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Directed evolution of acyl-CoA:diacylglycerol acyltransferase: Development and characterization ofBrassica napus DGAT1mutagenized libraries

Authors
Journal
Plant Physiology and Biochemistry
0981-9428
Publisher
Elsevier
Publication Date
Volume
47
Issue
6
Identifiers
DOI: 10.1016/j.plaphy.2008.12.019
Keywords
  • Error-Prone Pcr
  • High-Throughput Screening
  • Membrane Protein
  • Nile Red
  • Tag Synthase
  • Triacylglycerol Biosynthesis
  • Saccharomyces Cerevisiae
Disciplines
  • Biology

Abstract

Abstract Metabolic flux to triacylglycerol (TAG) may be limited by the level of acyl-CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) activity. In some species, this enzyme also appears to play a role in the channeling of specific fatty acyl moieties into TAG. The objective of this work is to implement a directed evolution approach to enhance the catalytic efficiency of type-1 DGAT from Brassica napus (BnDGAT1). We generated randomly mutagenized libraries of BnDGAT1 in a yeast expression vector using error-prone PCR. The mutagenized libraries were used to transform a Saccharomyces cerevisiae strain devoid of neutral lipid biosynthesis and analyzed using a high-throughput screening (HTS) system. The HTS, recently developed for this purpose, consisted of a positive selection of clones expressing active DGAT mutants followed by quantification of DGAT activity by fluorescence detection of TAG in yeast cells. The initial results indicated that the positive selection system efficiently eliminated DGAT mutants lacking enzyme activity. Screening of 1528 selected mutants revealed that some DGAT clones had enhanced ability to synthesize TAG in yeast. This was confirmed by analysis of individual clones that could carry mutations resulting in an increased catalytic efficiency. The directed evolution approach could lead to the development of an improved plant DGAT1 for increasing seed oil content in oleaginous crops.

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