Ribosomal protein S14 genes in broad bean mitochondrial DNA.

Abstract

Broad bean (Vicia faba) mtDNA contains an open reading frame with a predicted amino acid sequence that is 41% homologous to the ribosomal protein S14 (RPS14) of Escherichia coli, and which is located 1232 ntp upstream from a gene for cytochrome b (cob). A second putative rpS14 gene occurs in broad bean mtDNA, 344 ntp upstream from a gene for ATPase subunit 9 (atp9). However, the atp9-linked rpS14 gene is 12 codons shorter than the cob-linked rpS14 gene. Sequence homology is found upstream (for 218 ntp) but not downstream from the two rpS14 genes. Transcripts were detected in broad bean mtRNA only for the cob-linked rpS14 gene. All RNA molecules that include a transcript of the rpS14 gene also include a transcript of the cob gene. Sequences homologous to the broad bean mitochondrial rpS14 gene were detected in soybean mtDNA, but not in corn mtDNA. Relationships between the amino acid sequences of RPS14s encoded in broad bean mtDNA, in chloroplast DNAs of various angiosperms, and in E. coli are consistent with the view that the ancestral lines of these three kinds of DNA diverged from each other within a relatively short time period.