The genera Gymnostoma and Ceuthostoma (Casuarinaceae) can establish symbioses with cluster 1 and with cluster 3 Frankia.
ID: 613 / 454
Proposed Symposium Title: The genera Gymnostoma and Ceuthostoma (Casuarinaceae) can establish symbioses with cluster 1 and with cluster 3 Frankia.
Celestino Quintela-Sabarís1, Lo Chor Wai2, Hasna Boubakri3, Philippe Normand3, Sukaibin Sumail4, Aude Herrera-Belaroussi3, Manuel Aira1, Farnidah Jasnie2, Siti-Aminah Mohamad2, Jorge Domínguez1
Affiliations: 1 Animal Ecology Group, Universidade de Vigo, Vigo, Spain 2 Fakulti Sains Gunaan, Universiti Teknologi MARA – Cawangan Sabah, Kota Kinabalu, Malaysia 3 Laboratoire d'Écologie Microbienne, Université Lyon 1, Lyon, France 4 Kinabalu Park Herbarium, Sabah Parks, Kota Kinabalu, Malaysia
The family Casuarinaceae comprises four genera (from more basal to more recent): Gymnostoma, Ceuthostoma, Casuarina and Allocasuarina. Casuarinaceae have actinorhizal symbioses with Frankia N-fixing actinobacteria. This symbiosis is an intriguing model of evolution of plant-microbe interactions, as Gymnostoma established a nonspecific symbiotic association with easy-to-isolate, more saprophytic Frankia strains which belong to cluster 3 frankiae, whereas the genera Casuarina and Allocasuarina are in symbiosis with hard-to-isolate strains from the cluster 1c frankiae. To date, there is no information about the symbiont associated to the genus Ceuthostoma, whose origin is intermediate between Gymnostoma and Casuarina + Allocasuarina.
To advance our knowledge on the Frankia-Casuarinaceae symbioses and to obtain first evidences on the strains associated to Ceuthostoma, a genus with a narrow geographical range, we collected actinorhizal nodules from the species C. terminale, Gymnostoma nobile and G. sumatranum from different sites in Sabah (Malaysia). After surface sterilisation and peeling, we extracted DNA from the nodules and amplified and sequenced a fragment of the bacterial pgk gene, which has been used previously for the identification of Frankia strains. After aligning our sequences with published sequences of standard Frankia strains covering all the diversity in the bacterial genus, we constructed a maximum-likelihood tree.
We found that all the G. nobile and the majority of G. sumatranum and C. terminale trees had symbioses with cluster 3 frankiae, whereas 10% and 18% of the C. terminale and G. sumatranum trees had symbioses with Frankia strains in cluster 1. Interestingly, those strains were not grouped with the strains from Casuarina and Allocasuarina. Instead, they were in a different group, closer to Frankia species that enter symbiosis with Alnus and Morella.
Overall, this study points to a complex scenario of evolution of actinorhizal symbiosis in this group.