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

Al-Mayah AA, Hawkins JA. An account of the genus Cistanche (Orobanchaceae) in Iraq and taxonomic considerations in the Middle East

Species limits in the genus Cistanche are poorly understood, despite the plants' long history of use in traditional herbal medicine and food across their range. Here we present a taxonomic account for the genus Cistanche in Iraq, where several taxa have been reported, most of them doubtfully. Using herbarium specimens, images of living material, and taxonomic literature, we found evidence of only one species occurring with certainty in Iraq: Cistanchetubulosa. We found no evidence for the occurrence of other Cistanche species in Iraq, including a putative new entity reported for the region. Our work highlights inconsistencies in the literature, and underscores the importance of examining multiple stable characters for delimiting species in the genus Cistanche.

Studies on Cistanches Herba: A Bibliometric Analysis

As a famous tonic herb, Cistanches Herba is known for its broad medicinal functions, especially its hormone balancing, anti-aging, anti-dementia, anti-tumor, anti-oxidative, neuroprotective, and hepatoprotective effects. This study aims to provide a comprehensive bibliometric analysis of studies on Cistanche and to identify research hotspots and frontier topics on the genus. Based on the metrological analysis software CiteSpace, 443 Cistanche related papers were quantitatively reviewed. The results indicate that 330 institutions from 46 countries have publications in this field. China was the leading country in terms of research importance and number of publication (335 articles). In the past decades, studies on Cistanche have mainly focused on its rich active substances and pharmacological effects. Although the research trend shows that Cistanche has grown from an endangered species to an important industrial plant, its breeding and cultivation continue to be important areas for research. In the future, the application of Cistanche species as functional foods may be a new research trend. In addition, active collaborations among researchers, institutions, and countries are expected.

The Chromosome Number and rDNA Loci Evolution in Onobrychis (Fabaceae)

The evolution of chromosome number and ribosomal DNA (rDNA) loci number and localisation were studied in Onobrychis Mill. Diploid and tetraploid species, as well as two basic chromosome numbers, x = 7 and x = 8, were observed among analysed taxa. The chromosomal distribution of rDNA loci was presented here for the first time using fluorescence in situ hybridisation (FISH) with 5S and 35S rDNA probes. Onobrychis species showed a high polymorphism in the number and localisation of rDNA loci among diploids, whereas the rDNA loci pattern was very similar in polyploids. Phylogenetic relationships among the species, inferred from nrITS sequences, were used as a framework to reconstruct the patterns of basic chromosome number and rDNA loci evolution. Analysis of the evolution of the basic chromosome numbers allowed the inference of x = 8 as the ancestral number and the descending dysploidy and polyploidisation as the major mechanisms of the chromosome number evolution. Analyses of chromosomal patterns of rRNA gene loci in a phylogenetic context resulted in the reconstruction of one locus of 5S rDNA and one locus of 35S rDNA in the interstitial chromosomal position as the ancestral state in this genus.

Structural mutations of small single copy (SSC) region in the plastid genomes of five Cistanche species and inter-species identification

BACKGROUND

Cistanche is an important genus of Orobanchaceae, with critical medicinal, economic, and desertification control values. However, the phylogenetic relationships of Cistanche genus remained obscure. To date, no effective molecular markers have been reported to discriminate effectively the Cistanche closely related species reported here. In this study, we obtained and characterized the plastomes of four Cistanche species from China, to clarify the phylogenetic relationship within the genus, and to develop molecular markers for species discrimination.  RESULTS: Four Cistanche species (Cistanche deserticola, Cistanche salsa, Cistanche tubulosa and Cistanche sinensis), were deep-sequenced with Illumina. Their plastomes were assembled using SPAdes and annotated using CPGAVAS2. The plastic genomes were analyzed in detail, finding that all showed the conserved quadripartite structure (LSC-IR-SSC-IR) and with full sizes ranging from 75 to 111 Kbp. We observed a significant contraction of small single copy region (SSC, ranging from 0.4-29 Kbp) and expansion of inverted repeat region (IR, ranging from 6-30 Kbp), with C. deserticola and C. salsa showing the smallest SSCs with only one gene (rpl32). Compared with other Orobanchaceae species, Cistanche species showed extremely high rates of gene loss and pseudogenization, as reported for other parasitic Orobanchaceae species. Furthermore, analysis of sequence divergence on protein-coding genes showed the three genes (rpl22, clpP and ycf2) had undergone positive selection in the Cistanche species under study. In addition, by comparison of all available Cistanche plastomes we found 25 highly divergent intergenic spacer (IGS) regions that were used to predict two DNA barcode markers (Cis-mk01 and Cis-mk02 based on IGS region trnR-ACG-trnN-GUU) and eleven specific DNA barcode markers using Ecoprimer software. Experimental validation showed 100% species discrimination success rate with both type of markers.

CONCLUSION

Our findings have shown that Cistanche species are an ideal model to investigate the structure variation, gene loss and pseudogenization during the process of plastome evolution in parasitic species, providing new insights into the evolutionary relationships among the Cistanche species. In addition, the developed DNA barcodes markers allow the proper species identification, ensuring the effective and safe use of Cistanche species as medicinal products.

A pair of novel phenylethanol glycosides from Cistanche tubulosa (Schenk) Wight

A pair of differential epimers with opposite C-7 configurations, crenatosides A and B (1 and 2), and 10 known phenylethanoid glycosides (PhGs) (3-12) were obtained from the succulent stem of Cistanche tubulosa. The structures were elucidated based on extensive spectral data (UV, IR, 1D and 2D NMR, HR-ESIMS), which are first reported natural products with unique glycoside structures. After acid hydrolysis, the configuration of the sugar was determined by comparing it with the normative sugar by HPLC. The absolute configurations of both compounds were determined by ECD spectrum analysis. All the obtained compounds were examined for their inhibitory effect on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in mouse microglial cells (BV-2 cells), and compounds 1 and 2 showed potent inhibition on NO production with IC₅₀ values of 5.62 μM and 6.30 μM, respectively.

Phylogeny and historical biogeography analysis support Caucasian and Mediterranean centres of origin of key holoparasitic Orobancheae (Orobanchaceae) lineages

The extensive diversity of the tribe Orobancheae, the most species-rich lineage of holoparasitic Orobanchaceae, is concentrated in the Caucasus and Mediterranean regions of the Old World. This extant diversity has inspired hypotheses that these regions are also centres of origin of its key lineages, however the ability to test hypotheses has been limited by a lack of sampling and phylogenetic information about the species, especially in the Caucasus region. First, we assessed the phylogenetic relationships of several poorly known, problematic, or newly described species and host-races of four genera of Orobancheae occurring in the Caucasus region-Cistanche, Phelypaea, Phelipanche and Orobanche-using nuclear ribosomal (ITS) and plastid (trnL-trnF) sequence data. Then we applied a probablistic dispersal-extinction-cladogenesis model of historical biogeography across a more inclusive clade of holoparasites, to explicitly test hypotheses of Orobancheae diversification and historical biogeography shifts. In sum, we sampled 548 sequences (including 196 newly generated) from 13 genera, 140 species, and 175 taxa across 44 countries. We find that the Western Asia (particularly the Caucasus) and the Mediterranean are the centre of origin for large clades of holoparasitic Orobancheae within the last 6 million years. In the Caucasus, the centres of diversity are composed both of long-branch taxa and shallow, recently diversified clades, while Orobancheae diversity in the Mediterranean appears to represent mainly recent diversification.