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PubMed2000

Molecular, functional and ultrastructural characterisation of plastids from six species of the parasitic flowering plant genus Cuscuta.

Plastids of Cuscuta reflexa Roxb., C. subinclusa D. et H., C. gronovii Willd. and C. campestris Yunck. possess thylakoids and contain both chlorophyll a and b in a ratio similar to that of stem tissue of the systematically closely related but 'normal' green Ipomoea tricolor. In contrast, plastids of C. odorata R. et P. and C. grandiflora H.B.K. do not contain any chlorophyll or possess thylakoids. Light-driven electron transport, as measured by oxygen evolution and indicated by analysis of chlorophyll fluorescence, was present in all chlorophyll-containing species. The photosystem II efficiency was low and ranged from 0.511 to 0.687. The plastid rbcL gene could not be detected in C. odorata, but was present in all other tested species. Neither rbcL transcripts nor the large subunit of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) could be detected in C. odorata and C. grandiflora. Low amounts of the large subunit of Rubisco were detected immunologically in all other Cuscuta species. Apparently, the genus Cuscuta comprises species with different degrees of plastid functionality, ranging from intact chloroplasts, via plastids with impaired protein production and gene expression to plastids with reduced plastome gene content.

Blotting, Northern↗

PubMed2000

Developmental regulation of a gene coding for a low-molecular-weight heat shock protein during haustorium formation in the seedlings of a holoparasitic plant, Cuscuta japonica.

Dodder (Cuscuta japonica), a holoparasitic angiosperm, develops haustoria that are essential for parasitism. We have previously demonstrated that in Cuscuta seedlings, haustorial formation could be induced efficiently by cooperative effects of far-red light and tactile stimuli in the absence of any host plant [Tada et al. (1996) Plant Cell Physiol. 37: 1049]. In this study, we performed differential display and isolated several cDNAs that were expressed differentially during haustorium development in the seedlings. Sequence similarities identified one of them as a gene encoding a 17-kDa low-molecular-weight heat shock protein (CJHSP17). Northern blot analysis revealed that CJHSP17 mRNAs constitutively accumulated in the seedlings in the absence of environmental stress, and that the transcripts dramatically decreased to undetectable levels prior to emergence of haustoria upon irradiation with far-red light in the presence of tactile stimuli. When treated with either of the two stimuli, the CJHSP17 transcript levels did not decrease and there was no differentiation of haustoria. Moreover, irradiation of red light immediately after far-red light completely repressed both the decrease of mRNAs and the subsequent formation of haustoria. These observations suggest the involvement of down-regulation of CJHSP17 in haustorium development in Cuscuta seedlings.

Amino Acid Sequence↗

PubMed1984

Phloem Unloading of Amino Acids at the Site of Attachment of Cuscuta europaea.

By washing out (14)C-solutes or (3)H-solutes in 0.5 mm CaSO(4) during a period of 5 to 6 hours, the release of amino acids by excised stem segments of broad bean (Vicia faba L. cv Witkiem) was studied. Three hours after pulse labeling with l-valine, l-asparagine, or alpha-aminoisobutyric acid (AIB), hollow stem segments were excised from the plant and incubated in a washout solution.In experiments with valine and asparagine, stem segments parasitized by Cuscuta europaea released a higher percentage of labeled solutes into the bathing medium than control segments. This can be ascribed to enhanced phloem unloading at the site of attachment of Cuscuta. At low temperature (0 degrees C) and after addition of p-chloromercuribenzene sulfonate to the bathing medium, parasitized segments did not release an enhanced percentage of labeled solutes, in comparison with control segments. These data suggest a metabolic control of the phenomenon of enhanced phloem unloading of amino acids. In experiments with AIB, an enhanced release of labeled solutes could not clearly be observed, but at the site of attachment of Cuscuta an accumulation of labeled solutes was measured. Accumulation of AIB in parenchyma cells, before the start of a washout experiment, will tend to obscure the phenomenon of enhanced phloem unloading.

Journal Article↗

PubMed2004

The rbcL genes of two Cuscuta species, C. gronovii and C. subinclusa, are transcribed by the nuclear-encoded plastid RNA polymerase (NEP).

Some species of the holoparasitic flowering plant genus Cuscuta, like C. reflexa, have retained a plastid genome that encodes photosynthesis-related gene products as well as the plastid-encoded RNA polymerase (PEP). In contrast, other species like C. gronovii and C. subinclusa have lost the rpo genes coding for the PEP subunits while photosynthetic genes have been retained. In order to ensure expression of the photosynthesis-related genes in the absence of PEP, a number of adaptations within the plastid genome were required that enable gene transcription mediated exclusively by the nuclear-encoded plastid RNA polymerase (NEP). In this study we analyzed promoter sequence conservation and transcription start sites of a typical PEP gene of non-parasitic plants, rbcL, which codes for the large subunit of ribulose bisphosphate carboxylase/oxygenase. We show that despite high sequence conservation of the coding region of rbcL among different Cuscuta species and tobacco, the 5' non-coding regions of C. gronovii and C. subinclusa have suffered extensive deletions encompassing the PEP promoter that is present in C. reflexa and tobacco. Primer-extension analyses enabled the identification of transcripts initiated at NEP promoter motifs in C. gronovii and C. subinclusa that are not detectable in the 5' non-coding region of C. reflexa.

Amino Acid Sequence↗

PubMed2003

Development of Cuscuta species on a partially incompatible host: induction of xylem transfer cells.

The growth of dodders, Cuscuta reflexa and Cuscuta japonica, on the partially incompatible host poinsettia ( Euphorbia pulcherrima) is studied. Poinsettia responds by bark growths to the formation of the dodder haustoria and prevents dodder from obtaining normal growth. The growth instead becomes extremely branched, coral-like, and dodder lacks the ability to form haustoria. After a period of coral-like growth, long shoots sprout, resembling the normal growth. These long shoots mark an ending phase for dodder, which dies shortly after without having flowered. During the coral-like growth phase, dodder develops transfer cells in the parenchyma cells bordering the vessels of the xylem in the shoot. The transfer cells have not been observed when dodder is grown on the compatible host Pelargonium zonale. A coral-like growth phase has also been observed at the establishing phase when dodder is grown in vitro on agar; later a more normal growth form takes over. In this coral phase, xylem transfer cells are also developed. The fluorochromes carboxyfluorescein and Texas Red were loaded into the host in the phloem and xylem, respectively, and detection of these fluorochromes in the dodder stem indicated that a functional haustorial contact developed for both vascular systems. The results show that Cuscutaspp. have the genetic ability to develop xylem transfer cells and use this in response to developmental stress.

Cuscuta↗

PubMed2006

Hepatoprotective and antioxidant effects of Cuscuta chinensis against acetaminophen-induced hepatotoxicity in rats.

Tu-Si-Zi, the seeds of Cuscuta chinensis Lam. (Convolvulaceae), is a traditional Chinese medicine that is commonly used to nourish and improve the liver and kidney conditions in China and other Asian countries. As oxidative stress promotes the development of acetaminophen (APAP)-induced hepatotoxicity, the aim of the present study was to evaluate and compare the hepatoprotective effect and antioxidant activities of the aqueous and ethanolic extracts of C chinensis on APAP-induced hepatotoxicity in rats. The C chinensis ethanolic extract at an oral dose of both 125 and 250mg/kg showed a significant hepatoprotective effect relatively to the same extent (P<0.05) by reducing levels of glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), and alkaline phosphatase (ALP). In addition, the same ethanolic extract prevented the hepatotoxicity induced by APAP-intoxicated treatment as observed when assessing the liver histopathology. Regarding the antioxidant activity, C chinensis ethanolic extract exhibited a significant effect (P<0.05) by increasing levels of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), and by reducing malondialdehyde (MDA) levels. In contrast, the same doses of the aqueous extract of C chinensis did not present any hepatoprotective effect as seen in the ethanolic extract, and resulted in further liver deterioration. In conclusion, these data suggest that the ethanolic extract of Cuscuta chinensis can prevent hepatic injuries from APAP-induced hepatotoxicity in rats and this is likely mediated through its antioxidant activities.

Acetaminophen↗

PubMed2005

Tocochromanol content and composition in different species of the parasitic flowering plant genus Cuscuta.

The holoparasitic plant genus Cuscuta is comprised of species with various degrees of plastid functionality and significant differences in photosynthetic capacity, ranging from moderate to no photosynthetic carbon fixation. In the present study, several Cuscuta species were analyzed with respect to the overall contents of tocochromanols and plastoquinone and the levels of the individual tocochromanols. No correlations among photosynthetic capacity, the amount of carotenoids, of plastoquinone and of tocochromanols were observed. On the contrary, wide variation in the composition of the tocochromanol fraction was observed among different species, as well as in stems of the same species in response to starvation conditions. The implications of these findings are discussed.

Cuscuta↗

PubMed2002

Angiotensin converting enzyme inhibitors from Cuscuta japonica Choisy.

Bioassay-guided fractionation of the EtOAc-soluble extract of Cuscuta japonica afforded 3,5-Di-O-caffeoylquinic acid (1). methyl 3,5-Di-O-caffeoylquinate (2). 3,4-Di-O-caffeoylquinic acid (3). and methyl 3,4-Di-O-caffeoylquinate (4). Purification of these compounds was conducted with the application of various chromatographic methods. The structures of the compounds were elucidated on the basis of MS and NMR data analysis. Compounds 1-4 inhibited the angiotensin I converting enzyme activity in a dose-dependent manner. Compounds 1-4 showed the 50% inhibitory concentration values of 596, 483, 534, and 460 micro M, respectively. The presence of these active components may be responsible, at least in part, for the antihypertensive action of traditional crude drug Cuscuta Semen.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2006

An attack of the plant parasite Cuscuta reflexa induces the expression of attAGP, an attachment protein of the host tomato.

Dodder or Cuscutaceae are holoparasitic plants subsisting on other dicotyledonous plants. The infection process is initiated by adherence of Cuscuta prehaustoria to the host surface, followed by penetration attempts by hyphae. In the case of a successful infection, these organs connect the parasite's vascular tissue to that of the host. Here we show that contact of Cuscuta reflexa prehaustoria to tomato induces the expression of a new arabinogalactan protein (AGP), attAGP, in the tomato precisely at the site of dodder attack. We show that attAGP is a plasma membrane-bound cell wall-localized protein. Using the RNAi technique and attAGP-targeted virus-induced gene silencing, we observed a correlation between attAGP expression level and force of attachment of the parasite to host tomatoes. If the expression level of attAGP was reduced, the C. reflexa attachment capability was significantly reduced, too. We conclude that C. reflexa infection induced a signal in the host leading to expression of tomato attAGP, which promotes the parasite's adherence.

Cuscuta↗

PubMed2000

Blue light-sensitive plasma membrane bound exogenous NADH oxidase in Cuscuta reflexa.

Protoplasts isolated from Cuscuta reflexa exhibited a higher rate of exogenous NADH oxidation as compared to NADPH in the dark. NAD(P)H oxidation was monitored by measuring the rate of oxygen consumption and this oxidase system was sensitive to blue light. Both NADH oxidase and its blue light sensitivity were inhibited by -SH group reacting agents. The corresponding changes occurring in H+-extrusion activity and intracellular ATP levels were also monitored. Stimulation of NADH oxidation under blue light corresponded to increased rate of H+-extrusion and intracellular ATP level, the converse was also true under NADH oxidase inhibitory conditions. These observations suggested a close functional association between blue light-sensitive plasma membrane bound redox activity and H+-ATPase in this tissue. Further, concanavalin A binding of protoplasts resulted in a loss in NADH oxidase activity and its blue light sensitivity suggesting apoplastic location and glycoprotein nature of the blue light sensitive NADH oxidase system in Cuscuta.

Cell Membrane↗

PubMed2002

[Effects of flavonoids from semen Cuscutae on changes of beta-EP in hypothalamuses and FSH and LH in anterior pituitaries in female rats exposed to psychologic stress].

OBJECTIVE: To study the mechanism of flavonoids from Semen Cuscutae (FSC) improving the ovarian endocrine functions. METHODS: (1) FSC were obtained from the semen of Cuscuta chinensis through solvent extraction and polyamide columnar chromatography. (2) Sound, light and electricity were combined into a stressful stimulas to induce psychologic stress in female rats. (3) To observe the effects of FSC on the changes of beta-EP in hypothalamuses, FSH and LH in anterior pituitaries and the changes in pituitary morphology in female rats exposed to psychologic stress. RESULTS: FSC decreased the content of beta-EP in hypothalamuses, and increased the numbers of basophilic cell and content of LH in anterior pituitaries, didn't change content of FSH in anterior pituitaries in female rats exposed to psychologic stress. CONCLUSION: FSC decreases the contents of beta-EP in hypothalamuses and increases contents of LH in anterior pituitaries in female rats exposed to psychologic stress, which may be one of the mechanism of FSC improving hypothalamus-pituitary-ovary axis.

Animals↗

PubMed2002

[Studies on chemical constituents of Cuscuta chinensis].

OBJECTIVE: To study the chemical constituents of the seeds of Cuscuta chinensis. METHOD: The separation was carried out by polyamide and silica gel chromatography, and the compounds were identified by means of physico-chemical and spectroscopic methods. RESULTS: Eight compounds were isolated from the plant and identified as quercetin 3-O-beta-D-galactoside-7-O-beta-D-glucoside (I), quercetin 3-O-beta-D-apiofuranosyl-(1-->2)-beta-D-galactoside (II), hyperoside (III), isorhamnetin (IV), kaempferol (V), quercetin (VI), d-sesamin (VII) and 9(R)-hydroxy-d-sesamin (VIII). CONCLUSION: Compounds IV and VII were isolated from Cuscuta for the first time, and I, II and VIII were characteristic constituents for this vegetable drug.

Cuscuta↗

PubMed1994

Functional loss of all ndh genes in an otherwise relatively unaltered plastid genome of the holoparasitic flowering plant Cuscuta reflexa.

We have cloned and sequenced an area of about 9.0 kb of the plastid DNA (ptDNA) from the holoparasitic flowering plant Cuscuta reflexa to investigate the evolutionary response of plastid genes to a reduced selective pressure. The region contains genes for the 16S rRNA, a subunit of a plastid NAD(P)H dehydrogenase (ndhB), three transfer RNAs (trnA, trnI, trnV) as well as the gene coding for the ribosomal protein S7 (rps7). While the other genes are strongly conserved in C. reflexa, the ndhB gene is a pseudogene due to many frameshift mutations. In addition we used heterologous gene probes to identify the other ndh genes encoded by the plastid genome in higher plants. No hybridization signals could be obtained, suggesting that these genes are either lost or strongly altered in the ptDNA of C. reflexa. Together with evidence of deleted genes in the ptDNA of C. reflexa, the plastid genome can be grouped into four classes reflecting a different evolutionary rate in each case. The phylogenetic position of Cuscuta and the significance of ndh genes in the plastid genome of higher plants are discussed.

Base Sequence↗

PubMed1992

Organization and sequence of photosynthetic genes from the plastid genome of the holoparasitic flowering plant Cuscuta reflexa.

We have cloned and sequenced an area of about 6 kb of the plastid DNA (ptDNA) from the holoparasitic plant Cuscuta reflexa. This region contains (in the following order) genes for the cytochrome b6 f-complex subunit V (petG), tRNA(Val) (trnV), tRNA(Met) (trnM), the epsilon- and beta-subunit of the chloroplast ATP-synthase (atpE and atpB) and the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; rbcL). In addition we identified other photosynthesis-related genes (atpA, petB, psaA, psbA, psbB, psbC, and psbD) in C. reflexa by heterologous hybridization. The gene arrangement of the sequenced area is, except for the petG gene, the same as in ptDNAs of other higher plants (e.g. Nicotiana tabacum). Sequence homologies between the Cuscuta genes and corresponding genes from higher plants are in the range of 90%. The only significant difference is that the rbcL gene of C. reflexa encodes a polypeptide which is 18-23 amino acids longer than in other higher plants. This is remarkable since C. reflexa has lost its ability to grow photoautotrophically. The transcript level of the rbcL gene, however, is strongly reduced as compared to tobacco. These findings are compatible with results from Western blotting analysis, where no Rubisco large subunit was detectable, and with the lack of Rubisco activity in crude extracts of C. reflexa.

Amino Acid Sequence↗

PubMed1995

Structural and functional analysis of plastid genomes from parasitic plants: loss of an intron within the genus Cuscuta.

The gene cluster rps12/rps7/psi ndhB of the plastome from the holoparasitic plant Cuscuta europaea has been analysed at the nucleotide level. A comparison with the homologous region of the plastome from the closely related parasite Cuscuta reflexa reveals a complete loss of the cis-spliced intron of the rps12 gene in addition to a drastic size reduction of the ndhB pseudogene. It is demonstrated by RT-PCR analysis that the entire gene cluster is transcribed in the form of a multicistronic transcript which also includes the sequences encoded by the ndhB pseudogene. A cDNA containing the correctly transpliced exon 1 of the rps12 transcript can also be amplified. This shows that trans-splicing of the rps12 transcript persists in the plastids of the holoparasite despite the loss of the cis-spliced intron and the loss of many other gene functions. The rps12 and rps7 genes, therefore, still appear to code for functional ribosomal proteins CS12 and CS7, respectively. The conservation of apparently intact ribosomal-protein genes from which correctly processed transcripts are produced is taken as evidence that the translational apparatus of the plastids is still functional and necessary for the expression of the genes remaining in the reduced plastome of a parasitic plant.

Amino Acid Sequence↗

PubMed2000

Preliminary studies on the immunomodulatory effect of the C3 binding glycoprotein isolated from Cuscuta europea.

This study investigates the immunomodulatory effect of a C3 binding glycoprotein (C3bgp), isolated from the parasitic plant Cuscuta europea. When BALB/c mice, immunized with sheep red blood cells (SRBC), were given a single intraperitoneal injection of C3bgp a dose-dependent immunostimulation was observed. The stimulation was assessed by an increase in the number of haemolytic plaque forming cells (PFC) and haemaglutination titres. The induction was time dependent in respect to the administration of both the C3bgp and SRBC. When C3bgp was applied 24 h before SRBC at a dose of 30 microg per mouse (1.2 mg/kg), a well expressed immunostimulation was found. It was also found that giving C3bgp to mice, which had previously been treated with the immunosuppressive drug cyclophosphamide (CY), produced an increase in PFC. The immune response was also restored in vitro experiments were performed using human whole blood cultures stimulated with 30 microg/ml C3bgp in the presence or absence of egg albumin (OVA) as antigen for 72 to 168 h. In C3bgp stimulated cultures it was found that after 120 h there was a high expression of the CD 19+ subset of the activation antigen CD25 (IL-2R) as assessed by flow cytometric phenotype analysis. Supernatants from cultures with different stimuli were assayed by a solid phase ELISA for the determination of OVA-specific IgM at 120, 144 and 168 h. It was found that C3bgp application alone, failed to enhance OVA specific IgM, but significantly high levels of IgM in cultures containing C3bgp and OVA, were detected. Overall it has been shown that the C3 binding glycoprotein, as obtained from the parasitic plant Cuscuta europea, has strong immunostimulatory properties both in vivo and in vitro.

Adjuvants, Immunologic↗

PubMed2005

Influence of the obligate parasite Cuscuta campestris on growth and biomass allocation of its host Mikania micrantha.

As a means of biologically controlling Mikania micrantha H.B.K. in South China, the influence of the obligate parasite Cuscuta campestris Yuncker on its growth and biomass allocation was studied using pot trials. The effect of C. campestris on M. micrantha became greater with time, such that the host biomass was only 1.8% of the control after 60 d of parasitism and by day 72 almost all the aerial parts of the host plants had died. Afterwards, the hosts and the remnant parasite shoots re-grew but the total biomass of the hosts was still significantly lower than that of the controls. The infection by C. campestris greatly increased the shoot:root dry weight ratio and the allocation to stems of the infected plants from 40 to 50 d after parasitization, but decreased their relative growth rate and unit leaf rate starting from 20 d after parasitization and their leaf area ratio from 30 to 60 d after parasitization. Cuscuta campestris significantly reduced the total biomass, changed the biomass allocation patterns, and completely inhibited the flowering of the infected M. micrantha plants. These results indicate that the use of C. campestris could be a potentially effective way of controlling M. micrantha.

Asteraceae↗

PubMed1974

Photocontrol of Hook Opening in Cuscuta gronovii Willd.

Hook opening in seedlings of Cuscuta gronovii Willd. occurred only after prolonged exposures to blue, red, or far red light. Prolonged far red exposure was less effective than prolonged exposure to red or blue light. Brief far red irradiation inhibited the inductive effect of red light. The far red inhibition was in turn reversed by brief red irradiation. These effects suggest the involvement of two photosystems in the control of hook opening in Cuscuta gronovii Willd.: a phytochrome-mediated system and a separate high energy requirement.

Journal Article↗