Ecological genomics of a reef building coral in response to environmental stress

Nick Polato, Penn State

November 4, 2009 @ 12:20 pm to 01:10 pm

10 Tyson

Persistence of coral dominated reefs depends upon successful sexual recruitment. For some corals, this is accomplished by planktonic larvae that drift for hours to months before settling onto the benthos. Environmental stresses likely have a profound effect on larval development, settlement, and metamorphosis through altered gene expression, but our knowledge is limited. Microarray technology provides a powerful tool for rapidly characterizing differences in gene expression patterns among wild populations under changing environmental stresses. The scleractinian coral Montastrea faveolata is a common and often dominant species on reefs throughout the Caribbean. Symbiont free gametes were collected from Florida and Mexico during the summer of 2008 to characterize the transcriptome of M. faveolata larvae in response to thermal stress, testing the following hypotheses: Ho) Larval gene expression profiles do not differ with respect to habitat of origin or exposure to stress. Hi) Expression patterns differ among samples exposed to various stressors. Hii) Transcript profiles change with stress in a generalized ESR, but do not differ among treatment types or sample origins. Fluorescently labeled cDNA from pooled larval samples from both populations at 24 and 48 hours of development were applied to a 2000feature microarray to assay gene expression. Signal intensity data was analyzed using 2 different approaches; a baysian approach that allows for a continuous chain of comparisons and a linear model fitting approach. Genes were found that differ in their expression levels in response to all three effects (site, temperature, and developmental time), with site and developmental time providing the major contributions. Classification of gene ontology codes showed the majority of differentially expressed genes were involved in biological processes or molecular functioning. Several genes showing differential expression in response to temperature are involved in the response to oxidative stress that is thought to result as thermal stress promotes the formation of radical oxygen species, in agreement with proposed models of coral bleaching.