Project description:<h4>Background</h4>Crassostrea gigas accumulates paralytic shellfish toxins (PST) associated with red tide species as Gymnodinium catenatum. Previous studies demonstrated bivalves show variable feeding responses to toxic algae at physiological level; recently, only one study has reported biochemical changes in the transcript level of the genes involved in C. gigas stress response.<h4>Principal findings</h4>We found that 24 h feeding on toxic dinoflagellate cells (acute exposure) induced a significant decrease in clearance rate and expression level changes of the genes involved in antioxidant defense (copper/zinc superoxide dismutase, Cu/Zn-SOD), cell detoxification (glutathione S-transferase, GST and cytochrome P450, CPY450), intermediate immune response activation (lipopolysaccharide and beta glucan binding protein, LGBP), and stress responses (glutamine synthetase, GS) in Pacific oysters compared to the effects with the non-toxic microalga Isochrysis galbana. A sub-chronic exposure feeding on toxic dinoflagellate cells for seven and fourteen days (30×10³ cells mL?¹) showed higher gene expression levels. A significant increase was observed in Cu/Zn-SOD, GST, and LGBP at day 7 and a major increase in GS and CPY450 at day 14. We also observed that oysters fed only with G. catenatum (3×10³ cells mL?¹ produced a significant increase on the transcription level than in a mixed diet (3×10³ cells mL?¹ of G. catenatum+0.75×10? cells mL?¹ I. galbana) in all the analyzed genes.<h4>Conclusions</h4>Our results provide gene expression data of PST producer dinoflagellate G. catenatum toxic effects on C. gigas, a commercially important bivalve. Over expressed genes indicate the activation of a potent protective mechanism, whose response depends on both cell concentration and exposure time against these toxic microalgae. Given the importance of dinoflagellate blooms in coastal environments, these results provide a more comprehensive overview of how oysters respond to stress generated by toxic dinoflagellate exposure.
Project description:Viruses are key biogeochemical engines in the regulation of the dynamics of phytoplankton. However, there has been little research on viral communities in relation to algal blooms. Using the virMine tool, we analyzed viral information from metagenomic data of field dinoflagellate (Gymnodinium catenatum) blooms at different stages. Species identification indicated that phages were the main species. Unifrac analysis showed clear temporal patterns in virioplankton dynamics. The viral community was dominated by Siphoviridae, Podoviridae, and Myoviridae throughout the whole bloom cycle. However, some changes were observed at different phases of the bloom; the relatively abundant Siphoviridae and Myoviridae dominated at pre-bloom and peak bloom stages, while at the post-bloom stage, the members of Phycodnaviridae and Microviridae were more abundant. Temperature and nutrients were the main contributors to the dynamic structure of the viral community. Some obvious correlations were found between dominant viral species and host biomass. Functional analysis indicated some functional genes had dramatic response in algal-associated viral assemblages, especially the CAZyme encoding genes. This work expands the existing knowledge of algal-associated viruses by characterizing viral composition and function across a complete algal bloom cycle. Our data provide supporting evidence that viruses participate in dinoflagellate bloom dynamics under natural conditions.
Project description:Flavonoids, which are a diverse class of phytonutrients, are used by organisms to respond to nearly all abiotic stresses and are beneficial for human health. Glycosyltransferase, used during the last step of flavonoid biosynthesis, is important in flavonoid enrichment. However, little is known about glycosyltransferase in the orchid Dendrobium catenatum (D. officinale). In this study, we isolated a novel C-glycosyltransferase (designated DcaCGT) from the orchid D. catenatum by identifying and analyzing 82 putative genes in the GT1 family. DcaCGT could specifically catalyze not only di-C-glycosylation but also O-glycosylation. Apart from the normal function of catalyzing 2-hydroxynaringenin and phloretin to the respective di-C-glycosides, DcaCGT also catalyzes apigenin to cosmosiin. Targeted metabolic profiling of the substrates (2-hydroxynaringenin, phloretin, and apigenin) and products (vitexin, isovitexin, vicenin-2, nothofagin, 3’,5’-di-C-glucosylphloretin, and cosmosiin) in different tissues showed that vicenin-2 was the most abundant product of this novel enzyme. Cosmosiin was detected in flowers and flower buds. We also established that DcaCGT functions expanded throughout the evolution of D. catenatum. Residual OGT activity may help D. catenatum resist drought stress. Our study illustrates the function, origin, and differentiation of DcaCGT and provides insights into glycosylation and molecular propagation processes, which can be used to improve the production of flavonoids by the cultivated medicinal plant D. catenatum.
Project description:Highlights•Since 1986 Gymnodinium catenatum contaminates irregularly bivalves in Portugal with PSTs.•Acute neurological symptomology, such as paraesthesias, has often required hospitalization.•During an episode in October 2018, toxins in fluids of two victims and toxin ingestion were studied.•Preliminary confirmation was done by ELISA in serum and urine.•PSP toxins with an O-sulphate at C11, abundant in mussels, were absent in urine.
Project description:BACKGROUND:Dendrobium catenatum, as a precious Chinese herbal medicine, is an epiphytic orchid plant, which grows on the trunks and cliffs and often faces up to diverse environmental stresses. SET DOMAIN GROUP (SDG) proteins act as histone lysine methyltransferases, which are involved in pleiotropic developmental events and stress responses through modifying chromatin structure and regulating gene transcription, but their roles in D. catenatum are unknown. RESULTS:In this study, we identified 44 SDG proteins from D. catenatum genome. Subsequently, comprehensive analyses related to gene structure, protein domain organization, and phylogenetic relationship were performed to evaluate these D. catenatum SDG (DcSDG) proteins, along with the well-investigated homologs from the model plants Arabidopsis thaliana and Oryza sativa as well as the newly characterized 42 SDG proteins from a closely related orchid plant Phalaenopsis equestris. We showed DcSDG proteins can be grouped into eight distinct classes (I~VII and M), mostly consistent with the previous description. Based on the catalytic substrates of the reported SDG members mainly in Arabidopsis, Class I (E(z)-Like) is predicted to account for the deposition of H3K27me2/3, Class II (Ash-like) for H3K36me, Class III (Trx/ATX-like) for H3K4me2/3, Class M (ATXR3/7) for H3K4me, Class IV (Su (var)-like) for H3K27me1, Class V (Suv-like) for H3K9me, as well as class VI (S-ET) and class VII (RBCMT) for methylation of both histone and non-histone proteins. RNA-seq derived expression profiling showed that DcSDG proteins usually displayed wide but distinguished expressions in different tissues and organs. Finally, environmental stresses examination showed the expressions of DcASHR3, DcSUVR3, DcATXR4, DcATXR5b, and DcSDG49 are closely associated with drought-recovery treatment, the expression of DcSUVH5a, DcATXR5a and DcSUVR14a are significantly influenced by low temperature, and even 61% DcSDG genes are in response to heat shock. CONCLUSIONS:This study systematically identifies and classifies SDG genes in orchid plant D. catenatum, indicates their functional divergence during the evolution, and discovers their broad roles in the developmental programs and stress responses. These results provide constructive clues for further functional investigation and epigenetic mechanism dissection of SET-containing proteins in orchids.
Project description:In this study, we applied transcriptome and UHPLC-MS technologies to investigate the flavonoids and their biosynthesis- and accumulation-related genes in Dendrobium catenatum from three different locations. Eight flavonoid glycosides were identified using standard references or previously isolated substances with MS data analysis. The total flavonoid contents were determined by reagents, and all the data were analyzed. In total, 23139 unigenes were obtained using the Dendrobium catenatum genome data. Of these, 10398 were annotated in the Gene Ontology (GO) database, 4203 were annotated in the KEGG database, and 10917 were annotated in the EuKaryotic Orthologous Groups (KOG) database. Thirty-one of the unigenes annotated by the KEGG database were involved in flavonoid pathways. The genes involved in bio-modification, accumulation, transportation and the regulation of the flavonoid bio-synthesis process were investigated. In conclusion, the flavonoids in Dendrobium catenatum from three different locations were different in quantitative and qualitative which may contribute to the establishment of quality control method for this herbal plant. These differences were determined by flavonoids biosynthesis process and they were concluded by sorting out the expression level of certain biosynthesis related genes.
Project description:As an epiphyte orchid, Dendrobium catenatum relies on microorganisms for requisite nutrients. Metagenome pyrosequencing based on 16S rRNA and nifH genes was used to characterize the bacterial and diazotrophic communities associated with D. catenatum collected from 5 districts in China. Based on Meta-16S rRNA sequencing, 22 bacterial phyla and 699 genera were identified, distributed as 125 genera from 8 phyla and 319 genera from 10 phyla shared by all the planting bases and all the tissues, respectively. The predominant Proteobacteria varied from 71.81% (GZ) to 96.08% (YN), and Delftia (10.39-38.42%), Burkholderia (2.71-15.98%), Escherichia/Shigella (4.90-25.12%), Pseudomonas (2.68-30.72%) and Sphingomonas (1.83-2.05%) dominated in four planting bases. Pseudomonas (17.94-22.06%), Escherichia/Shigella (6.59-11.59%), Delftia (9.65-22.14%) and Burkholderia (3.12-11.05%) dominated in all the tissues. According to Meta-nifH sequencing, 4 phyla and 45 genera were identified, while 17 genera and 24 genera from 4 phyla were shared by all the planting bases and all the tissues, respectively. Burkholderia and Bradyrhizobium were the most popular in the planting bases, followed by Methylovirgula and Mesorhizobium. Mesorhizobium was the most popular in different tissues, followed by Beijerinckia, Xanthobacter, and Burkholderia. Among the genera, 39 were completely overlapped with the results based on the 16S rRNA gene. In conclusion, abundant bacteria and diazotrophs were identified in common in different tissues of D. catenatum from five planting bases, which might play a great role in the supply of nutrients such as nitrogen. The exact abundance of phylum and genus on the different tissues from different planting bases need deeper sequencing with more samples.
Project description:Dendrobium catenatum (D. catenatum) has long been used as an important medicinal herb in oriental medicine. Polysaccharide, flavonoid, and alkaloid are the major active ingredients, the production and accumulation of which are frequently affected by many environmental factors including water, temperature, and mycorrhizal fungus. However, how phytohormones frequently used in orchid tissue culture regulate the production of active components in D. catenatum is far from clear. Here, major medicinal metabolites were comparatively analyzed in 2-month-old D. catenatum seedlings exposed to phytohormones (0.1 mg/L NAA and/or 1.0 mg/L 6-BA) for three weeks, and eight transcriptomes (two replicates each) corresponding to the treatments were generated. Results demonstrated that the phytohormones triggered transcriptional reprograming, analysis of which revealed a tight association of β-glucosidase (BGLU) expression with the accumulation of polysaccharide. Subsequently, a second RNA-sequencing was further conducted to reveal that a relatively short period (2 w) of varied concentrations of 6-BA application might initially reduce BGLU expression and polysaccharide content and then increase their levels with prolonged treatments (4 w). The RNA-seq data was reconfirmed by functional analysis that 6-BA induced polysaccharide production, while knockdown of BGLU2L resulted in decreased polysaccharide levels. Therefore, the present study clearly demonstrated that BGLU is a key regulator for polysaccharide production and that it is extremely susceptible to NAA and 6-BA treatments in D. catenatum. Overall design: 1. Examination of the expression of medicinal components production related genes in response to 1.0 mg/L 6-BA and/or 0.1 mg/L NAA treatments for 3 w in Dendrobium catenatum 2. Examination of the expression of medicinal components production related genes in response to varied concentrations of 6-BA (0, 0.5, 1.0, and 2.0 mg/L) and treatment duration (2 w and 4w) in Dendrobium catenatum