Cloning and sequence characteristics of the genomic gene of a rice metallothionein

Northern blot analysis showed that a metallothionein gene, ricMT, is expres sed strongly in the stem of rice with an expression level that could be mor e than 100-fold stronger than in leaf blades. The results suggest that the 5' upstream region flanking the coding sequence of the ricMT may contain a fairly strong promoter. To elucidate its regulation and promoter structure, the genomic clones of ricMT were screened out from a rice genomic library and a fragment of about 4 084 bp was sequenced. The fragment included a 5' upstream region of ca. 2 970 bp, a transcription region of ca. 690 bp and a 3' downstream region of ca. 420 bp. Computer analysis of the sequence homo logy showed that the 5' upstream region included a putative TATA box, a put ative CAAT box, and a typical metal-responsive element TGCGCGCG. The result s will promote further understanding of the mechanisms of gene regulation a nd metal response of plant metallothionein proteins.