Induction of nitrate reductase host gene expression has a negative effect on the expression of transgenes driven by the nitrate reductase promoter

Autor: Michel Caboche, Hervé Vaucheret
Přispěvatelé: Laboratoire de biologie cellulaire et moléculaire, Institut National de la Recherche Agronomique (INRA), ProdInra, Migration
Rok vydání: 1995
Předmět:
Zdroj: Plant Science
Plant Science, Elsevier, 1995, 107, pp.95-104
ISSN: 0168-9452
Popis: In two previous studies the expression of the tobacco nitrate reductase genes ( Nia1 or Nia2 ) introduced into nitrate reductase deficient mutants or of glucuronidase reporter genes linked to the promoter of a tobacco Nia gene were characterized. In both cases no expression of the introduced genes was found in the leaves of approximately 85% of the transformants and only a low level of expression was detected in the remaining transformants ranging from 0.1 to 7% of the expression of host Nia genes. In this paper we show that reduced levels of transgene expression in leaves result from a negative effect of host Nia gene expression. Transformants have been generated carrying a neomycin phosphotransferase reporter gene ( Npt ) linked to a 1.4 kb promoter fragment (−1350 to +40) of the Nia1 gene by electroporation. The level of resistance to the antibiotic declined in transformed calli after 1 month of culture whereas a high level of resistance was recovered in cells freshly prepared from leaf protoplasts of the regenerated transgenic plants, conditions in which the expression of host Nia genes is severely down-regulated. The level of resistance in seedlings also declined after 1 month of growth when plants were grown on a medium containing nitrate whereas a high level of resistance was observed when plants were grown on a medium supplemented with ammonium as a sole nitrogen source, conditions that do not allow the induction of host Nia genes expression. The analysis of a series of progressive deletions covering the 5′ end of the promoter down to position −92 showed that such a negative correlation between the expression of pNia1-Npt transgenes and host Nia genes is found in approximately 70% of the transformants, irrespective of the size of the deletion. A model is proposed to explain how the expression of host Nia genes can impede the expression of pNia -driven transgenes.
Databáze: OpenAIRE
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