomac Group of Virginia, USA. The descriptions are based on a fossil leaf that was first reported in 1895 but identified as a fragment of a fossil fern. The new genus and species of angiosperm, Vernifolium tenuiloba Jud and Sohn, gen. et sp. nov., was likely herbaceous and is based on a twice odd-pinnatifid leaf with glandular teeth at the tips of the lobes, and minute resin bodies covering the lamina. Leaf architectural features and sedimentological context indicate that this leaf was produced by an herbaceous eudicot angiosperm, possibly associated with Ranunculales. The leaf mine Phytomyzites wardi Sohn and Jud, ichnosp. n. is a full depth linear-blotch mine with frass, a trace of puparium inside the blotch mine section, and feeding/oviposition-related puncture marks. The features of the mine are most consistent with those produced by agromyzid flies. This fossil extends the record of agromyzid flies by about 40 myr. Furthermore, data from molecular studies suggests that the ancestral hosts for agromyzid flies are asterids, with several later host-shifts to feeding on Ranunculaceae, but this fossil provides evidence that agromyzid flies or their ancestors were feeding on herbaceous basal eudicots similar to modern herbaceous ranunculids during the Early Cretaceous, prior to the appearance and diversification of asterids.

Functional and evolutionary analyses of the miR156 and miR529 families in land plants

BackgroundMicroRNAs (miRNAs) are important regulatory elements of gene expression. Similarly to coding genes, miRNA genes follow a birth and death pattern of evolution likely reflecting functional relevance and divergence. For instance, miRNA529 is evolutionarily related to miRNA156 (a highly conserved miRNA in land plants), but it is lost in Arabidopsis thaliana. Interestingly, both miRNAs target sequences overlap in some members of the SQUAMOSA promoter-binding protein like (SPL) family, raising important questions regarding the diversification of the miR156/miR529-associated regulatory network in land plants.ResultsIn this study, through phylogenic reconstruction of miR156/529 target sequences from several taxonomic groups, we have found that specific eudicot SPLs, despite miRNA529 loss, retained the corresponding target site. Detailed molecular evolutionary analyses of miR156/miR529-target sequence showed that loss of miR529 in core eudicots, such as Arabidopsis, is correlated with a more relaxed selection of the miRNA529 specific target element, while miRNA156-specific target sequence is under stronger selection, indicating that these two target sites might be under distinct evolutionary constraints. Importantly, over-expression in Arabidopsis of MIR529 precursor from a monocot, but not from a basal eudicot, demonstrates specific miR529 regulation of AtSPL9 and AtSPL15 genes, which contain conserved responsive elements for both miR156 and miR529.ConclusionsOur results suggest loss of functionality of MIR529 genes in the evolutionary history of eudicots and show that the miR529-responsive element present in some eudicot SPLs is still functional. Our data support the notion that particular miRNA156 family members might have compensated for the loss of miR529 regulation in eudicot species, which concomitantly may have favored diversification of eudicot SPLs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0716-5) contains supplementary material, which is available to authorized users.

ChemInform Abstract: New Caledonia: A “Hot Spot” for Valuable Chemodiversity. Part 2. Basal Angiosperms and Eudicot Rosids

AbstractReview: 117 refs.

New Caledonia: A ' Hot Spot' for Valuable Chemodiversity: Part 2: Basal Angiosperms and Eudicot Rosids.

The flora of New Caledonia encompasses more than 3000 plant species and almost 80% are endemic. New Caledonia is considered as a 'hot spot' for biodiversity. With the current global loss of biodiversity and the fact that several drugs and pesticides become obsolete, there is an urgent need to increase sampling and research on new natural products. In this context, we review the chemical knowledge available on New Caledonian native flora from economical perspectives. We expect that a better knowledge of the economic potential of plant chemistry will encourage the plantation of native plants for the development of a sustainable economy which will participate in the conservation of biodiversity. In the second part of this review, we focus on the results exposed in 60 scientific articles and describe the identification of 225 original compounds from basal angiosperms and eudicot rosids. We discuss the economic potential of plants and molecules from medicinal and industrial perspectives. This review also highlights several plants and groups, such as Amborella sp., Piperaceae, or Phyllanthaceae, that are unexplored in New Caledonia despite their high chemical interest. Those plants are considered to have priority in future chemical investigations.

Stochastic occurrence of trimery from pentamery in floral phyllotaxis of Anemone (Ranunculaceae)

Merosity, indicating the basic number of floral organs such as sepals and petals, has been constrained to specific and stable numbers during the evolution of angiosperms. The ancestral flower is considered to have a spiral arrangement of perianth organs, as in phyllotaxis, the arrangement of leaves. How has the ancestral spiral evolved into flowers with specific merosities? To address this question, we studied perianth organ arrangement in the <em>Anemone</em> genus of the basal eudicot family Ranunculaceae, because various merosities are found in this genus. In three species, <em>A. flaccida</em>, <em>A. scabiosa</em>, and <em>A. nikoensis</em> that are normally pentamerous, we found positional arrangement of the excessive sixth perianth organ indicating the possibility of a transition from pentamerous to trimerous arrangement. Arrangement was intraspecifically stochastic, but constrained to three of five types, where trimerous arrangement was the most frequent in all species except for a form of <em>A. scabiosa</em>. The rank of frequency of the other two types was species-dependent. We connect these observations with classical theories of spiral phyllotaxis. The phyllotaxis model for initiation of the sixth organ showed that the three arrangements occur at a divergence angle <144°, indicating the spiral nature of floral phyllotaxis rather than a perfect penta-radial symmetry of 144°. The model further showed that selective occurrence of trimerous arrangement is mainly regulated by the organ growth rate. Differential organ growth as well as divergence angle may regulate transitions between pentamerous and trimerous flowers in intraspecific variation as well as in species evolution.

Evolution of Angiosperm Pollen. 2. The Basal Angiosperms1

Recently, evolutionary relationships among the five major lineages of the basal angiosperms, i.e., Amborellanae, Nymphaeanae, Austrobaileyanae, Magnolianae, and Ceratophyllanae, still remain incompletely or controversially resolved. This study reviews and reevaluates the origin, evolution, and systematic significance of pollen morphology in basal angiosperms. Pollen grains from 34 species of 31 genera in 23 families of the basal angiosperms are investigated, using light microscopy (LM) and scanning electron microscopy (SEM), to illustrate the pollen diversity across the grade. Pollen data for 57 genera, representing all nine orders and 28 families of the basal angiosperms, were obtained from previous work and new investigations and were used to optimize character states onto recent molecular phylogenetic estimates. Two 18-character datasets were generated: a comprehensively coded dataset optimized with Fitch parsimony onto 12 recent phylogenies with differing topologies to evaluate the degree of pollen systematic significance of each topology, and a democratically coded dataset optimized by using Fitch parsimony, maximum likelihood, and hierarchical Bayesian inference onto a single recent phylogeny based on molecular data from Soltis et al. to evaluate the disparity of pollen evolutionary patterns among the three methods. Pollen morphology of the basal angiosperms is highly diverse, particularly in terms of pollen size, aperture number, aperture position, ectoaperture shape, tectum sculpture, and infratectal structure. Based on both datasets, the plesiomorphic pollen type for angiosperms was inferred to comprise monads of heteropolar, spheroidal, mono-apertural grains, with distal, colpate apertures, sculptured aperture membranes, and an infratectum and foot layer. Of the basal angiosperm phylogenies considered, when taxon sampling is taken into account, pollen characters provide greatest support for the topology represented in the three-mitochondrial-gene study from Qiu et al., in terms of number of synapomorphies plus what we term “likely synapomorphies” in which the subtending node is ambiguous and, therefore, the exact position of the synapomorphy is ambiguous. Thirty-six various lineages above family level are supported by pollen morphological synapomorphies or likely synapomorphies. We discuss the systematic significance of pollen morphology in basal angiosperm clades including the ANITA group (Amborellaceae, Nymphaeaceae, Schisandraceae, Trimeniaceae, and Austrobaileyaceae), Ceratophyllales, Chloranthales, and magnoliids, as well as in related lineages, i.e., monocots and basal eudicots. We also discuss present limitations in inferring the evolutionary history of pollen morphology in basal angiosperms.