Cytochemical Localization of Polysaccharides in Dendrobium officinale and the Involvement of DoCSLA6 in the Synthesis of Mannan Polysaccharides

Metabolite components and nutritional composition of the endosperm in seven species from Gleditsia

As an important agricultural product, the endosperm portion of Gleditsia sinensis seeds, called "zào jiǎo mǐ" (ZJM) in Chinese, has gradually gained popularity and has been accepted by the public. However, there is limited information on the nutritional value and metabolic components of endosperm among Gleditsia. This study compared the endosperm composition among seven species. The types of metabolites, content of nutrients and amino acids were determined. A total of 4495 types of metabolites were detected. Galactose metabolism (gmx00052) was enriched in all combinations compared with G. sinensis. The polysaccharides content ranged from 51.49 to 80.37 g/100 g. Based on considerations of growth rate, seed yield, amino acid content, and interspecific differences, G. fera could be an alternative planting option to G. sinensis. These results can provide a reference for growers in selecting Gleditsia varieties and provide insights into the industrial applications of Gleditsia endosperm products.

Cytochemical localization and synthesis mechanism of the glucomannan in pseudobulbs of Bletilla striata Reichb. f

The dried pseudobulbs of Bletilla striata, an important traditional Chinese medicine named BaiJi, have an extraordinary polysaccharide content and excellent prospects for medicinal effects. However, the distribution and molecular mechanism underlying biosynthesis are poorly understood. In this study, chemical and immunologic analyses were performed in representative tissues of B. striata, and the results showed that what are conventionally termed Bletilla striata polysaccharides (BSPs) are water-soluble polysaccharides deposited only in pseudobulbs. The structural component of BSPs is glucomannan, with a mannose:glucose mass ratio of ~3:2. BSPs are present in the parenchyma of the pseudobulbs in cells known as glucomannan idioblasts and distributed in the cytoplasm within cellular membranes, but are not contained in the vacuole. Comparative transcriptomics and bioinformatics analyses mapped the pathway from sucrose to BSP and identified BsGPI, BsmanA, and BsCSLAs as the key genes of BSP biosynthesis, suggesting that the functional differentiation of the cellulose synthase-like family A (CSLA) may be critical for the flow of glucomannan to the BSP or cell wall. Subsequently, virus-mediated gene silencing showed that silencing of two CSLAs (Bs03G11846 and Bs03G11849) led to a decrease in BSP content, and yeast two-hybrid and luciferase complementation experiments confirmed that four CSLAs (Bs03G11846, Bs03G11847, Bs03G11848, and Bs03G11849) can form homo- or heterodimers, suggesting that multiple CSLAs may form a large complex that functions in BSP synthesis. Our results provide cytological evidence of BSP and describe the isolation and characterization of candidate genes involved in BSP synthesis, laying a solid foundation for further research on its regulation mechanisms and the genetic engineering breeding of B. striata.

Genome-wide identification, characterization and transcriptional profile of the SWEET gene family in Dendrobium officinale

BACKGROUND

Dendrobium officinale Kimura et Migo (D. officinale) is a well-known traditional Chinese medicine with high content polysaccharides in stems. The SWEET (Sugars Will Eventually be Exported Transporters) family is a novel class of sugar transporters mediating sugar translocation among adjacent cells of plants. The expression patterns of SWEETs and whether they are associated with stress response in D. officinale remains uncovered.

RESULTS

Here, 25 SWEET genes were screened out from D. officinale genome, most of which typically contained seven transmembrane domains (TMs) and harbored two conserved MtN3/saliva domains. Using multi-omics data and bioinformatic approaches, the evolutionary relationship, conserved motifs, chromosomal location, expression patterns, correlationship and interaction network were further analyzed. DoSWEETs were intensively located in nine chromosomes. Phylogenetic analysis revealed that DoSWEETs were divided into four clades, and conserved motif 3 specifically existed in DoSWEETs from clade II. Different tissue-specific expression patterns of DoSWEETs suggested the division of their roles in sugar transport. In particular, DoSWEET5b, 5c, and 7d displayed relatively high expression levels in stems. DoSWEET2b and 16 were significantly regulated under cold, drought, and MeJA treatment, which were further verified using RT-qPCR. Correlation analysis and interaction network prediction discovered the internal relationship of DoSWEET family.

CONCLUSIONS

Taken together, the identification and analysis of the 25 DoSWEETs in this study provide basic information for further functional verification in D. officinale.

Bricks out of the wall: polysaccharide extramural functions

Plant polysaccharides are components of plant cell walls and/or store energy. However, this oversimplified classification neglects the fact that some cell wall polysaccharides and glycoproteins can localize outside the relatively sharp boundaries of the apoplastic moiety, where they adopt functions not directly related to the cell wall. Such polysaccharide multifunctionality (or 'moonlighting') is overlooked in current research, and in most cases the underlying mechanisms that give rise to unconventional ex muro trafficking, targeting, and functions of polysaccharides and glycoproteins remain elusive. This review highlights major examples of the extramural occurrence of various glycan cell wall components, discusses the possible significance and implications of these phenomena for plant physiology, and lists exciting open questions to be addressed by future research.

Transcriptomic and metabolomic analyses reveal the main metabolites in Dendrobium officinale leaves during the harvesting period

Dendrobium officinale, which is a medicine food homology plant, contains many metabolites, especially polysaccharides and flavonoids. Unlike flowers and stems, which are the most frequently harvested organs for a variety of uses, leaves tend to be discarded. This study assessed main metabolites in leaves to identify the most appropriate timing of collection during harvest, which was divided into three stages (S1-S3: 8, 10, and 11 months after sprouting, respectively). Metabolomic and transcriptomic analyses of S1-S3 were performed. Water-soluble polysaccharides (WSPs), flavonoids and free amino acids (FAAs) were detected in leaves. WSPs decreased from S1 to S3 but flavonoids and some FAAs (e.g., phophoserine) increased from S1 to S2, then decreased from S2 to S3. In all three stages, mannose was the dominant monosaccharide among WSPs, followed by glucose. In S2, 35 flavonoids were identified, the most abundant being rutin, schaftoside and vitexin, while 34 FAAs were identified in all three stages, the most abundant being tyrosine, phosphoserine and alanine. A total of 2584, 3414 and 2032 differentially expressed genes (DEGs) were discovered in S1 vs S2, S1 vs S3 and S1 vs S3, respectively. Correlation analysis revealed that five DEGs (DoSUS, DoXYLA, DoFRK, DoGMP, and DoCSLA), two DEGs (DoDFR, and DoANS) and a single DEG (DoPGAM) were involved in the metabolism of WSPs, flavonoids and phosphoserine, respectively. The findings of this study lay a foundation for the commercial exploitation of metabolites in the harvested leaves of D. officinale, and the use of detected DEGs in applied genetic studies.

Glucomannan in Dendrobium catenatum: Bioactivities, Biosynthesis and Perspective

Dendrobium catenatum is a classical and precious dual-use plant for both medicine and food in China. It was first recorded in Shen Nong’s Herbal Classic, and has the traditional functions of nourishing yin, antipyresis, tonifying the stomach, and promoting fluid production. The stem is its medicinal part and is rich in active polysaccharide glucomannan. As an excellent dietary fiber, glucomannan has been experimentally confirmed to be involved in anti-cancer, enhancing immunity, lowering blood sugar and blood lipids, etc. Here, the status quo of the D. catenatum industry, the structure, bioactivities, biosynthesis pathway and key genes of glucomannan are systematically described to provide a crucial foundation and theoretical basis for understanding the value of D. catenatum and the potential application of glucomannan in crop biofortification.

A Comparison of the Flavonoid Biosynthesis Mechanisms of Dendrobium Species by Analyzing the Transcriptome and Metabolome

Dendrobium huoshanense, Dendrobium officinale, and Dendrobium moniliforme, as precious Chinese medicinal materials, have a variety of medicinal properties. Flavonoids are important medicinal components of Dendrobium, but their accumulation rules and biosynthesis mechanisms remain unclear. To explore the similarities and differences of flavonoid accumulation and biosynthesis in these three Dendrobium species, we performed flavonoid content determination, widely-targeted metabolomics and transcriptome sequencing on 1-4 years old Dendrobium species. The results showed that in different growth years, D. huoshanense stems had the highest flavonoid content in the second year of growth, while D. officinale and D. moniliforme stems had the highest flavonoid content in the third year of growth. A total of 644 differentially accumulated metabolites (DAMs) and 10,426 differentially expressed genes (DEGs) were identified by metabolomic and transcriptomic analysis. It was found that DAMs and DEGs were not only enriched in the general pathway of "flavonoid biosynthesis", but also in multiple sub-pathways such as "Flavone biosynthesis", and "Flavonol biosynthesis" and "Isoflavonoid biosynthesis". According to a combined transcriptome and metabolome analysis, the expression levels of the F3'H gene (LOC110096779) and two F3'5'H genes (LOC110101765 and LOC110103762) may be the main genes responsible for the differences in flavonoid accumulation. As a result of this study, we have not only determined the optimal harvesting period for three Dendrobium plants, but also identified the key genes involved in flavonoid biosynthesis and provided a basis for further study of the molecular mechanism of flavonoid synthesis.

Comparison of the Antioxidant Activities and Polysaccharide Characterization of Fresh and Dry Dendrobium officinale Kimura et Migo

It is generally believed that fresh Dendrobium officinale (FDO) has more significant pharmacological activity than dried Dendrobium officinale (DDO); however, the difference has not been clearly shown. Our study compared their antioxidant properties both in vitro and in vivo, and the molecular weight arrangement and monosaccharide composition of the fresh Dendrobium officinale polysaccharides (FDOPs) and the dried Dendrobium officinale polysaccharides (DDOPs) were analyzed by HPLC-GPC and GC-MS. The results showed that the FDO and its polysaccharides had more significant effects on scavenging DPPH, ABTS, and hydroxyl radicals than the DDO. In addition, both the FDO and DDO significantly reduced lipid peroxidation levels and increased the SOD, T-AOC, CAT, and GSH levels in mice with acute liver damage caused by CCl₄, while the FDO and its polysaccharides were more effective. Histopathological analysis further verified the protective effect of the Dendrobium polysaccharides on CCl₄-induced liver injury. The determination of the polysaccharides revealed that the polysaccharide and mannose contents of the FDO were significantly higher than their dried counterparts, and the homogeneous arrangement of the polysaccharides in the FDO was degraded into three polysaccharide fragments of different molecular weights in the DDO. Overall, our data identified differences in the antioxidant activities of the FDO and DDO, as well as the reasons for these differences.

Identification of key gene networks controlling polysaccharide accumulation in different tissues of Polygonatum cyrtonema Hua by integrating metabolic phenotypes and gene expression profiles

Plant polysaccharides, a type of important bioactive compound, are involved in multiple plant defense mechanisms, and in particular polysaccharide-alleviated abiotic stress has been well studied. Polygonatum cyrtonema Hua (P. cyrtonema Hua) is a medicinal and edible perennial plant that is used in traditional Chinese medicine and is rich in polysaccharides. Previous studies suggested that sucrose might act as a precursor for polysaccharide biosynthesis. However, the role of sucrose metabolism and transport in mediating polysaccharide biosynthesis remains largely unknown in P. cyrtonema Hua. In this study, we investigated the contents of polysaccharides, sucrose, glucose, and fructose in the rhizome, stem, leaf, and flower tissues of P. cyrtonema Hua, and systemically identified the genes associated with the sucrose metabolism and transport and polysaccharide biosynthesis pathways. Our results showed that polysaccharides were mainly accumulated in rhizomes, leaves, and flowers. Besides, there was a positive correlation between sucrose and polysaccharide content, and a negative correlation between glucose and polysaccharide content in rhizome, stem, leaf, and flower tissues. Then, the transcriptomic analyses of different tissues were performed, and differentially expressed genes related to sucrose metabolism and transport, polysaccharide biosynthesis, and transcription factors were identified. The analyses of the gene expression patterns provided novel regulatory networks for the molecular basis of high accumulation of polysaccharides, especially in the rhizome tissue. Furthermore, our findings explored that polysaccharide accumulation was highly correlated with the expression levels of SUS, INV, SWEET, and PLST, which are mediated by bHLH, bZIP, ERF, ARF, C2H2, and other genes in different tissues of P. cyrtonema Hua. Herein, this study contributes to a comprehensive understanding of the transcriptional regulation of polysaccharide accumulation and provides information regarding valuable genes involved in the tolerance to abiotic stresses in P. cyrtonema Hua.

Modern mannan: a hemicellulose's journey

Hemicellulosic polysaccharides built of β-1,4-linked mannose units have been found throughout the plant kingdom and have numerous industrial applications. Here, I review recent advances in the biosynthesis and modification of plant β-mannans. These matrix polymers can associate with cellulose bundles to impact the mechanical properties of plant fibers or biocomposites. In certain algae, mannan microfibrils even replace cellulose as the dominant structural component of the cell wall. Conversely, patterned galactoglucomannan found in Arabidopsis thaliana seed mucilage significantly modulates cell wall architecture and abiotic stress tolerance despite its relatively low content. I also discuss the subcellular requirements for β-mannan biosynthesis, the increasing number of carbohydrate-active enzymes involved in this process, and the players that continue to be puzzling. I discuss how cellulose synthase-like enzymes elongate (gluco)mannans in orthogonal hosts and highlight the discoveries of plant enzymes that add specific galactosyl or acetyl decorations. Hydrolytic enzymes such as endo-β-1,4-mannanases have recently been involved in a wide range of biological contexts including seed germination, wood formation, heavy metal tolerance, and defense responses. Synthetic biology tools now provide faster tracks to modulate the increasingly-relevant mannan structures for improved plant traits and bioproducts.

Metabolic accumulation and related synthetic genes of O-acetyl groups in mannan polysaccharides of Dendrobium officinale

Mannan polysaccharides (MPs), which contain substituted O-acetyl groups in their backbone, are abundant in the medicinal plant Dendrobium officinale. Acetyl groups can influence the physiological and biochemical properties of polysaccharides, which mainly accumulate in the stems of D. officinale at four developmental stages (S1-S4), showing an increasing trend and a link with water-soluble polysaccharides (WSPs) and mannose. The genes coding for enzymes that catalyze O-acetyl groups to MPs are unknown in D. officinale. The TRICHOME BIREFRINGENCE-LIKE (TBL) gene family contains TBL and DUF231 domains that can transfer O-acetyl groups to various polysaccharides. Based on an established D. officinale genome database, 37 DoTBL genes were identified. Analysis of cis-elements in the promoter region showed that DoTBL genes might respond to different hormones and abiotic stresses. Most of the genes with MeJA-responsive elements were upregulated or downregulated after treatment with MeJA. qRT-PCR results demonstrated that DoTBL genes had significantly higher expression levels in stems and leaves than in roots. Eight DoTBL genes showed relatively higher expression at S2-S4 stages, which showed a link with the content of WSPs and O-acetyl groups. DoTBL35 and its homologous gene DoTBL34 displayed the higher mRNA level in different organs and developmental stages, which might participate in the acetylation of MPs in D. officinale. The subcellular localization of DoTBL34 and DoTBL35 reveals that the endoplasmic reticulum may play an important role in the acetylation of MPs.

Elastic and collapsible: current understanding of cell walls in succulent plants

Succulent plants represent a large functional group of drought-resistant plants that store water in specialized tissues. Several co-adaptive traits accompany this water-storage capacity to constitute the succulent syndrome. A widely reported anatomical adaptation of cell walls in succulent tissues allows them to fold in a regular fashion during extended drought, thus preventing irreversible damage and permitting reversible volume changes. Although ongoing research on crop and model species continuously reports the importance of cell walls and their dynamics in drought resistance, the cell walls of succulent plants have received relatively little attention to date, despite the potential of succulents as natural capital to mitigate the effects of climate change. In this review, we summarize current knowledge of cell walls in drought-avoiding succulents and their effects on tissue biomechanics, water relations, and photosynthesis. We also highlight the existing knowledge gaps and propose a hypothetical model for regulated cell wall folding in succulent tissues upon dehydration. Future perspectives of methodological development in succulent cell wall characterization, including the latest technological advances in molecular and imaging techniques, are also presented.

Are cell wall traits a component of the succulent syndrome?

Succulence is an adaptation to low water availability characterised by the presence of water-storage tissues that alleviate water stress under low water availability. The succulent syndrome has evolved convergently in over 80 plant families and is associated with anatomical, physiological and biochemical traits. Despite the alleged importance of cell wall traits in drought responses, their significance in the succulent syndrome has long been overlooked. Here, by analyzing published pressure-volume curves, we show that elastic adjustment, whereby plants change cell wall elasticity, is uniquely beneficial to succulents for avoiding turgor loss. In addition, we used comprehensive microarray polymer profiling (CoMPP) to assess the biochemical composition of cell walls in leaves. Across phylogenetically diverse species, we uncover several differences in cell wall biochemistry between succulent and non-succulent leaves, pointing to the existence of a 'succulent glycome'. We also highlight the glycomic diversity among succulent plants, with some glycomic features being restricted to certain succulent lineages. In conclusion, we suggest that cell wall biomechanics and biochemistry should be considered among the characteristic traits that make up the succulent syndrome.

Putative genes in alkaloid biosynthesis identified in Dendrobium officinale by correlating the contents of major bioactive metabolites with genes expression between Protocorm-like bodies and leaves

BACKGROUND

Dendrobium officinale, an endangered Chinese herb, possesses extensive therapeutic effects and contains bioactive ingredients such as major polysaccharides, alkaloids, and minimal flavonoids. We first obtained the protocorm-like bodies (PLBs) of this plant through tissue culture in order to determine the distribution of the main secondary metabolites in each organelle and the PLBs. We then analyzed the correlation between gene expression level from comparative transcriptome sequencing and metabolite content in different organs to identify putative genes encoding enzymes involved in the biosynthesis of polysaccharides, alkaloids, and flavonoids.

RESULTS

We used seeds as explants for protocorm induction and PLB propagation of D. officinale. The optimal medium formula for PLB propagation was 1/2 MS + α-NAA 0.5 mg·L- 1 + 6-BA 1.0 mg·L- 1 + 2, 4-D 1.5-2.0 mg·L- 1 + potato juice 100 g·L- 1. Stems, PLBs and leaves of D. officinale had the highest content of polysaccharides, alkaloids and flavonoids, respectively. Naringenin was only produced in stem; however, PLBs with high alkaloid content can replace other organs producing alkaloids. The hot water extraction method outperformed the ultrasound-assisted extraction method for extracting polysaccharides from D. officinale. A comparative transcriptome analysis of PLBs and leaves of D. officinale revealed differential expression of genes encoding enzymes involved in polysaccharide, alkaloid and flavonoid biosynthetic pathways. Putative genes encoding enzymes involved in these biosynthetic pathways were identified. Notably, we identified genes encoding the alkaloid biosynthesis enzymes strictosidine β-D-Glucosidase, geissoschizine synthase and vinorine synthase in D. officinale.

CONCLUSIONS

The identification of candidate genes encoding enzymes involved in metabolite biosynthesis will help to explore and protect this endangered species and facilitate further analysis of the molecular mechanism of secondary metabolite biosynthesis in D. officinale.

Isolation, structural properties, bioactivities of polysaccharides from Dendrobium officinale Kimura et. Migo: A review

Dendrobium officinale Kimura et Migo (D. officinale) is used as herbal medicine and new food resource in China, which is nontoxic and harmless, and can be used as common food. Polysaccharide as one of the main bioactive components in D. officinale, mainly composed of glucose and mannose (Manp: Glcp = 2.01:1.00-8.82:1.00), along with galactose, xylose, arabinose, and rhamnose in different molar ratios and types of glycosidic bonds. Polysaccharides of D. officinale exhibit a variety of biological effects, including immunomodulatory, anti-tumor, gastro-protective, hypoglycemic, anti-inflammatory, hepatoprotective, and vasodilating effects. This paper presents the extraction, purification, structural characteristics, bioactivities, structure-activity relationships and analyzes gaps in the current research on D. officinale polysaccharides. In addition, based on in vitro and in vivo experiments, the possible mechanisms of bioactivities of D. officinale polysaccharides were summarized. We hope that this work may provide helpful references and promising directions for further study and development of D. officinale polysaccharides.

Metabolomic and transcriptomic analyses reveal the regulation of pigmentation in the purple variety of Dendrobium officinale

We performed an integrated analysis of the transcriptome and metabolome from purple (Pr) and normal cultivated varieties (CK) of Dendrobium officinale to gain insights into the regulatory networks associated with phenylpropanoid metabolism and to identify the key regulatory genes of pigmentation. Metabolite and transcript profiling were conducted by ultra-performance liquid chromatography electrospray tandem mass spectrometry (UPLC-ESI-MS/MS) and RNA sequencing. Pr had more flavonoids in the stem than did CK. Metabolome analyses showed that 148 differential metabolites are involved in the biosynthesis of phenylpropanoids, amino acids, purines, and organic acids. Among them, the delphinidin and quercetin derivatives were significantly higher in Pr. A total of 4927 differentially expressed genes (DEGs) were significantly enriched (p ≤ 0.01) in 50 Gene Ontology (GO) terms. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed significantly enriched phenylpropanoid biosynthesis and phytohormone signal transduction in Pr versus CK. The expression levels of flavanone 3-hydroxylase (F3H) and leucoanthocyanidin dioxygenase (LDOX) affected the flux of dihydroflavonol, which led to a color change in Pr. Moreover, DEG enrichment and metabolite analyses reflected flavonoid accumulation in Pr related to brassinosteroid (BR) and auxin metabolism. The results of this study elucidate phenylpropanoid biosynthesis in D. officinale.

Transcriptome Analysis Reveals Biosynthesis of Important Bioactive Constituents and Mechanism of Stem Formation of Dendrobium huoshanense

The stem of Dendrobium huoshanense C.Z. Tang and S.J. Cheng was widely used as a medicinal herb in health care products due to its broad pharmacological activities. However, the molecular regulation mechanism of stem development and biosynthetic pathways of important bioactive substances are still unclear in D. huoshanense. In this study, the bioactive compounds in leaves, stems and roots, and the identification of candidate genes involved in stem formation and biosynthesis of active compounds via transcriptome sequence were analyzed. The accumulation of total polysaccharides and flavonoids were varied significantly in different tissues. A comparative transcriptomic analysis revealed several differentially expressed genes (DEGs) involved in polysaccharides biosynthesis (103 genes), including fructose and mannose related genes (29 genes) and glycosyltransferase genes (74 genes), and flavonoids biosynthesis (15 genes). Some candidate genes that participated in photoperiod regulation (27 genes), starch and sucrose metabolism (46 genes), and hormone-induced activation of signaling pathways (38 genes) may be involved in stem formation. In sum, this study provides a foundation for investigating the molecular processes in the biosynthesis of active compounds and stem development. The transcriptome data presented here provides an important resource for the future studies of the molecular genetics and functional genomics in D. huoshanense and optimized control of the active compounds produced by D. huoshanense.

Bioinformatics-assisted, integrated omics studies on medicinal plants

The immense therapeutic and economic values of medicinal plants have attracted increasing attention from the worldwide researchers. It has been recognized that production of the authentic and high-quality herbal drugs became the prerequisite for maintaining the healthy development of the traditional medicine industry. To this end, intensive research efforts have been devoted to the basic studies, in order to pave a way for standardized authentication of the plant materials, and bioengineering of the metabolic pathways in the medicinal plants. In this paper, the recent advances of omics studies on the medicinal plants were summarized from several aspects, including phenomics and taxonomics, genomics, transcriptomics, proteomics and metabolomics. We proposed a multi-omics data-based workflow for medicinal plant research. It was emphasized that integration of the omics data was important for plant authentication and mechanistic studies on plant metabolism. Additionally, the computational tools for proper storage, efficient processing and high-throughput analyses of the omics data have been introduced into the workflow. According to the workflow, authentication of the medicinal plant materials should not only be performed at the phenomics level but also be implemented by genomic and metabolomic marker-based examination. On the other hand, functional genomics studies, transcriptional regulatory networks and protein-protein interactions will contribute greatly for deciphering the secondary metabolic pathways. Finally, we hope that our work could inspire further efforts on the bioinformatics-assisted, integrated omics studies on the medicinal plants.

The GDP-mannose transporter gene (DoGMT) from Dendrobium officinale is critical for mannan biosynthesis in plant growth and development

Dendrobium officinale is a precious traditional Chinese medicinal herb because it is abundant in mannose-containing polysaccharides (MCPs). GDP-mannose transporter (GMT), which translocates GDP-mannose into the Golgi lumen, is indispensable for the biosynthesis of MCPs. In this study, we found that the dominant polysaccharides in D. officinale were MCPs in a range of varieties and different physiological phases. After a positive correlation between the accumulation of mannose and the transcript levels of candidate GMT genes was found, three GMT genes (DoGMT1-3) were identified in D. officinale. DoGMT1, DoGMT2 and DoGMT3 exhibited the highest transcript level in stem that an organ for MCPs storage. All three DoGMT proteins were targeted to Golgi apparatus, and had a GDP binding domain (GXL/VNK) that was homologous to a specially characterized GMT protein GONST1 in Arabidopsis thaliana. Moreover, DoGMT1, DoGMT2 and DoGMT3 complemented a GDP-mannose transport-defective yeast mutant (vrg4-2), meanwhile they also demonstrated a higher GDP-mannose uptake activity. Therefore, we conclude that DoGMT1, DoGMT2 and DoGMT3 are able to transport GDP-mannose while the expression patterns of these genes correspond to the accumulation of MCPs in D. officinale. These findings support the importance of GMT genes from D. officinale in the biosynthesis of MCPs.

Genome-wide characterization of the cellulose synthase gene superfamily in Solanum lycopersicum

The cellulose synthase gene superfamily, which includes the cellulose synthase (CesA) and cellulose synthase-like (Csl) gene families, plays a vital role in the biosynthesis of cellulose and hemicellulose in plants. However, these genes have not been extensively studied in tomato (Solanum lycopersicum), a model for Solanaceae plants and for fleshy fruit development. Here, we identified and systematically analyzed 38 CesA/Csl family members that contained cellulose synthase domain regions, and categorized their encoded proteins into 6 subfamilies (CesA, CslA, CslB, CslD, CslE, and CslG) based on phylogenetic analysis. Most CesA/Csl genes from tomato are closely related to those from Arabidopsis, but the families have distinct features regarding gene structure, chromosome distribution and localization, phylogeny, and deduced protein sequence, indicating that they arose via different evolutionary process. Furthermore, expression analysis of CesA/Csl genes in different tissues at various developmental stages showed that most CesAs were constitutively expressed with differential expression levels in various organs; three CslD genes were expressed specifically in flowers, and four CesA and five Csl putative genes were preferentially expressed in fruits. Our results provide insight into the general characteristics of the CesA/Csl genes in tomato, and lay the foundation for further functional studies of CesA/Csl genes in tomato and other Solanaceae species.

Genome-wide researches and applications on Dendrobium

This review summarizes current knowledge of chromosome characterization, genetic mapping, genomic sequencing, quality formation, floral transition, propagation, and identification in Dendrobium. The widely distributed Dendrobium has been studied for a long history, due to its important economic values in both medicine and ornamental. In recent years, some species of Dendrobium and other orchids had been reported on genomic sequences, using the next-generation sequencing technology. And the chloroplast genomes of many Dendrobium species were also revealed. The chromosomes of most Dendrobium species belong to mini-chromosomes, and showed 2n = 38. Only a few of genetic studies were reported in Dendrobium. After revealing of genomic sequences, the techniques of transcriptomics, proteomics and metabolomics could be employed on Dendrobium easily. Some other molecular biological techniques, such as gene cloning, gene editing, genetic transformation and molecular marker developing, had also been applied on the basic research of Dendrobium, successively. As medicinal plants, insights into the biosynthesis of some medicinal components were the most important. As ornamental plants, regulation of flower related characteristics was the most important. More, knowledge of growth and development, environmental interaction, evolutionary analysis, breeding of new cultivars, propagation, and identification of species and herbs were also required for commercial usage. All of these studies were improved using genomic sequences and related technologies. To answer some key scientific issues in Dendrobium, quality formation, flowering, self-incompatibility and seed germination would be the focus of future research. And genome related technologies and studies would be helpful.

Genome-wide analysis of the cellulose synthase-like (Csl) gene family in bread wheat (Triticum aestivum L.)

BACKGROUND

Hemicelluloses are a diverse group of complex, non-cellulosic polysaccharides, which constitute approximately one-third of the plant cell wall and find use as dietary fibres, food additives and raw materials for biofuels. Genes involved in hemicellulose synthesis have not been extensively studied in small grain cereals.

RESULTS

In efforts to isolate the sequences for the cellulose synthase-like (Csl) gene family from wheat, we identified 108 genes (hereafter referred to as TaCsl). Each gene was represented by two to three homeoalleles, which are named as TaCslXY_ZA, TaCslXY_ZB, or TaCslXY_ZD, where X denotes the Csl subfamily, Y the gene number and Z the wheat chromosome where it is located. A quarter of these genes were predicted to have 2 to 3 splice variants, resulting in a total of 137 putative translated products. Approximately 45% of TaCsl genes were located on chromosomes 2 and 3. Sequences from the subfamilies C and D were interspersed between the dicots and grasses but those from subfamily A clustered within each group of plants. Proximity of the dicot-specific subfamilies B and G, to the grass-specific subfamilies H and J, respectively, points to their common origin. In silico expression analysis in different tissues revealed that most of the genes were expressed ubiquitously and some were tissue-specific. More than half of the genes had introns in phase 0, one-third in phase 2, and a few in phase 1.

CONCLUSION

Detailed characterization of the wheat Csl genes has enhanced the understanding of their structural, functional, and evolutionary features. This information will be helpful in designing experiments for genetic manipulation of hemicellulose synthesis with the goal of developing improved cultivars for biofuel production and increased tolerance against various stresses.

Hybrid Sequencing of Full-Length cDNA Transcripts of Stems and Leaves in Dendrobium officinale

Dendrobium officinale is an extremely valuable orchid used in traditional Chinese medicine, so sought after that it has a higher market value than gold. Although the expression profiles of some genes involved in the polysaccharide synthesis have previously been investigated, little research has been carried out on their alternatively spliced isoforms in D. officinale. In addition, information regarding the translocation of sugars from leaves to stems in D. officinale also remains limited. We analyzed the polysaccharide content of D. officinale leaves and stems, and completed in-depth transcriptome sequencing of these two diverse tissue types using second-generation sequencing (SGS) and single-molecule real-time (SMRT) sequencing technology. The results of this study yielded a digital inventory of gene and mRNA isoform expressions. A comparative analysis of both transcriptomes uncovered a total of 1414 differentially expressed genes, including 844 that were up-regulated and 570 that were down-regulated in stems. Of these genes, one sugars will eventually be exported transporter (SWEET) and one sucrose transporter (SUT) are expressed to a greater extent in D. officinale stems than in leaves. Two glycosyltransferase (GT) and four cellulose synthase (Ces) genes undergo a distinct degree of alternative splicing. In the stems, the content of polysaccharides is twice as much as that in the leaves. The differentially expressed GT and transcription factor (TF) genes will be the focus of further study. The genes DoSWEET4 and DoSUT1 are significantly expressed in the stem, and are likely to be involved in sugar loading in the phloem.

The medicinal and pharmaceutical importance of Dendrobium species

Plants of the Dendrobium genus, one of the largest in the Orchidaceae, manifest a diversity of medicinal effects encompassing antiangiogenic, immunomodulating, antidiabetic, cataractogenesis-inhibiting, neuroprotective, hepatoprotective, anti-inflammatory, antiplatelet aggregation, antifungal, antibacterial, antiherpetic, antimalarial, aquaporin-5 stimulating, and hemagglutininating activities and also exert beneficial actions on colonic health and alleviate symptoms of hyperthyroidism. The active principles include a wide range of proteinaceous and non-proteinaceous molecules. This mini-review discusses the latest advances in what is known about the medicinal and pharmaceutical properties of members of the Dendrobium genus and explores how biotechnology can serve as a conduit to mass propagate valuable germplasm for sustainable exploration for the pharmaceutical industry.