Monday, August 13, 2012
Columbia Hall, Terrace Level (Washington Hilton)
Cyanobacterium is a potential renewable feedstock for producing biofuel and other bioproducts. Its economic viability and environmental sustainability require the characterization and optimization of relevant pathways to enrich for targeted bioproducts in model strains. Transcriptomic analysis is the requisite for genetic manipulation to reengineer strains. To analyze a global gene expression level in different pathways under certain stress conditions, we sequenced the transcriptome of Synechococcus that was cultured under light and dark conditions using the Ion Personal Genome Machine (PGM). PGM generated about one million high-quality uniquely mapped long-length reads from each 316 chip. Based on the known coding sequence (CDS) from Synechococcus, the CDS coverage reached 91% from each chip. The global quantitative gene profiling was reproducible by comparing different data sets generated at different times but the same culture conditions. We identified all enzymes involved in the pathways analyzed in this study. Under dark stress, most genes involved in photosynthesis pathways, NH3 production, and nitrite/nitrate transfer through the periplasm were down-regulated. Fatty acid synthesis seems light independent. In the starch synthesis pathway, we identified the putative neutral invertase that was upregulated under dark stress. This enzyme converts sucrose into b-D-fructose and hasnot been reported in Synechococcus. This implies that the strain may use sucrose instead of glucose as an alternative substrate for starch synthesis to balance and maintain certain metabolic functions. Transcriptome sequencing is a cost-effective and reproducible approach to evaluate dynamic change of genes involved in pathways that facilitates strain optimization of microalgae.