Meeting Abstract

12.1  Saturday, Jan. 4 10:15  Coral transcriptome-wide gene expression patterns at noon and midnight in a coral reef: insights into coral physiology RUIZ-JONES, GJ*; PALUMBI, SR; Stanford University, Hopkins Marine Station; Stanford University, Hopkins Marine Station gjrj@stanford.edu

In coral reefs there are many environmental fluctuations from day to night. Circadian gene expression studies on corals have been done in controlled lab settings; however, little is known about day-night gene expression patterns in corals living on the reef. We sampled coral transcriptomes at six noon and five midnight time-points from a colony living in a back-reef on Ofu, American Samoa. We also measured temperature, oxygen, pH, and aragonite saturation at each time point. Vigorous wave action and water motion during the sampling period led to only small changes in temperature, pH, and aragonite saturation from day to night, which is atypical for this particular back-reef, but removes the potential influences of these three environmental variables on any observed daily gene expression fluctuations. By contrast, dissolved oxygen saturation increased during daylight and decreased at night. We measured gene expression at over 16,000 genes and found several hundred genes to be variable from day to night. As expected the expression of light-sensitive cryptochromes was higher at noon than midnight. We observed higher expression during the day of some known calcification genes, including the skeletal organic matrix protein galaxin. Interestingly, a hypoxia-inducible factor prolyl hydroxylase showed higher expression levels at midnight, a time when our data show low oxygen concentrations nearby the sampled colony. These examples show that our transcriptome-wide gene expression analysis of coral physiology at noon and midnight in a coral reef reveals the cellular processes that distinguish cellular activity at these two time points.