Abstract
Al-tolerant cultivars of barley detoxify Al by secretion of citrate from the roots. Recently, a gene responsible for Al-activated citrate secretion (HvAACT1) has been identified (Furukawa et al., 2007). The expression of this gene is not induced by Al and Al-tolerant cultivars constitutively have higher expression than Al-sensitive cultivars. HvAACT1 protein is located at the epidermal cell. In the present study, to examine the mechanism regulating the expression of HvAACT1, we compared the sequence of UTR regions between Al-sensitive and tolerant cultivars. There was no correlation between Al tolerance and the sequence difference in the 3'-UTR region. In the 5'-region, we found that a specific region (about 1kb) was inserted in the genome of ORF upstream only in the Al-tolerant cultivars. 5'-RACE analysis showed that in Al-tolerant cultivars, there were multiple transcription start sites. These results suggest that this region may be involved in the higher expression of HvAACT1.
