Open AccessNodulation of Mimosa spp. by the β-Proteobacterium Ralstonia taiwanensis
Author(s) -
Wen-Ming Chen,
Euan K. James,
Alan R. Prescott,
Martin Kierans,
Janet I. Sprent
Publication year - 2003
Publication title -
molecular plant-microbe interactions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.565
H-Index - 153
eISSN - 1943-7706
pISSN - 0894-0282
DOI - 10.1094/mpmi.2003.16.12.1051
Subject(s) - biology , immunogold labelling , nitrogenase , rhizobia , botany , mimosa pudica , symbiosis , root nodule , rhizobium , nodule (geology) , microbiology and biotechnology , nitrogen fixation , inoculation , bacteria , ultrastructure , horticulture , paleontology , genetics
Several β-proteobacteria have been isolated from legume root nodules and some of these are thought to be capable of nodulating and fixing N 2 . However, in no case has there been detailed studies confirming that they are the active symbionts. Here, Ralstonia taiwanensis LMG19424, which was originally isolated from Mimosa pudica nodules, was transformed to carry the green fluorescent protein (gfp) reporter gene before being used to inoculate axenically-grown seedlings of M. pudica and M. diplotricha. Plants were harvested at various intervals for 56 days after inoculation, then examined for evidence of infection and nodule formation. Nodulation of both Mimosa spp. was abundant, and acetylene reduction assays confirmed that nodules had nitrogenase activity. Confocal laser scanning microscopy (CLSM) showed that fresh M. pudica nodules with nitrogenase activity had infected cells containing bacteroids expressing gfp. In parallel, fixed and embedded nodules from both Mimosa spp. were sectioned for light and electron microscopy, followed by immunogold labeling with antibodies raised against gfp and nitrogenase Fe (nifH) protein. Significant immunolabeling with these antibodies confirmed that R. taiwanensis LMG19424 is an effective N 2 -fixing symbiont of Mimosa spp. Both species were infected via root hairs and, in all respects, the nodule ontogeny and development was similar to that described for other mimosoid legumes. The nodules were indeterminate with a persistent meristem, an invasion zone containing host cells being invaded via prominent infection threads, and an N 2 -fixing zone with infected cells containing membrane-bound symbiosomes.