Bacterial Leaf Nodule Symbiosis

Identification of the bacterial endosymbionts in leaf nodules of Pavetta (Rubiaceae)

“…This pattern of specificity between bacteria and hosts provides molecular evidence for the hypothesis of relatively recent vertical transmission of endosymbionts at the intraspecific level, which has been postulated previously by Miller (1990) and Van Oevelen et al (2004). This host specificity suggests that endosymbionts are genetically separated as a consequence of the closed nature of the symbiotic cycle in nodulating Pavetta (von Teichman et al, 1982) and Psychotria species (von Faber, 1912;Miller, 1990), and that every endosymbiont is adapted and specialized to the different ecological niches provided by their specific host plants. The evolutionary and ecological properties of the leaf-nodulating endosymbionts proposed in this study should justify the separation of the endosymbiont into species according to their host species.…”

“…The two nodulated genera Pavetta and Psychotria are distantly related, belonging to different subfamilies of the Rubiaceae. Furthermore, the morphology of the bacterial nodules in Pavetta and Psychotria is different: in Psychotria, the nodular pores open on the abaxial leaf surface, whereas in Pavetta the nodular pores are situated on the adaxial leaf surface (Miller, 1990; Fig. 3a-c).…”

“…About 500 species of Rubiaceae and Primulaceae have been reported to house bacterial symbionts in leaf nodules or galls (Miller, 1990). In Rubiaceae, nodulating 'bacteriophilous' species are limited to three distantly related genera, i.e.…”

“…With approximately 350 accepted nodulated species, Pavetta contains the largest number of nodulated species, with 85 % of species in the genus harbouring bacterial endosymbionts within leaf nodules in tropical continental Africa and Asia (Miller, 1990). In Psychotria and Pavetta, bacterial leaf symbiosis was hypothesized to be obligate and cyclic: the presence of the bacterial partner is required for host survival (Gordon, 1963) and endosymbionts are retained within the host plant during all stages of its life cycle (von Faber, 1912;Miller, 1990). Although no-one has been able to trace the endosymbionts throughout the complete life cycle of Pavetta, the presence of endosymbionts has been proven in ovule and seed.…”

Turner's concise encyclopedia of tropical tree biology

“…For example, I was intrigued to learn of recent evidence for secondary seed dispersal by ants in the Neotropics (e.g., Pizo and Oliveira, 1998), of the recent discovery of a cockroach pollination syndrome (Nagamitsu and Inoue, 1997), and of obligate bacteria-plant symbioses in understory treelets within many species of Rubiaceae and Myrsinaceae (Miller, 1990). Some intriguing comparisons are also made to trees in biomes outside the tropics.…”