Template:Mitochondrion

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Annotated Information

Function

ATP synthase F0 subunit 9 (atp9) gene is known as the mitochondrial gene. Transgenic analysis of tobacco with an unedited atp9 gene from wheat has revealed that the main effect of the unedited atp9 expression in transgenic plants was male sterility[1], and it is also the case that the expression of the unedited gene was suppressed by using an antisense strategy resulting in the recovery of male fertility[2]. Thus, the protein ATP9 is clearly associated with male sterility. The study of the unedited atp9 transcript in rice mitochondria for the first time shows non-modified mRNA molecules may potentially influence male fertility through the accumulation of abnormal ATP9 or insufficient normal ATP9, which will influence the function of ATP synthase and then decrease the production of ATP. That is, unediting of atp9 transcript could be likely associated with cytoplasmic male sterility[3].

Expression

When performing the partial protein sequencing of the mitochondrial subunit 9 of ATP synthase (ATP 9), some residues differ from those encoded for by the mitochondrial atp9 gene. The differences are explained by assuming C-to-U transitions at the mRNA level. Thus, mRNA modifications by RNA editing are reflected at the translational level [4]. Extended observations to the cDNA sequence of atp9 demonstrate the presence of partially modified mRNA molecules. One C-to-U conversion transforms an argininecodon into a stop codon, shortening the protein to the “standard” size when compared with other mitochondrial ATP 9. The analysis of subunit 9 by peptide sequencing and amino acid composition confirms these results. The atp9 transcripts are modified by C-to-U changes in a process called RNA editing. Eight codons are involved in RNA editing: five lead to an amino acid change, two give no modification, and one transforms an Arg codon into astop codon. The editing process for wheat ATP 9 represents an important modification in genetic information, considering that the gene is only 243 nucleotides long [5]. Transcription of the single-copy rice mitochondrial atp9 gene has been analyzed. A hypothesis shows that transcription initiates from this promoter to yield a 0.65 kb precursor mRNA and that this primary transcript is processed to a smaller 0.45 kb mature mRNA. This smaller mRNA ends at a putative double stem-loop structure [6].

Evolution

The three atp9 transcripts and positions of RNA editing were not identical. However, the deduced peptide sequences were identical, indicating conservation of the amino acid sequence. And in their study, peptide sequences encoded by fully, partially and excessively edited clones were deduced to be the same [7]. Thus, the rice mitochondrial ATP9 polypeptide seems to be highly homogeneous and RNA editing might be necessary for production of the functional ATP9 peptide. The molecular weight of the rice atp9 protein is predicted to be 8.945kd. This is larger than in other species because of an additional 13 codons (compared to maize) at the 3' end of the gene. The nucleotide and amino acid sequence homologies to other sequenced plant atp9 genes (assuming no mRNA editing) are shown as follows: Nucleotide sequence homology and Amino Acid sequence homology in rice show 96.4% and 94.6% identity in wheat, 95.6% and 98.7% in maize, 91.6% and 96.1% in petunia, 92.0% and 96.1% in tobacco, and 86.2% and 94.7% in pea, respectively [8].

Labs working on this gene

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References

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Structured Information

Gene Name	{{{GeneName}}}
Description	{{{Description}}}
Version	{{{Version}}}
Length	{{{Length}}}
Definition	{{{Definition}}}
Source	{{{Source}}}
Chromosome	{{{Chromosome}}}
Location	{{{AP}}}
Sequence Coding Region	{{{CDS}}}
Genome Context	{{{GCID}}}
Gene Structure (RNA Editing)	{{{GSID}}}
Protein Sequence	{{{AA}}}
Gene Sequence	{{{DNA}}}
External Link(s)	{{{Link}}}