Identification of the cis-acting elements in Arabidopsis thaliana NHL10 promoter responsible for leaf senescence, the hypersensitive response against Cucumber mosaic virus infection, and spermine treatment

There are 45 NDR1/HIN1-like (NHL) genes in Arabidopsis thaliana. Of these, we have focused on the NHL10 gene because of its unique expression profiles: its transcripts are accumulated in a senescence-associated manner, during the hypersensitive response (HR) triggered with an avirulent Cucumber mosaic virus (CMV) strain, and by treatment with the polyamine spermine (Spm [M.S. Zheng, H. Takahashi, A. Miyazaki, H. Hamamoto, J. Shah, I. Yamaguchi, T. Kusano, Up-regulation of Arabidopsis thaliana NHL10 in the hypersensitive response to Cucumber mosaic virus infection and in senescing leaves is controlled by signalling pathways that differ in salicylate involvement, Planta 218 (2004) 740-750]). Here we have performed an analysis of NHL10 promoter using the β-glucuronidase (GUS) reporter gene-fusion constructs in transgenic A. thaliana plants. With the histochemical staining assay, it was demonstrated that the region between -697 and +53 from the putative transcriptional start site of the NHL10 promoter was essential for responses to leaf senescence, HR to CMV and Spm treatment. These data were confirmed by northern analysis using the GUS reporter gene as a probe. By further deletion analysis, all the cis-acting elements responsive to leaf senescence, CMV-induced HR, and Spm treatment, were narrowed down to the identical -198 to -93 region. It also demonstrated that the controlled expression of NHL10 gene at a transcriptional level.