Abstract
This exploratory study was designed to identify factors implicating microbial influence
on medicinal plant metabolomes. Utilizing a whole-microbiome approach, amplicon sequencing
was used to identify the makeup of fungal and bacterial assemblages from endophytic
(interior) and epiphytic (external) environments in two different sets of congeneric
host-plant pairs, with collection of multiple samples of two medicinal plant species
(Actaea racemosa, Rhodiola rosea) and two generic analogs (Actaea rubra, Rhodiola integrifolia). Diversity analysis of microbial assemblages revealed the influence of three primary
factors driving variance in microbial community composition: host-plant taxonomy,
the compartmentalization of microbial communities within discrete plant parts, and
the scale of distance (microhabitat heterogeneity) between sampling locations. These
three factors accounted for ~ 60% of variance within and between investigated microbiomes.
Across all our
collections, bacterial populations were more diverse than fungi (per compartment),
and microbial density in epiphytic compartments (aerial parts, rhizosphere) were higher
than those of endophytes (leaf and root). These comparative data point to key loci
associated with variation between congeneric pairs and plant genera, providing insight
into the complex and contrasting relationships found within this multi-kingdom coevolutionary
relationship. Although reflective of only a limited set of botanical source materials,
these data document the richness of a relatively unexplored component of the plant
world and highlight the relevance of a whole-microbiome ecology-driven approach to
botanical research and directed natural product investigations.
Keywords
plant microbiome - community composition - endophytes - epiphytes - alpha diversity
- beta diversity -
Actaea
-
Rhodiola
- Ranunculaceae - Crassulaceae