Titre du document / Document title

The actinorhizal symbiosis : Plant communication with other organisms: chemicals are the words

Auteur(s) / Author(s)

WALL Luis Gabriel ⁽¹⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Departamento de Ciencia y Tecnologia, Universidad Nacional de Quilmes, R. Sáenz Peña 180, B1876BXD Bernal, ARGENTINE

Résumé / Abstract

The term actinorhiza refers both to the filamentous bacteria Frankia, an actinomycete, and to the root location of nitrogen-fixing nodules. Actinorhizal plants are classified into four subclasses, eight families, and 25 genera comprising more than 220 species. Although ontogenically related to lateral roots, actinorhizal nodules are characterized by differentially expressed genes, supporting the idea of the uniqueness of this new organ. Two pathways for root infection have been described for compatible Frankia interactions: root hair infection or intercellular penetration. Molecular phylogeny groupings of host plants correlate with morphologic and anatomic features of actinorhizal nodules. Four clades of actinorhizal plants have been defined, whereas Frankia bacteria are classified into three major phylogenetic groups. Although the phylogenies of the symbionts are not fully congruent, a close relationship exists between plant and bacterial groups. A model for actinorhizal specificity is proposed that includes different levels or degrees of specificity of host-symbiont interactions, from fully compatible to incompatible. Intermediate, compatible, but delayed or limited interactions are also discussed. Actinorhizal plants undergo feedback regulation of symbiosis involving at least two different and consecutive signals that lead to a mechanism controlling root nodulation. These signals mediate the opening or closing of the window of susceptibility for infection and inhibit infection and nodule development in the growing root, independently of infection mechanism. The requirement for at least two molecular recognition steps in the development of actinorhizal symbioses is discussed.

Revue / Journal Title

Journal of plant growth regulation   ISSN 0721-7595   CODEN JPGRDI 

Source / Source

2000, vol. 19, n^o2, pp. 167-182 (4 p.3/4)

Langue / Language

Anglais

Editeur / Publisher

Springer, New York, NY, ETATS-UNIS  (1982) (Revue)

Mots-clés anglais / English Keywords

Actinorrhiza ; Development ; Morphology ; Anatomy ; Phylogeny ; Host specificity ; Signal transduction ; Regulation(control) ; Models ; Vegetal microorganism relation ; Nitrogen fixation ; Symbiosis ;

Mots-clés français / French Keywords

Actinorhize ; Développement ; Morphologie ; Anatomie ; Phylogenèse ; Spécificité hôte ; Transduction signal ; Régulation ; Modèle ; Relation microorganisme végétal ; Fixation azote ; Symbiose ;

Mots-clés espagnols / Spanish Keywords

Actinorriza ; Desarrollo ; Morfología ; Anatomía ; Filogénesis ; Especificidad huesped ; Transducción señal ; Regulación ; Modelo ; Relación microorganismo vegetal ; Fijación nitrogeno ; Simbiosis ;

Localisation / Location

INIST-CNRS, Cote INIST : 19223, 35400009321697.0050