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Premium Cloning, mutagenesis, and characterization of the microalga Parietochloris incisa acetohydroxyacid synthase, and its possible use as an endogenous selection marker
Grundman Omer,
KhozinGoldberg Inna,
Raveh Dina,
Cohen Zvi,
Vyazmensky Maria,
Boussiba Sammy,
Shapira Michal
Publication year2012
Publication title
biotechnology and bioengineering
Resource typeJournals
PublisherWiley Subscription Services
Abstract Parietochloris incisa is an oleaginous fresh water green microalga that accumulates an unusually high content of the valuable long‐chain polyunsaturated fatty acid (LC‐PUFA) arachidonic acid within triacylglycerols in cytoplasmic lipid bodies. Here, we describe cloning and mutagenesis of the P. incisa acetohydroxyacid synthase ( Pi AHAS) gene for use as an herbicide resistance selection marker for transformation. Use of an endogenous gene circumvents the risks and regulatory difficulties of cultivating antibiotic‐resistant organisms. AHAS is present in plants and microorganisms where it catalyzes the first essential step in the synthesis of branched‐chain amino acids. It is the target enzyme of the herbicide sulfometuron methyl (SMM), which effectively inhibits growth of bacteria and plants. Several point mutations of AHAS are known to confer herbicide resistance. We cloned the cDNA that encodes Pi AHAS and introduced a W605S point mutation ( Pi mAHAS). Catalytic activity and herbicide resistance of the wild‐type and mutant proteins were characterized in the AHAS‐deficient E. coli , BUM1 strain. Cloned Pi AHAS wild‐type and mutant genes complemented AHAS‐deficient bacterial growth. Furthermore, bacteria expressing the mutant Pi AHAS exhibited high resistance to SMM. Purified Pi AHAS wild‐type and mutant proteins were assayed for enzymatic activity and herbicide resistance. The W605S mutation was shown to cause a twofold decrease in enzymatic activity and in affinity for the Pyruvate substrate. However, the mutant exhibited 7 orders of magnitude higher resistance to the SMM herbicide than that of the wild type. Biotechnol. Bioeng. 2012;109: 2340–2348. © 2012 Wiley Periodicals, Inc.
Subject(s)amino acid , bacteria , biochemistry , biology , biosynthesis , enzyme , gene , genetics , mutagenesis , mutant , mutation , point mutation , wild type
SCImago Journal Rank1.136

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