Meeting Abstract
Reef-building corals exhibit substantial variation in their reproductive biology. Most corals mass spawn gametes, yet some taxa exhibit internal fertilization, releasing fully developed planula larvae, in the process known as ‘brooding’. Most corals acquire symbionts from their environment each generation in the process known as ‘horizontal’ transmission, but some species employ ‘vertical transmission’, and are capable of passing symbionts directly to their offspring. In addition to mining publicly available genomic resources, we sequenced a set of coral transcriptomes for species representing a variety of reproductive and symbiont transmission modes and used a comparative genomics approach to identify genes showing repeated signatures of non-neutral mutation rates in brooding and vertically transmitting lineages. Contigs for each transcriptome were converted into candidate protein coding sequences and 6,625 orthologs were inferred using the program FastOrtho in combination with a reciprocal best BLAST match. To identify genes showing differential signatures of selection, dN/dS ratios were calculated by comparing species exhibiting target traits (brooding or vertical transmission) with their closest divergent-trait relative (broadcast spawning or horizontal transmission). Purifying selection (i.e. dN/dS ratios<1) was more prevalent than positive selection (dN/dS ratios>1), but preliminary results highlight candidate genes involved in the process of cilium assembly as being highly conserved among coral species exhibiting transovarial vertical transmission of symbionts.
