An evolutionarily conserved mitochondrialorf108is associated with cytoplasmic male sterility in different alloplasmic lines ofBrassica junceaand induces male sterility in transgenicArabidopsis thaliana

• Published in: Journal of experimental botany 2012-01, Vol.63 (8), p.2921-2932
• Main Authors: Kumar, Pankaj, Vasupalli, Naresh, Srinivasan, R., Bhat, Shripad R.
• Format: Article
• Language: English
• Subjects: Anthers; Cytoplasmic male sterility; Genes; Genomes; Male infertility; Plants; Pollen; RESEARCH PAPER; Reverse transcriptase polymerase chain reaction; RNA; Transgenic plants
• ISSN: 0022-0957; 1460-2431

Nuclear–mitochondrial gene interactions governing cytoplasmic male sterility (CMS) in angiosperms have been found to be unique to each system. Fertility restoration of three diverse alloplasmic CMS lines ofBrassica junceaby a line carrying the fertility-restorer gene introgressed fromMoricandia arvensisprompted this investigation to examine the molecular basis of CMS in these lines. Since previous studies had found alteredatpAtranscription associated with CMS in these lines, theatpAgenes and transcripts of CMS, fertility-restored, and euplasmic lines were cloned and compared.atpAcoding and downstream sequences were conserved among CMS and euplasmic lines but major differences were found in the 5ʹ flanking sequences ofatpA. A unique open reading frame (ORF),orf108, co-transcribed withatpA, was found in male sterile flowers of CMS lines carrying mitochondrial genomes ofDiplotaxis berthautii, D. catholica, orD. erucoides. In presence of the restorer gene, the bicistronicorf108–atpAtranscript was cleaved withinorf108to yield a monocistronicatpAtranscript. Transgenic expression oforf108with anther-specificAtprx18promoter inArabidopsis thalianagave 50% pollen sterility, indicating that Orf108 is lethal at the gametophytic stage. Further, lack of transmission oforf108to the progeny showed for the first time that mitochondrial ORFs could also cause female sterility.orf108was found to be widely distributed among wild relatives ofBrassica, indicating its ancient origin. This is the first report that shows that CMS lines of different origin and morphology could share common molecular basis. The gametic lethality of Orf108 offers a novel opportunity for transgene containment.