Determination Of Physiological And Biochemical Indexes Of Dunaliella And Analysis Of GGPS Gene Characteristics

Dunaliella is a kind of halophilic microalgae with extremely high research value.It often lives in salty waters such as lakes and oceans with high salinity.Dunaliella is rich in ?-carotene.Geranylgeranyl pyrophosphate synthase(GGPS)in its body is also called GGPP synthase,which plays an important role in the synthesis and metabolism of ?-carotene.In this study,15 strains of Dunaliella species of different strains were cultured,morphological observations were carried out with optical microscope,and key physiological and biochemical indexes were determined.On this basis,the relationship between GGPS enzyme activity and ?-carotene synthesis in Dunaliella algae was studied,and the GGPS gene characteristics were analyzed.The research results are summarized as follows:1.Morphological description and physiological index determination of Dunaliella.Under the observation of an optical microscope,Dunaliella algae exists as a single cell.The algae cells are light green in color,have two flagella,and most of them are oval or pear-shaped.There is no typical cell wall outside the cell,with a cell membrane,a nucleus and a larger chloroplast.Among the 15 Dunaliella strains,D3,D5 and D10 had the largest single-cell individuals,and D1 and D14 had the smallest single-cell individuals.Among them,D15 has the strongest growth ability and the shortest growth cycle.The content of intracellular chlorophyll,carotenoid,and ?-carotene gradually increase with time.Among them,D1 has the highest ?-carotene content,which can be used as a bioreactor for industrial production of ?-carotene.In the logarithmic phase,the GGPS single-cell enzyme activity of D14 is the strongest,and the total GGPS enzyme activity is higher than the decay phase in the logarithmic phase.The combined analysis of the GGPS total enzyme activity and the ?-carotene content shows that the relationship between the two is positive.At the mature stage,D4 has the highest polysaccharide content,which can be used for the research and development of algae polysaccharides.2.GGPS gene characteristics of Dunaliella.The GGPS gene of D8 has a total length of 1724 bp after splicing,including 1072 bp in the CDS region,136 bp in 5'UTR,and 516 bp in 3'UTR.There are mutations in the GGPS amino acid sequences of 15 strains of Dunaliella algae.Among them,the GGPS amino acid sequence of D6 has the most mutations,with ten mutation sites;the GGPS amino acid sequences of D1,D10,D11 and D14 have three mutation sites respectively;D2,D9 and D15 each have a mutation site;D4has two mutation sites;D3,D5,D7,D8,D12,D13 have no mutations in the GGPS amino acid sequence.3.The structural characteristics of Dunaliella GGPS protein.The GGPS protein structure of Dunaliella algae has ?-helix,?-sheet and random coiled regions,which are spiral,sheet-like and rope-like,respectively.The GGPS gene has no protein transmembrane phenomenon,and the protein is hydrophobic as a whole.4.The phylogeny of GGPS gene.The 15 strains of Dunaliella species have high GGPS gene homology,and the coding gene is conservative.In the same species,the GGPS gene homology relationship is relatively far,so there are obvious differences.Therefore,the GGPS gene cannot be used as the basis for species identification;the phylogenetic results of the GGPS sequence between different algae species show that the representative algae strains of the Chlorophyta and Rhodophyta form two independent branches,and Dunaliella is located in the Chlorophyta branch.Therefore,GGPS genes can be used as the basis for classification of large-scale taxa.