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In their natural environment, plants live in close interaction with complex populations of microorganisms, including rhizobacteria species commonly referred to as 'Plant Growth Promoting Rhizobacteria' (PGPR). A growing body of evidence demonstrates the importance of sugar transport in plant pathogen resistance and in plant-microorganism mutualistic symbioses. Using an in vitro experimental system, including the model plant species Arabidopsis thaliana, two PGPR strains (Pseudomonas simiae PICF7 and Burkholderia phytofirmans PsJN) and a non-PGPR strain (Escherichia coli), we conducted a comprehensive set of phenotypic and gene expression analyses to explore the role and regulation of sugar transporter genes in plant-PGPR interactions. In physical contact with the seedling roots, or solely via the emission of bacterial volatile compounds, the two PGPR strains tested improved the growth and development of the Arabidopsis seedlings and altered the expression of several plant sugar transporter genes. Our results also revealed both conserved and strain-specific transcriptional regulation mechanisms. [ABSTRACT FROM AUTHOR] more...

Plants live in close relationships with complex populations of microorganisms, including rhizobacterial species commonly referred to as plant growth-promoting rhizobacteria (PGPR). PGPR are able to improve plant productivity, but the molecular mechanisms involved in this process remain largely unknown. Using an in vitro experimental system, the model plant Arabidopsis thaliana , and the well-characterized PGPR strain Pseudomonas simiae WCS417r (Ps WCS417r), we carried out a comprehensive set of phenotypic and gene expression analyses. Our results show that Ps WCS417r induces major transcriptional changes in sugar transport and in other key biological processes linked to plant growth, development, and defense. Notably, we identified a set of 13 genes of the SWEET and ERD6-like sugar transporter gene families whose expression is up- or down-regulated in response to seedling root inoculation with the PGPR or exposure to their volatile compounds. Using a reverse genetic approach, we demonstrate that SWEET11 and SWEET12 are functionally involved in the interaction and its plant growth-promoting effects, possibly by controlling the amount of sugar transported from the shoot to the root and to the PGPR. Altogether, our study reveals that PGPR-induced beneficial effects on plant growth and development are associated with changes in plant sugar transport. [ABSTRACT FROM AUTHOR] more...