Cloning and characterization of rice HMGB1 gene.

We isolated a 918 bp long full-length rice HMGB1 cDNA, which has an open reading frame of 471 bp encoding 157 amino acids, with a central domain of high sequence similarity to the HMG-box domain of other plant HMGB1 proteins. RNA gel blot analysis indicated that rice HMGB1 gene is constitutively expressed in various tissues and organs. Southern hybridization and sequence analyses suggested that a single copy of the HMGB1 gene composed of seven exons and six introns exists in rice. We have also cloned a 1755 bp long 5' flanking region of the rice HMGB1 gene, which can be regarded as its promoter. 5' deletion analysis of this promoter indicated that positive cis-elements residing between -1400 and -1115 are important to enhance quantitative expression, whereas negative cis-elements between -1755 and -1400 and between -1115 and -351 inhibit expression.