New Insights into Detection of a Dendrobine Compound From a Novel Endophytic Trichoderma longibrachiatum Strain and Its Toxicity Against Phytopathogenic Bacteria.

Surendra Sarsaiya,Qi Jia,Qinian Zhou,Jingshan Shi,Archana Jain,Jishuang Chen,Fuxing Shu,Xiaokuan Fan,Quan Xu

doi:10.3389/fmicb.2020.00337

Abstract

Dendrobium nobile is the only plant that could produce the natural bioactive dendrobine. No other source of dendrobine has been found to date except from D. nobile and via chemical synthesis. In this study, we aimed to examine the potential fungal endophyte isolated from D. nobile stem segments using the molecular method and to detect dendrobine compound through high-performance liquid chromatography (HPLC), gas chromatography–mass spectrometry (GC-MS), and liquid chromatography with tandem mass spectrometry (LC-MS/MS) and their metabolite for their antibacterial activity. The potential dendrobine producer strain was recognized as Trichoderma longibrachiatum based on molecular DNA sequencing and GenBank databases. The T. longibrachiatum MD33 produced dendrobine and other compounds in a potato dextrose medium (PDM), as confirmed by HPLC retention time peak analysis. The HPLC results revealed that T. longibrachiatum MD33 biomass showed a peak retention time of 5.28 ± 0.2 min, similar to wild D. nobile stem dendrobine (5.32 ± 0.2 min) and standard chemical reference dendrobine (5.30 ± 0.2 min), indicating the presence of dendrobine in the fungal biomass. Results of GC-MS and LC-MS analysis revealed that T. longibrachiatum MD33 produced the same molecular weight (263 in GC-MS and 264.195 in LC-MS) of dendrobine as compared with standard chemical reference dendrobine and D. nobile dendrobine. Antibacterial activity data revealed that T. longibrachiatum MD33 produced the strongest bactericidal activity against Bacillus subtilis, Bacillus mycoides, and Staphylococcus species, and the diameter of the bacterial growth inhibition zone was 12 ± 0.2, 9 ± 0.2, and 8 ± 0.2 mm, respectively. To the best of our knowledge, this was the first study to investigate T. longibrachiatum as a dendrobine producer, and the results revealed that T. longibrachiatum was directly involved in the potential production of a similar bioactive compound to D. nobile (dendrobine). In addition, the T. longibrachiatum metabolite exhibited potent antibacterial activity and can be a potential strain for medical and industrial purposes.

Highlights

Plant tissues are intracellularly colonized by a complex group of endophytic microbial species, where they play a vital role in plant development, health, and protection
We aimed to determine the presence of T. longibrachiatum MD33 endophytic fungal strain in D. nobile stems, to assess the potential of the fungi to produce dendrobine compounds, and to determine the antibacterial effects of bioactive compounds against phytopathogenic bacteria
We found that T. longibrachiatum MD33 was involved in the production of a similar bioactive compound of D. nobile such as dendrobine

Summary

Introduction

Plant tissues are intracellularly colonized by a complex group of endophytic microbial species, where they play a vital role in plant development, health, and protection. These endophytic microbes, especially fungi, have the ability to promote plant development via indirect and direct mechanisms. Endophytic fungi can directly help host plants through the production of several plant development regulators and by enabling nutrient uptake They can keep the host plant healthy through indirect responses by producing substances such as antibiotics and siderophores to inhibit phytopathogens (Bahroun et al, 2018). There are several medicinal plants species known for their phytoremediative abilities (Hegazy et al, 2011; Santal et al, 2019). The Dendrobium phytoremediation potentials of plant species have been considered in many previous researches (Sarawaneeyaruk et al, 2014; Sutantoa et al, 2016; Santal et al, 2019)

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