Metagenomic insights into the symbiotic relationships and functional roles of bark microbiomes in tea trees

Bark represents a fickle microbial habitat that is significantly influenced by environmental factors, tissue age, and etc. The permanent surface of Camellia sinensis bark exhibits the mosaic plaques resulting from the presence of epiphytic microorganisms, particularly on ancient trees. Investigation of microbiome focus on harvested parts of tea tree, but there remains a lack of understanding the associated bark microbial communities. This is significant, as the bark serves as a crucial link between the above-ground harvested components and the subterranean parts of the plant. Here, we utilized amplicon sequencing, microbial isolation and phenotype observation to examine the bark microbiomes of tea trees located on sunny and shady slopes in one grove. Additionally, we conducted metagenomic sequencing, assembly, and binning to explore the potential functions of microorganisms. Comparative analysis revealed significant differences in microbial taxa between epiphytic plaques of individual trees and in slope-associated community structures between the two trees. Co-occurrence networks, characterized by hub nodes of lichenicolous microorganisms, demonstrated positive symbiotic relationships among pathogenic and beneficial microbes. Moreover, the abundance of genes related to carbohydrate and amino acid production in the metagenome-assembled genomes (MAGs) of Acetobacteraceae suggests a potential role in carbon and nitrogen cycles. The genes involved in substance and signal exchange further support the stable symbiont. This study will serve as a valuable resource for guiding future research on utilizing bark microbial resources and genes of primary productivity for agronomical purposes.