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.".

Arceuthobium Species (Viscaceae) Parasitizing an Angiosperm: The Unique Case of A. azoricum in the Azores Islands.

Arceuthobium azoricum Wiens & Hawksw. is a rare Azorean endemic epiphytic hemiparasite (mistletoe), which typically parasitizes branches of the gymnosperm Juniperus brevifolia (Hochst. ex Seub.) Antoine (Cupressaceae), which is also an Azorean endemic. Here, we describe a population of A. azoricum, on Pico Island, parasitizing Erica azorica Hochst. ex Seub. (Ericaceae), which is also an Azorean endemic. Our molecular analysis (using nuclear ribosomal internal transcribed spacer) showed no differences between individuals parasitizing Erica and Juniperus species. Moreover, a preliminary analysis showed no differences in morphological characteristics between accessions sampled from different hosts. Given that this is the first bona fide record of Arceuthobium sp. parasitizing an angiosperm, this population represents a unique host-shifting event, and its conservation is important because it may allow new insights into host recognition mechanisms in mistletoes. Immediate attention should be given to characterizing this Pico Island population using appropriate molecular methods and additional morphological analyses.

Phytochemical Analysis and Biological Activities of Ripe Fruits of Mistletoe (Psittacanthus calyculatus).

Psittacanthus calyculatus is a hemiparasitic plant of an arboreal species (e.g., forest, fruit trees). Its foliage has therapeutic potential; however, little is known about its fruits. In this study, the phytochemical profile and biological activities of P. calyculatus fruits hosted by Prosopis laevigata and Quercus deserticola were evaluated. The fruits of P. calyculatus from P. laevigata showed the highest content of total phenols (71.396 ± 0.676 mg GAE/g DW). The highest content of flavonoids and anthocyanins was presented in those from Q. deserticola (14.232 ± 0.772 mg QE/g DW; 2.431 ± 0.020 mg C3GE/g DW). The anthocyanin cyanidin-3-glucoside was detected and quantified via high-performance thin-layer chromatography (HPTLC) (306.682 ± 11.804 mg C3GE/g DW). Acidified extracts from host P. laevigata showed the highest antioxidant activity via ABTS•+ (2,2'azinobis-(3-ethylbenzothiazdin-6-sulfonic acid) (214.810 ± 0.0802 mg TE/g DW). Fruit extracts with absolute ethanol from the P. laevigata host showed the highest antihypertensive activity (92 ± 3.054% inhibition of an angiotensin converting enzyme (ACE)). Fruit extracts from both hosts showed a minimum inhibitory concentration (MIC) of 6.25 mg/mL and a minimum bactericidal concentration (MBC) of 12.5 mg/mL against Escherichia coli, Salmonella choleraesuis and Shigella flexneri. Interestingly, a significant host effect was found. P. calyculatus fruits extract could be used therapeutically. However, further confirmation experiments should be carried out.

Host root exudates initiate a foraging preference by the root parasite Santalum album.

Haustoria of root-parasitic plants draw nutrients from the roots of host species. While recent studies have assessed host preferences of parasitic plants, how root-exuded chemicals can mediate host tropism and selection by root-parasitic plants is poorly understood. Under greenhouse conditions, we performed two pot experiments to determine whether the root parasite Santalum album selectively forages for superior hosts (N2-fixing Acacia confusa Merr. or Dalbergia odorifera T. Chen) rather than for inferior hosts (non-N2-fixing Bischofia polycarpa (levl.) Airy Shaw or Dracontomelon duperreranum Pierre), and whether S. album uses host root exudates and/or specific chemicals in these root exudates to locate and trigger haustorium formation. Lateral roots and haustoria of S. album seedlings exhibited greater growth in the direction of D. odorifera roots than toward roots from the other three hosts. Comparative metabolic analysis revealed that D. odorifera root exudates were enriched in isoflavonoid, flavonoid and flavone/flavonol biosynthesis pathways, and that the relative contents of flavonoids were significantly greater in the root exudates of D. odorifera than in those of the other three hosts. Root exudates from D. odorifera significantly promoted S. album root growth, haustorium formation and reactive oxygen species accumulation in haustoria. Our results demonstrate that the key step in plant parasitism by S. album is based on root exudation by a host plant; the exudates function as a metabolite signal that activate lateral root growth and haustorium formation. Our results also indicate that flavonoids in the root exudates could play an important role in S. album foraging activity. Information on the responses of root parasites to host root exudates and/or haustorium-inducing chemicals may be useful for selecting superior host species to plant with valuable species of root parasites.

Root hemiparasitic plants are associated with more even communities across North America.

Root hemiparasitic plants both compete with and extract resources from host plants. By reducing the abundance of dominant plants and releasing subordinates from competitive exclusion, they can have an outsized impact on plant communities. Most research on the ecological role of hemiparasites is manipulative and focuses on a small number of hemiparasitic taxa. Here, we ask whether patterns in natural plant communities match the expectation that hemiparasites affect the structure of plant communities. Our data were collected on 129 national park units spanning the continental United States. The most common hemiparasite genera were Pedicularis, Castilleja, Krameria, and Comandra. We used null models and linear mixed models to determine whether hemiparasites were associated with changes in community richness and evenness. Hemiparasite presence did not affect community metrics. Hemiparasite abundance was positively associated with increasing evenness of herbaceous species, but not with species richness. The associations that we observed on a continental scale are consistent with evidence that the impacts of root hemiparasitic plants on evenness can be substantial and abundance dependent but that effects on richness are less pronounced. Hemiparasites mediate competitive exclusion in communities to facilitate species coexistence and merit consideration of inclusion in ecological theories of coexistence.

Transcriptome Profiling of a Common Mistletoe Species Parasitizing Four Typical Host Species in Urban Southwest China.

Comparing gene expressions among parasitic plants infecting different host species can have significant implications for understanding host-parasite interactions. Taxillus nigrans is a common hemiparasitic species in Southwest China that parasitizes a variety of host species. However, a lack of nucleotide sequence data to date has hindered transcriptome-level research on T. nigrans. In this study, the transcriptomes of T. nigrans individuals parasitizing four typical host species (Broussonetia papyrifera (Bpap), a broad-leaved tree species; Cryptomeria fortunei (Cfor), a coniferous tree species; Cinnamomum septentrionale (Csep), an evergreen tree species; and Ginkgo biloba (Gbil), a deciduous-coniferous tree species) were sequenced, and the expression profiles and metabolic pathways were compared among hosts. A total of greater than 400 million reads were generated in nine cDNA libraries. These were de novo assembled into 293823 transcripts with an N50 value of 1790 bp. A large number of differentially expressed genes (DEGs) were identified when comparing T. nigrans individuals on different host species: Bpap vs. Cfor (1253 DEGs), Bpap vs. Csep (864), Bpap vs. Gbil (517), Cfor vs. Csep (259), Cfor vs. Gbil (95), and Csep vs. Gbil (40). Four hundred and fifteen unigenes were common to all six pairwise comparisons; these were primarily associated with Cytochrome P450 and environmental adaptation, as determined in a KEGG enrichment analysis. Unique unigenes were also identified, specific to Bpap vs. Cfor (808 unigenes), Bpap vs. Csep (329 unigenes), Bpap vs. Gbil (87 unigenes), Cfor vs. Csep (108 unigenes), Cfor vs. Gbil (32 unigenes), and Csep vs. Gbil comparisons (23 unigenes); partial unigenes were associated with the metabolism of terpenoids and polyketides regarding plant hormone signal transduction. Weighted gene co-expression network analysis (WGCNA) revealed four modules that were associated with the hosts. These results provide a foundation for further exploration of the detailed molecular mechanisms involved in plant parasitism.

Advances on the Visualization of the Internal Structures of the European Mistletoe: 3D Reconstruction Using Microtomography.

The European mistletoe (Viscum album) is a dioecious epiphytic evergreen hemiparasite that develops an extensive endophyte enabling the absorption of water and mineral salts from the host tree, whereas the exophytic leaves are photosynthetically active. The attachment mode and host penetration are well studied, but little information is available about the effects of mistletoe age and sex on haustorium-host interactions. We harvested 130 plants of Viscum album ssp. album growing on host branches of Aesculus flava for morphological and anatomical investigations. Morphometric analyses of the mistletoe and the (hypertrophied) host interaction site were correlated with mistletoe age and sex. We recorded the morphology of the endophytic systems of various ages by using X-ray microtomography scans and corresponding stereomicroscopic images. For detailed anatomical studies, we examined thin stained sections of the mistletoe-host interface by light microscopy. The diameter and length of the branch hypertrophy showed a positive linear correlation with the age of the mistletoe. Correlations with their sex were only found for ratios between host branch and hypertrophy size. A female bias of about 76% was found. In a 4-year-old mistletoe, several small, almost equally sized sinkers and the connected cortical strands extend over more than 5 cm within the host branch. In older mistletoes, one main sinker was predominant and occupied an increasingly large proportion of the stem cross-section. Bands of vessels ran along the axis of the wedge-shaped haustoria and sinkers and bent sideways toward the mistletoe-host interface. At the interface, the vascular elements of the host wood changed their direction and formed vortices near the haustorium.

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.

Changes in Antioxidative Compounds and Enzymes in Small-Leaved Linden (Tilia cordata Mill.) in Response to Mistletoe (Viscum album L.) Infestation.

Mistletoe infestation leads to a decrease in the growth of woody plants, their longevity, and partial or complete drying of the top, as well as premature death. Various environmental stress factors, both abiotic and biotic, stimulate the formation of reactive oxygen species and the development of oxidative stress in plant tissues. This study aimed to investigate the effect of mistletoe (Viscum album L.) infestation on the response of the antioxidative defense system in leaves of small-leaved linden (Tilia cordata Mill.). Leaves from infested trees were taken from branches (i) without mistletoe, (ii) with 1-2 mistletoe bushes (low degree of infestation), and (iii) with 5-7 mistletoe bushes (high degree of infestation). The relative water content and the chlorophyll a and b contents in leaves from linden branches affected by mistletoe were significantly lower than those in leaves from non-infested trees and from host-tree branches with no mistletoe. At the same time, leaves from branches with low and high degrees of infestation had significantly higher electrolyte leakage, malondialdehyde and hydrogen peroxide content, oxidized forms of ascorbic acid (dehydroascorbic and 2,3-diketogulonic acids), and oxidized glutathione. The results of principal component analysis show that the development of oxidative stress was accompanied by an increase in proline content and in superoxide dismutase, ascorbate peroxidase, glutathione peroxidase, and glutathione reductase activity. Several biochemical parameters (proline, ascorbic acid, dehydroascorbic acid, glutathione, glutathione peroxidase, ascorbate peroxidase, and dehydroascorbate reductase) were found to be altered in leaves from host-tree branches with no mistletoe. This result indicates that the mistletoe infestation of trees not only causes local changes in the locations of hemiparasite attachment, but also affects the redox metabolism in leaves from other parts of the infested tree.

Dynamics of Polyphenol Biosynthesis by Calli Cultures, Suspension Cultures and Wild Specimens of the Medicinal Plant Ligaria cuneifolia (Ruiz & Pav.) Tiegh. (Loranthaceae). Analysis of Their Biological Activity.

Ligaria cuneifolia (R. et P.) Tiegh. (Loranthaceae) is a South American hemiparasitic species with antioxidant, antitumoral, antimicrobial, and antilipidemic activities attributed to its polyphenolic content. We studied the polyphenolic pattern of L. cuneifolia during different phenological stages: flowering, fruiting, and post-fruiting. The highest total phenolic content was found in stems at post-fruiting (214 ± 12.1 mg gallic acid eq·g-1 DW) and fruiting (209 ± 13.7 mg gallic acid eq·g-1 DW), followed by post-fruiting leaves (207 ± 17.5 mg gallic acid eq·g-1 DW). Flavonoids accumulated at higher levels in leaves and hydroxycinnamic acids in leaves at flowering and post-fruiting. The polyphenolic pattern was similar between organs from wild plants and in vitro cultures, although at a significantly lower level in the latter ones. The performance of calli growing under a 16 h photoperiod in a modified White medium with 1-naphthalene acetic acid (2.50 µM) and Kinetin (9.20 µM) was better than in the dark. When calli grew in media only with auxins (IAA, NAA, and 2,4-D, all at 2.50 µM concentration), its growth and polyphenolic content improved. Cell suspensions with 2.50 µM NAA and 9.20 µM KIN grew slowly and produced very small amounts of polyphenols. As for the antioxidant activity, it was detected in all samples (approximately 1000 µmol trolox eq·g-1 DW) except fruits, where a lower value was found (328 µmol trolox eq·g-1 DW). In vitro cultures have the lowest antioxidant activity when compared to methanolic extracts from organs of wild specimens. Finally, antimutagenic or mutagenic activity in wild plants and in vitro culture extracts was not detected by the Ames test.

Plastid NDH Pseudogenization and Gene Loss in a Recently Derived Lineage from the Largest Hemiparasitic Plant Genus Pedicularis (Orobanchaceae).

The plastid genome (plastome) is highly conserved in both gene order and content and has a lower mutation rate than the nuclear genome. However, the plastome is more variable in heterotrophic plants. To date, most such studies have investigated just a few species or only holoheterotrophic groups, and few have examined plastome evolution in recently derived lineages at an early stage of transition from autotrophy to heterotrophy. In this study, we investigated the evolutionary dynamics of plastomes in the monophyletic and recently derived Pedicularis sect. Cyathophora (Orobanchaceae). We obtained 22 new plastomes, 13 from the six recognized species of section Cyathophora, six from hemiparasitic relatives and three from autotrophic relatives. Comparative analyses of gene content, plastome structure and selection pressure showed dramatic differences among species in section Cyathophora and in Pedicularis as a whole. In comparison with autotrophic relatives and other Pedicularis spp., we found that the inverted repeat (IR) region in section Cyathophora had expansions to the small single-copy region, with a large expansion event and two independent contraction events. Moreover, NA(D)H dehydrogenase, accD and ccsA have lost function multiple times, with the function of accD being replaced by nuclear copies of an accD-like gene in Pedicularis spp. The ccsA and ndhG genes may have evolved under selection in association with IR expansion/contraction events. This study is the first to report high plastome variation in a recently derived lineage of hemiparasitic plants and therefore provides evidence for plastome evolution in the transition from autotrophy to heterotrophy.

The complete chloroplast genome of Scurrula chingii (W.C. Cheng) H.S. Kiu (Loranthaceae), a hemiparasitic shrub.

Scurrula chingii (W.C. Cheng) H.S. Kiu is a stem hemiparasite of the genus Scurrula in the family Loranthaceae distributed in southwest China and northern Vietnam. Here, we report and characterize the complete plastid genome sequence of S. chingii to provide genomic resources useful for the phylogenetic studies of Santalales. The plastome of S. chingii is 122,764 bp in length, consisted of a large single-copy region (70,726 bp), a small single-copy region (6,091 bp), and a pair of inverted repeat regions (22,974 bp). The GC content of the whole plastome is 37.2%. It contains 109 genes, including 69 CDS (protein-coding genes), eight rRNAs, and 32 tRNAs. The alignment of 14 species complete chloroplast genomes of Loranthaceae was implemented and a phylogenetic tree was constructed using maximum-likelihood (ML) method, which revealed that S. chingii clustered with Scurrula parasitica and Taxillus thibetensis as a monophyletic group.

Integrated analyses of the transcriptome and small RNA of the hemiparasitic plant Monochasma savatieri before and after establishment of parasite-host association.

BACKGROUND: Monochasma savatieri is a medicinal root hemiparasitic herb that extracts water and nutrients from the host plant via a haustorium. M. savatieri exhibits an enhanced growth after the establishment of parasite-host associations, but little is known about the molecular mechanism responsible. In this study, endogenous hormones, RNA sequencing and small RNA sequencing analysis were performed on M. savatieri before and after establishment of parasite-host associations. RESULTS: When grown with the host, decreased contents of jasmonic acid (JA) and indole-3-acetic acid (IAA) and increased abscisic acid (ABA) content were observed in M. savatieri with the established parasitic relationship. When grown with the host, 46,424 differentially expressed genes (DEGs) and 162 differentially expressed miRNAs (DEmiRs) were identified in the comparison between M. savatieri with the established parasitic relationship and without the established parasitic relationship. Analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that these DEGs and targets of DEmiRs mostly participated in plant hormone signal transduction, starch and sucrose metabolism, carbohydrate metabolism, cell growth and death, and transport and catabolism. Furthermore, correlation analysis of mRNA and miRNA revealed that 10 miRNA-target pairs from novel_mir65, novel_mir40, novel_mir80, miR397-5p_1, novel_mir36, novel_mir25 and novel_mir17 may have important roles in regulating the parasitic development of M. savatieri. CONCLUSIONS: Our study not only expands the understanding of enhanced growth in M. savatieri after the establishment of parasite-host associations, but also first provides abundant resources for future molecular and genetic studies in M. savatieri.

The combined effects of water and nitrogen on the relationship between a native hemiparasite and its invasive host.

Stem hemiparasites are dependent on their hosts for water and nitrogen. Most studies, however, have assessed the influence of one factor on parasite : host associations, thus limiting our mechanistic understanding of their performance in nature. We investigated the combined effects of water and nitrogen (N) availability on both a host (Ulex europaeus) and its parasite (Cassytha pubescens). Parasite infection significantly decreased host shoot biomass and shoot : root ratio more severely in high water than low water, irrespective of N supply. Parasite stem [N] was significantly higher in high water than low water treatments, regardless of N supply, but parasite biomass did not vary among treatments. Irrespective of water and N supply, infected plants had significantly lower total, root and nodule biomass, predawn and midday quantum yields, maximum electron transport rates, water potentials and nitrogen concentration [N]. Parasite δ13 C was significantly higher than that of the host. Our results suggested that stem hemiparasites can better extract resources from hosts when water availability is high, resulting in a greater impact on the host under these conditions. When hemiparasitic plants are being investigated as a biocontrol for invasive weeds, they may be more effective in wetter habitats than in drier ones.

Does Epichloë Endophyte Enhance Host Tolerance to Root Hemiparasite?

Epichloë endophytes have been shown to be mutualistic symbionts of cool-season grasses under most environmental conditions. Although pairwise interactions between hemiparasites and their hosts are heavily affected by host-associated symbiotic microorganisms, little attention has been paid to the effects of microbe-plant interactions, particularly endophytic symbiosis, in studies examining the effects of parasitic plants on host performance. In this study, we performed a greenhouse experiment to examine the effects of hereditary Epichloë endophyte symbiosis on the growth of two host grasses (Stipa purpurea and Elymus tangutorum) in the presence or absence of a facultative root hemiparasite (Pedicularis kansuensis Maxim). We observed parasitism of both hosts by P. kansuensis: when grown with a host plant, the hemiparasite decreased the performance of the host while improving its own biomass and survival rate of the hemiparasite. Parasitized endophyte-infected S. purpurea plants had higher biomass, tillers, root:shoot ratio, and photosynthetic parameters and a lower number of functional haustoria than the endophyte-free S. purpurea conspecifics. By contrast, parasitized endophyte-infected E. tangutorum had a lower biomass, root:shoot ratio, and photosynthetic parameters and a higher number of haustoria and functional haustoria than their endophyte-free counterparts. Our results reveal that the interactions between the endophytes and the host grasses are context dependent and that plant-plant interactions can strongly affect their mutualistic interactions. Endophytes originating from S. purpurea alleviate the host biomass reduction by P. kansuensis and growth depression in the hemiparasite. These findings shed new light on using grass-endophyte symbionts as biocontrol methods for the effective and sustainable management of this weedy hemiparasite.

The ecophysiology of a neotropical mistletoe depends on the leaf phenology of its tree hosts.

PREMISE: Mistletoes parasitize many hardwood and softwood tree species; however, they play key roles in forest ecosystems. Adult individuals of Psittacanthus schiedeanus take up water and xylem nutrients from both deciduous and evergreen host trees, suggesting the ability to modify its physiology according to the availability of host resources. Yet, there is little information regarding the effects of mistletoes on their host trees from the eophyll stage to reproductive phases of the parasite. METHODS: Taking advantage of the fact that P. schiedeanus can reach sexual maturity in 1 year, we investigated its physiological performance during development on deciduous (Liquidambar styraciflua) and evergreen (Quercus germana) host trees in a cloud forest in eastern Mexico. Variables related to chlorophyll fluorescence, carbon assimilation, photosynthetic pigments, and nitrogen, phosphorus, and carbon contents of the parasite and non-infected and infected hosts were analyzed in a nursery experiment. RESULTS: Mistletoe had lower water-use efficiency and higher transpiration rates than the host species did. Despite the fact that P. schiedeanus obtained resources from species with differing phenology and resource availability, the parasite steadily improved its CO2 assimilation, electron transport rate, and nutrient content from seedling establishment to adult life stages. Mistletoe decreased the photosynthetic reactions of carbon metabolism in the deciduous host, photosynthetic light reactions in the evergreen host, and nutritional status of both host species, mostly in the evergreen host. CONCLUSIONS: The hypothesis that mistletoes adjust their physiology according to the availability of host resources could extend to the early growth of the parasite.

The changes of morphological and physiological characteristics in hemiparasitic Monochasma savatieri before and after attachment to the host plant.

BACKGROUND: Monochasma savatieri is an endangered hemiparasitic medicinal plant with a variety of antioxidant, antimicrobial and anti-inflammatory properties. Despite the urgent need to understand the parasitic biology of M. savatieri, parasite-host associations have long been neglected in studies of M. savatieri. METHODS: We conducted a pot cultivation experiment to analyze changes in the growth traits, physiological performance and anatomical structures of M. savatieri grown with the potential host Gardenia jasminoides E., before and after the establishment of the parasite-host association. RESULTS: Prior to the establishment of the parasite-host association, the presence of the host had no significant effect on the maximum root length, leaf indexes or total dry weight of M. savatieri seedlings, but had significant positive effect on seedling height, number of roots or number of haustoria. When it was continuously grown without a host, M. savatieri growth was rather slow. The establishment of the parasite-host association enhanced the growth of M. savatieri, and higher levels of photosynthetic pigments, increased antioxidant enzyme activity and lower malondialdehyde accumulation were observed in M. savatieri with an established parasite-host association. Furthermore, an analysis of the anatomical structures of M. savatieri showed that the establishment of the parasite-host association enabled better development of the seedling vegetative organs than that in seedlings without parasite-host associations. CONCLUSIONS: Our study demonstrates the physiological and anatomical changes that occurred in M. savatieri after connection with a host and suggests that the enhanced growth and development of M. savatieri were highly dependent on the parasite-host association.

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.

Characterization of the complete plastome of Dendrophthoe pentandra (Loranthaceae), a stem hemiparasite.

Dendrophthoe pentandra (Linnaeus) Miquel (Loranthaceae) is a stem hemiparasite distributed in southwest China and Indochina. Here, we present the first complete plastome of the plant. The plastome is 115,721 bp in length, and encodes 92 unique genes, including 63 protein-encoding gens, 4 rRNAs, and 25 tRNAs. Phylogenetic analysis indicated that D. pentandra is close to Macrosolen cochinchensis (Loureiro) Tieghem and Helixanthera parasitica Loureiro.

The complete plastome of Taxillus vestitus (Loranthaceae), a hemiparasitic plant.

Taxillus vestitus (Wallich) Danser (Loranthaceae) is a stem hemiparasite occurring in southwest China and Himalayas. In this study, we report the first complete plastome of this species. The plastome is 122,200 bp in size, which encodes 94 unique genes (64 protein-encoding gens, 4 ribosomal RNAs, and 26 tRNAs). Compared to the plastomes of the autotrophic relatives, the T. vestitus plastome is significantly reduced. A total of 15 protein-coding genes, and 4 tRNAs were deleted from the plastome.