Meeting Abstract
Symbioses between phototrophs and heterotrophs are common in many ecosystems, and mechanisms have evolved to ensure long-term and stable interactions for these intracellular symbioses. Factors that permit stability of the association, or enhance performance of one or the other partner, are often poorly understood. Both marine and freshwater sponges offer a number of unique opportunities to examine the pathways to persistence for phototrophic algal symbionts in heterotrophic host cells. The goal of this work is to elucidate genetic and cellular factors that contribute to tight integration of hosts and symbionts, while also exploring evidence of convergent evolution in partnerships involving distinct algal symbionts and heterotrophic hosts. We will discuss how we take advantage of unique properties of marine and freshwater sponge hosts (Cliona varians and Ephydatia muelleri) and their algal partners (Symbiodinium and Chlorella) to monitor and control the timing of symbiont reinfection. We sequenced transcriptomes and analyzed differential gene expression patterns observed in algal-free sponges and algal-free sponges exposed to bacteria, heat-killed algae, and live algae in both the marine and freshwater system. From these data, we identify genes and putative pathways involved in early symbiont acquisition and ask if some aspects of the regulation of these symbioses may be the product of convergent evolution. As well, we present preliminary data using pharmacological inhibitors to block identified gene/pathways to examine functional aspects of the host:symbiont association.
