Identification and characterization of the trnS/pseudo-tRNA/nad3/rps12 gene cluster from Coix lacryma-jobi L: organization, transcription and RNA editing

During a study of mitochondrial sequence conservation between the liverwort Marchantia polymorpha and several Angiosperm species, as revealed by heter ologous hybridization experiments, the trnS/psuedo-tRNA/nad3/rps12 gene clu ster in Coix lacrymajobi L., an Asian grass species from the Andropogoneae, was identified using the mitochondrial probe orf 167 from M. polymorpha. T he Coh gene cluster was cloned and sequenced, and its expression analyzed. The gene sequence and gene locus organization were found to be similar to t he corresponding cluster in wheat and maize. Northern hybridization and rev erse transcription-polymerase chain reaction analyses indicated that nad3 a nd rps12 genes were co-transcribed as a 1.25 kb RNA molecule. The transcrip t displayed 20 and six RNA edition sites, in the nad3 and rps12 genes, resp ectively, that changed the codon identities to amino acids, which are bette r conserved in different organisms. Twenty-three cDNA clones were analysed for the edition process and revealed different partial editing patterns wit hout apparent sequential processing. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.