title: DIVERSITY AND HOST SPECIFICITY OF AZOLLA CYANOBIONTS(1).
abstract: A unique, hereditary symbiosis exists between the water fern Azolla and cyanobacteria that reside within a cavity in the dorsal leaf-lobe of the plant. This association has been studied extensively, and questions have frequently been raised regarding the number and diversity of cyanobionts (cyanobacterial symbionts) among the different Azolla strains and species. In this work, denaturating gradient gel electrophoresis (DGGE) and a clone library based on the 16S rRNA gene were used to study the genetic diversity and host specificity of the cyanobionts in 35 Azolla strains covering a wide taxonomic and geographic range. DNA was extracted directly from the cyanobacterial packets, isolated after enzymatic digestion of the Azolla leaves. Our results indicated the existence of different cyanobiont strains among Azolla species, and diversity within a single Azolla species, independent of the geographic origin of the host. Furthermore, the cyanobiont exhibited host-species specificity and showed most divergence between the two sections of genus Azolla, Azolla and Rhizosperma. These findings are in agreement with the recent redefinition of the taxon Azolla cristata within the section Azolla. With regard to the taxonomic status of the cyanobiont, the genus Anabaena of the Nostocaceae family was identified as the closest relative by this work.
authors.affiliation: Department of Botany, Stockholm University, SE-106 91 Stockholm, SwedenLaboratory of Plant Biology, Faculty of Sciences, Catholic University of Louvain, Place Croix Du Sud 5, B-1348 Louvain-La-Neuve, BelgiumDepartment of Botany, Stockholm University, SE-106 91 Stockholm, SwedenCenter for Protein Engineering, Chemistry Institute (B6), University of Liége, 4000 Liége, Belgium.
authors.forename: Dimitra
authors.initials: D
authors.lastname: Papaefthimiou
authors.affiliation: Department of Botany, Stockholm University, SE-106 91 Stockholm, SwedenLaboratory of Plant Biology, Faculty of Sciences, Catholic University of Louvain, Place Croix Du Sud 5, B-1348 Louvain-La-Neuve, BelgiumDepartment of Botany, Stockholm University, SE-106 91 Stockholm, SwedenCenter for Protein Engineering, Chemistry Institute (B6), University of Liége, 4000 Liége, Belgium.
authors.forename: Charles
authors.initials: C
authors.lastname: Van Hove
authors.affiliation: Department of Botany, Stockholm University, SE-106 91 Stockholm, SwedenLaboratory of Plant Biology, Faculty of Sciences, Catholic University of Louvain, Place Croix Du Sud 5, B-1348 Louvain-La-Neuve, BelgiumDepartment of Botany, Stockholm University, SE-106 91 Stockholm, SwedenCenter for Protein Engineering, Chemistry Institute (B6), University of Liége, 4000 Liége, Belgium.
authors.forename: André
authors.initials: A
authors.lastname: Lejeune
authors.affiliation: Department of Botany, Stockholm University, SE-106 91 Stockholm, SwedenLaboratory of Plant Biology, Faculty of Sciences, Catholic University of Louvain, Place Croix Du Sud 5, B-1348 Louvain-La-Neuve, BelgiumDepartment of Botany, Stockholm University, SE-106 91 Stockholm, SwedenCenter for Protein Engineering, Chemistry Institute (B6), University of Liége, 4000 Liége, Belgium.
authors.forename: Ulla
authors.initials: U
authors.lastname: Rasmussen
authors.affiliation: Department of Botany, Stockholm University, SE-106 91 Stockholm, SwedenLaboratory of Plant Biology, Faculty of Sciences, Catholic University of Louvain, Place Croix Du Sud 5, B-1348 Louvain-La-Neuve, BelgiumDepartment of Botany, Stockholm University, SE-106 91 Stockholm, SwedenCenter for Protein Engineering, Chemistry Institute (B6), University of Liége, 4000 Liége, Belgium.
authors.forename: Annick
authors.initials: A
authors.lastname: Wilmotte
keywords: 16S rRNA; Anabaena; Azolla; DGGE; cyanobacteria; cyanobionts; diversity; genotypic; symbiosis