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ORFB is a subunit of F 1 F O ‐ATP synthase: insight into the basis of cytoplasmic male sterility in sunflower
Author(s) -
Sabar Mohammed,
Gagliardi Dominique,
Balk Janneke,
Leaver Christopher J
Publication year - 2003
Publication title -
embo reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.584
H-Index - 184
eISSN - 1469-3178
pISSN - 1469-221X
DOI - 10.1038/sj.embor.embor800
Subject(s) - biology , cytoplasmic male sterility , atp synthase , open reading frame , gene , genetics , chalcone synthase , peptide sequence , microbiology and biotechnology , gene expression
ORFB is the product of a gene that is conserved in plant mitochondrial genomes, and which, on the basis of sequence motif and structural similarity, is predicted to be the homologue of yeast and mammalian ATP8, part of the F O component of the F 1 F O ‐ATP synthase. We have shown that, in sunflower, orfB transcripts are edited, increasing the similarity of the predicted protein to ATP8 proteins from non‐plant species. Blue‐native polyacrylamide gel electrophoresis and peptide sequencing confirm that ORFB localizes to the ATP synthase complex. The predicted amino‐terminal 19 amino acids of ORFB are identical to those in the chimeric mitochondrial ORF522 protein, which is associated with cytoplasmic male sterility (CMS) in sunflower. Assays comparing respiratory complexes from a male‐sterile line expressing ORF522 with those from a male‐fertile line show a specific decrease in ATP hydrolysis by the ATP synthase. These observations allow us to propose a mechanism underlying CMS that is associated with the expression of chimeric open reading frames containing part of the orfB gene.