Biocontrol fungi induced stem-base rot disease resistance of Morinda officinalis How revealed by transcriptome analysis

Introduction

Morinda officinalis How (MO) is a Rubiaceae plant, and its medicinal part is dried root, which is one of the "Four Southern Medicines" in China. At present, the plant MO breed seedlings mainly by cutting methods. Long-term asexual propagation makes pathogenic fungi accumulate in MO, leading to stem-base rot, which is caused by Fusarium oxysporum (Fon).

Methods

In this study, we used Trichoderma harzianum and Pestalotiopsis sp. as biocontrol fungi to investigate their antagonistic ability to Fon through in vitro antagonism and pot experiments, and combined with transcriptome sequencing to explore the mechanism of biocontrol.

Results

The results showed that both Trichoderma harzianum and Pestalotiopsis sp. could inhibit the growth of Fon. In addition, Trichoderma harzianum and Pestalotiopsis sp. could also enhance the basic immunity to Fon by increasing the activities of defensive enzymes such as POD and SOD, chlorophyll content, soluble sugar content, and oligosaccharide content of MO. The mechanism of biological control of stem-base rot of MO was discussed by transcriptome technology. MO was treated with two treatments, root irrigation with biocontrol fungi or inoculation with Fon after root irrigation with biocontrol fungi. Transcriptome sequencing revealed that nearly 11,188 differentially expressed genes (DEGs) were involved in the process of inducing MO systemic resistance to Fon by biocontrol fungi. Meanwhile, Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, as well as transcription factor (TFs) prediction showed that there were significant differences in the expression levels of MO roots under different treatments. Also, the genes of the "MAPK signaling pathway" and "plant hormone signaling pathway" were analyzed, in which the ERFs gene of the ethylene signal transduction pathway participated in the metabolism of glycosyl compounds. It is speculated that the ethylene signal may participate in the immune response of the sugar signal to the infection of Fon. After qRT-PCR verification of 10 DEGs related to the ethylene signal transduction pathway, the expression trend is consistent with the results of transcriptome sequencing, which proves the reliability of transcriptome sequencing.

Discussion

In conclusion, this study preliminarily identified the molecular mechanism of the biological control of MO stem-base rot and provided a scientific basis for further research on the prevention and control mechanism of MO stem-base rot.

Physiological and transcriptomic analysis reveals the potential mechanism of Morinda officinalis How in response to freezing stress

BACKGROUND

Morinda officinalis How (MO) is a vine shrub distributed in tropical and subtropical regions, known as one of the "Four Southern Herbal Medicines" in China. The unclear responsive mechanism by which MO adapt to freezing stress limits progress in molecular breeding for MO freezing tolerance.

RESULTS

In this study, morphological, physiological and microstructure changes in MO exposed to -2℃ for 0 h, 3 h, 8 h and 24 h were comprehensively characterized. The results showed that freezing stress caused seedling dehydration, palisade cell and spongy mesophyll destruction. A significant increase in the content of proline, soluble protein and soluble sugars, as well as the activity of superoxide dismutase and peroxidase was observed. Subsequently, we analyzed the transcriptomic changes of MO leaves at different times under freezing treatment by RNA-seq. A total of 24,498 unigenes were annotated and 3252 unigenes were identified as differentially expressed genes (DEGs). Most of these DEGs were annotated in starch and sucrose metabolism, plant hormone signal transduction and MAPK signaling pathways. Family Enrichment analysis showed that the glucosyl/glucuronosyl transferases, oxidoreductase, chlorophyll a/b binding protein and calcium binding protein families were significantly enriched. We also characterized 7 types of transcription factors responding to freezing stress, among which the most abundant family was the MYBs, followed by the AP2/ERFs and NACs. Furthermore, 10 DEGs were selected for qRT-PCR analysis, which validated the reliability and accuracy of RNA-seq data.

CONCLUSIONS

Our results provide an overall view of the dynamic changes in physiology and insight into the molecular regulation mechanisms of MO in response to freezing stress. This study will lay a foundation for freezing tolerance molecular breeding and improving the quality of MO.

Quality markers for processed products of Morinda officinalis how based on the "oligosaccharides-spectrum-effect"

Morinda officinalis How (MO) possesses prominent tonifying kidney yang and strengthening bone and muscle effects in traditional Chinese medicine (TCM). Due to the complexity of MO components, the chemical mechanism leading to efficacy changes of MO caused by processing remain unclear. This study aimed to investigate and discover quality markers (Q-markers) related to the clinical efficacy of processed MO. The different processed products of MO have different clinical applications, although they originate from the same medicinal herb. The active chemical components from raw and processed MO that protect against reproductive oxidative stress damage were evaluated. The processed products of MO were prepared by different processing methods. The changes in oligosaccharides during processing were characterized by high-performance liquid chromatography with an evaporative light scattering detector (HPLC-ELSD), and the differential components in raw and processed MO were analyzed using SA, HCA, PCA, and OPLS-DA methods. The protective effects of raw and processed MO oligosaccharides (MOOs) against reproductive oxidative stress damage were evaluated based on the spermatic number, spermatic survival rate, abnormal sperm ratio and serum biochemical indicators in cyclophosphamide-induced (CTX-induced) male mice. The results revealed that processed MOOs had better pharmacological effects than raw MOOs. Therefore, gray correlation analysis (GRA) and the technique for order preference by similarity to ideal solution (TOPSIS) methods were used to investigate the spectrum-effect relationships of MOOs. Spectrum-effect relationship analysis revealed that all of the characteristic peaks contributed to the treatment of reproductive oxidative stress damage, and the relative correlation degrees were greater than 0.6. Among them, the peaks 1 F-fructofuranosylnystose, nystose, and 1-kestose and the peaks X2-X5, which were most closely correlated to the treatment of reproductive oxidative stress damage, were identified as inulin-oligosaccharides and inulo-oligosaccharides, respectively. It was proposed that these constituents could be considered Q-markers for processed products of MO. Thus, this study aimed to explore chemical markers that correlate with the clinical efficacy of processed MO.

Iridoids with anti-inflammatory effect from the aerial parts of Morinda officinalis How

Morinda officinalis How was widely applied to alleviate symptom like impotence, menstrual disorders, osteoporosis, and rheumatoid arthritis. To expand resources usage, phytochemistry of the aerial parts was studied and the structures of compounds were elucidated based on NMR, HRESIMS, IR and UV. Moreover, the anti-inflammatory effect and possible mechanism were investigated by Griess kit, RT-qPCR, ELISA, western blot and molecular docking on LPS-induced inflammation in RAW 264.7 cells. Herein, we isolated and identified 16 iridoid derivatives, including seven new iridoids officinaloside A-G (1-7) and nine known iridoids. All the compounds were safe to RAW 264.7 cells. Luckily, compounds 5 and 6 showed inhibitory effect on production of NO, and decreased the expression of inflammatory cytokines at mRNA and protein levels in a dose-dependent way. The possible mechanism of their anti-inflammation may be the affinity interaction between 5 with COX-2 protein, and 6 with iNOS protein. Overall, compounds 5 and 6 exert promising effects in inhibiting inflammatory cytokines, indicating that they could be used as lead compounds for developing health products or clinical practice for inflammation, which provides a scientific basis for further sustainable development and usage of the aerial parts of Morinda officinalis How.

Bioassay-guided isolation and evaluation of anti-osteoporotic polysaccharides from Morinda officinalis

ETHNOPHARMACOLOGICAL RELEVANCE

Morinda officinalis is a well-known Chinese tonic herb that has shown clinical efficacy in the treatment of bone disease. However, its anti-osteoporotic potential and the M. officinalis polysaccharides (MOPs) responsible for activity require further investigation.

AIM OF THE STUDY

This study aimed to investigate the anti-osteoporotic effects of different MOP fractions in ovariectomized (OVX) rats, and to identify the osteoprotective components by bioassay-guided isolation.

MATERIALS AND METHODS

MOPs were prepared by hot water and alkali extraction, separated into three fractions (MO50, MO70, and MOB) and evaluated in the classic OVX rat model and in MC3T3-E1 cells for anti-osteoporotic activity.

RESULTS

Administration of MOPs (400 mg/kg/day) provided significant protection against ovariectomy-induced bone loss and biomechanical dysfunction in rats. Treated animals exhibited reduced deterioration of trabecular microarchitecture and lower levels of bone turnover markers. Bioactivity-guided fractionation led to the isolation of two inulin-type fructans from MO50, MOW50-1 and MOP50-2, with potential anti-osteoporotic activities. These consisted of (2 → 1)-linked β-D-fructosyl residues with degrees of polymerization (DP) of 7 and 13, respectively. Furthermore, MOW50-1 promoted osteogenic differentiation of MC3T3-E1 cells by increasing alkaline phosphatase activity.

CONCLUSIONS

These data suggest very strongly that MOPs, especially MO50 and MOW50-1, may play important roles in the prevention and treatment of osteoporosis.

Inhibits osteoclastogenesis through blocking RANKL-induced NF-κB pathway

Rubiadin-1-methyl ether (RBM) is a natural anthraquinone compound isolated from the root of Morinda officinalis How. In our previous study, RBM was found to have inhibitory effects on the TRAP activity of osteoclasts, which means that RBM may be a candidate for therapy of bone diseases characterized by enhanced bone resorption. However, the further effect of RBM on osteoclasts and the underlying mechanism remain unclear. In the present study, we investigated the effects of RBM isolated from Morinda officinalis How. on osteoclasts derived from bone marrow macrophages (BMMs) and the underlying mechanism in vitro. RBM at the dose that did not affect the viability of cells significantly inhibited RANKL-induced osteoclastogenesis and actin ring formation of osteoclast, while RBM performed a stronger effect at the early stage. In addition, RBM downregulated the expression of osteoclast-related proteins, including nuclear factor of activated T cells cytoplasmic 1 (NFATc1), cellular oncogene Fos (c-Fos), matrix metallopeptidase 9 (MMP-9) and cathepsin K (CtsK) as shown by Western blot. Furthermore, RBM inhibited the phosphorylation of NF-κB p65 and the degradation of IκBα as well as decreased the nuclear translocation of p65. Collectively, the results suggest that RBM inhibit osteoclastic bone resorption through blocking NF-κB pathway and may be a promising agent for the prevention and treatment of bone diseases characterized by excessive bone resorption.