Pig heart mitochondrial ATPase : properties of purified and membrane-bound enzyme. Effects of flavonoids.

International audienceSoluble ATPase (F1) has been purified from pig heart mitochondria. The purified enzyme had a high specific activity and was homogeneous as checked by ultracentrifugation and electrofocusing. It could be dissociated into subunits by cold-treatment or sodium dodecyl sulfate denaturation. The molecular weights of the two major and three minor subunits could be estimated by sodium dodecyl sulfate gel electrophoresis. The native enzyme had an isoelectric point of 5.2 while the cold-denatured enzyme showed three main bands focusing at pH 5.0, 5.2, and 5.4. Kinetic properties (Vm and Km (atp) have been compared for the soluble and membrane bound ATPase in presence of various anions. Inhibitory effects of Quercetin and other flavonoids have been tested in order to get an insight on the interaction between ATPase and its natural inhibitor.Soluble ATPase (F1) has been purified from pig heart mitochondria. The purified enzyme had a high specific activity and was homogeneous as checked by ultracentrifugation and electrofocusing. It could be dissociated into subunits by cold-treatment or sodium dodecyl sulfate denaturation. The molecular weights of the two major and three minor subunits could be estimated by sodium dodecyl sulfate gel electrophoresis. The native enzyme had an isoelectric point of 5.2 while the cold-denatured enzyme showed three main bands focusing at pH 5.0, 5.2, and 5.4. Kinetic properties (Vm and Km (atp) have been compared for the soluble and membrane bound ATPase in presence of various anions. Inhibitory effects of Quercetin and other flavonoids have been tested in order to get an insight on the interaction between ATPase and its natural inhibitor

Physiological and cytological studies on the inhibition of Striga seed germination by the plant growth-promoting bacterium Azospirillum brasilense

International audienceStriga hermonthica (Del.) Benth. is an obligate parasitic weed of tropical cereals whose rhizosphere can also be colonised by bacteria of the genus Azospirillum. A previous study demonstrated that the two organisms (Azospirillum and striga) interacted during cerealroot colonisation. Two strains of A. brasilense isolated from an African sorghum rhizosphere prevented the germination of striga seeds although they were stimulated to germinate by the presence of sorghum roots. Azospirillum cells suspended in a synthetic germination stimulant (GR24) did not inhibit striga seed germination, but did block radicle elongation. Those radicles had an abnormal morphology, and contained no vacuolated cells in the root elongation zone. Lipophilic compounds extracted from the medium of bacteria in the log and stationary growth phases prevented the germination of striga seeds

Inhibition of Striga seed germination associated with sorghum growth promotion by soil bacteria

International audienceStriga spp. are obligate parasitic weeds of tropical cereals and generally have the same host range as rhizospheric bacteria of the genus Azospirillum. Four strains of Azospirillum brasilense, isolated from soil where sorghum is grown, have been tested for their effect on germination of Striga hermonthica seeds and on cereal (Sorghum vulgare) growth. Two out of four strains assayed significantly inhibited germination of the parasite. Moreover one of the two strains showed a plant growth promoting (PGPR) effect