10 research outputs found
Osmoprotection mechanisms in rhizobia isolated from Vicia faba var. major and Cicer arietinum
Research of mechanisms involved in osmoprotection of two rhizobia strains isolated
from nodules of Vicia faba var. major and one strain nodulating Cicer arietinum,
showed that choline and glycine-betaine improved growth in salt stress conditions.
Provided radioactive choline was converted into glycine betaine catabolized at low
osmolarity and accumulated under osmotic stress. Enzyme activities involved in the
synthesis of glycine betaine from choline were not modified by salt whereas
addition of choline to the growth medium enhanced them. Exogenous radioactive
glycine betaine was accumulated in salt stressed bacteria after one hour incubation
but catabolized four hours later, suggesting a transient accumulation. Growth
experiments indicated that betaine and its derivatives could be used as nitrogen
and carbon sources. An investigation, by liquid phase chromatography, revealated
accumulation of glutamate and alanine at different levels according to the strain
and degree of stress.Mécanismes d'osmoprotection chez les rhizobia isolés de Vicia faba var. major et
de Cicer arietinum. La recherche des mécanismes impliqués dans l'osmoprotection chez
deux souches de rhizobium isolées des nodosités de Vicia faba var. major et une
souche nodulant Cicer arietinum, a montré que la glycine bétaïne et la choline
améliorent la croissance bactérienne sous stress salin. Lors d'études métaboliques,
la choline intracellulaire radioactive est transformée en glycine bétaïne et ce
indépendamment de l'osmolarité du milieu. En effet, les activités choline déshydrogénase
et glycine bétaïne aldéhyde déshydrogénase ne sont pas modifiées par le sel. Néanmoins,
la présence de la choline dans le milieu augmente les deux activités enzymatiques.
L'incubation en présence de la glycine bétaïne durant une heure est suivie d'une
accumulation de ce composé chez les cellules cultivées à 0,15 M NaCl. Cette
accumulation n'a plus lieu quatre heures plus tard. Des expériences de croissance
avec la glycine bétaïne ou ses métabolites montrent son utilisation comme source de
carbone et d'azote. La recherche, par chromatographie en phase liquide a révélé
l'accumulation du glutamate et de l'alanine à des niveaux variables en fonction
de la souche et du degré de stress
Immunolocalization of ferritin in determinate and indeterminate legume root nodules
10 páginas,5 figurasIn eukaryotic organisms ferritin is a protein involved in the storage of iron. The occurrence of ferritin and its relationship to the effectiveness of the nitrogen-fixing activity have been previously studied during the early stages of the nodule development by biochemical methods. We have used immunocytochemistry techniques to determine the precise location of ferritin and the behavior of this protein along the nodule development. The major localization was
found in plastids and amyloplasts of infected and uninfected cells of the three legume nodules studied. A decrease of the immunolabelling was observed in infected cells of lupin and soybean senescing nodules and in the senescent zone of indeterminate alfalfa nodules. In the cortex of soybean and lupin nodules, ferritin increased during nodule ageing and the immunogold particles were mainly located in crystalline structures. The putative role of ferritin and plastids during nodule development is discussed.This work was supported by an EC Human and Capital Mobility grant, Project CHRX-CT94-0605.Peer reviewe