Sequence and transcript analysis of the orf140-nad3-rps12-atp1 gene cluster in the mitochondrial DNA of mung bean (Vigna radiata L. (Wilzek) cv. Tainan No. 5)

An orf140-nad3-rps12-atp1 gene cluster, which spans a 7.1 kb region of the mung bean mitochondrial genome, was identified and completely sequenced. Th e coding regions of nad3, rps12, and atp1 genes are highly conserved betwee n mung bean and other plant species. The nucleotide sequences of orf140 and its 5'-flanking region are homologous with ORFBs in sunflower and Oenother a, and are also found to be conserved in several chimeric ORFs of various p lant CMS lines. The region 3'-downstream from the mung bean atp1 is similar to its counterparts in soybean and common bean, which has been shown to be specific to a subset of legumes. Genes of this cluster are present as a si ngle copy in mung bean. Northern-blot hybridization and RT-PCR suggested th at the four genes are co-transcribed and then processed into transcripts of different sizes. Variation of accumulation levels of different transcripts was observed.