Cuscuta Species Research Articles

"Exploring therapeutic potential and toxicological profiles of Cuscuta species: insights from pharmacological studies and an anti-cholinergic toxicity report."

This study examines the therapeutic potential and toxicological profiles of Cuscuta species based on recent pharmacological investigations: "a therapeutic potential vs. toxicological risks of Cuscuta species: a pharmacological-toxicology dilemma." The study encompasses diverse research areas, including the mitigation of Bisphenol A (BPA)-induced ovarian damage using Cuscuta chinensis flavonoids (CCFs), acute and sub-acute toxicity assessments of Cuscuta chinensis Lam. water extract (CLW), and observations on Cuscuta campestris toxicity in horses. In addition, this scientific study discusses the interplant communication dynamics between soybean and the parasitic dodder (Cuscuta australis) under nutrient deficiency conditions. Key significant findings highlight the efficacy of CCFs in alleviating BPA-induced ovarian damage, the safety profile of CLW within specified doses, and clinical manifestations of C. campestris toxicity in horses. Moreover, insights into interplant communication mechanisms emphasise the significance of protein-mediated interactions in nutrient-deficient environments. The report illustrates the potential toxicity of Dodder in humans, and further research findings into its chemical composition and toxicological profiles reveal great data on its phytotoxicity. Greater awareness and understanding of the risks associated with consuming Dodder and other similar plant species are crucial for preventing plant intoxication and have been a significant major focus of the present toxicology study of Cuscuta species. Hence, by addressing these objectives, the scientific study aims to balance the therapeutic benefits of Cuscuta species with their potential toxicological risks, contributing to a more nuanced understanding of their role in pharmacology and toxicology. This dual focus is crucial for guiding future research and informing safe usage practices.

Comparative secretome analysis of Striga and Cuscuta species identifies candidate virulence factors for two evolutionarily independent parasitic plant lineages

BackgroundMany parasitic plants of the genera Striga and Cuscuta inflict huge agricultural damage worldwide. To form and maintain a connection with a host plant, parasitic plants deploy virulence factors (VFs) that interact with host biology. They possess a secretome that represents the complement of proteins secreted from cells and like other plant parasites such as fungi, bacteria or nematodes, some secreted proteins represent VFs crucial to successful host colonisation. Understanding the genome-wide complement of putative secreted proteins from parasitic plants, and their expression during host invasion, will advance understanding of virulence mechanisms used by parasitic plants to suppress/evade host immune responses and to establish and maintain a parasite-host interaction.ResultsWe conducted a comparative analysis of the secretomes of root (Striga spp.) and shoot (Cuscuta spp.) parasitic plants, to enable prediction of candidate VFs. Using orthogroup clustering and protein domain analyses we identified gene families/functional annotations common to both Striga and Cuscuta species that were not present in their closest non-parasitic relatives (e.g. strictosidine synthase like enzymes), or specific to either the Striga or Cuscuta secretomes. For example, Striga secretomes were strongly associated with ‘PAR1’ protein domains. These were rare in the Cuscuta secretomes but an abundance of ‘GMC oxidoreductase’ domains were found, that were not present in the Striga secretomes. We then conducted transcriptional profiling of genes encoding putatively secreted proteins for the most agriculturally damaging root parasitic weed of cereals, S. hermonthica. A significant portion of the Striga-specific secretome set was differentially expressed during parasitism, which we probed further to identify genes following a ‘wave-like’ expression pattern peaking in the early penetration stage of infection. We identified 39 genes encoding putative VFs with functions such as cell wall modification, immune suppression, protease, kinase, or peroxidase activities, that are excellent candidates for future functional studies.ConclusionsOur study represents a comprehensive secretome analysis among parasitic plants and revealed both similarities and differences in candidate VFs between Striga and Cuscuta species. This knowledge is crucial for the development of new management strategies and delaying the evolution of virulence in parasitic weeds.

Palynological studies of some species of the genus Cuscuta with emphasis on taxonomy

The main objective of this research was to conduct a comparative pollen morphological analysis of some representatives of the genus Cuscuta in relation to taxonomy. Investigations of 38 species and 1 variation revealed that not only the number, but the colpi length, as well as the exine ornamentation (at the SEM level), can be regarded as a diagnostic feature. For all the taxa studied, the common zonocolpate type of pollen was observed, represented by three variations: I) colpi long; II) colpi of medium length; III) colpi short. In combination with colpi length, variations in the number of colpi were also identified, such as: I) 3(4)-zonocolpate pollen grains with long colpi (in most of the species studied from subgenera Grammica and Cuscuta, as well as in C. monogyna from the subgenus Monogynella); II) 4(3)-zonocolpate pollen grains, with long colpi (C. cristata from subgenus Grammica); III) 3-zonocolpate pollen grains both with long colpi and colpi of medium length (C. abyssinica from subgenus Cuscuta and C. africana, C. angulata from subgenus Pachystigma); IV) 3-zonocolpate pollen grains with colpi of medium length were noted for species from all four subgenera (C. cassytoides, C. lupuliformis from subgenus Monogynella, C. kotschyana from subgenus Cuscuta, C. nitida from subgenus Pachystigma and C. jalapensis, C. rostrata, C. suaveolens from subgenus Grammica); V) 3–4- or 4-zonocolpate, with short colpi (C. lehmanniana and C. gigantea from subgenus Monogynella respectively); VI) 5–6-zonocolpate, with short colpi (C. reflexa from subgenus Monogynella). Using SEM, three main types of exine ornamentation were also identified: perforate, foveolate and reticulate. The last type in the vast majority of the cases was presented in combination with echinae (rarely with spines or granules). The data revealed that the presence of the significant similarity of palyno-morphological characteristics in representatives of the subgenera Cuscuta, Pachystigma and Grammica, with the exception of the species Lepidanche adpressa (syn. C. compacta), makes it difficult to create an identification key at the level of individual subgenera. Pollen features can be most clearly used only to distinguish the subgenus Monoginella, reflecting its certain isolation within the entire Cuscuta genus. The presence of a highly specialized reticulate exine ornamentation in Lepidanche adpressa (syn. C. compacta), not identified for the pollen of any of the studied taxa of the subgenus Grammica, indicates a significant proximity of this species to the subgenus Monogynella. For the species C. reflexa, the obtained palyno-morphological data are consistent with the previous opinion about the separation of this species, as well as its more advanced position within the genus Cuscuta.

Rising from the shadows: Selective foraging in model shoot parasitic plants.

Despite being sessile, plants nonetheless forage for resources by modulating their growth. Adaptative foraging in response to changes in resource availability and presence of neighbours has strong implications for performance and fitness. It is an even more pressing issue for parasitic plants, which draw resources directly from other plants. Indeed, parasitic plants were demonstrated over the years to direct their growth towards preferred hosts and invest resources in parasitism relative to host quality. In contrast to root parasites that rely mostly on chemical cues, some shoot parasites seem to profit from the ability to integrate different types of abiotic and biotic cues. While significant progress in this field has been made recently, there are still many open questions regarding the molecular perception and the integration of diverse signalling pathways under different ecological contexts. Addressing how different cues are integrated in parasitic plants will be important when unravelling variations in plant interaction pathways, and essential to predict the spread of parasites in natural and agricultural environments. In this review, we discuss this with a focus on Cuscuta species as an emerging parasitic model,and provide research perspectives based on the recent advances in the topic and plant-plant interactions in general.

Holoparasites Cuscuta platyloba and Cuscuta xanthochortos inhibit Staphylococcus aureus and biofilm: a metabolomics approach

IntroductionCuscuta platyloba Progel. and Cuscuta xanthochortos Mart. are holoparasites, which have been used to treat microbial infections, inflammation, and ulcers. Thus, the present study investigated the antibacterial and antibiofilm properties of these Cuscuta species, and applied metabolomics approaches to suggest the bioactive constituents. MethodsC. platyloba and C. xanthochortos were extracted by percolation to obtain the crude ethanol extract, and fractions by liquid-liquid extraction. These samples were evaluated against Staphylococcus aureus and Pseudomonas aeruginosa to determine bacterial growth and biofilm formation. The metabolomic profile was determined by liquid chromatography coupled to diode array detector and mass spectrometry (LC-DAD-MS), and statistical analysis (univariate and chemometrics) was applied to correlate the chemical compounds with antibacterial and antibiofilm activities. ResultsThe ethanol extracts were not active against S. aureus and P. aeruginosa. The ethyl acetate fractions were active against S. aureus and inhibited more than 74% of biofilm formation without changing the bacterial growth, while the dichloromethane fraction of C. platyloba inhibited approximately 94% of S. aureus biofilm formation and decreased the bacterial growth. Eighty-five compounds were annotated and the Pearson r correlation analysis showed mainly lignans, flavonoids, and phenylpropanoids positively correlated with the S. aureus antibiofilm activity. Additionally, iridoids and lignans were related to the antibacterial activity. ConclusionsC. platyloba and C. xanthochortos are natural sources of promising anti-S. aureus compounds, including flavonoids, phenylpropanoids, iridoids, and flavonoids.

Complete chloroplast genomes of five Cuscuta species and their evolutionary significance in the Cuscuta genus

BackgroundCuscuta, a parasitic plant species in the Convolvulaceae family, grows in many countries and regions. However, the relationship between some species is still unclear. Therefore, more studies are needed to assess the variation of the chloroplast (cp) genome in Cuscuta species and their relationship with subgenera or sections, thus, providing important information on the evolution of Cuscuta species.ResultsIn the present study, we identified the whole cp genomes of C. epithymum, C. europaea, C. gronovii, C. chinensis and C. japonica, and then constructed a phylogenetic tree of 23 Cuscuta species based on the complete genome sequences and protein-coding genes. The complete cp genome sequences of C. epithymum and C. europaea were 96,292 and 97,661 bp long, respectively, and lacked an inverted repeat region. Most cp genomes of Cuscuta spp. have tetragonal and circular structures except for C. epithymum, C. europaea, C. pedicellata and C. approximata. Based on the number of genes and the structure of cp genome and the patterns of gene reduction, we found that C. epithymum and C. europaea belonged to subgenus Cuscuta. Most of the cp genomes of the 23 Cuscuta species had single nucleotide repeats of A and T. The inverted repeat region boundaries among species were similar in the same subgenera. Several cp genes were lost. In addition, the numbers and types of the lost genes in the same subgenus were similar. Most of the lost genes were related to photosynthesis (ndh, rpo, psa, psb, pet, and rbcL), which could have gradually caused the plants to lose the ability to photosynthesize.ConclusionOur results enrich the data on cp. genomes of genus Cuscuta. This study provides new insights into understanding the phylogenetic relationships and variations in the cp genome of Cuscuta species.

Disruption of the standard kinetochore in holocentric Cuscuta species

The segregation of chromosomes depends on the centromere. Most species are monocentric, with the centromere restricted to a single region per chromosome. In some organisms, the monocentric organization changed to holocentric, in which the centromere activity is distributed over the entire chromosome length. However, the causes and consequences of this transition are poorly understood. Here, we show that the transition in the genus Cuscuta was associated with dramatic changes in the kinetochore, a protein complex that mediates the attachment of chromosomes to microtubules. We found that in holocentric Cuscuta species, the KNL2 genes were lost; the CENP-C, KNL1, and ZWINT1 genes were truncated; the centromeric localization of CENH3, CENP-C, KNL1, MIS12, and NDC80 proteins was disrupted; and the spindle assembly checkpoint (SAC) degenerated. Our results demonstrate that holocentric Cuscuta species lost the ability to form a standard kinetochore and do not employ SAC to control the attachment of microtubules to chromosomes.

Assembly, annotation, and comparative analysis of Ipomoea chloroplast genomes provide insights into the parasitic characteristics of Cuscuta species.

In the Convolvulaceae family, around 1650 species belonging to 60 genera are widely distributed globally, mainly in the tropical and subtropical regions of America and Asia. Although a series of chloroplast genomes in Convolvulaceae were reported and investigated, the evolutionary and genetic relationships among the chloroplast genomes of the Convolvulaceae family have not been extensively elucidated till now. In this study, we first reported the complete chloroplast genome sequence of Ipomoea pes-caprae, a widely distributed coastal plant with medical values. The chloroplast genome of I. pes-caprae is 161667 bp in length, and the GC content is 37.56%. The chloroplastic DNA molecule of I. pes-caprae is a circular structure composed of LSC (large-single-copy), SSC (small-single-copy), and IR (inverted repeat) regions, with the size of the three regions being 88210 bp, 12117 bp, and 30670 bp, respectively. The chloroplast genome of I. pes-caprae contains 141 genes, and 35 SSRs are identified in the chloroplast genome. Our research results provide important genomic information for the molecular phylogeny of I. pes-caprae. The Phylogenetic analysis of 28 Convolvulaceae chloroplast genomes showed that the relationship of I. pes-caprae with I. involucrata or I. obscura was much closer than that with other Convolvulaccae species. Further comparative analyses between the Ipomoea species and Cuscuta species revealed the mechanism underlying the formation of parasitic characteristics of Cuscuta species from the perspective of the chloroplast genome.

Pharmacological and phytochemicals potential of Cuscuta reflexa Roxb. as parasite and its some host plants: A review

Cuscuta reflexa Roxb. (Dodder) is a twinning angiospermic parasite on the various types of host plants but its loves to grow on spinous trees, shrubs and herbs. Stems and seeds of this plant are reported to have very high medicinal value. In vitro studies showed that antimicrobial compounds of this plant are effective in the treatment of several infectious diseases due to their selective toxicity and reported to have the ability to injure or kill or suppress an invading micro-organism without harming the cells of the host plants. Several studies on phytochemistry have also confirmed the presence of various types of phytochemicals in this plant such as alkaloids, flavonoids, tannins, phenolic compounds, steroids, carbohydrates, glycosides which have pharmacological values for biological activities such as antimicrobial, antibacterial, antifungal, antiulcer, antioxidant, anti-inflammatory and anticancerous activities. It also affects the behavior of pollinators, seed vectors and diversity of host plant. This magic plant also affects the economy of farmer due to spread into the crop field and growth and yield of agricultural crops. Soil quality of the field is also affected by Cuscuta sps. as it decreases the aerable surface, results in loss of quantitative and qualitative crop protection and represents a vector concerning the transmission of diseases through viruses and mycoplasmas to host plant. Its impact on the diversity determines the degradation of landscapes decoration aspect. Monitoring of Cuscuta sps. and their spreading tendencies and their prevention and therapy generates positive and immediate protection system of cultures. In many countries this genus has been targeted to control and quarantine measures are settled without ignoring the fact that some species of Cuscuta may be endangered or even threatened with extinction. Since this genus has tremendous pharmacological values present in phytochemicals extracted from these elite plants, therefore, it is an urgent need to preserve this plant by adopting appropriate techniques. In this direction plant tissue culture techniques may be a suitable approach not only to preserve this wonderful plant but also to evaluate its own pharmacological values and also of host plant. Another line of futuristic research might be to know its parasitic effect on pharmacological and phytochemicals potential of host plant and on Cuscuta itself.

Cuscuta species: Model organisms for haustorium development in stem holoparasitic plants.

Parasitic plants are notorious for causing serious agricultural losses in many countries. Specialized intrusive organs, haustoria, confer on parasitic plants the ability to acquire water and nutrients from their host plants. Investigating the mechanism involved in haustorium development not only reveals the fascinating mystery of how autotrophic plants evolved parasitism but also provides the foundation for developing more effective methods to control the agricultural damage caused by parasitic plants. Cuscuta species, also known as dodders, are one of the most well-known and widely spread stem holoparasitic plants. Although progress has been made recently in understanding the evolution and development of haustoria in root parasitic plants, more and more studies indicate that the behaviors between root and stem haustorium formation are distinct, and the mechanisms involved in the formation of these organs remain largely unknown. Unlike most endoparasites and root holoparasitic plants, which have high host-specificity and self- or kin-recognition to avoid forming haustoria on themselves or closely related species, auto-parasitism and hyper-parasitism are commonly observed among Cuscuta species. In this review, we summarize the current understanding of haustorium development in dodders and the unique characteristics of their parasitizing behaviors. We also outline the advantages of using Cuscuta species as model organisms for haustorium development in stem holoparasitic plants, the current unknown mysteries and limitations in the Cuscuta system, and potential future research directions to overcome these challenges.

Genetic identification of submersed dodder (Cuscuta: Convolvulaceae) in Texas, U.S.A.

Cuscuta plants that were observed growing entirely submersed and parasitizing the aquatic macrophyte Hygrophila polysperma in the San Marcos and Comal Rivers in Texas, are identified genetically as C. obtusiflora. This note documents the first molecular identification of any Cuscuta species naturally growing underwater or parasitizing a submersed aquatic plant.

Beneficial esthetic lightening effects of Cuscuta extract on skin darkness in healthy individuals: A clinical trial study.

Many biological activities and pharmacological usages have been revealed for the Cuscuta species. The present study aimed to assess the beneficial effects of Cuscuta on removing skin dark spots in healthy individuals, which is an important cosmetic concern, especially in women. This prospective, interventional before-after trial was conducted in 70 healthy individuals without any evidence of skin or systemic disorders who presented for consultation on removing skin darkening. The Cuscuta extract was prepared and then assessed for plant quality control and lack of microbial contamination. The content of melanin at baseline and at 1 and 3 months after intervention was assessed using Dermacatch, an accurate skin colorimetric measurement tool. Comparison of the melanin content of the lesions and treated area to the surrounding normal area at baseline and at 1 month after treatment showed a significant reduction in melanin content from 519.61 ± 45.09 to 498.50 ± 39.35 (P < 0.001). This reducing trend remained significant from the first month to the third month after treatment (from 498.50 ± 39.35 to 483.53 ± 40.99, P < 0.001). This decreasing trend was persistent even after adjusting baseline characteristics including gender, age, and duration of skin lesions. Both patients and investigators had high satisfaction level with the anti-melanogenesis effect of Cuscuta extract. Cuscuta extract is useful for removing hyperpigmented lesions and for skin lightening in healthy individuals.

The native stem holoparasitic Cuscuta japonica suppresses the invasive plant Ambrosia trifida and related mechanisms in different light conditions in northeast China.

Increasing evidence from low-latitude ranges has demonstrated that native parasitic plants are promising biocontrol agents for some major invasive weeds. However, related mechanisms and the effect of environments on the control effect of the parasite are still unclear. In addition, few related studies have been conducted in high latitude (>40°), where the exotic plant richness is the highest in the globe, but natural enemies are relatively scarce. During field surveys, a Cuscuta species was found on the cosmopolitan invasive weed Ambrosia trifida L. in Shenyang, northeast China. Here, we first studied the impacts of the parasite on the invader at three sites with different light regimes and related mechanisms, then the haustorial connections between the parasite and the invader using anatomy and measurement of carbon (C) and nitrogen (N) stable isotope compositions (δ13C, δ15N), and finally identified the parasite using two molecular marks. The parasite was identified as C. japonica Choisy. This native holoparasitic vine posed serious C rather than N limitation to the invader, explaining its greatly inhibitory effects on the invader. Its negative effects were stronger on reproductive relative to vegetative growth, and at high relative to low light habitats, which indicated that the higher the vigor of the host is, the higher the impact of the parasite pose. The parasite could establish haustorial connections with phloem, xylem, and pith of the invader and thus obtain resources from both leaves and roots, which was confirmed by difference of δ13C and δ15N between the two species. The parasite had significantly higher leaf C concentrations and δ13C than its invasive host, being a strong C sink of the parasitic association. Our results indicate that C. japonica may be a promising biological control agent for the noxious invader in China.

Regulatory Modules Involved in the Degradation and Modification of Host Cell Walls During Cuscuta campestris Invasion.

Haustoria of parasitic plants have evolved sophisticated traits to successfully infect host plants. The degradation and modification of host cell walls enable the haustorium to effectively invade host tissues. This study focused on two APETALA2/ETHYLENE RESPONSE FACTOR (ERF) genes and a set of the cell wall enzyme genes principally expressed during the haustorial invasion of Cuscuta campestris Yuncker. The orthogroups of the TF and cell wall enzyme genes have been implicated in the cell wall degradation and modification activities in the abscission of tomatoes, which are currently the phylogenetically closest non-parasitic model species of Cuscuta species. Although haustoria are generally thought to originate from root tissues, our results suggest that haustoria have further optimized invasion potential by recruiting regulatory modules from other biological processes.

Investigation on The Distribution of Cuscuta in Chengdu

Cuscuta is an annual parasitic herb in Convolvulaceae family Cuscuta. This project investigated the spread of cuscuta in 12 towns and 1 street that have 71 plots of the Chengdu, Tianfu New District by selecting a certain area of strip and circular plots, and proved the distribution pattern and growth situation of cuscuta in this area. The results showed that: (1) Cuscuta in this area 1 genus 2 species, respectively for Cuscuta chinensis and Cuscuta japonica, of which Cuscuta chinensis accounted for 80%, the Cuscuta japonica accounted for 20%; (2) The two cuscuta species parasitized 40 plants of 30 families, 37 genera in 14 sites, and three host plants of Magnoliaceae were found for the first time in this survey. (3) The parasitism of the cuscuta showed the following pattern: plot afforestation &gt; road afforestation &gt; park afforestation &gt; unmanaged wasteland, and the host plant species of plot afforestation was the largest, and the infection of road afforestation was the most serious. (4) Cuscuta for the parasitic environment sel-ection tends to high light intensity, air humidity about 80%, high plant density, more plant species conditions, in the selection of the parasitic site, is more likely to appear in the middle and upper region of the host plant. The results of this project can provide a theoretical reference for the studyof local landscape protection, and provide a theoretical basis for the development of local greening and tree cultivation.

(4Z)-Lachnophyllum Lactone, an Acetylenic Furanone from Conyza bonariensis, Identified for the First Time with Allelopathic Activity against Cuscuta campestris

Cuscuta species are obligate parasitic plants that infect the stems of a wide range of hosts including many crop and weed species causing severe agricultural problems. Using in vitro experiments to screen organic extracts prepared from fifteen autotrophic weed species found in agricultural fields infested with Cuscuta campestris, we have identified for the first time a strong phytotoxic activity in Conyza bonariensis extract against C. campestris. Additional pot experiments revealed that seven day-old Cuscuta seedlings had reduced capacity to coil and properly attach on Conyza plants, leading to reduced parasitic weed infection. Via activity-guided fractionation of Conyza extracts, we isolated and identified the acetylenic furanone (4Z)-lachnophyllum lactone as the major active component, with a concentration required to achieve reduction of 50% Cuscuta seedling growth (IC50) of 24.8 µg/mL. The discovery of (4Z)-lachnophyllum lactone bioactivity could aid the development of efficient and sustainable management strategies for C. campestris, whose control is limited or non-existent.

Heinz-resistant tomato cultivars exhibit a lignin-based resistance to field dodder (Cuscuta campestris) parasitism.

Cuscuta species (dodders) are agriculturally destructive, parasitic angiosperms. These parasitic plants use haustoria as physiological bridges to extract nutrients and water from hosts. Cuscuta campestris has a broad host range and wide geographical distribution. While some wild tomato relatives are resistant, cultivated tomatoes are generally susceptible to C. campestris infestations. However, some specific Heinz tomato (Solanum lycopersicum) hybrid cultivars exhibit resistance to dodders in the field, but their defense mechanism was previously unknown. Here, we discovered that the stem cortex in these resistant lines responds with local lignification upon C. campestris attachment, preventing parasite entry into the host. Lignin Induction Factor 1 (LIF1, an AP2-like transcription factor), SlMYB55, and Cuscuta R-gene for Lignin-based Resistance 1, a CC-NBS-LRR (CuRLR1) are identified as factors that confer host resistance by regulating lignification. SlWRKY16 is upregulated upon C. campestris infestation and potentially negatively regulates LIF1 function. Intriguingly, CuRLR1 may play a role in signaling or function as an intracellular receptor for receiving Cuscuta signals or effectors, thereby regulating lignification-based resistance. In summary, these four regulators control the lignin-based resistance response in specific Heinz tomato cultivars, preventing C. campestris from parasitizing resistant tomatoes. This discovery provides a foundation for investigating multilayer resistance against Cuscuta species and has potential for application in other essential crops attacked by parasitic plants.

Rare species of dodder (&lt;i&gt;Cuscuta&lt;/i&gt; L.; Convolvulaceae) in Quebec and a plea for their search in the wild

We report three rare dodders (Cuscuta L.) from Quebec: Buttonbush Dodder (Cuscuta cephalanthi Engelmann), Hazel Dodder (Cuscuta coryli Engelmann), and Smartweed Dodder (Cuscuta polygonorum Engelmann). Detailed descriptions of their morphological characteristics, ecology, and host range are discussed. The genus Cuscuta is severely under-collected in Quebec and elsewhere, and targetted fieldwork is needed to better assess the distribution and conservation status of the three rare (or overlooked) species reported here. An identification key to all Cuscuta species from Quebec is provided to aid botanists in accurately identifying these challenging species.

Mitochondrial genomes of two parasitic Cuscuta species lack clear evidence of horizontal gene transfer and retain unusually fragmented ccmFC genes

BackgroundThe intimate association between parasitic plants and their hosts favours the exchange of genetic material, potentially leading to horizontal gene transfer (HGT) between plants. With the recent publication of several parasitic plant nuclear genomes, there has been considerable focus on such non-sexual exchange of genes. To enhance the picture on HGT events in a widely distributed parasitic genus, Cuscuta (dodders), we assembled and analyzed the organellar genomes of two recently sequenced species, C. australis and C. campestris, making this the first account of complete mitochondrial genomes (mitogenomes) for this genus.ResultsThe mitogenomes are 265,696 and 275,898 bp in length and contain a typical set of mitochondrial genes, with 10 missing or pseudogenized genes often lost from angiosperm mitogenomes. Each mitogenome also possesses a structurally unusual ccmFC gene, which exhibits splitting of one exon and a shift to trans-splicing of its intron. Based on phylogenetic analysis of mitochondrial genes from across angiosperms and similarity-based searches, there is little to no indication of HGT into the Cuscuta mitogenomes. A few candidate regions for plastome-to-mitogenome transfer were identified, with one suggestive of possible HGT.ConclusionsThe lack of HGT is surprising given examples from the nuclear genomes, and may be due in part to the relatively small size of the Cuscuta mitogenomes, limiting the capacity to integrate foreign sequences.

Palynological characterization of the Southeast Asian woody climbers Decalobanthus Ooststr. (Convolvulaceae)

Decalobanthus is a genus of woody climbers of Convolvulaceae, recently expanded from a monotypic genus to including 17 species, mainly distributed in Asia and the Pacific. Despite the monophyly and the strong morphological and geographical coherence of the genus, only five of its species have been sampled in a molecular phylogenetic study and their relationships remain poorly understood. As a pillar to further systematic and evolutionary studies of Decalobanthus, this study offers a full characterisation of its pollen variation. To date, only seven of the 17 species have been palynologically documented in the literature (as Merremia s.l.). We here offer new data for seven species, which adding up to the already available data, totals a characterisation of 14 out of the 17 species in the genus. The pollen of Decalobanthus is, in most cases, tricolpate, with one species presenting hexapantocolpate polymorphism, which could suggest di/polyploidy; the presence of a reticulate exine (‘reticulum cristatum’ type) is remarkable, in Convolvulaceae only known otherwise in some species of Cuscuta.