Project description:Mycorrhizal fungi colonize orchid seed and induce the germination. This so-called symbiotic germination is a critical developmental process in the lifecycle of all orchids. However, the molecular changes taking place during the orchid seed symbiotic germination still remains largely unknown. To better understand the molecular mechanism of orchid seed germination, we performed comparative transcriptomic and proteomic analysis on Chinese traditional medicinal orchid plants, Dendrobium officinale to explore protein expression change at the different developmental stages between asymbiotic and symbiotic germination and identify the key proteins regulated symbiotic germination of orchid seeds. iTRAQ analysis from 8 samples identified 2256 plant proteins, of which, 308 proteins were differentially expressed across three developmental stages within asymbiotic or symbiotic accession and 229 proteins are differentially expressed in the symbiotic germination compared to asymbiotic germination. 32 proteins are co-upregulated in both proteomic and transcriptomic level for symbiotic germination compared to asymbiotic germination. Our results revealed that symbiotic germination of D. officinale seeds probably shares the common signal pathway with asymbiotic germination during the early germination stage.
Project description:Orchid Dendrobium Sonia (Sonia) has wide demand in floral market throughout the world due to its vibrant coloured flowers, flowering recurrence and dense inflorescence. Effects of different monochromatic light qualities (red, far-red, blue, white) on different developmental and growth responses such as seed gemination, shoot and root growth, chlorophyll and carotenoid accumulation were studied in Sonia. Asymbiotic seed germination was the highest under blue or white light (80%, p<0.001) and least under far-red (55%, p<0.001) suggesting that it could either be controlled by an exceptional novel function of Cryptochrome 1 or the blue wavelengths perceived by PHYA or PHYB in Sonia. All analyses were done in 6-months-old plants till 1 year of age. Shoot length increased significantly in white or red light (3.7-fold, 3.5-fold respectively) while was least under far-red (decreased by 1.6-fold) indicating the major regulatory role of PHYB for shoot growth. Root growth in red in Sonia was more similar to hypocotyl adventitious root (HAR) formation genetically considering PHYB transcript expression. We suggest that the root growth (HAR) under red in Sonia is partly attributed to PHYB, negatively regulated with HY5 transcription factor and positively associated with auxin biosynthesis and accumulation gene BABY BOOM (BBM2) and efflux carriers such as LIKE AUXIN RESISTANT 2 and 3 (LAX2, LAX3). Highest chlorophyll content under far-red and blue might be a hyper-response of SAR under FR light in Sonia. Taxonomic tree analysis finds Sonia closer to Phalenopsis and Dendrobium catenatum Lindl. The three phytochromes and one cryptochrome sequences which were similar to PHYA, B, C and CRY1 respectively. CRY1 was retrieved with one more isoform CRY1_X2, with all these sequences more similar to those of Oryza.sativa. Further study can clarify the indicating reason of a probable gene loss which is evident from the absence of any sequence similar to CRY2 in root RNA isolates of Dendrobium Sonia.
Project description:Dendrobium plants are perennial herbs in the family Orchidaceae (Dendrobium Sw.). Due to protocorm can also produce plant-specific useful metabolites, protocorm is becoming a good substitute. MicroRNAs play essential roles in plant growth, development, and the response to environmental stresses, and they are widely used for prediction of molecular functions for biosynthesizing active comportments in medicinal plants. To obtain insight into the function of miRNAs in Dendrobium plants. Illumina sequencing of D. nobile protocorm, D. officinale protocorm and D. nobile leaf were conducted. A total of 439, 412 and 432 miRNAs were identified in three samples, and their expression levels were significantly different. Specially, 2, 12 and 4 specific miRNAs were identified. Through integrated GO and KEGG function annotation, miRNAs mainly involved in metabolic pathways, plant hormone signal transduction, biological regulation and protein binding. AACT, MK, DXR and HDS as important enzymes in synthesizing basic precursor isoprene pyrophosphate (IPP). were predicted controlled by 6 different miRNAs in terpenoid backbone biosynthesis pathway. 26 miRNAs participated in Auxin, Cytoklinine, Abscisic acid, Jasmonic acid and Salicylic acid signal transduction pathway. Our results could provide valuable information about miRNAs involved in terpenoid biosynthesis and plant hormone signal transduction pathway in D. nobile and candidate genes for increasing the yield of dendrobine.
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.