Salinity Effect on Germination and Further Development of Parasitic Cuscuta spp. and Related Non-Parasitic Vines

Plants are continuously subjected to the unfavorable impact of abiotic stress factors, of which soil salinity is among the most adverse. Although away from direct soil contact throughout most of their lifecycle, stem parasitic plants of the genus Cuscuta, family Convolvulaceae are also affected by salinity. The present study aimed to assess salt stress impact on germination and early establishment of three Cuscuta species, in comparison to related nonparasitic vines of the same family. It was found, that Cuscuta spp. are highly sensitive to NaCl concentration within the range of 200 mM. Germination was delayed in time and reduced by nearly 70%, accompanied by decrease in further seedling growth, ability to infect host plants and growth rate of established parasites. The nonparasitic vines showed similar sensitivity to salinity at germination level, but appeared to adapt better after the stress factor was removed. However, the negative effect of salinity did not fully prevent some of the Cuscuta species from infecting hosts, probably a beneficial characteristic at a species level, allowing the parasite to successfully thrive under the scarce host availability under saline conditions.

An Integrated Approach for Efficient and Accurate Medicinal Cuscutae Semen Identification

To guarantee the safety and efficacy of herbal medicines, accurate identification and quality evaluation are crucial. The ripe dried seeds of Cuscuta australis R.Br. and C. chinensis Lam. are known as Cuscutae Semen (CS) and are widely consumed in Northeast Asia; however, the seeds of other species can be misidentified as CS owing to morphological similarities, leading to misuse. In this report, we propose a multilateral strategy combining microscopic techniques with statistical analysis and DNA barcoding using a genus-specific primer to facilitate the identification and authentication of CS. Morphology-based identification using microscopy revealed that the useful diagnostic characteristics included general shape, embryo exudation, hairiness, and testa ornamentation, which were used to develop an effective identification key. In addition, we conducted DNA barcoding-based identification to ensure accurate authentication. A novel DNA barcode primer was produced from the chloroplast rbcL gene by comparative analysis using Cuscuta chloroplast genome sequences, which allowed four Cuscuta species and adulterants to be discriminated completely. Therefore, this investigation overcame the limitations of universal DNA barcodes for Cuscuta species with high variability. We believe that this integrated approach will enable CS to be differentiated from other species, thereby improving its quality control and product safety in medicinal markets.

Cuscuta Species Identification Based on the Morphology of Reproductive Organs and Complete Chloroplast Genome Sequences

The genus Cuscuta (Convolvulaceae) comprises well-known parasitic plants. Cuscuta species are scientifically valuable, as their life style causes extensive crop damage. Furthermore, dried seeds of C. chinensis are used as a Korean traditional herbal medicine. Despite the importance of Cuscuta species, it is difficult to distinguish these plants by the naked eye. Moreover, plastid sequence information available for Cuscuta species is limited. In this study, we distinguished between C. chinensis and C. japonica using morphological characterisation of reproductive organs and molecular characterisation of chloroplast genomes. The differences in morphological characteristics of reproductive organs such as style, stigma, infrastaminal scale, seed shape and testa ornamentation were useful for distinguishing between C. japonica and C. chinensis. Analysis of chloroplast genomes revealed drastic differences in chloroplast genome length and gene order between the two species. Although both species showed numerous gene losses and genomic rearrangements, chloroplast genomes showed highly similar structure within subgenera. Phylogenetic analysis of Cuscuta chloroplast genomes revealed paraphyletic groups within subgenera Monogynella and Grammica, which is consistent with the APG IV system of classification. Our results provide useful information for the taxonomic, phylogenetic and evolutionary analysis of Cuscuta and accurate identification of herbal medicine.

Cuscuta chinensis and C. campestris Attenuate Scopolamine-Induced Memory Deficit and Oxidative Damage in Mice

The seeds of Cuscuta chinensis Lam. and C. campestris Yuncker have been commonly used as Chinese medical material for preventing aging. Our previous studies have found that C. chinensis and C. campestris possess anti-inflammatory activities in rodents. However, their other biological activities, such as memory-improving properties, have not yet been explored. In the present study, we examined the memory-improving effects of the extracts of C. chinensis and C. campestris on scopolamine (SCOP)-induced memory deficit and explored their underlying mechanism in mice. Both Cuscuta species improved SCOP-induced memory deficits in the passive avoidance test, elevated plus-maze, and spatial performance test of the Morris water maze in mice. In addition, compared with mice injected with SCOP, mice pretreated with both Cuscuta species stayed for a longer time on the platform for the probe test of the Morris water maze. Moreover, both Cuscuta species reduced brain acetylcholinesterase activity and malondialdehyde levels that were increased by SCOP, and the species restored the activities of antioxidant enzymes (superoxide dismutase and catalase) and the levels of glutathione that were decreased by SCOP in the brains of mice. Both Cuscuta species further decreased brain interleukin-1β and tumor necrosis factor-α levels that were elevated by SCOP. We demonstrated that both Cuscuta species exhibited a protective activity against SCOP-induced memory deficit, cholinergic dysfunction, oxidative damage, and neuroinflammation in mice, and C. campestris has better potential than C. chinensis. In addition, we provided evidence that the seeds of C. campestris can be used as Cuscutae Semen in Traditional Chinese Medicine.

Replication of Grapevine leafroll-associated virus-7 (GLRaV-7) by Cuscuta Species and Its Transmission to Herbaceous Plants

Grapevine leafroll-associated virus-7 (GLRaV-7) was transmitted from an Albanian grapevine accession to Tetragonia expansa by the parasitic dodder Cuscuta reflexa and to Nicotiana occidentalis by Cuscuta europea. Cuscuta campestris was infected by GLRaV-7 but could not transfer the virus to an experimental host. Transmission of the virus was verified by reverse transcription–polymerase chain reaction (RT-PCR) from total nucleic acid (TNA) and double-stranded RNA (dsRNA) extracts from all five plant species. DsRNA extractions separated on agarose gels showed strong visible bands corresponding to high-molecular-weight virus genome and to subgenomic RNA. GLRaV-7 was maintained in C. reflexa, C. campestris, T. expansa, and N. occidentalis for more than 4 years. Infected T. expansa and the Cuscuta species remained symptomless while N. occidentalis showed severe symptoms leading to stunting and decline of the plants. Quantitative PCR showed great differences in the titer of GLRaV-7 between the tissues of its natural and experimental host plants. This is the first report on a virus of the Closteroviridae that was successfully transmitted to an herbaceous plant by dodder. Virus replication could be demonstrated in Cuscuta. Both the new experimental hosts of GLRaV-7 and Cuscuta allowed extraction of dsRNA for further characterization of the viral genome, which previously required grapevine scraping of phloem. This is time-consuming and does not always lead to satisfactory results. These alternative hosts of GLRaV-7 facilitate nucleic acid extractions and could be used as model plants for etiological studies.