In the Nicotiana sylvestris CMSII mutant, a recombination‐mediated change 5′ to the first exon of the mitochondrial nad1 gene is associated with lack of the NADH:ubiquinone oxidoreductase (complex I) NAD1 subunit

Abstract

We previously reported that the Nicotiana sylvestris CMSII mutant mitochondrial DNA carried a large deletion. Several expressed sequences, most of which are duplicated, and the unique copy of the nad7 gene encoding the NAD7 subunit of the NADH:ubiquinone oxidoreductase complex (complex I) are found in the deletion. Here, we show that the orf87‐nad3‐nad1/A cotranscription unit transcribed from a unique promoter element in the wild‐type, is disrupted in CMSII. Nad3, orf87 and the promoter element are part of the deleted sequence, whilst the nad1/A sequence is present and transcribed from a new promoter brought by the recombination event, as indicated by Northern and primer extension experiments. However, Western analyses of mitochondrial protein fractions and of complex I purified using anti‐NAD9 affinity columns, revealed that NAD1 is lacking in CMSII mitochondria. Our results suggest that translation of nad1 transcripts rather than transcription itself could be altered in the mutant. Consequences of lack of this submit belonging the membrane arm of complex I and thought to contain the ubiquinone‐binding site, are discussed.

Remodeled Respiration in ndufs4 with Low Phosphorylation Efficiency Suppresses Arabidopsis Germination and Growth and Alters Control of Metabolism at Night

“…The mutant exhibits a slower growth rate at all stages of development, and many of the transcripts for housekeeping functions (RNA and protein metabolism, cell cycle) are decreased in abundance, indicating a slower pace of cellular function. This growth delay has also been observed in other characterized plant complex I mutants, such as the CMSII tobacco mutant (Gutierres et al, 1999) …”

Targeting the NAD7 Subunit to Mitochondria Restores a Functional Complex I and a Wild Type Phenotype in the Nicotiana sylvestris CMS II Mutant Lacking nad7

“…To ensure a proper cleavage of the presequence, the downstream formate dehydrogenase primer carried 12 bp coding for the four amino acids located downstream the processing site. The construct was cloned under control of the 35 S CAMV promoter in the pCW162 vector.…”

“…2) at flowering time as regards plant height, leaf and flower shape, and set seeds. They were fertile, although the 35 S promoter is not expressed in pollen, suggesting that enough stable complex I assembled in mother pollen cells can function and allow fertile pollen production in mature anthers.…”

“…We have shown that a recombination/amplification process resulted in a 72-kb deletion in the mutant mitochondrial genome (31,32). A number of genes and orfs appeared to be deleted following this event or to exhibit rearranged promoter regions (33)(34)(35). Of the deleted sequences, only the nad7 gene is present as a single copy, whereas others such as nad3 or orf87 are duplicated in the mitochondrial genome.…”

The Pentatricopeptide Repeat GeneOTP43Is Required fortrans-Splicing of the Mitochondrialnad1Intron 1 inArabidopsis thaliana

“…This mutant carries a mitochondrial deletion in the nad7 gene encoding a 40-kD subunit of Complex I (Pla et al, 1995). The mutant plants develop slowly, exhibit conditional male sterility, and have no detectable Complex I, increased amounts and activity of AOX, and multiple perturbations to primary metabolism (Gutierres et al, 1997(Gutierres et al, , 1999Lelandais et al, 1998;Sabar et al, 2000;Dutilleul et al, 2003aDutilleul et al, , 2003bDutilleul et al, , 2005Pineau et al, 2005;Priault et al, 2006aPriault et al, , 2006bVidal et al, 2007). A second Complex I mutant has been described from maize (Karpova and Newton, 1999).…”