title: Ultraviolet and 5'fluorodeoxyuridine induced random mutagenesis in Chlorella vulgaris and its impact on fatty acid profile: a new insight on lipid-metabolizing genes and structural characterization of related proteins.
abstract: The present study was aimed at randomly mutating the microalga, Chlorella vulgaris, in order to alter its cellular behaviour towards increased lipid production for efficient biodiesel production from algal biomass. Individual mutants from ultraviolet light (UV-1 (30 s exposure), UV-2 (60 s exposure) and UV-3 (90 s exposure)) and 5'fluorodeoxyuridine (5'FDU-1 (0.25 mM) and 5'FDU-2 (0.50 mM)) exposed cells were identified to explore an alternative method for lipid enhancement. A marginally significant decrease in biomass in the UV mutants; marked increase in the lipid content in UV-2 and 5'FDU-1 mutants; significant increase in saturated fatty acids level, especially in UV-2 mutant; insignificant increase in lipid production when these mutants were subjected to an additional stress of nitrogen starvation and predominantly enhanced level of unsaturated fatty acids in all the strains except UV-2 were noted. Chloroplast ultrastructural alterations and defective biosynthesis of chloroplast specific lipid constituents were observed in the mutants. Modelling of three-dimensional structures of acetyl coA carboxylase (ACCase), omega-6, plastid delta-12 and microsomal delta-12 fatty acid desaturases for the first time and ligand-interaction studies greatly substantiated our findings. A replacement of leucine by a serine residue in the acetyl coA carboxylase gene of UV-2 mutant suggests the reason behind lipid enhancement in UV-2 mutant. Higher activity of ACCase in UV-2 and 5'FDU-1 strongly proves the functional consequences of gene mutation to lipid production. In conclusion, algal mutants exhibited significant impact on biodiesel production through structural alterations in the lipid-metabolizing genes, thereby enhancing lipid production and saturated fatty acid levels.
authors.affiliation: Marine Biotechnology Division, ESSO-National Institute of Ocean Technology, Ministry of Earth Sciences, Government of India, Pallikaranai, Chennai, 600 100, India, ajosephineanthony@gmail.com.
authors.forename: Josephine
authors.initials: J
authors.lastname: Anthony
authors.forename: Vijaya Raghavan
authors.initials: VR
authors.lastname: Rangamaran
authors.forename: Dharani
authors.initials: D
authors.lastname: Gopal
authors.forename: Kumar T
authors.initials: KT
authors.lastname: Shivasankarasubbiah
authors.forename: Mary Leema J
authors.initials: ML
authors.lastname: Thilagam
authors.forename: Magesh
authors.initials: M
authors.lastname: Peter Dhassiah
authors.forename: Divya Shridhar M
authors.initials: DS
authors.lastname: Padinjattayil
authors.forename: VinithKumar N
authors.initials: VN
authors.lastname: Valsalan
authors.forename: Vijayakumaran
authors.initials: V
authors.lastname: Manambrakat
authors.forename: Sivakumar
authors.initials: S
authors.lastname: Dakshinamurthy
authors.forename: Sivaraman
authors.initials: S
authors.lastname: Thirunavukkarasu
authors.forename: Kirubagaran
authors.initials: K
authors.lastname: Ramalingam
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000737:chemistry; D000704:Analysis of Variance; D001483:Base Sequence; D056804:Biofuels / Q000382:microbiology*; D048408:Chlorella vulgaris / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D002855:Chromatography, Thin Layer; D017931:DNA Primers / Q000235:genetics; D044943:Fatty Acid Desaturases / Q000737:chemistry*; D005227:Fatty Acids / Q000235:genetics / Q000378:metabolism*; D005467:Floxuridine / Q000494:pharmacology; D007218:Industrial Microbiology / Q000379:methods; D050356:Lipid Metabolism / Q000235:genetics*; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000187:drug effects / Q000528:radiation effects; D010078:Oxazines; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014466:Ultraviolet Rays
chemical_list: D056804:Biofuels; D017931:DNA Primers; D005227:Fatty Acids; D010078:Oxazines; D005467:Floxuridine; D044943:Fatty Acid Desaturases; D000103:Acetyl-CoA Carboxylase; C044808:nile red; C025034:doxifluridine