Genomes of leafy and leafless Platanthera orchids illuminate the evolution of mycoheterotrophy

To improve our understanding of the origin and evolution of mycoheterotrophic plants, we here present the chromosome-scale genome assemblies of two sibling orchid species: partially mycoheterotrophic Platanthera zijinensis and holomycoheterotrophic Platanthera guangdongensis. Comparative analysis shows that mycoheterotrophy is associated with increased substitution rates and gene loss, and the deletion of most photoreceptor genes and auxin transporter genes might be linked to the unique phenotypes of fully mycoheterotrophic orchids. Conversely, trehalase genes that catalyse the conversion of trehalose into glucose have expanded in most sequenced orchids, in line with the fact that the germination of orchid non-endosperm seeds needs carbohydrates from fungi during the protocorm stage. We further show that the mature plant of P. guangdongensis, different from photosynthetic orchids, keeps expressing trehalase genes to hijack trehalose from fungi. Therefore, we propose that mycoheterotrophy in mature orchids is a continuation of the protocorm stage by sustaining the expression of trehalase genes. Our results shed light on the molecular mechanism underlying initial, partial and full mycoheterotrophy.

Cypripedium lichiangense (Orchidaceae) mimics a humus-rich oviposition site to attract its female pollinator, Ferdinandea cuprea (Syrphidae)

Most species in the genus Cypripedium (Cypripedioideae) produce trap flowers, making it a model lineage to study deceptive pollination. Floral attractants in most species studied appear to target bee species of different sizes. However, more recent publications report fly pollination in some subalpine species, suggesting novel suites of adaptive floral traits. Cypripedium lichiangense (section Trigonopedia) is an endangered subalpine species endemic to the Hengduan Mountains, China. We observed and analysed its floral traits, pollinators and breeding systems over 2 years in situ and in the lab. Cypripedium lichiangense was visited by females of Ferdinandea cuprea (Syrphidae). The pollinia were carried dorsally on the fly thoraces. The eggs of this fly were frequently found in the saccate labellum and on other floral organs, suggesting brood-site mimesis. The orchid is self-compatible, but cross-pollination produces more viable embryos. We propose a new mode of floral mimesis, humus-rich oviposition site mimicry, for C. lichiangense. Compared with the mimesis of aphid colonies attracting syrphid pollinators (subfamily Syrphinae), whose larvae are entomophagic, as reported in some Paphiopedilum species (Cypripedioideae), pollination by deceit in C. lichiangense represents a distinct and separate mode of exploitation of another saprophagic (or phytophagic) larvae syrphid lineage in the subfamily Eristalinae and appears to indicate diversity of pollination strategies in Section Trigonopedia of Cypripedium. However, this new brood-site mimesis seems to be less attractive to pollinators. As a possible adaptation to the weak attracted pollination strategy, this plant species has a long flowering period and extended lifespan of individual flowers to ensure reproductive success.

Phylogenetic analysis and character evolution of tribe Arethuseae (Orchidaceae) reveal a new genus Mengzia

Delimitation of the tribe Arethuseae has varied considerably since it was first defined. The relationships within Arethuseae, particularly within the subtribe Arethusinae, remain poorly elucidated. In this study, we reconstructed the phylogeny of Arethuseae, using six plastid markers (matK, ycf1, rbcL rpoc1, rpl32-trnL and trnL-F) from 83 taxa. The ancestral state reconstruction of 11 selected morphological characters was also conducted to identify synapomorphies and assess potential evolutionary transitions. Morphological character comparision between the distinct species Bletilla foliosa and other species are conducted. Our results unequivocally supported the monophyly of Arethuseae, which included highly supported clades and a clear synapomorphy of non-trichome-like lamellae. Furthermore, B. foliosa formed a separate clade in the subtribe Arethusinae, instead of clustering with the other Bletilla species in the subtribe Coelogyninae. The morphological characters comparision further showed that the B. foliosa clade could be distinguished from other genera in Arethuseae by multiple characters, including presence of lateral inflorescence, three lamellae with trichome-like apex and four pollinia. In light of these molecular and morphological evidences, we propose Mengzia as a new genus to accommodate B. foliosa and accordingly provide descriptions of this new genus and combination.

[Research progress on molecular mechanism of Dendrobium officinale and its active components to metabolic syndrome]

Metabolic syndrome,a kind of clinical syndrome marked by the presence of symptoms such as hyperglycemia,dyslipidemia and hypertension,has an increasing incidence and comes to be present in younger people. More importantly,prolonged maintenance of this condition can significantly increase the incidence of chronic diseases such as diabetes,cardiovascular disease and cancer.However,the formation mechanism of metabolic syndrome is very complex and has not been fully studied and revealed. Dendrobium officinale is a traditional medicine and food substance with multiple physiological functions. In recent years,D. officinale has attracted much attention from the scholars both at home and abroad due to its functions such as improving blood lipid,lowering blood pressure and regulating blood sugar. However,there is no systematic review on the current studies about D. officinale in intervening metabolic syndrome and its underlying molecular mechanism. In this paper,the biological activity of the main active components,and the research or application status of D. officinale extract in the recent years were reviewed. Then,we analyzed the digestion,absorption and the safety and toxicity of D. officinale and its active components in the body. Finally,we summarized the effects of D. officinale and its active components on metabolic syndrome in animals and human bodies,and discussed its possible molecular mechanisms at the cellular level. This paper provides solid theoretical guidance and reliable molecular basis for further research and advanced development of D. officinale and its active components,especially for its oncoming clinical application.

[The effect and mechanism of transient receptor potential M(2) in antigen-induced arthritis mice]

The purpose of this study was to explore the role and mechanism of transient receptor potential M(2) (TRPM(2)) in antigen-induced arthritis (AIA) mice. Twelve C57BL/6 mice and 12 TRPM(2) knockout mice were divided into 4 groups, includingwild type control group, wild type AIA group, TRPM(2) knockout control group and TRPM(2) knockout AIA group, with 6 mice in each group. Methylated bovine serum albumin (mBSA) was used to establish AIA mouse model. The degree of joint swelling and inflammatory cell infiltration were recorded, as well as synovial hyperplasia of the knee joints. Real-time quantitative polymerase chain reaction (PCR) was used to detect the expression of interleukin (IL)-6, IL-8, chemokine ligand 6 (CXCL-6) and tumor necrosis factor alpha (TNFα) mRNA in synovial cells of knee joints. The results showed that compared with the wild-type AIA group, the TRPM(2) knockout AIA group had more significant synovial proliferation and inflammatory cell infiltration in the synovial tissue.The neutrophil and macrophage counts rather than monocytes in the knee joints of TRPM(2) knockout AIA group were higher than those in wild-type AIA mice. The expression of IL-6, IL-8 and CXCL-6 mRNA were significantly increased in the knock out mice. In summary, TRPM(2) may inhibit inflammatory cytokines such as IL-6 and IL-8 in knee joints of AIA mice by reducing the infiltration of neutrophils and macrophages, the refore alleviates the manifestations of knee arthritis.

[Clinical research progression of molecular-targeted drugs and PD-1 inhibitors for advanced hepatocellular carcinoma]

Since sorafenib has been first-line molecular-targeted drug for advanced hepatocellular carcinoma (HCC), clinical studies in the last 10 years failed to confirm that a new molecular-targeted drug or immune checkpoint inhibitor was superior or non-inferior to sorafenib, or approved second-line treatment for patients with the failure of sorafenib. However, many clinical studies published in 2017 have changed people's previous understanding. REFLECT trial showed that as the first-line treatment of advanced HCC, lenvatinib was non-inferior than sorafenib. In addition, RESORCE trial and CheckMate-040 trial confirmed respectively that regorafenib and PD-1 inhibitor nivolumab were options of second-line treatment for patients with advanced HCC after sorafenib treatment. The development of these drugs will bring a new prospect for advanced HCC patients.

[Herbal textual research on relationship between Chinese medicine"Shihu" (Dendrobium spp.) and "Tiepi Shihu" (D. catenatum)]

Dendrobium species on the ancient Chinese herbal texts were investigated in this paper, including their dscriptions of original species, producing areas and quality. Our results indicated that the major producing areas were Lu'an, Anhui province and Wenzhou, Taizhou, Zhejiang province. In addition, the sweet flavor, short, thin and solid stems were standing for good quality. Based on the stable producing areas and quality descriptions, D. catenatum (D. officinale) ("Tiepi Shihu") and D. houshanense were high quality medicinal Dendrobium species ("Shihu" ) in ancient China. Besides, there were 3 scientific names for "Tiepi Shihu", including D. candidum, D. officinale, D. catenatum. After textual investigation, We suggest that D. catenatum should be its scientific name, and D. officinale was synonyms published later. However, the name "D. officinale" could be reserved as it is much more popular used in publication and commodities. Moreover, its Chinese name should be "Tiepi Shihu".

An assessment of the Chinese medicinal Dendrobium industry: Supply, demand and sustainability

ETHNOPHARMACOLOGICAL RELEVANCE

A high proportion of species native to China from the genus Dendrobium (Orchidaceae) have been used as folk medicine for more than 2300 years. The fresh or dried stem of many Dendrobium species are regarded as "superior grade" tonic in Traditional Chinese Medicine (TCM), for their traditional properties of nourishing the kidney, moisturizing the lung, benefiting the stomach, promoting the production of body fluids and clearing heat.

AIM OF THE STUDY

This review aims to provide comprehensive and updated information on the diversity of Dendrobium species used in TCM and the development of the Dendrobium industry. The supply and demand of the Chinese medicinal Dendrobium are investigated. Moreover, we discuss the problems the industry faces and the relationship between the cultivation and species conservation.

MATERIALS AND METHODS

The available information on many Dendrobium species (especially D. officinale) was collected from the electronic databases (using Pubmed, CNKI, Baidu scholar, Google scholar and Web of Science). We also obtained information from communication with specialists with profound knowledge in related research field and industry practitioners. Information was also obtained from website of the Forestry Bureau or relevant government departments, online databases, books, Ph.D. dissertations and M.Sc. theses.

RESULTS

Approximately 41 species in genus Dendrobium have been recorded in TCM. The development of the Dendrobium industry could be divided into three phases: (a) the wild-collection phase, (b) the massive commercial artificial-sheltered cultivation phase and (c) the diversified ecologically-friendly cultivation phase. The development of seedlings production technology, the improvement of substrates and the integration of cultivation technology support the rapid increase of Dendrobium herbs in the Chinese TCM market. Doubts around the quality and efficacy of product in artificial-sheltered cultivation, the lack of product standards and the low level of product development have limited the utilization for TCM and hampered the development of the Dendrobium industry. Both the artificial-sheltered cultivation and ecologically-friendly cultivation contribute to the conservation of Dendrobium species, through the use seedlings derived from seeds of sexual reproduction rather than meristematic-based clonal propagation.

CONCLUSIONS

This review summarizes the species and cultivation history of medicinal herbs in the Dendrobium. The review can help inform future scientific research towards the TCM in Dendrobium, including mycorrhizal technology and microorganism fertilizer, pharmacological studies, the directed cultivation of varieties and diversified product. It is suggested that Dendrobium cultivation has a great potential to link the commercial TCM industry together with initiatives of biodiversity conservation.

Morphological Type Identification of Self-Incompatibility in Dendrobium and Its Phylogenetic Evolution Pattern

Self-incompatibility (SI) is a type of reproductive barrier within plant species and is one of the mechanisms for the formation and maintenance of the high diversity and adaptation of angiosperm species. Approximately 40% of flowering plants are SI species, while only 10% of orchid species are self-incompatible. Intriguingly, as one of the largest genera in Orchidaceae, 72% of Dendrobium species are self-incompatible, accounting for nearly half of the reported SI species in orchids, suggesting that SI contributes to the high diversity of orchid species. However, few studies investigating SI in Dendrobium have been published. This study aimed to address the following questions: (1) How many SI phenotypes are in Dendrobium, and what are they? (2) What is their distribution pattern in the Dendrobium phylogenetic tree? We investigated the flowering time, the capsule set rate, and the pollen tube growth from the representative species of Dendrobium after artificial pollination and analysed their distribution in the Asian Dendrobium clade phylogenetic tree. The number of SI phenotypes exceeded our expectations. The SI type of Dendrobium chrysanthum was the primary type in the Dendrobium SI species. We speculate that there are many different SI determinants in Dendrobium that have evolved recently and might be specific to Dendrobium or Orchidaceae. Overall, this work provides new insights and a comprehensive understanding of Dendrobium SI.

[Breakthrough in key science and technologies in Dendrobium catenatum industry]

In view of the significant difficulties of propagation, planting and simple product in Dendrobium catenatum(D. officinale)industry development, a series of research were carried out. Genome study showed that D. catenatum is a specie of diploid with 38 chromosomes and 28 910 protein-coding genes. It was identified that specific genes accumulated in different organs at the transcriptome level. We got an insight into the gene regulation mechanism of the loss of the endospermous seed, the wide ecological adaptability and the synthesis of polysaccharides, which provided a theoretical basis for genetic engineering breeding and development and utilization of active pharmaceutical ingredients. The rapid propagation system was established for applying to industrialized production by overcoming breeding problems on seed setting and sprouting, which laid a foundation for artificial cultivation of D. catenatum. And in order to give a clear explanation of genetic variation of important economic traits, we built up the breeding system. Since special varieties of D. catenatum were bred, it helped solve the problem of trait segregation of seedling progeny and support the improvement of D. catenatum industry. The regulation of dynamic variation of target compounds, together with the mechanism of nutrient uptake, was revealed. The breakthrough of key technologies including culture substrates, light regulation and precisely collection was carried out. Several cultivation modes like facility cultivation, original ecological cultivation, cliff epiphytic cultivation, stereoscopic cultivation and potting cultivation were set up. Above all, the goal of cultivating D. catenatum as well as producing good D. catenatum will be achieved.

[Original materials of traditional Chinese medicinal names of "Jinchai" and "Jinchai Shihu" based on vegetative morphology]

"Jinchai Shihu" were called Jinchai and recoded in "Taishang Zhouhou Yujingfang" of Tang Dynasty, which first clearly documented the name of Shihu in complex Dendrobium medicines and were condiered as superior medicinal articles. Morphological features are one of the naming principles for Chinese medicines. In this paper, botanical origin plants under the names of "Jinchai" and "Jinchai Shihu" were investigated. Based on documents from the local Chronicles and historical accounts, the Chinese characters of Jinchai have the distinctive features of gold color and two hair clasps. Moreover, the hair clasps are usually cylindrical in shape with uniform thickness in middle and upper part, and tapers off to the foot. And its bottom part style is simple and head part is complex. Thus we speculated the herbal "Jinchai" and "Jinchai Shihu" should have similar morphologic features as Chinese characters of Jinchai, including golden color and hairpin shape of stems without braches, short and solid sterm. After comparing the dried vegetative morphology of 10 common medicinal Dendrobium species, we suggested that of Dendrobium flexicaule matches well with the morphological features from historical herbal records.

The Apostasia genome and the evolution of orchids

WebComparing the whole genome sequence of Apostasia shenzhenica with transcriptome and genome data from five orchid subfamilies permits the reconstruction of an ancestral gene toolkit, providing insight into orchid origins, evolution and diversification.

Around 10 per cent of flowering plant species are orchids, with a broad diversity in both morphology and lifestyle. Apostasia is one of the earliest-diverging genera of Orchidaceae. To study the evolution and diversity of Orchidaceae, Zhong-Jian Liu, Yves Van de Peer and colleagues sequenced the genome of Apostasia shenzhenica, a self-pollinating species found in southeast China. The authors also report improved genomes for two species of Epidendroideae, Phalaenopsis equestris and Dendrobium catenatum, as well as transcriptome analysis of representatives of subfamilies of Orchidaceae. Their analyses provide insights into orchid origins, genome evolution, adaptation and diversification.

Constituting approximately 10% of flowering plant species, orchids (Orchidaceae) display unique flower morphologies, possess an extraordinary diversity in lifestyle, and have successfully colonized almost every habitat on Earth^1,2,3. Here we report the draft genome sequence of Apostasia shenzhenica⁴, a representative of one of two genera that form a sister lineage to the rest of the Orchidaceae, providing a reference for inferring the genome content and structure of the most recent common ancestor of all extant orchids and improving our understanding of their origins and evolution. In addition, we present transcriptome data for representatives of Vanilloideae, Cypripedioideae and Orchidoideae, and novel third-generation genome data for two species of Epidendroideae, covering all five orchid subfamilies. A. shenzhenica shows clear evidence of a whole-genome duplication, which is shared by all orchids and occurred shortly before their divergence. Comparisons between A. shenzhenica and other orchids and angiosperms also permitted the reconstruction of an ancestral orchid gene toolkit. We identify new gene families, gene family expansions and contractions, and changes within MADS-box gene classes, which control a diverse suite of developmental processes, during orchid evolution. This study sheds new light on the genetic mechanisms underpinning key orchid innovations, including the development of the labellum and gynostemium, pollinia, and seeds without endosperm, as well as the evolution of epiphytism; reveals relationships between the Orchidaceae subfamilies; and helps clarify the evolutionary history of orchids within the angiosperms.

Lack of S-RNase-Based Gametophytic Self-Incompatibility in Orchids Suggests That This System Evolved after the Monocot-Eudicot Split

Self-incompatibility (SI) is found in approximately 40% of flowering plant species and at least 100 families. Although orchids belong to the largest angiosperm family, only 10% of orchid species present SI and have gametophytic SI (GSI). Furthermore, a majority (72%) of Dendrobium species, which constitute one of the largest Orchidaceae genera, show SI and have GSI. However, nothing is known about the molecular mechanism of GSI. The S-determinants of GSI have been well characterized at the molecular level in Solanaceae, Rosaceae, and Plantaginaceae, which use an S-ribonuclease (S-RNase)-based system. Here, we investigate the hypothesis that Orchidaceae uses a similar S-RNase to those described in Rosaceae, Solanaceae, and Plantaginaceae SI species. In this study, two SI species (Dendrobium longicornu and D. chrysanthum) were identified using fluorescence microscopy. Then, the S-RNase- and SLF-interacting SKP1-like1 (SSK1)-like genes present in their transcriptomes and the genomes of Phalaenopsis equestris, D. catenatum, Vanilla shenzhenica, and Apostasia shenzhenica were investigated. Sequence, phylogenetic, and tissue-specific expression analyses revealed that none of the genes identified was an S-determinant, suggesting that Orchidaceae might have a novel SI mechanism. The results also suggested that RNase-based GSI might have evolved after the split of monocotyledons (monocots) and dicotyledons (dicots) but before the split of Asteridae and Rosidae. This is also the first study to investigate S-RNase-based GSI in monocots. However, studies on gene identification, differential expression, and segregation analyses in controlled crosses are needed to further evaluate the genes with high expression levels in GSI tissues.

De novo transcriptome assembly databases for the butterfly orchid Phalaenopsis equestris

Orchids are renowned for their spectacular flowers and ecological adaptations. After the sequencing of the genome of the tropical epiphytic orchid Phalaenopsis equestris, we combined Illumina HiSeq2000 for RNA-Seq and Trinity for de novo assembly to characterize the transcriptomes for 11 diverse P. equestris tissues representing the root, stem, leaf, flower buds, column, lip, petal, sepal and three developmental stages of seeds. Our aims were to contribute to a better understanding of the molecular mechanisms driving the analysed tissue characteristics and to enrich the available data for P. equestris. Here, we present three databases. The first dataset is the RNA-Seq raw reads, which can be used to execute new experiments with different analysis approaches. The other two datasets allow different types of searches for candidate homologues. The second dataset includes the sets of assembled unigenes and predicted coding sequences and proteins, enabling a sequence-based search. The third dataset consists of the annotation results of the aligned unigenes versus the Nonredundant (Nr) protein database, Kyoto Encyclopaedia of Genes and Genomes (KEGG) and Clusters of Orthologous Groups (COG) databases with low e-values, enabling a name-based search.

Seasonal variation in the mating system of a selfing annual with large floral displays

BACKGROUND AND AIMS

Flowering plants display considerable variation in mating system, specifically the relative frequency of cross- and self-fertilization. The majority of estimates of outcrossing rate do not account for temporal variation, particularly during the flowering season. Here, we investigated seasonal variation in mating and fertility in Incarvillea sinensis (Bignoniaceae), an annual with showy, insect-pollinated, 'one-day' flowers capable of delayed selfing. We examined the influence of several biotic and abiotic environmental factors on day-to-day variation in fruit set, seed set and patterns of mating.

METHODS

We recorded daily flower number and pollinator abundance in nine 3 × 3-m patches in a population at Mu Us Sand land, Inner Mongolia, China. From marked flowers we collected data on daily fruit and seed set and estimated outcrossing rate and biparental inbreeding using six microsatellite loci and 172 open-pollinated families throughout the flowering period.

KEY RESULTS

Flower density increased significantly over most of the 50-d flowering season, but was associated with a decline in levels of pollinator service by bees, particularly on windy days. Fruit and seed set declined over time, especially during the latter third of the flowering period. Multilocus estimates of outcrossing rate were obtained using two methods (the programs MLTR and BORICE) and both indicated high selfing rates of ∼80 %. There was evidence for a significant increase in levels of selfing as the flowering season progressed and pollinator visitation declined. Biparental inbreeding also declined significantly as the flowering season progressed.

CONCLUSIONS

Temporal variation in outcrossing rates may be a common feature of the mating biology of annual, insect-pollinated plants of harsh environments but our study is the first to examine seasonal mating-system dynamics in this context. Despite having large flowers and showy floral displays, I. sinensis attracted relatively few pollinators. Delayed selfing by corolla dragging largely explains the occurrence of mixed mating in I. sinensis, and this mode of self-fertilization probably functions to promote reproductive assurance when pollinator service is limited by windy environmental conditions and competition from co-occurring flowering plants.

The Dendrobium catenatum Lindl. genome sequence provides insights into polysaccharide synthase, floral development and adaptive evolution

Orchids make up about 10% of all seed plant species, have great economical value, and are of specific scientific interest because of their renowned flowers and ecological adaptations. Here, we report the first draft genome sequence of a lithophytic orchid, Dendrobium catenatum. We predict 28,910 protein-coding genes, and find evidence of a whole genome duplication shared with Phalaenopsis. We observed the expansion of many resistance-related genes, suggesting a powerful immune system responsible for adaptation to a wide range of ecological niches. We also discovered extensive duplication of genes involved in glucomannan synthase activities, likely related to the synthesis of medicinal polysaccharides. Expansion of MADS-box gene clades ANR1, StMADS11, and MIKC(*), involved in the regulation of development and growth, suggests that these expansions are associated with the astonishing diversity of plant architecture in the genus Dendrobium. On the contrary, members of the type I MADS box gene family are missing, which might explain the loss of the endospermous seed. The findings reported here will be important for future studies into polysaccharide synthesis, adaptations to diverse environments and flower architecture of Orchidaceae.

The Dendrobium catenatum Lindl. genome sequence provides insights into polysaccharide synthase, floral development and adaptive evolution

Orchids make up about 10% of all seed plant species, have great economical value, and are of specific scientific interest because of their renowned flowers and ecological adaptations. Here, we report the first draft genome sequence of a lithophytic orchid, Dendrobium catenatum. We predict 28,910 protein-coding genes, and find evidence of a whole genome duplication shared with Phalaenopsis. We observed the expansion of many resistance-related genes, suggesting a powerful immune system responsible for adaptation to a wide range of ecological niches. We also discovered extensive duplication of genes involved in glucomannan synthase activities, likely related to the synthesis of medicinal polysaccharides. Expansion of MADS-box gene clades ANR1, StMADS11, and MIKC(*), involved in the regulation of development and growth, suggests that these expansions are associated with the astonishing diversity of plant architecture in the genus Dendrobium. On the contrary, members of the type I MADS box gene family are missing, which might explain the loss of the endospermous seed. The findings reported here will be important for future studies into polysaccharide synthesis, adaptations to diverse environments and flower architecture of Orchidaceae.

DNA double-strand breaks disrupted the spindle assembly in porcine oocytes

We used etoposide (25-100 µg/mL) to induce DNA double-strand breaks (DSBs) in porcine oocytes at the germinal vesicle (GV) stage to determine how such damage affects oocyte maturation. We observed that DNA damage did not delay the rate of germinal vesicle breakdown (GVBD), but did inhibit the final stages of maturation, as indicated by the failure to extrude the first polar body. Oocytes with low levels of DSBs failed to effectively activate ataxia telangiectasia-mutated (ATM) kinase, while those with severe DNA DSBs failed to activate checkpoint kinase 1 (CHK1)--the two regulators of the DNA damage response pathway--indicating that porcine oocytes lack an efficient G2/M phase checkpoint. DSBs induced spindle defects and chromosomal misalignments, leading to the arrest of these oocytes at meiotic metaphase I. The activity of maturation-promoting factor also did not increase appropriately in oocytes with DNA DSBs, although its abundance was sufficient to promote GVBD and chromosomal condensation. Following parthenogenetic activation, embryos from etoposide-treated oocytes formed numerous micronuclei. Thus, our results indicate that DNA DSBs do not efficiently activate the ATM/CHK1-dependent DNA-damage checkpoint in porcine oocytes, allowing these DNA-impaired oocytes to enter M phase. Oocytes with DNA damage did, however, arrest at metaphase I in response to spindle defects and chromosomal misalignments, which limited the ability of these oocytes to reach meiotic metaphase II.

Distinct subcellular localization and potential role of LINE1-ORF1P in meiotic oocytes

LINE-1 is an autonomous non-LTR retrotransposon in mammalian genomes and encodes ORF1P and ORF2P. ORF2P has been clearly identified as the enzyme supplier needed in LINE-1 retrotransposition. However, the role of ORF1P is not well explored. In this study, we employed loss/gain-of-function approach to investigate the role of LINE1-ORF1P in mouse oocyte meiotic maturation. During mouse oocyte development, ORF1P was observed in cytoplasm as well as in nucleus at germinal vesicle (GV) stage while was localized on the spindle after germinal vesicle breakdown (GVBD). Depletion of ORF1P caused oocyte arrest at the GV stage as well as down-regulation of CDC2 and CYCLIN B1, components of the maturation-promoting factor (MPF). Further analysis demonstrated ORF1P depletion triggered DNA damage response and most of the oocytes presented altered chromatin configuration. In addition, SMAD4 showed nuclear foci signal after Orf1p dsRNA injection. ORF1P overexpression held the oocyte development at MI stage and the chromosome alignment and spindle organization were severely affected. We also found that ORF1P could form DCP1A body-like foci structure in both cytoplasm and nucleus after heat shock. Taken together, accurate regulation of ORF1P plays an essential role in mouse oocyte meiotic maturation.

Different fates of oocytes with DNA double-strand breaks in vitro and in vivo

In female mice, despite the presence of slight DNA double-strand breaks (DSBs), fully grown oocytes are able to undergo meiosis resumption as indicated by germinal vesicle breakdown (GVBD); however, severe DNA DSBs do reduce and delay entry into M phase through activation of the DNA damage checkpoint. But little is known about the effect of severe DNA DSBs on the spindle assembly checkpoint (SAC) during oocyte maturation. We showed that nearly no first polar body (PB1) was extruded at 12 h of in vitro maturation (IVM) in severe DNA DSBs oocytes, and the limited number of oocytes with PB1 were actually at telophase. However, about 60% of the severe DNA DSBs oocytes which underwent GVBD at 2 h of IVM released a PB1 at 18 h of IVM and these oocytes did reach the second metaphase (MII) stage. Chromosome spread at MI and MII stages showed that chromosomes fragmented after GVBD in severe DNA DSBs oocytes. The delayed PB1 extrusion was due to the disrupted attachment of microtubules to kinetochores and activation of the SAC. At the same time, misaligned chromosome fragments became obvious at the first metaphase (MI) in severe DNA DSBs oocytes. These data implied that the inactivation of SAC during the metaphase-anaphase transition of first meiosis was independent of chromosome integrity. Next, we induced DNA DSBs in vivo, and found that the number of superovulated oocytes per mouse was significantly reduced; moreover, this treatment increased the percentage of apoptotic oocytes. These results suggest that DNA DSBs oocytes undergo apoptosis in vivo.

Reticulate evolution and sea-level fluctuations together drove species diversification of slipper orchids (Paphiopedilum) in South-East Asia

South-East Asia covers four of the world's biodiversity hotspots, showing high species diversity and endemism. Owing to the successive expansion and contraction of distribution and the fragmentation by geographical barriers, the tropical flora greatly diversified in this region during the Tertiary, but the evolutionary tempo and mode of species diversity remain poorly investigated. Paphiopedilum, the largest genus of slipper orchids comprising nearly 100 species, is mainly distributed in South-East Asia, providing an ideal system for exploring how plant species diversity was shaped in this region. Here, we investigated the evolutionary history of this genus with eight cpDNA regions and four low-copy nuclear genes. Discordance between gene trees and network analysis indicates that reticulate evolution occurred in the genus. Ancestral area reconstruction suggests that vicariance and long-distance dispersal together led to its current distribution. Diversification rate variation was detected and strongly correlated with the species diversity in subg. Paphiopedilum (~80 species). The shift of speciation rate in subg. Paphiopedilum was coincident with sea-level fluctuations in the late Cenozoic, which could have provided ecological opportunities for speciation and created bridges or barriers for gene flow. Moreover, some other factors (e.g. sympatric distribution, incomplete reproductive barriers and clonal propagation) might also be advantageous for the formation and reproduction of hybrid species. In conclusion, our study suggests that the interplay of reticulate evolution and sea-level fluctuations has promoted the diversification of the genus Paphiopedilum and sheds light into the evolution of Orchidaceae and the historical processes of plant species diversification in South-East Asia.

PLK4 is essential for meiotic resumption in mouse oocytes

Polo-like kinase (PLK) 4 is a unique member of the PLK family that plays vital roles in centriole biogenesis during mitosis. The localization of PLK4 on centrioles must be precisely regulated during mitosis to ensure correct centriole duplication. However, little is known about the function of PLK4 in mammalian oocyte meiosis. We addressed this question by examining the expression and localization of PLK4 in mouse oocytes and using RNA interference and protein overexpression to investigate its function in meiosis. PLK4 expression peaked at the germinal vesicle breakdown (GVBD) stage, and the protein was localized in the cytoplasm throughout meiotic maturation. Depletion of PLK4 caused meiotic arrest at the GV stage and suppressed CYCLINB1 and CDC2 activities. Moreover, PLK4 depletion prevented the de-phosphorylation of CDC2-Tyr15 in nucleus and induced a decrease in the level of the CDC25C protein. PLK1 overexpression failed to rescue GV-stage arrest in PLK4-depleted oocytes, whereas overexpressing PLK4 resulted in normal GVBD in oocytes in which PLK1 activity was inhibited. In addition, PLK4 overexpression did not cause abnormal spindle formation or affect extrusion of the first polar body. These results illustrate the fact that PLK4 is essential for meiotic resumption but may not influence spindle formation in mouse oocytes during meiotic maturation.

The genome sequence of the orchid Phalaenopsis equestris

Orchidaceae, renowned for its spectacular flowers and other reproductive and ecological adaptations, is one of the most diverse plant families. Here we present the genome sequence of the tropical epiphytic orchid Phalaenopsis equestris, a frequently used parent species for orchid breeding. P. equestris is the first plant with crassulacean acid metabolism (CAM) for which the genome has been sequenced. Our assembled genome contains 29,431 predicted protein-coding genes. We find that contigs likely to be underassembled, owing to heterozygosity, are enriched for genes that might be involved in self-incompatibility pathways. We find evidence for an orchid-specific paleopolyploidy event that preceded the radiation of most orchid clades, and our results suggest that gene duplication might have contributed to the evolution of CAM photosynthesis in P. equestris. Finally, we find expanded and diversified families of MADS-box C/D-class, B-class AP3 and AGL6-class genes, which might contribute to the highly specialized morphology of orchid flowers.

Laser microbeam-induced DNA damage inhibits cell division in fertilized eggs and early embryos

DNA double-strand breaks are caused by both intracellular physiological processes and environmental stress. In this study, we used laser microbeam cut (abbreviated microcut or cut), which allows specific DNA damage in the pronucleus of a fertilized egg and in individual blastomere(s) of an early embryo, to investigate the response of early embryos to DNA double-strand breaks. Line type γH2AX foci were detected in the cut region, while Chk2 phosphorylation staining was observed in the whole nuclear region of the cut pronuclei or blastomeres. Zygotes with cut male or female pronucleus showed poor developmental capability: the percentage of cleavage embryos was significantly decreased, and the embryos failed to complete further development to blastocysts. The cut blastomeres in 2-cell, 4-cell, and 8-cell embryos ceased cleavage, and they failed to incorporate into compacted morulae, but instead underwent apoptosis and cell death at the blastocyst stage; the uncut part of embryos could develop to blastocysts, with a reduced percentage or decreased cell number. When both blastomeres of the 2-cell embryos were cut by laser microbeam, cell death occurred 24 h earlier, suggesting important functions of the uncut blastomere in delaying cell death of the cut blastomere. Taken together, we conclude that microbeam-induced DNA damage in early embryos causes compromised development, and that embryos may have their own mechanisms to exclude DNA-damaged blastomeres from participating in further development.

Maternal factors required for oocyte developmental competence in mice: transcriptome analysis of non-surrounded nucleolus (NSN) and surrounded nucleolus (SN) oocytes

During mouse antral follicle development, the oocyte chromatin gradually transforms from a less condensed state with no Hoechst-positive rim surrounding the nucleolus (NSN) to a fully condensed chromatin state with a Hoechst-positive rim surrounding the nucleolus (SN). Compared with SN oocytes, NSN oocytes display a higher gene transcription activity and a lower rate of meiosis resumption (G2/M transition), and they are mostly arrested at the two-cell stage after in vitro fertilization. To explore the differences between NSN and SN oocytes, and the maternal factors required for oocyte developmental competence, we compared the whole-transcriptome profiles between NSN and SN oocytes. First, we found that the NSN and SN oocytes were different in their metabolic pathways. In the phosphatidylinositol signaling pathway, the SN oocytes tend to produce diacylglycerol, whereas the NSN oocytes tend to produce phosphatidylinositol (3,4,5)-trisphosphate. For energy production, the SN oocytes and NSN oocytes differed in the gluconeogenesis and in the synthesis processes. Second, we also found that the key genes associated with oocyte meiosis and/or preimplantation embryo development were differently expressed in the NSN and SN oocytes. Our results illustrate that during the NSN-SN transition, the oocytes change their metabolic activities and accumulate maternal factors for further oocyte maturation and post-fertilization embryo development.

Cyclin O regulates germinal vesicle breakdown in mouse oocytes

It is well accepted that oocyte meiotic resumption is mainly regulated by the maturation-promoting factor (MPF), which is composed of cyclin B1 (CCNB1) and cyclin-dependent kinase 1 (CDC2). Maturation-promoting factor activity is regulated by the expression level of CCNB1, phosphorylation of CDC2, and their germinal vesicle (GV) localization. In addition to CCNB1, cyclin O (CCNO) is highly expressed in oocytes, but its biological functions are still not clear. By employing short interfering RNA microinjection of GV-stage oocytes, we found that Ccno knockdown inhibited CDC2 (Tyr15) dephosphorylation and arrested oocytes at the GV stage. To rescue meiotic resumption, cell division cycle 25 B kinase (Cdc25b) and Ccnb1 were overexpressed in the Ccno knockdown oocytes. Unexpectedly, we found that Ccno knockdown did not affect CDC25B entry into the GV, and overexpression of CDC25B was not able to rescue resumption of oocyte meiosis. However, GV breakdown (GVBD) was significantly increased after overexpression of Ccnb1 in Ccno knockdown oocytes, indicating that GVBD block caused by cyclin O knockdown can be rescued by cyclin B1 overexpression. We thus conclude that cyclin O, as an upstream regulator of MPF, plays an important role in oocyte meiotic resumption in mouse oocytes.

MBTD1 is associated with Pr-Set7 to stabilize H4K20me1 in mouse oocyte meiotic maturation

H4K20me1 is a critical histone lysine methyl modification in eukaryotes. It is recognized and "read" by various histone lysine methyl modification binding proteins. In this study, the function of MBTD1, a member of the Polycomb protein family containing four MBT domains, was comprehensively studied in mouse oocyte meiotic maturation. The results showed that depletion of MBTD1 caused reduced expression of histone lysine methyl transferase Pr-Set7 and H4K20me1 as well as increased oocyte arrest at the GV stage. Increased γH2AX foci were formed, and DNA damage repair checkpoint protein 53BP1 was downregulated. Furthermore, depletion of MBTD1 activated the cell cycle checkpoint protein Chk1 and downregulated the expression of cyclin B1 and cdc2. MBTD1 knockdown also affected chromosome configuration in GV stage oocytes and chromosome alignment at the MII stage. All these phenotypes were reproduced when the H4K20 methyl transferase Pr-Set7 was depleted. Co-IP demonstrated that MBTD1 was correlated with Pr-Set7 in mouse oocytes. Our results demonstrate that MBTD1 is associated with Pr-Set7 to stabilize H4K20me1 in mouse oocyte meiotic maturation.

Specific disruption of Tsc1 in ovarian granulosa cells promotes ovulation and causes progressive accumulation of corpora lutea

Tuberous sclerosis complex 1 (Tsc1) is a tumor suppressor negatively regulating mammalian target of rapamycin complex 1 (mTORC1). It is reported that mice lacking Tsc1 gene in oocytes show depletion of primordial follicles, resulting in premature ovarian failure and subsequent infertility. A recent study indicated that deletion of Tsc1 in somatic cells of the reproductive tract caused infertility of female mice. However, it is not known whether specific disruption of Tsc1 in granulosa cells influences the reproductive activity of female mice. To clarify this problem, we mated Tsc1^flox/flox mice with transgenic mice strain expressing cyp19-cre which exclusively expresses in granulosa cells of the ovary. Our results demonstrated that Tsc1^flox/flox; cyp19-cre mutant mice were fertile, ovulating more oocytes and giving birth to more pups than control Tsc1^flox/flox mice. Progressive accumulation of corpora lutea occurred in the Tsc1^flox/flox; cyp19-cre mutant mice with advanced age. These phenotypes could be explained by the elevated activity of mTORC1, as indicated by increased phosphorylation of rpS6, a substrate of S6 in the Tsc1^flox/flox; cyp19-cre mutant granulosa cells. In addition, rapamycin, a specific mTORC1 inhibitor, effectively rescued the phenotype caused by increased mTORC1 activity in the Tsc1^cko ovaries. Our data suggest that conditional knockout of Tsc1 in granulosa cells promotes reproductive activity in mice.

Evolution and biogeography of the slipper orchids: Eocene vicariance of the conduplicate genera in the Old and New World Tropics

Intercontinental disjunctions between tropical regions, which harbor two-thirds of the flowering plants, have drawn great interest from biologists and biogeographers. Most previous studies on these distribution patterns focused on woody plants, and paid little attention to herbs. The Orchidaceae is one of the largest families of angiosperms, with a herbaceous habit and a high species diversity in the Tropics. Here we investigate the evolutionary and biogeographical history of the slipper orchids, which represents a monophyletic subfamily (Cypripedioideae) of the orchid family and comprises five genera that are disjunctly distributed in tropical to temperate regions. A relatively well-resolved and highly supported phylogeny of slipper orchids was reconstructed based on sequence analyses of six maternally inherited chloroplast and two low-copy nuclear genes (LFY and ACO). We found that the genus Cypripedium with a wide distribution in the northern temperate and subtropical zones diverged first, followed by Selenipedium endemic to South America, and finally conduplicate-leaved genera in the Tropics. Mexipedium and Phragmipedium from the neotropics are most closely related, and form a clade sister to Paphiopedilum from tropical Asia. According to molecular clock estimates, the genus Selenipedium originated in Palaeocene, while the most recent common ancestor of conduplicate-leaved slipper orchids could be dated back to the Eocene. Ancestral area reconstruction indicates that vicariance is responsible for the disjunct distribution of conduplicate slipper orchids in palaeotropical and neotropical regions. Our study sheds some light on mechanisms underlying generic and species diversification in the orchid family and tropical disjunctions of herbaceous plant groups. In addition, we suggest that the biogeographical study should sample both regional endemics and their widespread relatives.

Overexpression Nanog activates pluripotent genes in porcine fetal fibroblasts and nuclear transfer embryos

Nanog as an important transcription factor plays a pivotal role in maintaining pluripotency and in reprogramming the epigenome of somatic cells. Its ability to function on committed somatic cells and embryos has been well defined in mouse and human, but rarely in pig. To better understand Nanog's function on reprogramming in porcine fetal fibroblast (PFF) and nuclear transfer (NT) embryo, we cloned porcine Nanog CDS and constructed pcDNA3.1 (+)/Nanog and pEGFP-C1/Nanog overexpression vectors and transfected them into PFFs. We studied the cell biological changes and the expression of Nanog, Oct4, Sox2, Klf4, C-myc, and Sall4 in transfected PFFs. We also detected the development potential of the cloned embryos harboring Nanog stably overexpressed fibroblasts and the expression of Oct4, Sox2, and both endogenous and exogenous Nanog in these embryos. The results showed that transient overexpression Nanog in PFF could activate the expression of Oct4 (5-fold), C-myc (2-fold), and Sall4 (5-fold) in somatic cells, but they could not be maintained during G418 selection. In NT embryos, although Nanog overexpression did not have a significant effect on blastocyst development rate and blastocyst cell number, it could significantly activate the expression of endogenous Nanog, Oct4, Sox2 to 160-fold, 93-fold, and 182-fold, respectively (P < 0.05). Our results demonstrate that Nanog could interact with and activate other pluripotent genes both in PFFs and embryos.

Development of polymorphic microsatellite markers for Incarvillea sinensis (Bignoniaceae)

PREMISE OF THE STUDY

Microsatellite markers were developed for Incarvillea sinensis var. sinensis (Bignoniaceae), an annual herb endemic to Inner Mongolia, to study the degree to which delayed self-fertilization is favored.

METHODS AND RESULTS

Eight polymorphic primer sets were isolated and characterized in two Inner Mongolia populations of I. sinensis var. sinensis with a relatively simple and fast subcloning method. Numbers of alleles per locus ranged from 2 to 7, with observed and expected heterozygosities ranging from 0 to 0.261 and from 0 to 0.778, respectively.

CONCLUSIONS

These markers will be useful for future studies of self-fertilization adaptability in I. sinensis var. sinensis.

Purification, characterization, and milk coagulating properties of ginger proteases

Ginger proteases are used as milk coagulants in making a Chinese traditional milk product (Jiangzhinai or Jiangzhuangnai), suggesting their potential as a source of rennet substitute that might be applicable in the modern dairy industry. In this study, ginger proteases were extracted from fresh ginger rhizome by using phosphate buffer and subsequently purified by ion exchange chromatography. Ginger proteases, all with a molecular weight around 31 kDa, were found to exist in 3 forms with isoelectric point values around 5.58, 5.40, and 5.22, respectively. These enzymes had very similar biochemical behavior, exhibiting optimal proteolytic activity from 40 to 60 °C and maximum milk clotting activity at 70 °C. They were capable of hydrolyzing isolated α(S1)-, β-, and κ-casein, of which α(S1)-casein was most susceptible to the enzyme; κ-casein was hydrolyzed with a higher specificity than α(S1)- and β-casein. In addition, the ginger proteases exhibited a similar affinity for κ-casein and higher specificity with increasing temperature. Gel electrophoresis and mass spectra indicated that Ala90-Glu91 and His102-Leu103 of κ-casein were the preferred target bonds of ginger proteases. The milk clotting activity, affinity, and specificity toward κ-casein showed that ginger protease is a promising rennet-like protease that could be used in manufacturing cheese and oriental-style dairy foods.

Reproductive isolation and pollination success of rewarding Galearis diantha and non-rewarding Ponerorchis chusua (Orchidaceae)

BACKGROUND AND AIMS

Increasing evidence challenges the conventional perception that orchids are the most distinct example of floral diversification due to floral or prezygotic isolation. Regarding the relationship between co-flowering plants, rewarding and non-rewarding orchids in particular, few studies have investigated whether non-rewarding plants affect the pollination success of rewarding plants. Here, floral isolation and mutual effects between the rewarding orchid Galearis diantha and the non-rewarding orchid Ponerorchis chusua were investigated.

METHODS

Flowering phenological traits were monitored by noting the opening and wilting dates of the chosen individual plants. The pollinator pool and pollinator behaviour were assessed from field observations. Key morphological traits of the flowers and pollinators were measured directly in the field. Pollinator limitation and interspecific compatibility were evaluated by hand-pollination experiments. Fruit set was surveyed in monospecific and heterospecific plots.

KEY RESULTS

The species had overlapping peak flowering periods. Pollinators of both species displayed a certain degree of constancy in visiting each species, but they also visited other flowers before landing on the focal orchids. A substantial difference in spur size between the species resulted in the deposition of pollen on different regions of the body of the shared pollinator. Hand-pollination experiments revealed that fruit set was strongly pollinator-limited in both species. No significant difference in fruit set was found between monospecific plots and heterospecific plots.

CONCLUSIONS

A combination of mechanical isolation and incomplete ethological isolation eliminates the possibility of pollen transfer between the species. These results do not support either the facilitation or competition hypothesis regarding the effect of nearby rewarding flowers on non-rewarding plants. The absence of a significant effect of non-rewarding P. chusua on rewarding G. diantha can be ascribed to low levels of overlap between the pollinator pools of two species.

Parthenogenesis maintains male sterility in a gynodioecious orchid

The invasion of male-sterile (female) individuals into hermaphroditic populations, leading to gynodioecy, is common in flowering plants. Both theoretical and empirical studies have shown that as the frequency of females increases in a population, pollen limitation reduces seed production more in females than in hermaphrodites, leading to higher fitness for hermaphrodites and a consequent decrease in female frequency. Here we show that contrary to this expectation, females of the gynodioecious orchid Satyrium ciliatum are maintained only in populations that experience high pollen limitation caused by low pollinator service and high pollen herbivory. This species avoids the typical problem of pollen limitation for seed production and can therefore maintain high frequencies of females in pollen-limited populations because females produce more seeds than hermaphrodites via facultative parthenogenesis in the absence of pollinia. Our results therefore demonstrate that parthenogenesis is a novel mechanism favoring the maintenance of gynodioecy.

Molecular phylogenetics and morphological reappraisal of the Platanthera clade (Orchidaceae: Orchidinae) prompts expansion of the generic limits of Galearis and Platanthera

BACKGROUND AND AIMS

The Platanthera clade dominates the North American orchid flora and is well represented in eastern Asia. It has also generated some classic studies of speciation in Platanthera sections Platanthera and Limnorchis. However, it has proved rich in taxonomic controversy and near-monotypic genera. The clade is reviewed via a new molecular phylogenetic analysis and those results are combined with brief reconsideration of morphology in the group, aiming to rationalize the species into a smaller number of larger monophyletic genera and sections.

METHODS

Nuclear ribosomal internal transcribed spacer (ITS) sequences were obtained from 86 accessions of 35 named taxa, supplemented from GenBank with five accessions encompassing a further two named taxa.

KEY RESULTS

Using Pseudorchis as outgroup, and scoring indels, the data matrix generated 30 most-parsimonious trees that differed in the placement of two major groups plus two closely related species. Several other internal nodes also attracted only indifferent statistical support. Nonetheless, by combining implicit assessment of morphological divergence with explicit assessment of molecular divergence (when available), nine former genera can be rationalized into four revised genera by sinking the monotypic Amerorchis, together with Aceratorchis and Chondradenia (neither yet sequenced), into Galearis, and by amalgamating Piperia, Diphylax and the monotypic Tsaiorchis into the former Platanthera section Platanthera. After further species sampling, this section will require sub-division into at least three sections. The present nomenclatural adjustments prompt five new combinations.

CONCLUSIONS

Resolution of major groups should facilitate future species-level research on the Platanthera clade. Recent evidence suggests that ITS sequence divergence characterizes most species other than the P. bifolia group. The floral differences that distinguished Piperia, Diphylax and Tsaiorchis from Platanthera, and Aceratorchis and Chondradenia from Galearis, reflect various forms of heterochrony (notably paedomorphosis); this affected both the perianth and the gynostemium, and may have proved adaptive in montane habitats. Floral reduction was combined with lateral expansion of the root tubers in Piperia and Diphylax (including Tsaiorchis), whereas root tubers were minimized in the putative (but currently poorly supported) Neolindleya-Galearis clade. Allopolyploidy and/or autogamy strongly influenced speciation in Platanthera section Limnorchis and perhaps also Neolindleya. Reproductive biology remains an important driver of evolution in the clade, though plant-pollinator specificity and distinctness of the species boundaries have often been exaggerated.

The pollination of a self-incompatible, food-mimic orchid, Coelogyne fimbriata (Orchidaceae), by female Vespula wasps

BACKGROUND AND AIMS

The study of specialized interactions between species is crucial to our understanding of processes in evolutionary ecology due to their profound effect on life cycles and diversification. Obligate pollination by a single wasp species is rare in Orchidaceae except in species with sexually deceptive flowers that are pollinated exclusively by male insects. The object of this study was to document pollination of the food-deceptive flowers of Coelogyne fimbriata, a species pollinated exclusively by female wasps.

METHODS

Field observations and experiments were conducted in two populations of C. fimbriata. Floral phenology was recorded, and functional floral architecture was measured. Insect visitors to flowers were observed from 2005 to 2007. Bioassay experiments were conducted to check whether the floral odour attracted pollinators. Natural (insect-mediated) rates of pollinarium removal, pollinium deposition on stigmas, and fruit set were recorded. To determine the importance of cross-pollination, the breeding system was assessed via controlled, hand-pollination experiments.

KEY RESULTS

Two populations of C. fimbriata with fragrant, nectarless flowers are pollinated by females of the same Vespula species (Vespidae, Hymenoptera). Experiments on wasps show that they crawl towards the source of the odour. The flowering period appears to coincide with an annual peak in Vespula colony expansion when additional workers forage for carbohydrates. Rates of pollinarium removal (0.069-0.918) and pollinium deposition on stigmas (0.025-0.695) are extremely variable. However, fruit set in C. fimbriata is always low (0.014-0.069) and appears to be based on self-incompatibility coupled with intraclonal (geitonogamous) deposition of pollinia.

CONCLUSIONS

Coelogyne fimbriata and Steveniella satyrioides are now the only orchid species known to have food-deceptive flowers that are pollinated exclusively by eusocial, worker wasps. In C. fimbriata, floral odour appears to be the major attractant. Sub-populations may go through flowering seasons when pollinators are abundant or infrequent, but fruit set always remains low because the obligate pollinator does not often appear to transfer pollinaria between intercompatible genets.

Reproductive success of non-rewarding Cypripedium japonicum benefits from low spatial dispersion pattern and asynchronous flowering

BACKGROUND AND AIMS

Outcrossing animal-pollinated plants, particularly non-rewarding species, often experience pollinator limitation to reproduction. Pollinator visitation is affected by various factors, and it is hypothesized that reproduction in non-rewarding plants would benefit from low spatial flower abundance and asynchronous flowering. In order to test this hypothesis, the influence of spatial pattern and flowering phenology on male and female reproductive success (RS) was investigated in a non-rewarding orchid, Cypripedium japonicum, in central China over two flowering seasons.

METHODS

The probabilities of intrafloral self-pollination and geitonogamy caused by pollinator behaviours were estimated from field observations. Pollinator limitation was evaluated by hand-pollination experiments. RS was surveyed in different spatial flower dispersal patterns and local flower densities. The effects of flowering phenological traits on RS were assessed by univariate and multivariate regression analyses.

KEY RESULTS

Hand-pollination experiments revealed that fruit production was strongly pollen limited throughout the entire reproductive season - over two seasons, 74.3 % of individuals set fruit following hand pollination, but only 5.2-7.7 % did so under natural conditions. Intrafloral self-pollination and geitonogamy within the potential clones might be rare. Both male and female fitness were substantially lower in clustered plants than in those growing singly. An increase in local conspecific flower density significantly and negatively influenced male RS, but had no effect on female RS. Phenotypic selection analysis indicated that individuals flowering earlier have the greatest probability of RS. Over 85 % of sampled flowering individuals had a flowering synchrony value >0.7; however, highly synchronous flowering was not advantageous for RS, as indicated by the negative directional selection differentials and gradients, and by the positive quadratic selection gradients.

CONCLUSIONS

These results support the hypothesis that, as a consequence of density-dependent selection, low spatio-temporal flower abundance is advantageous for attracting pollinators and for reproduction in natural populations of non-rewarding C. japonicum.

Pollination biology of basal angiosperms (ANITA grade)

The first three branches of the angiosperm phylogenetic tree consist of eight families with ∼201 species of plants (the ANITA grade). The oldest flower fossil for the group is dated to the Early Cretaceous (115-125 Mya) and identified to the Nymphaeales. The flowers of extant plants in the ANITA grade are small, and pollen is the edible reward (rarely nectar or starch bodies). Unlike many gymnosperms that secrete "pollination drops," ANITA-grade members examined thus far have a dry-type stigma. Copious secretions of stigmatic fluid are restricted to the Nymphaeales, but this is not nectar. Floral odors, floral thermogenesis (a resource), and colored tepals attract insects in deceit-based pollination syndromes throughout the first three branches of the phylogenetic tree. Self-incompatibility and an extragynoecial compitum occur in some species in the Austrobaileyales. Flies are primary pollinators in six families (10 genera). Beetles are pollinators in five families varying in importance as primary (exclusive) to secondary vectors of pollen. Bees are major pollinators only in the Nymphaeaceae. It is hypothesized that large flowers in Nymphaeaceae are the result of the interaction of heat, floral odors, and colored tepals to trap insects to increase fitness.

Pollination of Schisandra henryi (Schisandraceae) by female, pollen-eating Megommata species (Cecidomyiidae, Diptera) in south-central China

BACKGROUND AND AIMS

The mutualistic interaction between insects and flowers is considered to be a major factor in the early evolution of flowering plants. The Schisandraceae were, until now, the only family in the ANITA group lacking information on pollination biology in natural ecosystems. Thus, the objective of this research was to document the pollination biology and breeding system of Schisandra henryi.

METHODS

Field observations were conducted in three populations of S. henryi and the floral phenology, floral characters and insect activities were recorded. Floral fragrances were sampled in the field and analysed using TCT-GC-MS. Floral thermogenesis was measured with a TR-71U Thermo Recorder. Pollen loads and location of pollen grains on insect bodies (including the gut) were checked with a scanning electron microscope and under a light microscope.

KEY RESULTS

Schisandra henryi is strictly dioecious. Male flowers are similar to female flowers in colour, shape, and size, but more abundant than female flowers. The distance between tepals and the androecium or gynoecium is narrow. Neither male nor female flowers are fragrant or thermogenic. Schisandra henryi is pollinated only by adult female Megommata sp. (Cecidomyiidae, Diptera) that eat the pollen grains as extra nutrition for ovary maturation and ovipositing. Both male and female flowers attract the pollinators using similar visual cues and thus the female flowers use deceit as they offer no food.

CONCLUSIONS

Schisandra henryi exhibits a specialized pollination system, which differs from the generalized pollination system documented in other ANITA members. Pollen is the sole food resource for Megommata sp. and the female flowers of S. henryi attract pollinators by deceit. This is the first report of predacious gall midges utilizing pollen grains as a food source. The lack of floral thermogenesis and floral odours further enforces the visual cues by reducing attractants for other potential pollinators.