title: Screening for leaf-associated endophytes in the genus Psychotria (Rubiaceae).
abstract: Burkholderia endophytes were identified within the leaves of non-nodulated members of the genus Psychotria. In contrast to leaf-nodulated Psychotria species, which are known to accommodate their endosymbionts into specialized endosymbiont-housing structures, non-nodulated species lack bacterial leaf nodules and harbor endosymbionts intercellularly between mesophyll cells. Based on molecular data (rps16, trnG, and trnLF), the phylogenetic reconstruction of the host plants revealed a separate origin of leaf-nodulated and non-nodulated Psychotria species. Despite a distinct phylogenetic position of the two host clades, the endophytes of the non-nodulated plants were not placed into a single monophyletic group but were found to be closely related to the leaf-nodulated endosymbionts. The observation of genetically similar endophytes in both nodulated and non-nodulated Psychotria lineages suggests that the host plant is playing a crucial role in the induction of leaf nodule formation. Moreover, the concentration of endosymbionts into specialized leaf nodules may be considered as a more derived evolutionary adaptation of the host plant, serving as an interface structure to facilitate metabolic exchange between plant and endosymbiont.
authors.affiliation: Laboratory of Plant Systematics, KULeuven, Leuven, Belgium. benny.lemaire@bio.kuleuven.be
authors.forename: Benny
authors.initials: B
authors.lastname: Lemaire
authors.forename: Olivier
authors.initials: O
authors.lastname: Lachenaud
authors.forename: Claes
authors.initials: C
authors.lastname: Persson
authors.forename: Erik
authors.initials: E
authors.lastname: Smets
authors.forename: Steven
authors.initials: S
authors.lastname: Dessein
mesh_terms: D005075:Biological Evolution; D019117:Burkholderia / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D004269:DNA, Bacterial / Q000235:genetics; D060026:Endophytes / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D010802:Phylogeny; D018515:Plant Leaves / Q000382:microbiology*; D032069:Psychotria / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D004269:DNA, Bacterial