Chitinase-resistant hydrophilic symbiotic factors secreted by Frankia activate both Ca(2+) spiking and NIN gene expression in the actinorhizal plant Casuarina glauca.
Although it is now well-established that decorated lipo-chitooligosaccharide Nod factors are the key rhizobial signals which initiate infection/nodulation in host legume species, the identity of the equivalent microbial signaling molecules in the Frankia/actinorhizal association remains elusive. With the objective of identifying Frankia symbiotic factors we present a novel approach based on both molecular and cellular pre-infection reporters expressed in the model actinorhizal species Casuarina glauca. By introducing the nuclear-localized cameleon Nup-YC2.1 into Casuarina glauca we show that cell-free culture supernatants of the compatible Frankia CcI3 strain are able to elicit sustained high frequency Ca(2+) spiking in host root hairs. Furthermore, an excellent correlation exists between the triggering of nuclear Ca(2+) spiking and the transcriptional activation of the ProCgNIN:GFP reporter as a function of the Frankia strain tested. These two pre-infection symbiotic responses have been used in combination to show that the signal molecules present in the Frankia CcI3 supernatant are hydrophilic, of low molecular weight and resistant to chitinase degradation. In conclusion, the biologically active symbiotic signals secreted by Frankia appear to be chemically distinct from the currently known chitin-based rhizobial/arbuscular mycorrhizal signaling molecules. Convenient bioassays in Casuarina glauca are now available for their full characterization.
Laboratory of Plant-Microbe Interactions, Institut National de la Recherche Agronomique (UMR 441), Centre National de la Recherche Scientifique (UMR 2594), F-31320, Castanet-Tolosan, France.
Mireille
M
Chabaud
Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (IRD/Université Montpellier), F-34394, Montpellier Cedex 5, France.|Laboratoire des Symbioses Tropicales et Méditerranéennes (IRD/INRA/CIRAD/Université Montpellier/Supagro), 34398, Montpellier Cedex 5, France.
Hassen
H
Gherbi
Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (IRD/Université Montpellier), F-34394, Montpellier Cedex 5, France.|Laboratoire des Symbioses Tropicales et Méditerranéennes (IRD/INRA/CIRAD/Université Montpellier/Supagro), 34398, Montpellier Cedex 5, France.
Elodie
E
Pirolles
Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (IRD/Université Montpellier), F-34394, Montpellier Cedex 5, France.
Virginie
V
Vaissayre
Laboratory of Plant-Microbe Interactions, Institut National de la Recherche Agronomique (UMR 441), Centre National de la Recherche Scientifique (UMR 2594), F-31320, Castanet-Tolosan, France.
Joëlle
J
Fournier
Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (IRD/Université Montpellier), F-34394, Montpellier Cedex 5, France.
Daniel
D
Moukouanga
Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (IRD/Université Montpellier), F-34394, Montpellier Cedex 5, France.
Claudine
C
Franche
Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (IRD/Université Montpellier), F-34394, Montpellier Cedex 5, France.
Didier
D
Bogusz
Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH, 03824-2617, USA.
Louis S
LS
Tisa
Laboratory of Plant-Microbe Interactions, Institut National de la Recherche Agronomique (UMR 441), Centre National de la Recherche Scientifique (UMR 2594), F-31320, Castanet-Tolosan, France.
David G
DG
Barker
Unité Mixte de Recherche Diversité Adaptation et Développement des Plantes (IRD/Université Montpellier), F-34394, Montpellier Cedex 5, France.|Laboratoire des Symbioses Tropicales et Méditerranéennes (IRD/INRA/CIRAD/Université Montpellier/Supagro), 34398, Montpellier Cedex 5, France.|Laboratoire Mixte International Adaptation des Plantes et Microorganismes Associés aux Stress Environnementaux, Centre de Recherche de Bel Air, CP 18524, Dakar, Sénégal.|Laboratoire Commun de Microbiologie, Institut de Recherche pour le Développement/Institut Sénégalais des Recherches Agricoles/Université Cheikh Anta Diop, BP 1386, Dakar, Sénégal.
Sergio
http://orcid.org/0000-0001-8554-2922
S
Svistoonoff
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002688:Chitinases / Q000378:metabolism; D040161:Frankia / Q000235:genetics / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D057927:Hydrophobic and Hydrophilic Interactions; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D019684:Magnoliopsida / Q000235:genetics / Q000382:microbiology*; D038821:Mycorrhizae / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000235:genetics / Q000382:microbiology; D030821:Plants, Genetically Modified; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013559:Symbiosis
D001426:Bacterial Proteins; D008164:Luminescent Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins; C507867:yellow cameleon 2.1; D002688:Chitinases; D002118:Calcium
Frankia culture supernatant; NIN gene expression; actinorhiza; chitinase-resistance; nuclear Ca2+ spiking; plant-microbe signaling; transgenic Casuarina glauca