A NOVEL STRESS-INDUCIBLE METALLOTHIONEIN-LIKE GENE FROM RICE

A novel rice genomic sequence encoding coding segments homologous to o ther metallothionein-like genes was isolated from Oryza sativa genomic library. This sequence, hereby designated as rgMT (rice genomic metal iothionein-like gene), consists of two exons and one intron. From the coding sequence, it is predicted that rgMT encodes one protein of 74 a mino acids. Differential expression of rgMT in rice plants was observe d as mature transcripts were more abundant in roots than in leaves and sheaths. Under different stress conditions, such as excess heavy meta ls and heat shock, expression of rgMT was significantly elevated. This was especially noticeable with 250 mu M CuCl2 for 16 h, 40 degrees C heat for 2 h and 0.06% DMSO for 1 h. Under sucrose starvation, rgMT tr anscripts also increased with time up to 72 h. During recovery from su crose starvation, the transcripts declined slightly within 12 h of rec overy. rgMT transcripts were also seen to have increased expression in senescent leaves. These results support the notion that rgMT is a str ess-inducible gene in rice heretofore unreported.