Phylogeny of the parasitic plant family Orobanchaceae inferred from phytochrome A

Complete mitochondrial genomes of the hemiparasitic genus Cymbaria (Orobanchaceae): insights into repeat-mediated recombination, phylogenetic relationships, and horizontal gene transfer

BACKGROUND

The Orobanchaceae family is widely recognized as an exemplary model system for examining the evolutionary dynamics of parasitic plants. However, reports on the mitochondrial genome (mitogenome) of the hemiparasitic tribe Cymbarieae are currently lacking. Here, we sequenced, assembled and characterized the complete mitogenome of the genus Cymbaria L. sensu stricto (C. mongolica and C. daurica).

RESULTS

A total of 51 unique mitochondrial genes, including 33 protein-coding genes, three rRNA genes, and 15 tRNA genes, are shared by the mitogenomes of the two hemiparasitic plants, exhibiting the gene content characteristic of autotrophic plants. The mitogenomes of C. mongolica and C. daurica are characterized by a pentacyclic chromosome structure (their major conformation), with lengths of 1,576,465 bp and 1,539,836 bp, respectively. Moreover, we identified and validated the presence of four minor conformations mediated by four pairs of large repeats (> 1000 bp in size) in C. mongolica and eight minor conformations mediated by six large repeats in C. daurica. We further explored codon usage, RNA editing sites, selective pressure, and nucleotide diversity in two Cymbaria mitogenomes. Phylogenetic analyses of 26 species of Lamiales revealed that the two Cymbaria species form a sister clade to the other lineages of Orobanchaceae. Extensive mitogenomic rearrangements are also observed between Cymbaria and five closely related species. Although we identified mitochondrial plastid sequences in the Cymbaria mitogenomes, The mitochondrial plastid sequences (MTPTs) in their mitogenomes represent only 2.37% and 1.74%, respectively. Additionally, there is minimal evidence of intracellular and horizontal gene transfer, with only a few genes (rpl22, rps3, and ycf2) showing low bootstrap support (BS ≤ 70%) for the relationships with the potential host plants Allium mongolicum, Leymus chinensis, and Saposhnikovia divaricata, respectively.

CONCLUSIONS

We reported the mitochondrial genome in hemiparasitic Cymbaria species for the first time, which are characterized by multiple repeat-mediated recombination and little to no intracellular and horizontal gene transfer. Our findings provide valuable genetic insights for further studies on the mitogenome evolution of hemiparasitic plants.

Pseudomonas produce various metabolites displaying herbicide activity against broomrape

Pseudomonads are well-known for their plant growth-promoting properties and biocontrol capabilities against microbial pathogens. Recently, their potential to protect crops from parasitic plants has garnered attention. This study investigates the potential of different Pseudomonas strains to inhibit broomrape growth and to protect host plants against weed infestation. Four Pseudomonas strains, two P. fluorescens JV391D17 and JV391D10, one P. chlororaphis JV395B and one P. ogarae F113 were cultivated using various carbon sources, including fructose, pyruvate, fumarate, and malate, to enhance the diversity of potential Orobanche growth inhibition (OGI)-specialized metabolites produced by Pseudomonas strains. Both global and targeted metabolomic approaches were utilized to identify specific OGI metabolites. Both carbon sources and Pseudomonas genetic diversity significantly influenced the production of OGI metabolites. P. chlororaphis JV395B and P. ogarae F113 produced unique OGI metabolites belonging to different chemical families, such as hydroxyphenazines and phloroglucinol compounds, respectively. Additionally, metabolomic analyses identified an unannotated potential OGI ion, M375T65. This ion was produced by all Pseudomonas strains but was found to be over-accumulated in JV395B, which likely explains its superior OGI activity. Then, greenhouse experiments were performed to evaluate the biocontrol efficacy of selected strains: they showed the efficacy of these strains, particularly JV395B, in reducing broomrape infestation in rapeseed. These findings suggest that certain Pseudomonas strains, through their metabolite production, can offer a sustainable biocontrol strategy against parasitic plants. This biocontrol activity can be optimized by environmental factors, such as carbon amendments. Ultimately, this approach presents a promising alternative to chemical herbicides.

Complete chloroplast genomes of the hemiparasitic genus Cymbaria: Insights into comparative analysis, development of molecular markers, and phylogenetic relationships

The hemiparasitic tribe Cymbarieae (Orobanchaceae) plays a crucial role in elucidating the initial stage of the transition from autotrophism to heterotrophism. However, the complete chloroplast genome of the type genus Cymbaria has yet to be reported. In addition, the traditional Mongolian medicine Cymbaria daurica is frequently subjected to adulteration or substitution because of the minor morphological differences with Cymbaria mongolica. In this study, the complete chloroplast genomes of the two Cymbaria species were assembled and annotated, and those of other published 52 Orobanchaceae species were retrieved for comparative analyses. We found that the Cymbaria chloroplast genomes are characterized by pseudogenization or loss of stress-relevant genes (ndh) and a unique rbcL-matK inversion. Unlike the high variability observed in holoparasites, Cymbaria and other hemiparasites exhibit high similarity to autotrophs in genome size, guanine-cytosine (GC) content, and intact genes. Notably, four pairs of specific DNA barcodes were developed and validated to distinguish the medicinal herb from its adulterants. Phylogenetic analyses revealed that the genus Cymbaria and the Schwalbea-Siphonostegia clade are grouped into the tribe Cymbarieae, which forms a sister clade to the remaining Orobanchaceae parasitic lineages. Moreover, the diversification of monophyletic Cymbaria occurred during the late Miocene (6.72 Mya) in the Mongol-Chinese steppe region. Our findings provide valuable genetic resources for studying the phylogeny of Orobanchaceae and plant parasitism, and genetic tools to validate the authenticity of the traditional Mongolian medicine "Xinba.".

Responses of Three Pedicularis Species to Geological and Climatic Changes in the Qinling Mountains and Adjacent Areas in East Asia

The Qinling Mountains in East Asia serve as the geographical boundary between the north and south of China and are also indicative of climatic differences, resulting in rich ecological and species diversity. However, few studies have focused on the responses of plants to geological and climatic changes in the Qinling Mountains and adjacent regions. Therefore, we investigated the evolutionary origins and phylogenetic relationships of three Pedicularis species in there to provide molecular evidence for the origin and evolution of plant species. Ecological niche modeling was used to predict the geographic distributions of three Pedicularis species during the last interglacial period, the last glacial maximum period, and current and future periods, respectively. Furthermore, the distribution patterns of climate fluctuations and the niche dynamics framework were used to assess the equivalence or difference of niches among three Pedicularis species. The results revealed that the divergence of three Pedicularis species took place in the Miocene and Holocene periods, which was significantly associated with the large-scale uplifts of the Qinling Mountains and adjacent regions. In addition, the geographic distributions of three Pedicularis species have undergone a northward migration from the past to the future. The most important environmental variables affecting the geographic distributions of species were the mean diurnal range and annual mean temperature range. The niche divergence analysis suggested that the three Pedicularis species have similar ecological niches. Among them, P. giraldiana showed the highest niche breadth, covering nearly all of the climatic niche spaces of P. dissecta and P. bicolor. In summary, this study provides novel insights into the divergence and origins of three Pedicularis species and their responses to climate and geological changes in the Qinling Mountains and adjacent regions. The findings have also provided new perspectives for the conservation and management of Pedicularis species.

Monochasma Savatieri Aqueous Extract inhibits Human Breast Cancer Cell Line Migration and Adhesion Without Generating Toxicity

BACKGROUND

Monochasma savatieri, is a rare and endangered plant used to treat cancer in Chinese traditional medicine.

OBJECTIVE

To evaluate the anti-cancer activity of M. savatieri aqueous extract by determining its cytotoxicity, anti-migratory, and anti-adhesion effects on breast cancer cells.

METHODS

Cell viability, migration, adhesion, circularity, and cell cycle were evaluated by crystal violet (CV) staining, wound-healing, and transwell assays and flow cytometry in MCF7 and MDA-MB-231 cells. Caveolin-1, snail, vimentin and activated Erk and Akt expression were determined by western blot in MDA-MB-231 cells. Immunofluorescent assays confirmed caveolin-1 expression in MDA-MB-231 cells.

RESULTS

Survival and cell cycle of MCF7 and MDA-MB-231 cells were not modified by doses up to 500 μg/mL of the extract. The extract inhibited cell migration and adhesion of MDA-MB-231 cells. When cells were exposed to the extract, there was a slight decrease in protein expression of factors related to epithelial-to-mesenchymal transition (snail and vimentin) and a strong decrease in the expression of the oncogenic membrane protein caveolin- 1. Furthermore, the levels of phosphorylated Erk and Akt were also decreased. The content of acteoside, a phenylpropanoid glycoside with reported anti-cancer activity present in M. savatieri, was almost 5 times as much as isoacteoside.

CONCLUSION

M. savatieri possesses anti-cancer activity without exerting cytotoxicity on breast cancer cells. The extract exhibited anti-migratory and anti-adhesion effects on breast cancer cells by regulating Erk and Akt signaling pathways and the expression of caveolin-1. In addition, acteoside present in M. savatieri could be responsible for the observed effects.

Inhibition of broomrape germination by 2,4-diacetylphloroglucinol produced by environmental Pseudomonas

Parasitic weeds such as broomrapes (Phelipanche ramosa and Orobanche cumana) cause severe damage to crops and their development must be controlled. Given that phloroglucinol compounds (PGCs) produced by environmental Pseudomonas could be toxic towards certain plants, we assessed the potential herbicidal effect of the bacterial model Pseudomonas ogarae F113, a PGCs-producing bacterium, on parasitic weed. By combining the use of a mutagenesis approach and of pure PGCs, we evaluated the in vitro effect of PGC-produced by P. ogarae F113 on broomrape germination and assessed the protective activity of a PGC-producing bacteria on oilseed rape (Brassica napus) against P. ramosa in non-sterile soils. We showed that the inhibition of the germination depends on the PGCs molecular structure and their concentrations as well as the broomrape species and pathovars. This inhibition caused by the PGCs is irreversible, causing a brown coloration of the broomrape seeds. The inoculation of PGCs-producing bacteria limited the broomrape infection of P. ramosa, without affecting the host growth. Moreover, elemental profiling analysis of oilseed rape revealed that neither F113 nor applied PGCs affected the nutrition capacity of the oilseed rape host. Our study expands the knowledge on plant-beneficial Pseudomonas as weed biocontrol agents and opens new avenues for the development of natural bioherbicides to enhance crop yield.

Historical development of karst evergreen broadleaved forests in East Asia has shaped the evolution of a hemiparasitic genus Brandisia (Orobanchaceae)

Brandisia is a shrubby genus of about eight species distributed basically in East Asian evergreen broadleaved forests (EBLFs), with distribution centers in the karst regions of Yunnan, Guizhou, and Guangxi in southwestern China. Based on the hemiparasitic and more or less liana habits of this genus, we hypothesized that its evolution and distribution were shaped by the development of EBLFs there. To test our hypothesis, the most comprehensive phylogenies of Brandisia hitherto were constructed based on plastome and nuclear loci (nrDNA, PHYA and PHYB); then divergence time and ancestral areas were inferred using the combined nuclear loci dataset. Phylogenetic analyses reconfirmed that Brandisia is a member of Orobanchaceae, with unstable placements caused by nuclear-plastid incongruences. Within Brandisia, three major clades were well supported, corresponding to the three subgenera based on morphology. Brandisia was inferred to have originated in the early Oligocene (32.69 Mya) in the Eastern Himalayas-SW China, followed by diversification in the early Miocene (19.45 Mya) in karst EBLFs. The differentiation dates of Brandisia were consistent with the origin of keystone species of EBLFs in this region (e.g., Fagaceae, Lauraceae, Theaceae, and Magnoliaceae) and the colonization of other characteristic groups (e.g., Gesneriaceae and Mahonia). These findings indicate that the distribution and evolution of Brandisia were facilitated by the rise of the karst EBLFs in East Asia. In addition, the woody and parasitic habits, and pollination characteristics of Brandisia may also be the important factors affecting its speciation and dispersal.

Large-scale mRNA transfer between Haloxylon ammodendron (Chenopodiaceae) and herbaceous root holoparasite Cistanche deserticola (Orobanchaceae)

Exchanges of mRNA were shown between host and stem parasites but not root parasites. Cistanche deserticola (Orobanchaceae) is a holoparasitic herb which parasitizes on the roots of woody plant Haloxylon ammodendron (Chenopodiaceae). We used transcriptome sequencing and bioinformatic analyses to identify nearly ten thousand mobile mRNAs. Transcript abundance appears to be a driving force for transfer event and mRNA exchanges occur through haustorial junction. Mobility of selected mRNAs was confirmed in situ and in sunflower-Orobanche cumana heterologous parasitic system. Four C. deserticola →H. ammodendron mobile mRNAs appear to facilitate haustorium development. Of interest, two mobile mRNAs of putative resistance genes CdNLR1 and CdNLR2 cause root-specific hypersensitive response and retard parasite development, which might contribute to parasitic equilibrium. The present study provides evidence for the large-scale mRNA transfer event between a woody host and a root parasite, and demonstrates the functional relevance of six C. deserticola genes in host-parasite interactions.

Comparing complete organelle genomes of holoparasitic Christisonia kwangtungensis (Orabanchaceae) with its close relatives: how different are they?

BACKGROUND

Orobanchaceae is the only flowering plant family with species from free-living nonparasite, hemi-parasite to holoparasite, making it an ideal system for studying the evolution of parasitism. However, both plastid and mitochondrial genome have been sequenced in only few parasitic species in Orobanchaceae. Therefore, further comparative study is wanted to investigate the impact of holoparasitism on organelle genomes evolution between close relatives. Here, we sequenced organelle genomes and transcriptome of holoparasitic Christisonia kwangtungensis and compared it with its closely related groups to analyze similarities and differences in adaption strategies to the holoparasitic lifestyle.

RESULTS

The plastid genome of C. kwangtungensis has undergone extensive pseudogenization and gene loss, but its reduction pattern is different from that of Aeginetia indica, the close relative of C. kwangtungensis. Similarly, the gene expression detected in the photosynthetic pathway of these two genera is different. In Orobanchaceae, holoparasites in Buchnereae have more plastid gene loss than Rhinantheae, which reflects their longer history of holoparasitism. Distinct from severe degradation of the plastome, protein-coding genes in the mitochondrial genome of C. kwangtungensis are relatively conserved. Interestingly, besides intracellularly transferred genes which are still retained in its plastid genome, we also found several horizontally transferred genes of plastid origin from diverse donors other than their current hosts in the mitochondrial genome, which probably indicate historical hosts.

CONCLUSION

Even though C. kwangtungensis and A. indica are closely related and share severe degradation of plastome, they adapt organelle genomes to the parasitic lifestyle in different ways. The difference between their gene loss and gene expression shows they ultimately lost photosynthetic genes but through different pathways. Our study exemplifies how parasites part company after achieving holoparasitism.

Molecular Characterization of a New Ecotype of Holoparasitic Plant Orobanche L. on Host Weed Xanthium spinosum L

A species of Orobanche was observed on spiny cocklebur (Xanthium spinosum) for the first time in Iran and tentatively was named IR-Iso.This study was conducted to make a phylogenetic analysis of the Orobanche using 5.8S rRNA region sequences, and also to better understand its sequence pattern. The full-length ITS1-ITS2 region of the new Orobanche isolate was PCR-amplified from the holoparasitic plant parasitizing X. spinosum. Sequences of the amplicons from the isolate were 100% identical but differed by 5.6-6.7% from most homologous GenBank accessions to 37.9% divergence from distant species. The analysis of the molecular variance showed that variation between-population (61.9%, SE = 0.04) was larger than within-population. Neighbor-joining analysis placed the Iranian isolate in the same clade as most of the Orobanche and Phelipanche species. The isolate was more closely related to Orobanche aegyptiaca (from China), and this was confirmed by using a structure analysis. However, complementary analyses showed that the Iranian isolate has a unique nucleotide substitution pattern, and hence it was considered as an ecotype of O. aegyptiaca (ecotype Alborzica). In this paper we report on the association between this new ecotype of Orobanche and X. spinosum.

The complete chloroplast genome sequence of Melampyrum koreanum (Orobanchaceae), an endemic and hemi-parasitic herb in Korea

Melampyrum koreanum K.-J. Kim and S.-M. Yun 2012 (Orobanchaceae) is a hemi-parasitic herb, endemic to Korea. Here, the chloroplast genome of this species is reported. It was found to be 143,865 bp long, with a large single-copy region of 83,133 bp, a small single-copy region of 10,308 bp, and a pair of inverted repeat regions of 25,212 bp each. The chloroplast genome harbors 124 genes, including 79 protein-coding genes, 37 transfer RNA genes, and eight ribosomal RNA genes. Among the identified genes, rpoA and several ndh genes were determined to be pseudogenized due to the stop codon in the middle of the gene. The phylogenetic tree of the family was reconstructed based on 20 protein-coding genes, conserved across studied taxa. As a result, Melampyrum L. 1753 species were found to form a monophyletic group in the family.

Complete Plastid and Mitochondrial Genomes of Aeginetia indica Reveal Intracellular Gene Transfer (IGT), Horizontal Gene Transfer (HGT), and Cytoplasmic Male Sterility (CMS)

Orobanchaceae have become a model group for studies on the evolution of parasitic flowering plants, and Aeginetia indica, a holoparasitic plant, is a member of this family. In this study, we assembled the complete chloroplast and mitochondrial genomes of A. indica. The chloroplast and mitochondrial genomes were 56,381 bp and 401,628 bp long, respectively. The chloroplast genome of A. indica shows massive plastid genes and the loss of one IR (inverted repeat). A comparison of the A. indica chloroplast genome sequence with that of a previous study demonstrated that the two chloroplast genomes encode a similar number of proteins (except atpH) but differ greatly in length. The A. indica mitochondrial genome has 53 genes, including 35 protein-coding genes (34 native mitochondrial genes and one chloroplast gene), 15 tRNA (11 native mitochondrial genes and four chloroplast genes) genes, and three rRNA genes. Evidence for intracellular gene transfer (IGT) and horizontal gene transfer (HGT) was obtained for plastid and mitochondrial genomes. ψndhB and ψcemA in the A. indica mitogenome were transferred from the plastid genome of A. indica. The atpH gene in the plastid of A. indica was transferred from another plastid angiosperm plastid and the atpI gene in mitogenome A. indica was transferred from a host plant like Miscanthus siensis. Cox2 (orf43) encodes proteins containing a membrane domain, making ORF (Open Reading Frame) the most likely candidate gene for CMS development in A. indica.

Three-dimensional reconstructions of haustoria in two parasitic plant species in the Orobanchaceae

Parasitic plants infect other plants by forming haustoria, specialized multicellular organs consisting of several cell types, each of which has unique morphological features and physiological roles associated with parasitism. Understanding the spatial organization of cell types is, therefore, of great importance in elucidating the functions of haustoria. Here, we report a three-dimensional (3-D) reconstruction of haustoria from two Orobanchaceae species, the obligate parasite Striga hermonthica infecting rice (Oryza sativa) and the facultative parasite Phtheirospermum japonicum infecting Arabidopsis (Arabidopsis thaliana). In addition, field-emission scanning electron microscopy observation revealed the presence of various cell types in haustoria. Our images reveal the spatial arrangements of multiple cell types inside haustoria and their interaction with host roots. The 3-D internal structures of haustoria highlight differences between the two parasites, particularly at the xylem connection site with the host. Our study provides cellular and structural insights into haustoria of S. hermonthica and P. japonicum and lays the foundation for understanding haustorium function.

Broomrape Species Parasitizing Odontarrhena lesbiaca (Brassicaceae) Individuals Act as Nickel Hyperaccumulators

The elemental defense hypothesis supports that metal hyperaccumulation in plant tissues serves as a mechanism underpinning plant resistance to herbivores and pathogens. In this study, we investigate the interaction between Odontarrhena lesbiaca and broomrape parasitic species, in the light of the defense hypothesis of metal hyperaccumulation. Plant and soil samples collected from three serpentine sites in Lesbos, Greece were analyzed for Ni concentrations. Phelipanche nowackiana and Phelipanche nana were found to infect O. lesbiaca. In both species, Ni concentration decreased gradually from tubercles to shoots and flowers. Specimens of both species with shoot nickel concentrations above 1000 mg.kg^-1 were found, showing that they act as nickel hyperaccumulators. Low values of parasite to O. lesbiaca leaf or soil nickel quotients were observed. Orobanche pubescens growing on a serpentine habitat but not in association with O. lesbiaca had very low Ni concentrations in its tissues analogous to excluder plants growing on serpentine soils. Infected O. lesbiaca individuals showed lower leaf nickel concentrations relative to the non-infected ones. Elevated leaf nickel concentration of O. lesbiaca individuals did not prevent parasitic plants to attack them and to hyperaccumulate metals to their tissues, contrary to predictions of the elemental defense hypothesis.

A multilocus phylogeny of the non-photosynthetic parasitic plant Cistanche (Orobanchaceae) refutes current taxonomy and identifies four major morphologically distinct clades

Phylogenetic relationships of and within non-photosynthetic parasitic lineages are notoriously poorly known, which negatively affects our understanding of parasitic plants. This is also the case for Cistanche (Orobanchaceae), an Old World genus with about two dozen species, whose relationships have not yet been addressed using molecular phylogenetic approaches. Here we infer phylogenetic relationships within the genus, employing a taxonomically and geographically broad sampling covering all previously distinguished infrageneric groups and most of the currently recognized species. A combined matrix of three plastid markers (trnL-trnF, including the trnL intron and the intergenic spacer (IGS), trnS-trnfM IGS and psbA-trnH IGS) and one nuclear marker (ITS) was analyzed using maximum parsimony, maximum likelihood and Bayesian inference. Cistanche falls into four well-supported and geographically differentiated clades: East Asian Clade, Northwest African Clade, Southwest Asian Clade and Widespread Clade. Of those, only the East Asian Clade corresponds to a previously recognized taxonomic section, whereas the others either contain members of two or three sections (Widespread Clade and Southwest Asian Clade, respectively) or have not been taxonomically recognized so far (Northwest African Clade). Whereas the Southwest Asian Clade exhibits strong phylogenetic structure among and partly within species (the East Asian Clade and the Northwest African Clade are monospecific), phylogenetic resolution within the Widespread Clade is often low and hampered by discrepancies between nuclear and plastid markers. Both molecular and morphological data indicate that species diversity in Cistanche is currently underestimated.

The loss of photosynthesis pathway and genomic locations of the lost plastid genes in a holoparasitic plant Aeginetia indica

BACKGROUND

With three origins of holoparasitism, Orobanchaceae provides an ideal system to study the evolution of holoparasitic lifestyle in plants. The evolution of holoparasitism can be revealed by plastid genome degradation and coordinated changes in the nuclear genome, since holoparasitic plants lost the capability of photosynthesis. Among the three clades with holoparasitic plants in Orobanchaceae, only Clade VI has no available plastid genome sequences for holoparasitic plants. In this study, we sequenced the plastome and transcriptome of Aeginetia indica, a holoparasitic plant in Clade VI of Orobanchaceae, to study its plastome evolution and the corresponding changes in the nuclear genome as a response of the loss of photosynthetic function.

RESULTS

The plastome of A. indica is reduced to 86,212 bp in size, and almost all photosynthesis-related genes were lost. Massive fragments of the lost plastid genes were transferred into the mitochondrial and/or nuclear genomes. These fragments could not be detected in its transcriptomes, suggesting that they were non-functional. Most protein coding genes in the plastome showed the signal of relaxation of purifying selection. Plastome and transcriptome analyses indicated that the photosynthesis pathway is completely lost, and that the porphyrin and chlorophyll metabolism pathway is partially retained, although chlorophyll synthesis is not possible.

CONCLUSIONS

Our study suggests the loss of photosynthesis-related functions in A. indica in both the nuclear and plastid genomes. The lost plastid genes are transferred into its nuclear and/or mitochondrial genomes, and exist in very small fragments with no expression and are thus non-functional. The Aeginetia indica plastome also provides a resource for comparative studies on the repeated evolution of holoparasitism in Orobanchaceae.

Extensive plastome reduction and loss of photosynthesis genes in Diphelypaea coccinea, a holoparasitic plant of the family Orobanchaceae

BACKGROUND

Parasitic plants have the ability to obtain nutrients from their hosts and are less dependent on their own photosynthesis or completely lose this capacity. The reduction in plastid genome size and gene content in parasitic plants predominantly results from loss of photosynthetic genes. Plants from the family Orobanchaceae are used as models for studying plastid genome evolution in the transition from an autotrophic to parasitic lifestyle. Diphelypaea is a poorly studied genus of the Orobanchaceae, comprising two species of non-photosynthetic root holoparasites. In this study, we sequenced the plastid genome of Diphelypaea coccinea and compared it with other Orobanchaceae, to elucidate patterns of plastid genome evolution. In addition, we used plastid genome data to define the phylogenetic position of Diphelypaea spp.

METHODS

The complete nucleotide sequence of the plastid genome of D. coccinea was obtained from total plant DNA, using pyrosequencing technology.

RESULTS

The D. coccinea plastome is only 66,616 bp in length, and is highly rearranged; however, it retains a quadripartite structure. It contains only four rRNA genes, 25 tRNA genes and 25 protein-coding genes, being one of the most highly reduced plastomes among the parasitic Orobanchaceae. All genes related to photosynthesis, including the ATP synthase genes, had been lost, whereas most housekeeping genes remain intact. The plastome contains two divergent, but probably intact clpP genes. Intron loss had occurred in some protein-coding and tRNA genes. Phylogenetic analysis yielded a fully resolved tree for the Orobanchaceae, with Diphelypaea being a sister group to Orobanche sect. Orobanche.

The Complete Chloroplast Genome of Euphrasia regelii, Pseudogenization of ndh Genes and the Phylogenetic Relationships Within Orobanchaceae

Euphrasia (Orobanchaceae) is a genus which is widely distributed in temperate regions of the southern and northern hemisphere. The taxonomy of Euphrasia is still controversial due to the similarity of morphological characters and a lack of genomic resources. Here, we present the first complete chloroplast (cp) genome of this taxonomically challenging genus. The cp genome of Euphrasia regelii consists of 153,026 bp, including a large single-copy region (83,893 bp), a small single-copy region (15,801 bp) and two inverted repeats (26,666 bp). There are 105 unique genes, including 71 protein-coding genes, 30 tRNA and 4 rRNA genes. Although the structure and gene order is comparable to the one in other angiosperm cp genomes, genes encoding the NAD(P)H dehydrogenase complex are widely pseudogenized due to mutations resulting in frameshifts, and stop codon positions. We detected 36 dispersed repeats, 7 tandem repeats and 65 simple sequence repeat loci in the E. regelii plastome. Comparative analyses indicated that the cp genome of E. regelii is more conserved compared to other hemiparasitic taxa in the Pedicularideae and Buchnereae. No structural rearrangements or loss of genes were detected. Our analyses suggested that three genes (clpP, ycf2 and rps14) were under positive selection and other genes under purifying selection. Phylogenetic analysis of monophyletic Orobanchaceae based on 45 plastomes indicated a close relationship between E. regelii and Neobartsia inaequalis. In addition, autotrophic lineages occupied the earliest diverging branches in our phylogeny, suggesting that autotrophy is the ancestral trait in this parasitic family.

Genome-wide identification of MST, SUT and SWEET family sugar transporters in root parasitic angiosperms and analysis of their expression during host parasitism

BACKGROUND

Root parasitic weeds are a major constraint to crop production worldwide causing significant yearly losses in yield and economic value. These parasites cause their destruction by attaching to their hosts with a unique organ, the haustorium, that allows them to obtain the nutrients (sugars, amino acids, etc.) needed to complete their lifecycle. Parasitic weeds differ in their nutritional requirements and degree of host dependency and the differential expression of sugar transporters is likely to be a critical component in the parasite's post-attachment survival.

RESULTS

We identified gene families encoding monosaccharide transporters (MSTs), sucrose transporters (SUTs), and SWEETs (Sugars Will Eventually be Exported Transporters) in three root-parasitic weeds differing in host dependency: Triphysaria versicolor (facultative hemiparasite), Phelipanche aegyptiaca (holoparasite), and Striga hermonthica (obligate hemiparasite). The phylogenetic relationship and differential expression profiles of these genes throughout parasite development were examined to uncover differences existing among parasites with different levels of host dependence. Differences in estimated gene numbers are found among the three parasites, and orthologs within the different sugar transporter gene families are found to be either conserved among the parasites in their expression profiles throughout development, or to display parasite-specific differences in developmentally-timed expression. For example, MST genes in the pGLT clade express most highly before host connection in Striga and Triphysaria but not Phelipanche, whereas genes in the MST ERD6-like clade are highly expressed in the post-connection growth stages of Phelipanche but highest in the germination and reproduction stages in Striga. Whether such differences reflect changes resulting from differential host dependence levels is not known.

CONCLUSIONS

While it is tempting to speculate that differences in estimated gene numbers and expression profiles among members of MST, SUT and SWEET gene families in Phelipanche, Striga and Triphysaria reflect the parasites' levels of host dependence, additional evidence that altered transporter gene expression is causative versus consequential is needed. Our findings identify potential targets for directed manipulation that will allow for a better understanding of the nutrient transport process and perhaps a means for controlling the devastating effects of these parasites on crop productivity.

Does the Enigmatic Wightia Belong to Paulowniaceae (Lamiales)?

The familial placement of Wightia has been controversial in the Lamiales, and the genus is currently placed in Paulowniaceae in APG IV. Phylogenetic analyses of Wightia and its close relatives in Lamiales are conducted using sequences of the complete chloroplast genomes as well as sequence data from nine chloroplast DNA regions (atpB, matK, ndhF, psbBTNH, rbcL, rps4, rps16 intron, trnL-F, and trnV-atpE) and one mitochondrial gene rps3. The maximum likelihood and Bayesian analyses do not support a close relationship between Wightia and Paulownia of Paulowniaceae; instead the enigmatic Wightia is sister to Phrymaceae with strong support in all analyses. Hence Wightia should not be placed in Paulowniaceae. Because morphological data show Wightia's affinity to both Phrymaceae and Paulowniaceae and prior nrITS data suggest its sister relationship to Paulownia of Paulowniaceae, it is likely that Wightia may have had a hybrid origin between early lineages of Phrymaceae and Paulowniaceae. It is therefore the best to exclude Wightia from Paulowniaceae and place the genus as unassigned until further nuclear data to test the hybrid hypothesis. The seven species of Paulownia constitute a monophyletic group, and Paulowniaceae is supported to be a monogeneric family, consistent with a series of morphological and floral development characters. The genus Brandisia, which was sometimes regarded as a close relative of Wightia, is supported to be nested within Orobanchaceae, as sister to Pterygiella. This sister relationship can be corroborated by fruit, seed and pollen morphological characters.

Phylogenetic Relationships in Orobanchaceae Inferred From Low-Copy Nuclear Genes: Consolidation of Major Clades and Identification of a Novel Position of the Non-photosynthetic Orobanche Clade Sister to All Other Parasitic Orobanchaceae

Molecular phylogenetic analyses have greatly advanced our understanding of phylogenetic relationships in Orobanchaceae, a model system to study parasitism in angiosperms. As members of this group may lack some genes widely used for phylogenetic analysis and exhibit varying degrees of accelerated base substitution in other genes, relationships among major clades identified previously remain contentious. To improve inferences of phylogenetic relationships in Orobanchaceae, we used two pentatricopeptide repeat (PPR) and three low-copy nuclear (LCN) genes, two of which have been developed for this study. Resolving power and level of support strongly differed among markers. Despite considerable incongruence among newly and previously sequenced markers, monophyly of major clades identified in previous studies was confirmed and, especially in analyses of concatenated data, strongly supported after the exclusion of a small group of East Asian genera (Pterygiella and Phtheirospermum) from the Euphrasia-Rhinanthus clade. The position of the Orobanche clade sister to all other parasitic Orobanchaceae may indicate that the shift to holoparasitism occurred early in the evolution of the family. Although well supported in analyses of concatenated data comprising ten loci (five newly and five previously sequenced), relationships among major clades, most prominently the Striga-Alectra clade, the Euphrasia-Rhinanthus clade, and the Castilleja-Pedicularis clade, were uncertain because of strongly supported incongruence also among well-resolving loci. Despite the limitations of using a few selected loci, congruence among markers with respect to circumscription of major clades of Orobanchaceae renders those frameworks for detailed, species-level, phylogenetic studies.

Horizontal Gene Transfer in Five Parasite Plant Species in Orobanchaceae

We sequenced genomes of five parasite species in family Orobanchaceae to explore the evolutionary role of horizontal gene transfer in plants. Orobanche minor and Aeginetia indica are obligate parasites with no photosynthetic activity, whereas the other three (Pedicularis keiskei, Phtheirospermum japonicum, and Melampyrum roseum) are facultative parasites. By using reference genome sequences and/or transcriptomes of 14 species from Fabaceae and Poaceae, their major host families, we detected 106 horizontally transferred genes (HGT genes), only in the genomes of the two obligate parasites (22 and 84 for Oro. minor and Ae. indica, respectively), whereas none in the three facultative parasites. The HGT genes, respectively, account for roughly 0.1% and 0.2% of the coding genes in the two species. We found that almost all HGT genes retained introns at the same locations as their homologs in potential host species, indicating a crucial role of DNA-mediated gene transfer, rather than mRNA mediated retro transfer. Furthermore, some of the HGT genes might have transferred simultaneously because they located very closely in the host reference genome, indicating that the length of transferred DNA could exceed 100 kb. We confirmed that almost all introns are spliced in the current genome of the parasite species, and that about half HGT genes do not have any missense mutations or frameshift-causing indels, suggesting that some HGT genes may be still functional. Evolutionary analyses revealed that the nonsynonymous–synonymous substitution ratio is on average elevated on the lineage leading to HGT genes, due to either relaxation of selection or positive selection.

Genuine and Sequestered Natural Products from the Genus Orobanche (Orobanchaceae, Lamiales)

The present review gives an overview about natural products from the holoparasitic genus Orobanche (Orobanchaceae). We cover both genuine natural products as well as compounds sequestered by Orobanche taxa from their host plants. However, the distinction between these two categories is not always easy. In cases where the respective authors had not indicated the opposite, all compounds detected in Orobanche taxa were regarded as genuine Orobanche natural products. From the about 200 species of Orobanche s.l. (i.e., including Phelipanche) known worldwide, only 26 species have so far been investigated phytochemically (22 Orobanche and four Phelipanche species), from 17 Orobanche and three Phelipanche species defined natural products (and not only natural product classes) have been reported. For two species of Orobanche and one of Phelipanche dedicated studies have been performed to analyze the phenomenon of natural product sequestration by parasitic plants from their host plants. In total, 70 presumably genuine natural products and 19 sequestered natural products have been described from Orobanche s.l.; these form the basis of 140 chemosystematic records (natural product reports per taxon). Bioactivities described for Orobanche s.l. extracts and natural products isolated from Orobanche species include in addition to antioxidative and anti-inflammatory effects, e.g., analgesic, antifungal and antibacterial activities, inhibition of amyloid β aggregation, memory enhancing effects as well as anti-hypertensive effects, inhibition of blood platelet aggregation, and diuretic effects. Moreover, muscle relaxant and anti-spasmodic effects as well as anti-photoaging effects have been described.

The Hemiparasitic Plant Phtheirospermum (Orobanchaceae) Is Polyphyletic and Contains Cryptic Species in the Hengduan Mountains of Southwest China

Phtheirospermum (Orobanchaceae), a hemiparasitic genus of Eastern Asia, is characterized by having long and viscous glandular hairs on stems and leaves. Despite this unifying character, previous phylogenetic analyses indicate that Phtheirospermum is polyphyletic, with Phtheirospermum japonicum allied with tribe Pedicularideae and members of the Ph. tenuisectum complex allied with members of tribe Rhinantheae. However, no analyses to date have included broad phylogenetic sampling necessary to test the monophyly of Phtheirospermum species, and to place these species into the existing subfamiliar taxonomic organization of Orobanchaceae. Two other genera of uncertain phylogenetic placement are Brandisia and Pterygiella, also both of Eastern Asia. In this study, broadly sampled phylogenetic analyses of nrITS and plastid DNA revealed hard incongruence between these datasets in the placement of Brandisia. However, both nrITS and the plastid datasets supported the placement of Ph. japonicum within tribe Pedicularideae, and a separate clade consisting of the Ph. tenuisectum complex and a monophyletic Pterygiella. Analyses were largely in agreement that Pterygiella, the Ptheirospermum complex, and Xizangia form a clade not nested within any of the monophyletic tribes of Orobanchaceae recognized to date. Ph. japonicum, a model species for parasitic plant research, is widely distributed in Eastern Asia. Despite this broad distribution, both nrITS and plastid DNA regions from a wide sampling of this species showed high genetic identity, suggesting that the wide species range is likely due to a recent population expansion. The Ph. tenuisectum complex is mainly distributed in the Hengduan Mountains region. Two cryptic species were identified by both phylogenetic analyses and morphological characters. Relationships among species of the Ph. tenuisectum complex and Pterygiella remain uncertain. Estimated divergence ages of the Ph. tenuisectum complex corresponding to the last two uplifts of the Qinghai-Tibet Plateau at around 8.0-7.0 Mya and 3.6-1.5 Mya indicated that the development of a hot-dry valley climate during these uplifts may have driven species diversification in the Ph. tenuisectum complex.

Gene loss and genome rearrangement in the plastids of five Hemiparasites in the family Orobanchaceae

BACKGROUND

The chloroplast genomes (plastome) of most plants are highly conserved in structure, gene content, and gene order. Parasitic plants, including those that are fully photosynthetic, often contain plastome rearrangements. These most notably include gene deletions that result in a smaller plastome size. The nature of gene loss and genome structural rearrangement has been investigated in several parasitic plants, but their timing and contributions to the adaptation of these parasites requires further investigation, especially among the under-studied hemi-parasites.

RESULTS

De novo sequencing, assembly and annotation of the chloroplast genomes of five photosynthetic parasites from the family Orobanchaceae were employed to investigate plastome dynamics. Four had major structural rearrangements, including gene duplications and gene losses, that differentiated the taxa. The facultative parasite Aureolaria virginica had the most similar genome content to its close non-parasitic relative, Lindenbergia philippensis, with similar genome size and organization, and no differences in gene content. In contrast, the facultative parasite Buchnera americana and three obligate parasites in the genus Striga all had enlargements of their plastomes, primarily caused by expansion within the large inverted repeats (IRs) that are a standard plastome feature. Some of these IR increases were shared by multiple investigated species, but others were unique to particular lineages. Gene deletions and pseudogenization were also both shared and lineage-specific, with particularly frequent and independent loss of the ndh genes involved in electron recycling.

CONCLUSIONS

Five new plastid genomes were fully assembled and compared. The results indicate that plastome instability is common in parasitic plants, even those that retain the need to perform essential plastid functions like photosynthesis. Gene losses were slow and not identical across taxa, suggesting that different lineages had different uses or needs for some of their plastome gene content, including genes involved in some aspects of photosynthesis. Recent repeat region extensions, some unique to terminal species branches, were observed after the divergence of the Buchnera/Striga clade, suggesting that this otherwise rare event has some special value in this lineage.

Primers for Castilleja and their utility across Orobanchaceae: I. Chloroplast primers

PREMISE OF THE STUDY

Chloroplast primers were developed from genomic data for the taxonomically challenging genus Castilleja. We further tested the broader utility of these primers across Orobanchaceae, identifying a core set of chloroplast primers amplifying across the clade.

METHODS AND RESULTS

Using a combination of three low-coverage Castilleja genomes and sequence data from 12 Castilleja plastomes, 76 primer combinations were specifically designed and tested for Castilleja. The primers targeted the most variable portions of the plastome and were validated for their applicability across the clade. Of these, 38 primer combinations were subsequently evaluated in silico and then validated across other major clades in Orobanchaceae.

CONCLUSIONS

These results demonstrate the utility of these primers, not only across Castilleja, but for other clades in Orobanchaceae-particularly hemiparasitic lineages-and will contribute to future phylogenetic studies of this important clade of parasitic plants.

Primers for Castilleja and their utility across Orobanchaceae: II. Single-copy nuclear loci

PREMISE OF THE STUDY

We developed primers targeting nuclear loci in Castilleja with the goal of reconstructing the evolutionary history of this challenging clade. These primers were tested across other major clades in Orobanchaceae to assess their broader utility.

METHODS AND RESULTS

We assembled low-coverage genomes for three taxa in Castilleja and developed primer combinations for the single-copy conserved ortholog set (COSII) and the pentatricopeptide repeat (PPR) gene family. These primer combinations were designed to take advantage of the Fluidigm microfluidic PCR platform and are well suited for high-throughput sequencing applications. Eighty-seven primers were designed for Castilleja, and 27 were found to have broader utility in Orobanchaceae.

CONCLUSIONS

These results demonstrate the utility of these primers, not only across Castilleja, but for other lineages within Orobanchaceae as well. This expanded molecular toolkit will be an asset to future phylogenetic studies in Castilleja and throughout Orobanchaceae.

Testing the Hypothesis of Multiple Origins of Holoparasitism in Orobanchaceae: Phylogenetic Evidence from the Last Two Unplaced Holoparasitic Genera, Gleadovia and Phacellanthus

Orobanchaceae is the largest family among the parasitic angiosperms. It comprises non-parasites, hemi- and holoparasites, making this family an ideal test case for studying the evolution of parasitism. Previous phylogenetic analyses showed that holoparasitism had arisen at least three times from the hemiparasitic taxa in Orobanchaceae. Until now, however, not all known genera of Orobanchaceae were investigated in detail. Among them, the unknown phylogenetic positions of the holoparasites Gleadovia and Phacellanthus are the key to testing how many times holoparasitism evolved. Here, we provide clear evidence for the first time that they are members of the tribe Orobancheae, using sequence data from multiple loci (nuclear genes ITS, PHYA, PHYB, and plastid genes rps2, matK). Gleadovia is an independent lineage whereas Phacellanthus should be merged into genus Orobanche section Orobanche. Our results unambiguously support the hypothesis that there are only three origins of holoparasitism in Orobanchaceae. Divergence dating reveals for the first time that the three origins of holoparasitism were not synchronous. Our findings suggest that holoparasitism can persist in specific clades for a long time and holoparasitism may evolve independently as an adaptation to certain hosts.

New records of parasitized plants by Escobedia grandiflora (Orobanchaceae) in natural habitats

Abstract Hemiparasitic plant roots adhere to neighboring plants in order to meet part or all of their nutritional requirements. Escobedia grandiflora (L. f.) Kuntze is a hemiparasitic plant found throughout the America. Its orange colored roots are used as a natural colorant in food and medicines, but there is little information about plant requirements. The aim of this study was to identify host plants of E. grandiflora in five natural habitats within the department of Antioquia (Colombia). There, E. grandiflora plants were selected and an area of 50 × 50 cm around them was demarcated, in order to identify the vegetation in the quadrant with adhering haustoria. The Amount of haustoria of E. grandiflora on these plants was established. Twenty-two species belonging to seven botanical families were recorded as being parasitized by E. grandiflora, the most predominant family being Poaceae, with twelve species. Greater compatibility or preference was suggested for 18.2% of the identified plant species. It was concluded that E. grandiflora has a wide host range, especially within the Poaceae family. This record contributes to an increased knowledge of this species, and constitutes basic information for future studies.

Research survey on iridoid and phenylethanoid glycosides among seven populations of Euphrasia rostkoviana Hayne from the Alps

The traditional use of extracts of Euphrasia rostkoviana to relieve ocular inflammation or infections is well documented and supported by clinical studies. Various classes of chemical compounds such as iridoids, phenylethanoids, flavonoids and hydroxycinnamic acids have been reported. The present work aims to assess the chemical diversity among seven populations of Euphrasia rostkoviana found in northern Italy. A meticulous separation of components led to the isolation and structural characterization of two previously unrecorded phenylethanoids methoxycrassifolioside and deoxycrassifolioside and one previously undescribed terpene glucoside (1E,6E)-8-hydroxy-3,7-dimethyl-octa-1,6-dienyl 1-O-β-D-glucopyranoside. We have also identified known phenylethanoids and iridoids that are reported in this genus for the first time. Finally, a targeted quantitative analysis for the standardization of herbal preparations revealed that iridoids occur in all populations whereas the presence and the levels of rutin and phenylethanoids are highly variable.

Flora of the cangas of Serra dos Carajás, Pará, Brazil: Orobanchaceae

Abstract This is a taxonomic study of the representatives of Orobanchaceae from the cangas of Serra dos Carajás, Pará state, Brazil. We recorded Buchnera carajasensis and B. longifolia in Serra dos Carajás, but only the former occurs in areas of canga and will be treated in this work. Here we present a detailed description, photographs and notes on morphology, distribution and phenology of this species.

Marker Development for Phylogenomics: The Case of Orobanchaceae, a Plant Family with Contrasting Nutritional Modes

Phylogenomic approaches, employing next-generation sequencing (NGS) techniques, have revolutionized systematic and evolutionary biology. Target enrichment is an efficient and cost-effective method in phylogenomics and is becoming increasingly popular. Depending on availability and quality of reference data as well as on biological features of the study system, (semi-)automated identification of suitable markers will require specific bioinformatic pipelines. Here, we established a highly flexible bioinformatic pipeline, BaitsFinder, to identify putative orthologous single copy genes (SCGs) and to construct bait sequences in a single workflow. Additionally, this pipeline has been constructed to be able to cope with challenging data sets, such as the nutritionally heterogeneous plant family Orobanchaceae. To this end, we used transcriptome data of differing quality available for four Orobanchaceae species and, as reference, SCG data from monkeyflower (Erythranthe guttata, syn. Mimulus g.; 1,915 genes) and tomato (Solanum lycopersicum; 391 genes). Depending on whether gaps were permitted in initial blast searches of the four Orobanchaceae species against the reference, our pipeline identified 1,307 and 981 SCGs with average length of 994 bp and 775 bp, respectively. Automated bait sequence construction (using 2× tiling) resulted in 38,170 and 21,856 bait sequences, respectively. In comparison to the recently published MarkerMiner 1.0 pipeline BaitsFinder identified about 1.6 times as many SCGs (of at least 900 bp length). Skipping steps specific to analyses of Orobanchaceae, BaitsFinder was successfully used in a group of non-parasitic plants (three Asteraceae species and, as reference, SCG data from Arabidopsis thaliana based on previously compiled SCGs). Thus, BaitsFinder is expected to be broadly applicable in groups, where only transcriptomes or partial genome data of differing quality are available.

Limited mitogenomic degradation in response to a parasitic lifestyle in Orobanchaceae

In parasitic plants, the reduction in plastid genome (plastome) size and content is driven predominantly by the loss of photosynthetic genes. The first completed mitochondrial genomes (mitogenomes) from parasitic mistletoes also exhibit significant degradation, but the generality of this observation for other parasitic plants is unclear. We sequenced the complete mitogenome and plastome of the hemiparasite Castilleja paramensis (Orobanchaceae) and compared them with additional holoparasitic, hemiparasitic and nonparasitic species from Orobanchaceae. Comparative mitogenomic analysis revealed minimal gene loss among the seven Orobanchaceae species, indicating the retention of typical mitochondrial function among Orobanchaceae species. Phylogenetic analysis demonstrated that the mobile cox1 intron was acquired vertically from a nonparasitic ancestor, arguing against a role for Orobanchaceae parasites in the horizontal acquisition or distribution of this intron. The C. paramensis plastome has retained nearly all genes except for the recent pseudogenization of four subunits of the NAD(P)H dehydrogenase complex, indicating a very early stage of plastome degradation. These results lend support to the notion that loss of ndh gene function is the first step of plastome degradation in the transition to a parasitic lifestyle.

Massive intracellular gene transfer during plastid genome reduction in nongreen Orobanchaceae

Plastid genomes (plastomes) of nonphotosynthetic plants experience extensive gene losses and an acceleration of molecular evolutionary rates. Here, we inferred the mechanisms and timing of reductive genome evolution under relaxed selection in the broomrape family (Orobanchaceae). We analyzed the plastomes of several parasites with a major focus on the genus Orobanche using genome-descriptive and Bayesian phylogenetic-comparative methods. Besides this, we scanned the parasites' other cellular genomes to trace the fate of all genes that were purged from their plastomes. Our analyses indicate that the first functional gene losses occurred within 10 Myr of the transition to obligate parasitism in Orobanchaceae, and that the physical plastome reduction proceeds by small deletions that accumulate over time. Evolutionary rate shifts coincide with the genomic reduction process in broomrapes, suggesting that the shift of selectional constraints away from photosynthesis to other molecular processes alters the plastid rate equilibrium. Most of the photosynthesis-related genes or fragments of genes lost from the plastomes of broomrapes have survived in their nuclear or mitochondrial genomes as the results of multiple intracellular transfers and subsequent fragmentation. Our findings indicate that nonessential DNA is eliminated much faster in the plastomes of nonphotosynthetic parasites than in their other cellular genomes.

Floral Volatiles in Parasitic Plants of the Orobanchaceae. Ecological and Taxonomic Implications

The holoparasitic broomrapes, Orobanche spp. and Phelipanche spp. (Orobanchaceae), are root parasites that completely depend on a host plant for survival and reproduction. There is considerable controversy on the taxonomy of this biologically and agronomically important family. Flowers of over 25 parasitic Orobanchaceae and a number of close, parasitic and non-parasitic, relatives emitted a complex blend of volatile organic compounds (VOCs), consisting of over 130 VOCs per species. Floral VOC blend-based phylogeny supported the known taxonomy in internal taxonomic grouping of genus and eliminated the uncertainty in some taxonomical groups. Moreover, phylogenetic analysis suggested separation of the broomrapes into two main groups parasitizing annual and perennial hosts, and for the annual hosts, into weedy and non-weedy broomrapes. We conclude that floral VOCs are a significant tool in species identification and possibly even in defining new species and can help to improve controversial taxonomy in the Orobanchaceae.

Complete Plastid Genome of the Recent Holoparasite Lathraea squamaria Reveals Earliest Stages of Plastome Reduction in Orobanchaceae

Plants from the family Orobanchaceae are widely used as a model to study different aspects of parasitic lifestyle including host–parasite interactions and physiological and genomic adaptations. Among the latter, the most prominent are those that occurred due to the loss of photosynthesis; they include the reduction of the photosynthesis-related gene set in both nuclear and plastid genomes. In Orobanchaceae, the transition to non-photosynthetic lifestyle occurred several times independently, but only one lineage has been in the focus of evolutionary studies. These studies included analysis of plastid genomes and transcriptomes and allowed the inference of patterns and mechanisms of genome reduction that are thought to be general for parasitic plants. Here we report the plastid genome of Lathraea squamaria, a holoparasitic plant from Orobanchaceae, clade Rhinantheae. We found that in this plant the degree of plastome reduction is the least among non-photosynthetic plants. Like other parasites, Lathraea possess a plastome with elevated absolute rate of nucleotide substitution. The only gene lost is petL, all other genes typical for the plastid genome are present, but some of them–those encoding photosystem components (22 genes), cytochrome b₆/f complex proteins (4 genes), plastid-encoded RNA polymerase subunits (2 genes), ribosomal proteins (2 genes), ccsA and cemA–are pseudogenized. Genes for cytochrome b₆/f complex and photosystems I and II that do not carry nonsense or frameshift mutations have an increased ratio of non-synonymous to synonymous substitution rates, indicating the relaxation of purifying selection. Our divergence time estimates showed that transition to holoparasitism in Lathraea lineage occurred relatively recently, whereas the holoparasitic lineage Orobancheae is about two times older.

Development of 14 microsatellite markers in Odontites vernus s.l. (Orobanchaceae) and cross-amplification in related taxa

PREMISE OF THE STUDY

Microsatellite primers were developed for the first time in the root hemiparasite herb Odontites vernus (Orobanchaceae). These markers will be useful to investigate the role of polyploidization in the evolution of this diploid-tetraploid complex, as well as the extent of gene flow between different ploidy levels.

METHODS AND RESULTS

Fourteen polymorphic and reproducible loci were identified and optimized from O. vernus using a microsatellite-enriched library and 454 Junior sequencing. The set of primers amplified di- to pentanucleotide repeats and showed two to 13 alleles per locus. Transferability was tested in 30 taxa (19 belonging to Odontites and 11 from eight other genera of Orobanchaceae tribe Rhinantheae).

CONCLUSIONS

The results indicate the utility of the newly developed microsatellites in O. vernus and several other species, which will be useful for taxon delimitation and conservation genetics studies.

Broomrape Weeds. Underground Mechanisms of Parasitism and Associated Strategies for their Control: A Review

Broomrapes are plant-parasitic weeds which constitute one of the most difficult-to-control of all biotic constraints that affect crops in Mediterranean, central and eastern Europe, and Asia. Due to their physical and metabolic overlap with the crop, their underground parasitism, their achlorophyllous nature, and hardly destructible seed bank, broomrape weeds are usually not controlled by management strategies designed for non-parasitic weeds. Instead, broomrapes are in current state of intensification and spread due to lack of broomrape-specific control programs, unconscious introduction to new areas and may be decline of herbicide use and global warming to a lesser degree. We reviewed relevant facts about the biology and physiology of broomrape weeds and the major feasible control strategies. The points of vulnerability of some underground events, key for their parasitism such as crop-induced germination or haustorial development are reviewed as inhibition targets of the broomrape-crop association. Among the reviewed strategies are those aimed (1) to reduce broomrape seed bank viability, such as fumigation, herbigation, solarization and use of broomrape-specific pathogens; (2) diversion strategies to reduce the broomrape ability to timely detect the host such as those based on promotion of suicidal germination, on introduction of allelochemical interference, or on down-regulating host exudation of germination-inducing factors; (3) strategies to inhibit the capacity of the broomrape seedling to penetrate the crop and connect with the vascular system, such as biotic or abiotic inhibition of broomrape radicle growth and crop resistance to broomrape penetration either natural, genetically engineered or elicited by biotic- or abiotic-resistance-inducing agents; and (4) strategies acting once broomrape seedling has bridged its vascular system with that of the host, aimed to impede or to endure the parasitic sink such as those based on the delivery of herbicides via haustoria, use of resistant or tolerant varieties and implementation of cultural practices improving crop competitiveness.

Shifts in diversification rates linked to biogeographic movement into new areas: An example of a recent radiation in the Andes

PREMISE OF THE STUDY

Clade-specific bursts in diversification are often associated with the evolution of key innovations. However, in groups with no obvious morphological innovations, observed upticks in diversification rates have also been attributed to the colonization of a new geographic environment. In this study, we explore the systematics, diversification dynamics, and historical biogeography of the plant clade Rhinantheae in the Orobanchaceae, with a special focus on the Andean clade of the genus Bartsia.

METHODS

We sampled taxa from across Rhinantheae, including a representative sample of Andean Bartsia species. Using standard phylogenetic methods, we reconstructed evolutionary relationships, inferred divergence times among the clades of Rhinantheae, elucidated their biogeographic history, and investigated diversification dynamics.

KEY RESULTS

We confirmed that the South American Bartsia species form a highly supported monophyletic group. The median crown age of Rhinantheae was determined to be ca. 30 Myr, and Europe played an important role in the biogeographic history of the lineages. South America was first reconstructed in the biogeographic analyses around 9 Myr ago, and with a median age of 2.59 Myr, this clade shows a significant uptick in diversification.

CONCLUSIONS

Increased net diversification of the South American clade corresponds to biogeographic movement into the New World. This movement happened at a time when the Andes were reaching the necessary elevation to host an alpine environment. Although a specific route could not be identified with certainty, we provide plausible hypotheses to how the group colonized the New World.

Towards a comprehensive phylogeny of the large temperate genus Pedicularis (Orobanchaceae), with an emphasis on species from the Himalaya-Hengduan Mountains

BACKGROUND

Striking interspecific variations in floral traits of the large temperate genus Pedicularis have given rise to controversies concerning infra-generic classifications. To date, phylogenetic relationships within the genus have not been well resolved. The main goal of this study is to construct a backbone phylogeny of Pedicularis, with extensive sampling of species from the Himalaya-Hengduan Mountains. Phylogenetic analyses included 257 species, representing all 13 informal groups and 104 out of 130 series in the classification system of Tsoong, using sequences of the nuclear ribosomal internal transcribed spacer (nrITS) and three plastid regions (matK, rbcL and trnL-F). Bayesian inference and maximum likelihood methods were applied in separate and combined analyses of these datasets.

RESULTS

Thirteen major clades are resolved with strong support, although the backbone of the tree is poorly resolved. There is little consensus between the phylogenetic tree and Tsoong's classification of Pedicularis. Only two of the 13 groups (15.4 %), and 19 of the 56 series (33.9 %) with more than one sampled species were found to be strictly monophyletic. Most opposite-/whorled-leaved species fall into a single clade, i.e. clade 1, while alternate leaves species occur in the remaining 12 clades. Excluding the widespread P. verticillata in clade 1, species from Europe and North America fall into clades 6-8.

CONCLUSIONS

Our results suggest that combinations of morphological and geographic characters associated with strongly supported clades are needed to elucidate a comprehensive global phylogeny of Pedicularis. Alternate leaves are inferred to be plesiomorphic in Pedicularis, with multiple transitions to opposite/whorled phyllotaxy. Alternate-leaved species show high diversity in plant habit and floral forms. In the Himalaya-Hengduan Mountains, geographical barriers may have facilitated diversification of species with long corolla tubes, and the reproductive advantages of beakless galeas in opposite-/whorled-leaved species may boost speciation at high altitude.

Hydathode trichomes actively secreting water from leaves play a key role in the physiology and evolution of root-parasitic rhinanthoid Orobanchaceae

BACKGROUND AND AIMS

Root hemiparasites from the rhinanthoid clade of Orobanchaceae possess metabolically active glandular trichomes that have been suggested to function as hydathode trichomes actively secreting water, a process that may facilitate resource acquisition from the host plant's root xylem. However, no direct evidence relating the trichomes to water secretion exists, and carbon budgets associated with this energy-demanding process have not been determined.

METHODS

Macro- and microscopic observations of the leaves of hemiparasitic Rhinanthus alectorolophus were conducted and night-time gas exchange was measured. Correlations were examined among the intensity of guttation, respiration and transpiration, and analysis of these correlations allowed the carbon budget of the trichome activity to be quantified. We examined the intensity of guttation, respiration and transpiration, correlations among which indicate active water secretion.

KEY RESULTS

Guttation was observed on the leaves of 50 % of the young, non-flowering plants that were examined, and microscopic observations revealed water secretion from the glandular trichomes present on the abaxial leaf side. Night-time rates of respiration and transpiration and the presence of guttation drops were positively correlated, which is a clear indicator of hydathode trichome activity. Subsequent physiological measurements on older, flowering plants indicated neither intense guttation nor the presence of correlations, which suggests that the peak activity of hydathodes is in the juvenile stage.

CONCLUSIONS

This study provides the first unequivocal evidence for the physiological role of the hydathode trichomes in active water secretion in the rhinanthoid Orobanchaceae. Depending on the concentration of organic elements calculated to be in the host xylem sap, the direct effect of water secretion on carbon balance ranges from close to neutral to positive. However, it is likely to be positive in the xylem-only feeding holoparasites of the genus Lathraea, which is closely related to Rhinanthus. Thus, water secretion by the hydathodes might be viewed as a physiological pre-adaptation in the evolution of holoparasitism in the rhinanthoid lineage of Orobanchaceae.

Planteose as a storage carbohydrate required for early stage of germination of Orobanche minor and its metabolism as a possible target for selective control

Root parasitic weeds in Orobanchaceae cause serious damage to worldwide agriculture. Germination of the parasites requires host-derived germination stimulants, such as strigolactones, as indicators of host roots within reach of the parasite's radicles. This unique germination process was focused on to identify metabolic pathways required for germination, and to design a selective control strategy. A metabolomic analysis of germinating seeds of clover broomrape, Orobanche minor, was conducted to identify its distinctive metabolites. Consequently, a galactosyl-sucrose trisaccharide, planteose (α-d-galactopyranosyl-(1→6)-β-d-fructofuranosyl-(2→1)-α-d-glucopyranoside), was identified as a metabolite that decreased promptly after reception of the germination stimulant. To investigate the importance of planteose metabolism, the effects of several glycosidase inhibitors were examined, and nojirimycin bisulfite (NJ) was found to alter the sugar metabolism and to selectively inhibit the germination of O. minor. Planteose consumption was similar in NJ-treated seeds and non-treated germinating seeds; however, NJ-treated seeds showed lower consumption of sucrose, a possible intermediate of planteose metabolism, resulting in significantly less glucose and fructose. This inhibitory effect was recovered by adding glucose. These results suggest that planteose is a storage carbohydrate required for early stage of germination of O. minor, and NJ inhibits germination by blocking the supply of essential glucose from planteose and sucrose. Additionally, NJ selectively inhibited radicle elongation of germinated seeds of Orobanchaceae plants (Striga hermonthica and Phtheirospermum japonicum). Thus, NJ will be a promising tool to develop specific herbicides to the parasites, especially broomrapes, and to improve our understanding of the molecular mechanisms of this unique germination.

Comparative transcriptome analyses reveal core parasitism genes and suggest gene duplication and repurposing as sources of structural novelty

The origin of novel traits is recognized as an important process underlying many major evolutionary radiations. We studied the genetic basis for the evolution of haustoria, the novel feeding organs of parasitic flowering plants, using comparative transcriptome sequencing in three species of Orobanchaceae. Around 180 genes are upregulated during haustorial development following host attachment in at least two species, and these are enriched in proteases, cell wall modifying enzymes, and extracellular secretion proteins. Additionally, about 100 shared genes are upregulated in response to haustorium inducing factors prior to host attachment. Collectively, we refer to these newly identified genes as putative “parasitism genes.” Most of these parasitism genes are derived from gene duplications in a common ancestor of Orobanchaceae and Mimulus guttatus, a related nonparasitic plant. Additionally, the signature of relaxed purifying selection and/or adaptive evolution at specific sites was detected in many haustorial genes, and may play an important role in parasite evolution. Comparative analysis of gene expression patterns in parasitic and nonparasitic angiosperms suggests that parasitism genes are derived primarily from root and floral tissues, but with some genes co-opted from other tissues. Gene duplication, often taking place in a nonparasitic ancestor of Orobanchaceae, followed by regulatory neofunctionalization, was an important process in the origin of parasitic haustoria.

Polar compounds from Parentucellia viscosa (L.) Caruel from Sardinia

In this work, we examined a sample of Parentucellia viscosa from Sardinia island, showing similarities and differences of the secondary metabolite content with respect to previous study conducted on an accession of continental origin, and also with Bellardia trixago, a species very close to Parentucellia. In this aspect, the proximity between these species, previously stated by a phylogenetic study, was confirmed by a phytochemical approach. Within the non-iridoidic fraction a chiral polyol (mannitol) and two aromatic acids (benzoic acid and gallic acid) were evidenced. These two acids are not common in Scropulariaceae since they have been reported only from a few species, and it is worth to note that gallic acid was never reported from the Orobanchaceae family.