Genetic Analysis And Annotation Of The Halophytic Microalgae Dunaliella Salina:Prediction Of Core Metabolic Pathways And Genes Discovery

Dunaliella salina(Dunal),the unicellular green algae without cell wall,thriving in hyper saline environments,is a classical model to investigate the salt tolerance mechanism.As the important sources for the nature ?-carotene and biodiesel precursors,Dunaliella has a great economic,nutritional and commercial value.The adaptation of the halophytes to the salt stress is a complex adjustment process and there are still many salt-tolerance genes which have not been found and we know little about the salt tolerance mechanism in Dunaliellla.To better understand the salt-tolerance mechanism and investigate novel salt inducible genes,a high-quality c DNA library was constructed for D.salina.Through screening the library,37 unique salt-tolerance genes were isolated finally and those coding for DsPDI and DsCYP1 were found to be implicated in protein folding under salt stress.Most notably,the latter gene Dscyp1 was speculated to regulate the expression of the downstream salt-tolerance genes.In addition,the components of the translation system,F-box protein SKIP5,the proteins possessing NADH:flavorubredoxin oxidoreductase domain and CY domain were also found related to the salt stress tolerance.Besides glycerol,polyamines were found to be synthesized in D.salina owing to the identification of DsSPDS.In addition,many novel salt-tolerance ESTs were discovered in our study and all of them conferred E.coli different abilities of salt tolerance.Further annotation of these data may help us understand the salt-tolerance mechanism of Dunaliella salina in the future.Then we can improve the salt tolerance of crop so as to grown them on the saline soil using genetic engineering and operation technology and the modern genetic breeding technology.In order to complete the genome information of Dunaliella salina,we attempted to use the Illumina Hiseq2000 platform to preform high-throughput paired end RNA-sequencing with 5.86 gigabases of data.Following the cleaning processes to filter the low quality reads and generated 29,326,716 high-quality reads.Following assembly using the Trinity program and CodonCode aligner,29,326,716 cleaned reads were assembled into 39,820 unique genes.In order to investigate the genetic information and construct the core metabolic network,through annotation of the transcriptome,we characterized the metabolic processes of D.salina with a focus on stress-related compounds(osmoytes and polyamines),energy molecules(lipid and starch)and valuable metabolites(carotenoids),providing candidate genes and theoretical basis for manipulating D.salina to achieve greater economic value in large-scale production through a bioengineering strategy with more feasibility and high successful rate of genetic operation.The prediction of the regulatory mechanism of metabolic adjustment in response to salt stress provides deeper insight into understanding salt tolerance.Analysis of the polyamine metabolic process suggested that decreasing of the substrate supply for spermine biosynthesis would augment growth under stresses.Moreover,Dunaliella possesses the energy combined carbonate transport system and two isoforms of kinds of enolketoacid type phosphate carboxylases(PPC)to fix carbon wih high efficiency.The first full-scale transcriptome of D.salina with a high resolution lays a foundation for further comparative genomic research.