Alloplasmic male sterility in Brassica napus (CMS 'Tournefortii-Stiewe') is associated with a special gene arrangement around a novel atp9 gene

authored by

J. H. Dieterich, Hans-Peter Braun, Udo Schmitz

Abstract

To identify regions of the mitochondrial genome potentially involved in the expression of alloplasmic 'Tournefortii-Stiewe' cytoplasmic male sterility (CMS) in Brassica napus, transcripts of 25 mitochondrial genes were analysed in fertile and near isogenic male-sterile plants (BC₈ generation). Differences were detected in the transcription of genes for subunit 9 of ATP synthase (atp9), cytochrome b (cob) and subunit 2 of NADH dehydrogenase (nad2). Structural analysis of these gene regions revealed differences in genome organisation around atp9 between male-sterile and fertile plants. Three atp9 genes, two of which were hitherto unknown, are present in the mitochondria of CMS plants, and rearrangements upstream of one of these genes have generated a chimeric 193-codon ORF, designated orf193. This region is transcribed as a CMS specific bicistronic mRNA of 1.58 kb comprising orf193 and atp9. The level of the aberrant 1.58-kb transcript is reduced in plants restored to fertility by as yet uncharacterized nuclear genes, orf193 encodes a polypeptide of 22.7 kDa which exhibits partial sequence identity to the subunit 6 of the ATP synthase complex. However, as it forms an uninterrupted ORF with one of the newly discovered atp9 genes it may also be translated as a chimeric 30.2-kDa protein. It is likely that either or both gene products interfere with the function or assembly of the mitochondrial F₀F₁-ATP synthase, thus impairing the highly ATP-dependent process of pollen development. The novel molecular features of alloplasmic 'Tournefortii-Stiewe' CMS are discussed with respect to the other known mechanisms of CMS in B. napus.

Organisation(s)

Section Plant Molecular Biology and Plant Proteomics

External Organisation(s)

Max Planck Institute of Molecular Plant Physiology (MPI-MP)

Type

Article

Journal

Molecular Genetics and Genomics

Volume

269

Pages

723-731

No. of pages

9

ISSN

1617-4615

Publication date

30.07.2003

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Molecular Biology, Genetics

Electronic version(s)

https://doi.org/10.1007/s00438-003-0886-3 (Access: Unknown)