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Impact of auxin signaling on root colonization of Arabidopsis thaliana by Azospirillum brasilense.

Plant-growth promoting rhizobacteria (PGPR) can directly or indirectly influence growth and development of plants. The best known example of direct plant growth promotion is the bacterial synthesis of plant hormones. The synthesis of auxins in the rhizosphere, with indole-3-acetic acid (IAA) being the most important, leads to stimulation of lateral root formation and root hair development. Recent investigations brought up an entirely new aspect of auxin signalling in plants. Auxin signalling is part of the innate immune system of Arabidopsis, and is repressed following infection with phytopathogens. These pathogens can interfere with the auxin signalling network as a strategy to penetrate the basal defense system of plants. These findings are very relevant  to the study of bacterial plant growth promotion, since many rhizobacteria (e.g. Azospirillum) are capable of producing auxins. The question remaining  is whether or not this auxin production is involved in root colonization and to what extent.
The general goal of this research is to perform a quantitative and qualitative analysis of root colonization of Azospirillum brasilense on Arabidopsis thaliana, with an emphasis on the role of bacterial auxin synthesis. This general goal contains two tasks. The first task is to characterize the differential gene expression in Arabidopsis upon inoculation with Azospirillum. Mutants of Azospirillum that are altered in IAA synthesis and cell surface will be included. This will lead to the identification of Arabidopsis genes and possibly pathways that are involved in root colonization. The second task is to determine the role of Azospirillum surface components and auxin production in the colonization process, by making use of Arabidopis mutants. This will give a more clear picture of how the identified Arabidopsis genes and pathways affect the colonization process. The results of this research can be of use for further development of bacterial inoculants in plant production systems, and can serve as input for plant breeding programs.
Date:1 Jan 2009  →  15 Sep 2013
Keywords:root development, colonization, microarray, PGPR, auxin signaling, Azospirillum
Disciplines:Plant biology
Project type:PhD project