Higher plant mitochondria encode an homologue of the nuclear‐encoded 30‐kDa subunit of bovine mitochondrial complex I

Abstract

We describe the structure and expression of a wheat mitochondrial gene, which codes for a subunit of mitochondrial NADH dehydrogenase. The deduced protein sequence has 70% similarity to the 30-kDa subunit of bovine mitochondrial complex I and 65% similarity to the 31-kDa subunit of Neurospora crassa complex I, components of the iron-sulfur-protein fraction, both nuclear-encoded proteins. We named this wheat mitochondrial gene as nad9. The wheat nad9 gene is transcribed in a single mRNA of 0.9 kb that is edited (C-to-U conversions) in 14 positions. Transcript mapping revealed that the first ATG codon is just 20 nucleotides downstream of the mRNA 5' end and that the 3' end is just 23 nucleotides downstream of the nad9 stop codonThe expression of the nad9 gene in plant mitochondria was studied. Polyclonal antibodies prepared against a wheat NAD9 fusion protein specifically recognise the 30-kDa subunit of bovine mitochondrial complex I and a 27.5-kDa protein in the membrane fractions of wheat, maize and common bean mitochondria, whereas the same serum recognizes a 30-kDa protein in the mitochondria of pea, chickpea and lentil.Higher plants contain the larger mitochondrial genomic DNA described up to now, with sizes varying in the range 250-2500 kb (compared with the 16 kb of mammalian mitochondria) [l]. The greater size of plant mitochondrial DNA may be taken as an indication of the presence of additional genes that are not found in the organelles from other species. Indeed, several ribosomal protein genes and the atpA gene coding for the a subunit of the H+-ATPase [2] have been found in plant mitochondrial genomes in contrast with other mitochondrial genomes. Most of the identified plant mitochondrial genes have counterparts in animal and yeast mitochondrial genomes. However, the recent determination of the Marchantia polymorpha mtDNA sequence [3] has shown that plant mitochondrial genomes contain a number of unidentified open reading frames which may correspond to either nuclear-encoded proteins in animal and fungi or to plant-specific polypeptides.Plant mitochondria seem to express and modulate the genetic information in a relatively complex way. Recently, editing [4-71 and trans-splicing [8-111 of plant mitochondrial mRNA have been described. Editing involves all plant mitoCorrespondence to J

AtnMat2, a nuclear-encoded maturase required for splicing of group-II introns in Arabidopsis mitochondria

“…Antibodies to hydroxymethyltransferase (SHMT), cytochrome oxidase subunit 2 (COX2), NADH dehydrogenase subunit 9 (NAD9) (Lamattina et al 1993), and the plastidic 33-kDa subunit of the photosystem II oxygen-evolving enzyme (PsbO) confirmed that the organelle preparations were reasonably pure (Fig. 3A).…”

“…3A), confirming that nMat2 was largely reduced in the mutant. While COX2 and SHMT accumulated to similar levels in wild-type and nMat2 plants, immunoblot analysis with antibodies raised in wheat NAD9 protein (Lamattina et al 1993) indicated that the protein was reduced by several folds in the mutant (Fig. 3A, NAD9).…”

Dual Location of the Mitochondrial Preprotein Transporters B14.7 and Tim23-2 in Complex I and the TIM17:23 Complex in Arabidopsis Links Mitochondrial Activity and Biogenesis

“…The CV was determined by calculating the ratio of the standard deviation of the mean, providing a statistical indication of the spread/variation in abundance. Antibodies used were raised against Tim17-2 ( Murcha et al, 2005a), Tom20-2, 20-3, 20-4, Metaxin (Lister et al, 2007, Tom40, RISP, Sam50 (Carrie et al, 2010b), AOX, a-subunit of ATP synthase, Porin (Elthon et al, 1989), Nad9 (Lamattina et al, 1993), COXII, cytochrome c, b-subunit of ATP synthase (Agrisera), and Ndufs4 . For the remaining antibodies, recombinant proteins of Tim9 (At3g46560, amino acids 1 to 93), Tim50 (At1g55900, amino acids 110 to 269), Tim44 (At2g36070, amino acids 100 to 472), Tim21 (At4g00026, amino acids 160 to 376), Tim23-2 (At1g72750, amino acids 3 to 32 and 103 to 143), Tim23-3 (At3g04800, amino acids 6 to 32 and 64 to 132), At3g25120 (amino acids, amino acids 89 to 189), were expressed and purified as previously outlined (Carrie et al, 2010b).…”

The Pentatricopeptide Repeat Proteins TANG2 and ORGANELLE TRANSCRIPT PROCESSING439 Are Involved in the Splicing of the Multipartite nad5 Transcript Encoding a Subunit of Mitochondrial Complex I

“…Proteins were transferred onto a polyvinylidene difluoride membrane (Bio-Rad), in cathode buffer for 15 h at 40 mA, using a Bio-Rad Mini Transblot Cell. Western-blot analysis was performed using an anti-Nad9 antibody (Lamattina et al, 1993) and a goat anti-rabbit secondary antibody conjugated to horseradish peroxidase, and the results were subsequently revealed using enhanced chemiluminescence reagents (GE Healthcare).…”