Journal of Applied Phycology

, Volume 16, Issue 2, pp 135–144 | Cite as

Isolation of quizalofop-resistant mutants of Nannochloropsis oculata (Eustigmatophyceae) with high eicosapentaenoic acid following N-methyl-N-nitrosourea-induced random mutagenesis

  • Ratnesh Chaturvedi
  • Srinivasa Rao Uppalapati
  • Mohammad Amin Alamsjah
  • Yuji Fujita


Nannochloropsis oculata was subjected to N-methyl-N-nitrosourea-induced mutagenesis under the selection pressure of quizalofop, a known inhibitor of acetyl-CoA carboxylase (ACCase) activity with the objective of generating genetically tractable mutants with altered fatty acid metabolism. Two mutants, QUIZ1 and QUIZ2, with stable resistance to quizalofop were isolated and partially characterized. The growth properties and morphology of the mutants appeared identical with the parent strain. However thermo-tolerance was observed in the mutants. Enhanced resistance to quizalofop suggested the presence of herbicide resistant isoforms of ACCase. In vitro assays for ACCase activity showed that ACCase in the wild strains was much more sensitive to quizalofop than the mutant strains. Gas chromatographic analysis of fatty acids revealed that the mutant strains were rich in polyunsaturated fatty acids (n− 3PUFAs), as well as total fatty acid contents; this was accompanied by a concomitant increase in triacylglycerol (TAG) followed by linoleic acid (18:2), arachidonic acid (20:4 n− 6) and EPA (20:5 n− 3). These results suggest that an increased substrate pool (malonyl-CoA) (due to increased specific activity of ACCase) in the mutant strains in vivo and in vitro may have led to the increased TAG accumulation. Random mutagenesis was shown to be a good tool to manipulate PUFAs and EPA in Nannochloropsis. The strains developed will be useful in understanding fatty acid metabolism using genetic and biochemical approaches and also for their direct use in mariculture.

acetyl-CoA carboxylase EPA genetic mutants herbicide resistance N-methyl-N-nitrosourea Nannochloropsis oculata polyunsaturated fatty acids random mutagenesis strain improvement 


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Copyright information

© Kluwer Academic Publishers 2004

Authors and Affiliations

  • Ratnesh Chaturvedi
  • Srinivasa Rao Uppalapati
  • Mohammad Amin Alamsjah
  • Yuji Fujita

There are no affiliations available

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