title: Oligogalacturonides: novel signaling molecules in Rhizobium-legume communications.
abstract: Oligogalacturonides are pectic fragments of the plant cell wall, whose signaling role has been described thus far during plant development and plant-pathogen interactions. In the present work, we evaluated the potential involvement of oligogalacturonides in the molecular communications between legumes and rhizobia during the establishment of nitrogen-fixing symbiosis. Oligogalacturonides with a degree of polymerization of 10 to 15 were found to trigger a rapid intracellular production of reactive oxygen species in Rhizobium leguminosarum bv. viciae 3841. Accumulation of H(2)O(2), detected by both 2',7'-dichlorodihydrofluorescein diacetate-based fluorescence and electron-dense deposits of cerium perhydroxides, was transient and did not affect bacterial cell viability, due to the prompt activation of the katG gene encoding a catalase. Calcium measurements carried out in R. leguminosarum transformed with the bioluminescent Ca(2+) reporter aequorin demonstrated the induction of a rapid and remarkable intracellular Ca(2+) increase in response to oligogalacturonides. When applied jointly with naringenin, oligogalacturonides effectively inhibited flavonoid-induced nod gene expression, indicating an antagonistic interplay between oligogalacturonides and inducing flavonoids in the early stages of plant root colonization. The above data suggest a novel role for oligogalacturonides as signaling molecules released in the rhizosphere in the initial rhizobium-legume interaction.
authors: Dipartimento di Biologia, Universita di Padova, Padova, Italy.
authors: Roberto
authors: R
authors: Moscatiello
authors: Barbara
authors: B
authors: Baldan
authors: Andrea
authors: A
authors: Squartini
authors: Paola
authors: P
authors: Mariani
authors: Lorella
authors: L
authors: Navazio
mesh_terms: D002118:Calcium / Q000378:metabolism; D007887:Fabaceae / Q000378:metabolism / Q000382:microbiology*; D009586:Nitrogen Fixation / Q000502:physiology; D009844:Oligosaccharides / Q000378:metabolism*; D016961:Rhizobium leguminosarum / Q000378:metabolism* / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D009844:Oligosaccharides; C412763:oligogalacturonic acid; D002118:Calcium