The male sterile G cytoplasm of wild beet displays modified mitochondrial respiratory complexes.
Cytoplasmic male sterility (CMS) in higher plants has been mainly studied in cultivated species. In most cases, pollen abortion is linked to the presence of an additional mitochondrial polypeptide leading to organelle dysfunction in reproductive tissues. In wild beet, both CMS and hermaphrodite plants coexist in natural populations. The G cytoplasm is widely distributed along the Western European coast, and previous genetic studies have demonstrated that this cytoplasm confers male sterility in beet. In the present study, we have identified two mutations of G mitochondrial genes, each of which results in the production of a respiratory chain complex subunit with an altered molecular weight; the NAD9 subunit has a C-terminal extension while the COX2 subunit has a truncated C-terminus. NADH dehydrogenase activity was unchanged in leaves, but cytochrome c oxidase activity was reduced by 50%. Moreover, Western blot analyses revealed that alternative oxidase was more abundant in male sterile G plants than in a fertile control (Nv), suggesting that this alternative pathway might compensate for the cytochrome c oxidase deficiency. Implications of respiratory chain changes and a putative link with CMS are discussed.
Ducos
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Laboratoire de Génétique et Evolution des Populations Végétales, UPRESA-CNRS 8016, FR CNRS 1818, Université de Lille I, F-59655 Villeneuve d'Ascq cedex, France.
Touzet
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Boutry
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D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D015153:Blotting, Western; D019663:Chenopodiaceae / Q000235:genetics / Q000378:metabolism*; D051546:Cyclooxygenase 2; D003593:Cytoplasm / Q000145:classification / Q000235:genetics; D004579:Electron Transport / Q000235:genetics / Q000502:physiology; D042967:Electron Transport Complex I; D003576:Electron Transport Complex IV / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D005298:Fertility; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation; D009247:NADH, NADPH Oxidoreductases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D010088:Oxidoreductases / Q000096:biosynthesis; D010940:Plant Proteins; D011058:Pollen / Q000235:genetics; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D017421:Sequence Analysis; D000099188:Alternative Oxidase
D051546:Cyclooxygenase 2; D042967:Electron Transport Complex I; D003576:Electron Transport Complex IV; D007527:Isoenzymes; D024101:Mitochondrial Proteins; D009247:NADH, NADPH Oxidoreductases; D010088:Oxidoreductases; D010940:Plant Proteins; D011451:Prostaglandin-Endoperoxide Synthases; D000099188:Alternative Oxidase