Abstract
The complex interactions between plants and their microbiome can have a profound effect on the health and productivity of the plant host. A better understanding of the microbial mechanisms that promote plant health and stress tolerance will enable strategies for improving the productivity of economically important plants. Pantoea sp. YR343 is a motile, rod-shaped bacterium isolated from the roots of Populus deltoides that possesses the ability to solubilize phosphate and produce the phytohormone indole-3-acetic acid (IAA). Pantoea sp. YR343 readily colonizes plant roots and does not appear to be pathogenic when applied to the leaves or roots of selected plant hosts. To better understand the molecular mechanisms involved in plant association and rhizosphere survival by Pantoea sp. YR343, we constructed a mutant in which the crtB gene encoding phytoene synthase was deleted. Phytoene synthase is responsible for converting geranylgeranyl pyrophosphate to phytoene, an important precursor to the production of carotenoids. As predicted, the ΔcrtB mutant is defective in carotenoid production, and shows increased sensitivity to oxidative stress. Moreover, we find that the ΔcrtB mutant is impaired in biofilm formation and production of IAA. Finally we demonstrate that the ΔcrtB mutant shows reduced colonization of plant roots. Taken together, these data suggest that carotenoids are important for plant association and/or rhizosphere survival in Pantoea sp. YR343.
Highlights
The rhizosphere is the site of a complex network of plant–microbe and microbe–microbe interactions which influence plant health and productivity
YR343 clusters (100% of bootstrap replicates) with another Pantoea strain isolated from the Poplar rhizosphere
YR343 was isolated from the rhizosphere of a healthy Populus deltoides tree in North Carolina and is a robust colonizer of plant roots
Summary
The rhizosphere is the site of a complex network of plant–microbe and microbe–microbe interactions which influence plant health and productivity. Microbes can be considered pathogenic, neutral, or beneficial depending on the plant host with which they associate (Raaijmakers et al, 2009) Among these bacteria is a group of plant growth-promoting. YR343 bacteria (PGPB) that can colonize within the plant, on leaf or root surfaces, or in the surrounding rhizosphere (Hayat et al, 2010; Barret et al, 2011; Beneduzi et al, 2012) These bacteria can promote plant growth via phytohormone production, nitrogen fixation, and/or enhancement of water and mineral uptake (Kloos et al, 2001; Perrig et al, 2007; Bashan and de-Bashan, 2010; del Amor and Cuadra-Crespo, 2011). Well-studied genera like Azospirillum and Rhizobium are included in the PGPB group, the mechanisms by which these bacteria interact with and influence plant growth are not yet fully understood
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