Abstract
BackgroundPlant root exudates have been shown to play an important role in mediating interactions between plant growth-promoting rhizobacteria (PGPR) and their host plants. Most investigations were performed on Gram-negative rhizobacteria, while much less is known about Gram-positive rhizobacteria. To elucidate early responses of PGPR to root exudates, we investigated changes in the transcriptome of a Gram-positive PGPR to plant root exudates.ResultsBacillus amyloliquefaciens FZB42 is a well-studied Gram-positive PGPR. To obtain a comprehensive overview of FZB42 gene expression in response to maize root exudates, microarray experiments were performed. A total of 302 genes representing 8.2% of the FZB42 transcriptome showed significantly altered expression levels in the presence of root exudates. The majority of the genes (261) was up-regulated after incubation of FZB42 with root exudates, whereas only 41 genes were down-regulated. Several groups of the genes which were strongly induced by the root exudates are involved in metabolic pathways relating to nutrient utilization, bacterial chemotaxis and motility, and non-ribosomal synthesis of antimicrobial peptides and polyketides.ConclusionsHere we present a transcriptome analysis of the root-colonizing bacterium Bacillus amyloliquefaciens FZB42 in response to maize root exudates. The 302 genes identified as being differentially transcribed are proposed to be involved in interactions of Gram-positive bacteria with plants.
Highlights
Plant root exudates have been shown to play an important role in mediating interactions between plant growth-promoting rhizobacteria (PGPR) and their host plants
Composition of maize root exudates Maize root exudates were collected from axenic hydroponic cultures and analysed by HPLC for organic acids, amino acids, and oligosaccharides, which have been previously reported to be among the major ingredients in root exudates [8,22,23,24]
Corroborating an earlier report [25], we found that lactic acid was a main constituent of maize root exudates
Summary
Plant root exudates have been shown to play an important role in mediating interactions between plant growth-promoting rhizobacteria (PGPR) and their host plants. Root exudates contain low molecular-weight carbon such as sugars and organic acids that primarily act as energy sources for rhizobacteria and shape bacterial communities in the rhizosphere [11]. To date, it remains unclear how root exudates exert differential effects on rhizobacteria and which mechanisms or pathways make rhizobacteria responsive to plant root exudates
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