Williams, B. R. | bioRxiv Science

bioRxiv2021

In their sister's footsteps: Taxonomic divergence obscures substantial functional overlap among the metabolically diverse symbiotic gut communities of adult and larval turtle ants

Gut bacterial symbionts can support animal nutrition by facilitating digestion and providing valuable metabolites. While the composition of gut symbiont communities shifts with host development in holometabolous insects, changes in symbiotic roles between immature and adult stages are not well documented, especially in ants. Here, we explored the metabolic capabilities of microbiomes sampled from herbivorous turtle ant (Cephalotes sp.) larvae and adult workers through genomic and metagenomic screenings and targeted in vitro metabolic assays. We reveal that larval guts harbor bacterial symbionts from the Enterobacteriales, Lactobacillales and Rhizobiales orders, with impressive metabolic capabilities, including catabolism of plant and fungal recalcitrant fibers common in turtle ant diets, and energy-generating fermentation. Additionally, several members of the specialized turtle ant adult gut microbiome, sampled downstream of an anatomical barrier that dams large food particles, show a conserved potential to depolymerize many dietary fibers and other carbohydrates. Symbionts from both life stages have the genomic capacity to recycle nitrogen, synthesize amino acids and B-vitamins, and perform several key aspects of sulfur metabolism. We also document, for the first time in ants, an adult-associated Campylobacterales symbiont with an apparent capacity to anaerobically oxidize sulfide, reduce nitrate, and fix carbon dioxide. With help of their gut symbionts, including several bacteria likely acquired from the environment, turtle ant larvae appear as an important component of turtle ant colony digestion and nutrition. In addition, the conserved nature of the digestive, energy-generating, and nutritive capacities among adult-enriched symbionts suggests that nutritional ecology of turtle ant colonies has long been shaped by specialized, behaviorally-transferred gut bacteria with over 46 million years of residency.

evolutionary biology↗

bioRxiv2020

Epigenomic patterns reflect irrigation and grafting in the grapevine clone 'Chambourcin'

Although DNA methylation has largely been shown to be stable in plants, mounting evidence indicates methylation patterns may reflect environmental sensitivity. Perennial plants experience seasonal and inter-annual environmental variation, and clonal replicates of some long-lived plants, including many perennial crops, survive in a broad range of environments. This makes perennial crops a compelling study system to investigate links between the plant epigenome and environmental variation. In this study, we used whole genome bisulfite sequencing and small RNA sequencing to characterize the epigenome in 12 clonal replicates of the winegrape cultivar Chambourcin. We asked whether DNA methylation varied in response to a full factorial combination of irrigation and grafting treatments. We found signatures of both irrigation and grafting in the Chambourcin epigenome, as well as compelling evidence for a unique interaction effect whereby grafting appeared to override or mitigate epigenomic changes associated with irrigation in ungrafted vines. These findings indicate that the epigenome responds to environmental and agronomic manipulations, suggesting the epigenome might be a mechanism underlying how long-lived, clonal plants respond at the molecular level to their environment. Further research is needed to assess the potential relevance of variation in DNA methylation to plant form and function, and to address the implications of environmentally-inducible patterns of DNA methylation on the adaptive capacity of long-lived woody perennials in nature and under cultivation.

genomics↗