| Title |
Identification, Origin, and Evolution of Leaf Nodulating Symbionts of Sericanthe (Rubiaceae) |
| Author |
Benny Lemaire1*, Elmar Robbrecht2, Braam van Wyk3, Sandra Van Oevelen4, Brecht Verstraete1, Els Prinsen4, Erik Smets1,5,6, and Steven Dessein2 |
| Address |
1Laboratory of Plant Systematics, K.U.Leuven, Kasteelpark Arenberg 31, PO Box 2437, BE-3001 Leuven, Belgium, 2National Botanic Garden of Belgium, Domein van Bouchout, BE-1860 Meise, Belgium, 3H.G.W.J. Schweickerdt Herbarium, University of Pretoria, Pretoria 0002, South Africa, 4Laboratory of Plant Biochemistry and Physiology, University of Antwerp, Universiteitsplein 1, BE-2610 Antwerp, Belgium, 5Netherlands Centre for Biodiversity Naturalis, PO Box 9517, 2300 RA Leiden, the Netherlands, 6National Herbarium of the Netherlands, Leiden University, PO Box 9514, 2300 RA Leiden, the Netherlands |
| Bibliography |
Journal of Microbiology, 49(6),935-941, 2011,
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| DOI |
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| Key Words |
Burkholderia, endosymbionts, bacterial leaf nodulation, Sericanthe, Rubiaceae |
| Abstract |
Bacterial leaf symbiosis is an intimate association between bacteria and plants in which endosymbionts are housed within leaf nodules. This phenomenon has been reported in three genera of Rubiaceae (Pavetta, Psychotria, and Sericanthe), but the bacterial partner has only been identified in Psychotria and Pavetta. Here we report the identification of symbiotic bacteria in two leaf nodulating Sericanthe species. Using 16S rRNA data and common housekeeping genetic markers (recA and gyrB) we studied the phylogenetic relationships of bacterial endosymbionts in Rubiaceae. Endosymbionts of leaf nodulating Rubiaceae were found to be closely related and were placed as a monophyletic group within the genus Burkholderia (β-Proteobacteria). The phylogenetic analyses revealed a pattern of strict host specificity and placed the two investigated endosymbionts at two distinct positions in the topology of the tree, suggesting at least two different evolutionary origins. The degree of sequence divergence between the Sericanthe endosymbionts and their relatives was large enough to propose the Sericanthe endosymbionts as new species (‘Candidatus Burkholderia andongensis’ and ‘Candidatus Burkholderia petitii’). In a second part of this study, the pylogenetic relationships among nodulating and non-nodulating Sericanthe species were investigated using sequence data from six chloroplast regions (rps16, trnG, trnL-trnF, petD, petA-psbJ, and atpI-atpH). Overall, genetic variation among the plastid markers was insufficient to enable phylogenetic estimation. However, our results could not rule out the possibility that bacterial leaf symbiosis originated once in a common ancestor of the Sericanthe species. |
