THE PLANT CELL, Vol 6, Issue 12 1955-1968, Copyright © 1994 by American Society of Plant Biologists
A Single Homogeneous Form of ATP6 Protein Accumulates in Petunia Mitochondria Despite the Presence of Differentially Edited atp6 Transcripts
B. Lu and M. R. Hanson
Section of Genetics and Development, Biotechnology Building, Cornell University, Ithaca, New York 14853
Transcripts encoding ATP synthase subunit 6 (ATP6) in petunia mitochondria
were shown to be edited at 15 sites, leading to 14 amino acid changes.
Certain sites are partially edited, including a site that introduces a new
translation termination codon that is 13 codons upstream of the genomically
encoded stop codon. Transcripts lacking the new stop codon are present in
an ~2.5:1 ratio to transcripts carrying the stop codon created by RNA
editing. To investigate whether partially edited transcripts are
represented as proteins, we generated an antibody against a 12-residue
peptide that is specific for translation products of unedited transcripts.
This antibody did not recognize any ATP6 protein in either total
mitochondrial protein preparations or ATP6 samples purified by organic
solvent extraction and reverse phase HPLC procedures. According to analysis
by mass spectrometry, only one form of ATP6 protein accumulates in
mitochondria despite the presence of abundant partially edited transcripts.
Partially edited atp6 transcripts were associated with ribosomes,
suggesting that a screening mechanism(s) acts cotranslationally or
post-translationally to exclude the expression of incompletely edited
transcripts.
