bacterial leaf symbiosis in angiosperms host specificity without co-speciation在被子植物宿主特异性没有co-speciation细菌性叶的共生关系.pdf

Bacterial Leaf Symbiosis in Angiosperms: Host Specificity without Co-Speciation 1 2 3 1,3,4 5 Benny Lemaire *, Peter Vandamme , Vincent Merckx , Erik Smets , Steven Dessein 1 Laboratory of Plant Systematics, K.U.Leuven, Leuven, Belgium, 2 Laboratory of Microbiology, Ghent University, Gent, Belgium, 3 Netherlands Centre for Biodiversity Naturalis, Leiden, The Netherlands, 4 National Herbarium of the Netherlands, Leiden University, Leiden, The Netherlands, 5 National Botanic Garden of Belgium, Meise, Belgium Abstract Bacterial leaf symbiosis is a unique and intimate interaction between bacteria and flowering plants, in which endosymbionts are organized in specialized leaf structures. Previously, bacterial leaf symbiosis has been described as a cyclic and obligate interaction in which the endosymbionts are vertically transmitted between plant generations and lack autonomous growth. Theoretically this allows for co-speciation between leaf nodulated plants and their endosymbionts. We sequenced the nodulated Burkholderia endosymbionts of 54 plant species from known leaf nodulated angiosperm genera, i.e. Ardisia, Pavetta, Psychotria and Sericanthe. Phylogenetic reconstruction of bacterial leaf symbionts and closely related free-living bacteria indicates the occurrence of multiple horizontal transfers of bacteria from the environment to leaf nodulated plant species. This rejects the hypothesis of a long co-speciation process between the bacterial endosymbionts and their host plants. Our results indicate a recent evolutionary process towards a stable and host specific interaction confirming the proposed maternal transmission mode of the endosymbiont