Marchantia liverworts as a proxy to plants basal microbiomes.

Abstract

Microbiomes influence plant development, establishment, nutrient acquisition, pathogen defense, and the myriad of roles that ultimately impacts plant health. Plants microbiome are shaped through interactions between the microbes (ranging from cooperative functions to chemical warfare) and a selection process entailed by the host plants that distinguishes between pathogens, commensals, symbionts and transient bacteria. The soil is a primary source for microbes colonizing plants, along with other environmental sources including rain and interactions with other organisms. In this work, we explore the microbiomes through massive sequencing of the 16S rRNA gene in the eldest terrestrial plants: Marchantia liverworts. We compared microbiomes from M. polymorpha, and M. paleacea plants collected in the wild and their soils, all together luckily in the same geographical location (sympatric) thus reducing geographic effects; and also from plants grown in vitro and established from gemmae obtained from the same population of wild plants. Qualitative and quantitative microbiome analysis allowed us to identify microbes conserved in both native and in vitro Marchantia species. While M. polymorpha native plants microbiomes richness is reduced about M. paleacea, containing almost half of the Operative Taxonomic Units (OTUs) observed in M. paleacea, M. polymorpha grown in vitro exhibits larger OTUs. This diversity differences might be the result of impairment to recognize their microbial partners and being an open niche for opportunistic bacteria. The main OTUs in Marchantia microbiomes were assigned to the genera: Methylobacterium, Rhizobium, Paenibacillus, Lysobacter, Pirellula, Steroidobacter, and Bryobacter. The assigned genera correspond to bacteria capable of plant-growth promotion, complex exudates degradation, nitrogen fixation, methylotrophs, and disease-suppressive bacteria, all hosted in the relatively simple anatomy of the plant that provides refuge on their surfaces, rhizoids, and multiple gas chambers that work as specialized niches for different bacterial groups. Marchantia is a promising model to study not only long-term relationships between plants and their microbes but also the transgenerational impact of microbiomes because of Marchantia long 450 million years under climate change conditions testing microbiome configurations.