ISOLATION OF THE CHLAMYDOMONAS REGULATORY GENE NIT2 BY TRANSPOSON TAGGING

Citation
Ra. Schnell et Pa. Lefebvre, ISOLATION OF THE CHLAMYDOMONAS REGULATORY GENE NIT2 BY TRANSPOSON TAGGING, Genetics, 134(3), 1993, pp. 737-747
Citations number
50
Categorie Soggetti
Genetics & Heredity
Journal title
ISSN journal
00166731
Volume
134
Issue
3
Year of publication
1993
Pages
737 - 747
Database
ISI
SICI code
0016-6731(1993)134:3<737:IOTCRG>2.0.ZU;2-9
Abstract
Genetic evidence suggests that the NIT2 gene of Chlamydomonas reinhard tii encodes a positive regulator of the nitrate-assimilation pathway. To learn more about the function of the NIT2 gene product, we isolated the gene using a transposon-tagging strategy. A nit2 mutation caused by the insertion of a transposon was identified by testing spontaneous nit2 mutants for the presence of new copies of Gulliver or TOC1, tran sposable elements that have been identified in Chlamydomonas. In 2 of the 14 different mutants that were analyzed, a Gulliver element was fo und to be genetically and phenotypically associated with the nit2 muta tion. Using the Gulliver element as a probe, one of the transposon-ind uced nit2 alleles was isolated, and a sequence adjoining the transposo n was used to isolate the corresponding wild-type locus. The NIT2 gene was delimited by mapping DNA rearrangements associated with nit2 muta tions and mutant rescue by genetic transformation. The NIT2 gene encod es a 6-kb transcript that was not detected in cells grown in the prese nce of ammonium. Likewise, NIT2-dependent genes are repressed in ammon ium-grown cells. These results suggest that repression of the NIT2 gen e may mediate metabolite repression of the nitrate assimilation pathwa y in Chlamydomonas.