Antimicrobial drimane sesquiterpenes and their effect on endophyte communities in the medical tree Warburgia ugandensis

Abstract

Metabolite profiles (GC–−MS), drimane sesquiterpenes, sugars and sugar alcohols, were compared with bacterial and fungal endophyte communities (T-RFLP, DNA clones, qPCR) in leaves and roots of the pepper bark tree, Warburgia ugandensis (Canellaceae). Ten individuals each were assessed from two locations east and west of the Great Rift Valley, Kenya, Africa, which differed in humidity and vegetation, closed forest versus open savannah. Despite organ- and partially site-specific variation of drimane sesquiterpenes, no clear effects on bacterial and fungal endophyte communities could be detected. The former were dominated by gram-negative Gammaproteobacteria, Pseudomonadaceae and Enterobacteriaceae, as well as gram-positive Firmicutes; the fungal endophyte communities were more diverse but no specific groups dominated. Despite initial expectations, the endophyte community of the pepper bark tree did not differ from other trees that much.

Antimicrobial Drimane Sesquiterpenes Contribute to Balanced Antagonism but Do Not Structure Bacterial and Fungal Endophytes in the African Pepper Bark Tree Warburgia ugandensis

“…As a consequence, considerable interest exists from traditional medicine. A cultureindependent approach, T-RFLP (terminal restriction fragment length polymorphism) combined with PCR cloning, was used to characterize the endophyte communities in the leaves and roots from ten trees growing in two different sites along the Rift valley in Kenya, Eastern Africa (Drage et al, 2014). Contrary to initial expectations, no correlations between the variable accumulation patterns of drimane sesquiterpenes in the roots and leaves of ten individuals and their fungal and bacterial endophyte communities could be found.…”

“…Procedures of DNA isolation and PCR targeting bacterial 16S rDNA and fungal ITS and partial 28S rRNA genes were standard and have been described previously (Drage et al, 2012(Drage et al, , 2014. The nucleotide sequences determined in this study have been deposited in the GenBank database; accession numbers JF836819-45 and HQ130661-721.…”

“…In a previous paper (Drage et al, 2014), we described the fungal and bacterial endophytes that could be detected in the roots, fruits, and leaves of the African pepper bark tree, Warburgia ugandensis Sprague, syn. W. salutaris (Bertol.f.)…”

“…The second (Saunders and Kohn, 2009) found that fungi, which tolerated benzoxazines, were more abundant in producing maize plants than in non-producing mutant individuals. In a previous study, we explored if bacterial and fungal endophyte community structures in the pepper bark tree W. ugandensis correlated with drimane sesquiterpene patters, which not only varied between organs but also between individuals (Drage et al, 2014). None, however, could be found.…”

“…In the former study, the community analysis was performed culture-independently by T-RFLP, the present study explores the same scenario by assaying selected endophytic isolates and non-associated strains against drimane sesquiterpenes. (Drage et al, 2014).…”