HOOVER, C.A.*; MARSH, A.G.; SLATTERY, M.; Univ. of Delaware; Univ. of Delaware; Univ. of Mississippi: Secondary metabolite synthesis and variability in the soft coral, Sinularia polydactyla

Defensive secondary metabolites are present in Indo-Pacific soft corals presumably to deter predators, prevent epiphytic fouling, and/or to compete for space with other corals. The soft coral, Sinularia polydactyla, is abundant in shallow coral reef habitats in Guam and synthesizes a secondary metabolite, pukalide, which is known to have both predator-deterrent and antimicrobial properties. Temporal and spatial variation is observed in pukalide levels. This biochemical phenotypic plasticity may be an adaptation to local environmental factors, such as predation intensity by butterflyfishes, Chaetodon spp. To assess the affect of predation on both chemical and genetic changes in S. polydactyla, 20 colonies were transplanted between two sites exhibiting both high and low levels of predation. In addition, 10 colonies were back-transplanted at the high predation site. After 19 days, bite scars on each coral were counted and tissues preserved for chemical and genetic analyses. An independent samples T-test indicates a highly significant difference between the numbers of bite scars found on transplants versus back-transplants. This suggests site-specific variation in secondary metabolite concentrations in response to predation levels. Differences in pukalide levels will be analyzed using LC-MS. Additionally, variation in metabolite production is likely to occur at the level of gene regulation. Changes in mRNA pool complexity (transcriptome profiling) and the expression of specific pukalide pathway genes will be quantified to indicate shifts in metabolite flux between treatment groups. Examining the complexity of the RNA pool in these corals is the first step to understanding the mechanisms of pukalide plasticity at a biochemical and molecular level.