The complete nucleotide sequence of the mitochondrial genome of sugar beet (Beta vulgaris L.) reveals a novel gene for tRNACys(GCA)

Abstract

We determined the complete nucleotide sequence of the mitochondrial genome of an angiosperm, sugar beet (Beta vulgaris cv TK81-O). The 368 799 bp genome contains 29 protein, five rRNA and 25 tRNA genes, most of which are also shared by the mitochondrial genome of Arabidopsis thaliana, the only other completely sequenced angiosperm mitochondrial genome. However, four genes identified here (namely rps13, trnF-GAA, ccb577 and trnC2-GCA) are missing in Arabidopsis mitochondria. In addition, four genes found in Arabidopsis (ccb228, rpl2, rpl16 and trnY2-GUA) are entirely absent in sugar beet or present only in severely truncated form. Introns, duplicated sequences, additional reading frames and inserted foreign sequences (chloroplast, nuclear and plasmid DNA sequences) contribute significantly to the overall size of the sugar beet mitochondrial genome. Nevertheless, 55.6% of the genome has no obvious features of information. We identified a novel tRNA(Cys) gene (trnC2-GCA) which shows no sequence homology with any tRNA(Cys) genes reported so far in higher plants. Intriguingly, this tRNA gene is actually transcribed into a mature tRNA, whereas the native tRNA(Cys) gene (trnC1-GCA) is most likely a pseudogene.

Interactions of Mitochondrial and Nuclear Genes That Affect Male Gametophyte Development

“…Plant mtDNAs contain sequences obviously derived from chloroplast and nuclear genomes, as well as considerable sequences of unknown origin. Analysis of the complete sequences of the mitochondrial genomes from three vascular plants shows that they carry a complement of 55 to 60 genes that encode either known mitochondrial genes or conserved mitochondrial orfs of unknown function Kubo et al, 2000;Notsu et al, 2002). Strikingly, the remainder of the DNA in each of the sequenced genomes contains many sequences and orfs not found in either of the other two genomes.…”

Genomics-based dissection of the cross-talk of chloroplasts with the nucleus and mitochondria in Arabidopsis

“…On the contrary, migration of chondrome-derived sequences to plastid DNA has not been described yet. Between 1% and 6% of the mitochondrial genomes of Arabidopsis thaliana, sugar beet and rice derive from plastid DNA, while retrotransposons seem to be the source of nucleus-derived mitochondrial DNA (Unseld et al, 1997;Kubo et al, 2000;Notsu et al, 2002). However, only very few of such promiscuous DNA sequences are functional, namely plastid-derived mitochondrial tRNA genes.…”

Punctuated evolution of mitochondrial gene content: High and variable rates of mitochondrial gene loss and transfer to the nucleus during angiosperm evolution

“…Plant mtDNAs contain many more protein genes than do animals or fungi, 30-39 in the case of the three sequenced plant mtDNAs (8)(9)(10). Within angiosperms, mitochondrial gene loss and gene transfer are relatively frequent, ongoing phenomena.…”

“…Within angiosperms, mitochondrial gene loss and gene transfer are relatively frequent, ongoing phenomena. The completely sequenced mtDNAs of Arabidopsis and sugar beet are each missing, entirely or in part, 9-10 genes that are present in other angiosperm mtDNAs (9,10). In Arabidopsis, most of these genes have been relocated to the mostly sequenced nuclear genome (ref.…”