Deciphering deep-sea chemosynthetic symbiosis by single-nucleus RNA-sequencing

Abstract

Bathymodioline mussels dominate deep-sea methane seep and hydrothermal vent habitats and obtain nutrients and energy primarily through chemosynthetic endosymbiotic bacteria in the bacteriocytes of their gill. However, the molecular mechanisms that orchestrate mussel host-symbiont interactions remain unclear. Here, we constructed a comprehensive cell atlas of the gill in the mussel Gigantidas platifrons from the South China Sea methane seeps (1100m depth) using single-nucleus RNA sequencing (snRNA-seq) and whole-mount in situ hybridisation. We identified 13 types of cells, including three previously unknown ones, uncovered unknown tissue heterogeneity. Every cell type has a designated function in supporting the gill's structure and function, creating an optimal environment for chemosynthesis, and effectively acquiring nutrients from the endosymbiotic bacteria. Analysis of snRNA-seq of in situ transplanted mussels clearly showed the shifts in cell state in response to environmental oscillations. Our findings provide insight into principles of host-symbiont interaction and the bivalves' environmental adaption mechanisms.

Single-cell RNA-seq reveals distinct metabolic “microniches” and close host-symbiont interactions in deep-sea chemosynthetic tubeworm

“…3P ). In a previous study ( 45 ), a similar cell type called the interlaminar cell was observed in the symbiotic tissue of the deep-sea mussel Gigantidas platifrons . These cells were found in the tissue where bacteriocytes were attached between two sheets of gill laminae.…”