Isolation and characterization of a nitrate reductase deficient mutant of <Emphasis Type="Italic">Chlorella ellipsoidea</Emphasis> (Chlorophyta) |
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Authors: | Yiqin?Wang Yan?Chen Xiaoyu?Zhang Peng?Wang Degui?Geng Shimin?Zhao Liming?Zhang Email author" target="_blank">Yongru?SunEmail author |
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Institution: | (1) Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, P. R. China;(2) Department of Biotechnology, Beijing Forestry University, Beijing, P. R. China |
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Abstract: | Using X-ray mutagenesis and a chlorate-resistance selection method, a nitrate reductase (NR)-deficient mutant of Chlorella ellipsoidea nrm-4 was isolated, which is incapable of using NO3− as a nitrogen source. NR activity was not detected in nrm-4, suggesting this is a null mutation. Molecular analysis revealed that nrm-4 has a two base deletion at position 2348–49 of its DNA sequence, which produced a frame-shift mutation. The nrm-4 mutation is stable and nrm-4 algae could only use NH4+ and NO2− as nitrogen sources. Expression of a wild-type NR gene could complement this NR-deficient mutant. Furthermore, this transgenic strain was able to grow in NO3− medium, when the growth rate of the nrm-4 strain was equal to that of the wide type alga. The nrm-4 strain could potentially be used as a bioreactor that uses nitrate as a selectable marker instead of an antibiotic or herbicide. |
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Keywords: | Chlorella ellipsoidea complementation experiment mutant analysis nitrate reductase-deficient mutant |
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