Analysis of Endophytic Bacterial Diversity From Different Dendrobium Stems and Discovery of an Endophyte Produced Dendrobine-Type Sesquiterpenoid Alkaloids

Abstract

As the unique component of Dendrobium, dendrobine-type sesquiterpenoid alkaloids (DSAs) possess a variety of medicinal properties. It has been well documented that plant endophytes can in vitro synthesize secondary metabolites identical or similar to metabolites produced by their host plants. This study aimed to investigate the composition and distribution of endophytic bacteria of Dendrobium stems by Illumina MiSeq platform sequencing and cultivation-dependent methods and then to assess the potential for endophytic bacteria to produce DSAs. Results indicated that it was necessary to combine both cultivation-dependent and cultivation-independent methods to analyze the community structure of endophytic bacterial in plants comprehensively. The length of the Dendrobium stems influenced the endophytic bacterial community. The diversity and richness of endophytic bacteria in group J10_15cm of stems were the highest, which showed a significant difference from the other stem groups. However, there was no certain connection between the diversity and richness of endophytic bacteria and the content of dendrobine. It was most likely due to the influence of several specific endophytic bacteria genera, such as Sphingomonas and Rhodococcus. Athelia rolfsii, Myrothecium roridum, as pathogenic fungi, and Pectobacterium carotovorum subsp. actinidiae, as pathogenic bacteria of Dendrobium, were used to determine the antimicrobial activities. In these assays, six strains belonging to five genera showed antimicrobial activity against at least two phytopathogens. The strain BL-YJ10_15-29 (Paracoccus pueri THG-N2.35, 98.98%) showed the best antimicrobial activity against the three phytopathogens. In addition, 2 DSAs (6-hydroxydendrobine and nobilonine) were identified in the fermentation supernatant of the strain CM-YJ10_15-44 (Pseudomonas protegens CHA0, 99.24%), whereas the whole-genome analysis results further demonstrated that the precursors of the two DSAs [geranyl-PP and (E, E)-famesyl-PP] were synthesized mainly through the methyl-D-erythritol 4-phosphate pathway in this strain. This study provides new insight into the studies on the biosynthesis of DSAs and provides potential biocontrol bacteria.

Exogenous and Endophytic Fungal Communities of Dendrobium nobile Lindl. across Different Habitats and Their Enhancement of Host Plants’ Dendrobine Content and Biomass Accumulation

“…Xu et al (2022) reported that the TPS and CYP450 gene families might also contribute to alkaloid biosynthesis in D. nobile . Wang et al (2022) reported that two dendrobine-type sesquiterpenoid alkaloids (6-hydroxydendrobine and nobilonine) from the Dendrobium endophytic bacterium Pseudomonas protegens CHA0 were synthesized mainly through the MEP pathway . However, the mechanism through which Phyllosticta stimulates dendrobine accumulation is still unclear and requires further exploration.…”

“…The population dynamics and distribution of endophytic fungi are primarily dependent on the availability of host species-specific habitats, organs, nutrients, and climatic factors . Research on D. nobile suggests that endophytic bacterial community structure is dependent on stem length . However, exogenous fungi, growing or originating from outside an organism, are abundant in natural environments, particularly in polluted environments. , Exogenous fungi can improve the stress resistance of their host plants, including to pathogens, drought, and heavy metals .…”

“… 20 Research on D. nobile suggests that endophytic bacterial community structure is dependent on stem length. 21 However, exogenous fungi, growing or originating from outside an organism, are abundant in natural environments, particularly in polluted environments. 22 , 23 Exogenous fungi can improve the stress resistance of their host plants, including to pathogens, drought, and heavy metals.…”

Picrotoxane sesquiterpenoids: chemistry, chemo- and bio-syntheses and biological activities

“…207 It is noteworthy that 6-hydroxydendrobine ( 97 ) and nobilonine ( 109 ) were identified from the endophyte ( Pseudomonas protegens CHA0, 99.24%), which was isolated from the Dendrobium stems and the entire-genome analysis resulted in the biosynthesis of FPP mainly via the MEP pathway. 208…”

Endophytic Fungi: An Effective Alternative Source of Plant-Derived Bioactive Compounds for Pharmacological Studies

“…They have been isolated and cultured from the roots and above-ground parts of various plants, including algae, mosses, ferns, gymnosperms, and angiosperms. Evidence from microorganism's records in the fossil plant tissue indicated that the plant-endophytic fungal interactions have existed for approximately 400 million years, and during this time, endophytic fungi co-evolved unique biosynthetic pathways and metabolic mechanisms to synthesize complex secondary metabolites [13]. To date, only 5% of 1.5 million fungal species on Earth have been described in detail, and out of this percentage (69,000 fungal species), only 16% (11,500 species) have been cultured and studied.…”