Transcriptional response of Emiliania huxleyi CCMP2090 exposed to the bacterial signaling molecule 2-heptyl-4-quinolone

In order to determine how the bacterial quorum-sensing precursor molecule 2-heptyl-4-quinolone (HHQ) induces cellular senescence in populations of some eukaryotic marine phytoplankton, we examined the transcriptional response of Emiliania huxleyi CCMP2090 to HHQ exposure. Quadruplicate batch cultures were treated with HHQ at three concentrations (1, 10 and 100 ng/ml) and compared to a vehicle control after 24 and 72 hours of exposure. The majority of gene expression changes occurred after 24 hr of exposure in the 10 and 100 ng/ml treatments and many of these changes persisted for 72 hr in the 100 ng/ml treatment. RNAseq analysis revealed that HHQ exposure impacts many aspects of Emiliania huxleyi metabolism including: chlorophyll biosynthesis and light harvesting, vitamin biosynthesis, vesicle trafficking, and general signals related to energy production. Changes in genes involved in intraphase cell cycle check points implicate DNA damage as the primary driver of HHQ-induced cellular senescence. Overall design: At 2 timepoints, samples from 4 biological replicate axenic Emiliania huxleyi cultures exposed to either 1, 10, or 100 ng/ml of 2-heptyl-4-quinolone (HHQ) are compared to 4 biological replicates exposed to a vehicle control.