Deletion analysis of the tobacco Nii1 promoter in Arabidopsis thaliana

A 1 kb promoter fragment of the Nii1 gene, encoding a tobacco foliar nitrite reductase, has been fused to the beta-glucuronidase (Gus) or luciferase (Luc) reporter genes. These constructs were introduced in Arabidopsis thaliana by in planta infiltration. Analysis of transformants shows that GUS or LUC activities are induced by nitrate. Deletions of the Nii1 promoter fused to the Luc gene have been made in order to delineate cis-sequences necessary for nitrate induction. The Nii1, Delta C, Delta M and Delta H constructs ending, respectively at - 962, - 678, - 202 and - 76 bp before the putative transcription start of the Nii1 gene were fused transcriptionally to the Luc reporter gene. Analysis of LUC activities shows that nitrate induction occurs in the Delta MLuc construct, so promoter sequences required for nitrate induction of the reporter gene are retained in the proximal 200 bp fragment of the promoter. For the smallest construct, nitrate inducibility is maintained in one transformant. Yet, the low level of LUC activity detected in the other transformants does not allow us to assume that nitrate regulatory elements are still present in the Delta HLuc construct. We will discuss these results in relation to those obtained with deletions of other Nia or Nii promoters by different laboratories. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.