Differential protein profiles ofBradyrhizobium japonicumUSDA110 bacteroid during soybean nodule development

Abstract

During nodule development of legumes, together with the morphological alteration of plant cells, the rhizobia undergo marked biochemical and physiological changes and differentiate to bacteroids. Bacteroids invading a nodule are no longer free-growing cells, instead depending on the plant cell for all resources. To elucidate the molecular mechanism of the bacteroid differentiation of Bradyrhizobium japonicum, a time-course analysis of bacteroid protein profiles was studied by 2-D gel electrophoresis in soybean nodules. Using proteomic analysis, protein expressions in soybean nodule bacteroids 7, 10, 14, 28, and 49 days after inoculation (DAI) were monitored. The time points coincide with the early stage of nodule formation (7-10 DAI), the onset of nitrogen fixation (14-28 DAI), and nodule senescence (49 DAI). In this study, 275 annotated protein spots were successfully identified, and a cluster analysis of their expression was performed. A large portion of putative, upregulated proteins were observed in bacteroids at 7 or 10 DAI, and these upregulated proteins were mainly related to transcription, translation, protein folding, and degradation. In the later period (14-28 DAI) of bacteroid differentiation, a number of Nif and Fix proteins were upregulated. In addition, proteins related to the chaperonin and a synthetic enzyme of the poly-beta-hydroxybutyrate were expressed at high abundance. A number of proteins related to solute transporter were upregulated in the bacteroids and dominantly detected throughout nodule development. Changes of relative abundance of these proteins are discussed in relation to symbiosis.

Bacterial adaptation to life in association with plants – A proteomic perspective from culture to in situ conditions

“…A number of studies have adapted protocols for the separation of bacteria by density gradient centrifugation using percoll or sucrose gradients (e.g. 58–62).…”

High-Resolution Transcriptomic Analyses of Sinorhizobium sp. NGR234 Bacteroids in Determinate Nodules of Vigna unguiculata and Indeterminate Nodules of Leucaena leucocephala

“…High throughput transcriptomics and proteomics studies have revealed global gene expression profiles of enlarged bacteroids in indeterminate nodules [7], [8], [9], [10], [11] or morphologically unchanged bacteroids in determinate nodules [12], [13], [14], [15], [16]. Few of them compared host-specific bacteroid transcripts and/or proteins [11], [16].…”

Plant-bacterium interactions analyzed by proteomics

“…Protocols had been proposed for the bacterial separation by density gradient centrifugation using percoll or sucrose gradients (Gourion et al, 2006; Nomura et al, 2010). Jacobs et al (2012) discussed the transcriptomics profile of R. solanacearum in vitro and he discussed the importance of T3SS in vir cascade of Ralsotonia (45% regulated by HR and Hrp gene).…”

“…On the other hand, proteins involved in photosynthesis were decreased, pointing toward a heterotrophic lifestyle under symbiotic conditions (Dixon and Kahn, 2004). The general proteome analysis of bacteroids is compared with in vitro grown cells in order to identify nodule specific adaptations, over time or when plants were exposed to drought stress (Delmotte et al, 2010; Nomura et al, 2010). ABC-type transporters was present in nodule bacteria for transport of amino acids and inorganic ions along with proteins involved in vitamin synthesis, fatty acid, nucleic acid, cell surface synthesis, and stress-related processes (Sarma and Emerich, 2006).…”

“…An increased abundance of proteins involved in protein synthesis and degradation was observed during the early stage of nodule development, which may be explained by a restructuring of the proteome to attain a symbiotic lifestyle. Transformation of a free-living bacterium to a nitrogen-fixing endosymbiont results in significant physiological and developmental changes in the rhizobia, including the expression of nif and fix genes, which encode the proteins involved in the nitrogen fixation process in later stages of infection (Karunakaran et al, 2009; Nomura et al, 2010). To withstand changing environmental conditions, the bacteria must possess the ability to undergo specialized physiological adaptations.…”