Abstract: Plant mitochondrial genes are often transcribed into complex sets of mRNA. To characterize the transcription initiation and promoter structure, the transcript termini of four mitochondrial genes, atp1, atp6, cob, rps7, in rice (Oryza sativa L.), were determined by using a modified circularized RNA reverse transcription-polymerase chain reaction method. The results revealed that three genes (atp1, atp6, rps7) were transcribed from multiple initiation sites, indicating the presence of multiple promoters. Two transcription termination sites were detected in three genes (atp6, cob, rps7), respectively. Analysis on the promoter architecture showed that the YRTA (Y=T or C, R=A or G) motifs that are widely present in the mitochondrial promoters of other monocot and dicot plant species were detected only in two of the 12 analyzed promoters. Our data suggest that the promoter sequences in the rice mitochondrial genome are highly diverged in comparison to those in other plants, and the YRTA motif is not an essential element for the promoter activity. (Author for correspondence: Tel: +86 (0)20 8528 1908; Fax: +86 (0)20 8528 0200; E-mail: ygliu@scau.edu.cn)

Key words: mitochondrial gene, promoter, rice, transcription initiation site, transcription termination site.