Abstract
Supply of nitrogen, one of macronutrients, affects expression levels of numerous genes in plants. Previously, we performed microarray analysis and selected genes encoding putative transcription factors involved in nitrogen supply-induced modulations in gene expression in rice. The selected genes include MYB-NR1 of which expression are rapidly induced by nitrate. In this study, we show the result of a DNA-binding site selection experiment using a recombinant protein of MYB-NR1. As the result revealed the sequence necessary for MYB-NR1 binding, we then investigated activity of MYB-NR1 as a transcription factor by maize protoplast transient assay using a reporter plasmid in which the identified sequence was fused to the 35S minimal promoter. Two expression vectors for MYB-NR1 and a fusion protein of MYB-NR1 and the VP16 transcription activation domain were also employed. The expression of the fusion protein could elevate reporter enzyme activity, while the reporter enzyme activity was decreased by the expression of intact MYB-NR1. Based on these results, we discuss the possibility that MYB-NR1 binds the identified sequence in vivo to repress transcription.
