Biology subjects

Camilli, S.

Publications and source records attributed to Camilli, S..

3 recordsLinked to original sources

bioRxiv2021

Insights into early stages of the establishment of host:algal endosymbioses: Genetic responses to live versus heat-killed algae and bacterial prey in a sponge host

The freshwater sponge Ephydatia muelleri and its Chlorella-like green algal partner is an emerging model for studying animal:algal endosymbiosis. The sponge host is a highly tractable laboratory organism, and the symbiotic algae are easily cultured. We took advantage of these traits to experimentally interrogate fundamental questions about cellular mechanisms that govern the establishment of durable intracellular partnerships between hosts and symbionts in facultative symbioses. We modified a classical experimental approach to discern the phagocytotic mechanisms that might be co-opted to permit persistent infections, and identified genes differentially expressed in E. muelleri sponges early in the establishment of endosymbiosis. We exposed algal-free E. muelleri to live native algal symbionts, native heat-killed algae, and bacteria, and then performed RNASeq so we could compare patterns of gene expression in each treatment. We contrasted differential gene expression patterns between potential food items (bacteria and heat-killed algae) and the live native Chlorella-like symbiont. We found a relatively small but interesting suite of genes that are uniquely and differentially expressed in the host exposed to live algal symbionts, and a larger number of genes uniquely triggered by host exposure to heat-killed algae. One of the host genes, an ABC transporter that is downregulated in response to live algal symbionts, was further evaluated for its possible role in establishment of the algal symbiosis. We discuss the gene expression profiles associated with host responses to living algal cells in the context of conditions necessary for long-term residency within host cells by phototrophic symbionts as well as the genetic responses to sponge phagocytosis and immune driven pathways.

evolutionary biology↗

bioRxiv2020

Freshwater sponge hosts and their green algae symbionts: a tractable model to understand intracellular symbiosis

In many freshwater habitats, green algae form intracellular symbioses with a variety of heterotrophic host taxa including several species of freshwater sponge. These sponges perform important ecological roles in their habitats, and the poriferan:green algae partnerships offers unique opportunities to study the evolutionary origins and ecological persistence of endosymbioses. We examined the association between Ephydatia muelleri and its chlorophyte partner to identify features of host cellular and genetic responses to the presence of intracellular algal partners. Chlorella-like green algal symbionts were isolated from field-collected adult E. muelleri tissue harboring algae. The sponge-derived algae were successfully cultured and subsequently used to reinfect aposymbiotic E. muelleri tissue. We used confocal microscopy to follow the fate of the sponge-derived algae after inoculating algae-free E. muelleri grown from gemmules to show temporal patterns of symbiont location within host tissue. We also infected aposymbiotic E. muelleri with sponge-derived algae, and performed RNASeq to study differential expression patterns in the host relative to symbiotic states. We compare and contrast our findings with work in other systems (e.g., endosymbiotic Hydra) to explore possible conserved evolutionary pathways that may lead to stable mutualistic endosymbioses. Our work demonstrates that freshwater sponges offer many tractable qualities to study features of intracellular occupancy and thus meet criteria desired for a model system.

evolutionary biology↗

bioRxiv2020

The genomic basis of animal origins: a chromosomal perspective from the sponge Ephydatia muelleri

The genomes of non-bilaterian metazoans are key to understanding the molecular basis of early animal evolution. However, a full comprehension of how animal-specific traits such as nervous systems arose is hindered by the scarcity and fragmented nature of genomes from key taxa, such as Porifera. Ephydatia muelleri is a freshwater sponge found across the northern hemisphere. Here we present its 326 Mb genome, assembled to high contiguity (N50: 9.88 Mb) with 23 chromosomes on 24 scaffolds. Our analyses reveal a metazoan-typical genome architecture, with highly shared synteny across Metazoa, and suggest that adaptation to the extreme temperatures and conditions found in freshwater often involves gene duplication. The pancontinental distribution and ready laboratory culture of E. muelleri make this a highly practical model system, which with RNAseq, DNA methylation and bacterial amplicon data spanning its development and range allows exploration of genomic changes both within sponges and in early animal evolution.

evolutionary biology↗